Chronic arterial insufficiency is a progressive narrowing or occlusion of the arterial lumen, most commonly due to atherosclerosis, resulting in inadequate blood flow to the distal tissues and manifesting as intermittent claudication, rest pain, and eventual tissue loss.

Exam domain	One-glance essentials
Definition / diagnosis	*Chronic arterial insufficiency is a gradual reduction in limb perfusion developing over more than 2 weeks* ^[1] Chronic disease permits collateral formation; acute occlusion is a distinct entity ^[1] Intermittent claudication is non-critical disease; rest pain, ulceration or gangrene indicate CLI ^[1]
Epidemiology / risks	*Major atherosclerotic risks: smoking, diabetes, hypertension, hyperlipidaemia and family history* ^[1] *Atherosclerosis is systemic: assess for coronary and cerebrovascular disease ^[1] Buerger disease* suggests a young smoker with distal ischaemia; popliteal entrapment suggests a young athlete without risk factors ^[1]
Core mechanism	Atherosclerotic plaque progressively narrows the lumen, limiting exercise flow before resting flow ^[1] *Collateral vessels develop gradually and explain the better tolerance of chronic occlusion* ^[1] Common patterns are femoropopliteal and aorto-iliac disease; multilevel disease may progress to CLI ^[1]
Clinical picture	*Claudication is reproducible muscular pain at a fixed walking distance, relieved by rest* ^[1] Calf pain suggests SFA disease; buttock/thigh pain suggests aorto-iliac disease ^[1] *Rest pain is worse at night and relieved by dependency; ulcers and gangrene are tissue loss ^[1] Leriche syndrome*: bilateral absent femoral pulses, buttock claudication and impotence ^[1]
Investigations	*Assess clinically: arterial disease, acuity, severity, obstruction level and cause* ^[1] ABI confirms haemodynamic disease; a falsely high result from calcification requires TBI or TcPO₂ ^[1] Exercise ABI can reveal disease when resting ABI is normal but suspicion remains high ^[1] *Duplex is first-line imaging; DSA is reserved for planned intervention* ^[1]
Management	*All patients need smoking cessation, diabetes and hypertension control, lipid lowering and antiplatelet therapy* ^[1] Supervised exercise is first-line for claudication; consider intervention only for disabling symptoms despite conservative therapy ^[1] *CLI requires urgent revascularisation for limb salvage; use endovascular treatment for suitable short lesions and bypass for extensive disease ^[1] Revascularise before amputating ischaemic digits* ^[1]
Complications	Untreated CLI progresses from ulceration to gangrene, secondary infection and sepsis ^[1] *Myocardial infarction and stroke are major causes of death because atherosclerosis is systemic* ^[1] Reperfusion injury may cause compartment syndrome or rhabdomyolysis with hyperkalaemia and AKI ^[1] Graft failure, restenosis and prosthetic graft infection complicate revascularisation ^[1]
Prevention / follow-up	*Complete smoking cessation is the key modifiable intervention, particularly in Buerger disease ^[1] Control diabetes, blood pressure and lipids, and continue antiplatelet therapy for cardiovascular risk reduction ^[1] Maintain walking through a supervised exercise programme* to improve functional capacity ^[1] After revascularisation, monitor the limb and graft clinically so recurrent ischaemia is detected early ^[1]
Exam traps	*Do not label every exertional leg pain as claudication: neurogenic pain is variable, relieved by flexion and usually has palpable pulses ^[1] Sudden deterioration in a patient with PAD may be acute-on-chronic ischaemia* and needs urgent assessment ^[1] *Never amputate digits before revascularisation* when salvage is possible ^[1] *Treat the patient, not the angiogram*: do not intervene on an asymptomatic stenosis ^[1]

References

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p1, p2, p8, p14, p22, p23)

Chronic Arterial Insufficiency

Chronic arterial insufficiency (also called chronic limb ischaemia or peripheral arterial disease, PAD) is defined as a gradual reduction in limb perfusion — developing over more than 2 weeks — that threatens limb viability or impairs function ^[1]^[2]^[3].

The key conceptual distinction from acute limb ischaemia is time: the chronicity allows the body to mount a compensatory response (collateral vessel formation), which is why patients may walk a surprising distance before symptoms appear. However, once the disease progresses beyond the compensatory capacity of collaterals, the limb enters a state of critical limb ischaemia (CLI) — a clinical emergency where the tissue is at imminent risk of death.

Think of it this way: arteries are pipes. Chronic arterial insufficiency is a slowly rusting pipe that gradually narrows. The body tries to build detour pipes (collaterals), but eventually the demand outstrips supply.

Acute & chronic occlusion are distinct entities ^[1].

The condition is broadly subdivided into:

Non-critical limb ischaemia: manifests as intermittent claudication (IC) — the limb is not immediately threatened
Critical limb ischaemia (CLI): manifests as rest pain, tissue loss (ischemic ulcers), or gangrene — the limb is at risk ^[1]^[2]^[3]

What does 'claudication' mean?

"Claudicatio" is Latin for "to limp." Emperor Claudius himself was named for his limp. Intermittent claudication = intermittent limping due to muscle pain on walking, relieved by rest.

2. Epidemiology

PAD affects approximately 200 million people worldwide.
Prevalence increases sharply with age: ~3–10% in the general population, rising to 15–20% in those aged > 70.
In Hong Kong, the ageing population and high prevalence of diabetes mellitus (affecting ~10% of adults), hypertension, and historically high rates of male smoking make PAD a significant and growing clinical burden.
PAD patients have 2–3× increased cardiovascular mortality — most die of MI or stroke, not limb loss. Atherosclerosis is a systemic disease ^[1].
Only ~5–10% of patients with intermittent claudication progress to CLI over 5 years, but those who do face a 1-year major amputation rate of ~25% and 1-year mortality of ~25%.

Male:Female ratio ≈ 2:1, though narrows after menopause.
The superficial femoral artery (SFA) is the single most commonly affected segment (~70% of symptomatic PAD) ^[2]^[3].
Aorto-iliac disease accounts for ~30% ^[1]^[3].
Diabetics develop more distal (infrapopliteal) disease, making reconstruction harder.

Atherosclerotic Occlusive Disease: Risk Factors — Smoking, Diabetes mellitus, Hypertension, Hyperlipidemia, Family history ^[1].

Risk Factor	Mechanism / Notes
Smoking	Single most important modifiable risk factor. Nicotine causes endothelial damage, promotes thrombosis (↑ fibrinogen, ↑ platelet aggregation), ↑ LDL oxidation, vasoconstriction. Risk of PAD is 3–4× higher in smokers. Dose-dependent.
Diabetes mellitus	Accelerates atherosclerosis via advanced glycation end-products (AGEs) damaging endothelium, promotes small-vessel disease (microangiopathy), neuropathy masks pain → late presentation. DM doubles the risk of PAD and is particularly associated with distal (below-knee) disease.
Hypertension	Chronically elevated shear stress damages endothelium → facilitates lipid infiltration and plaque formation.
Hyperlipidaemia	↑ LDL cholesterol is directly atherogenic (oxidised LDL → foam cells → fatty streak → plaque).
Family history	Genetic predisposition to lipid disorders, endothelial dysfunction, pro-thrombotic states.
Age > 65	Cumulative exposure to risk factors; natural arterial stiffening and endothelial senescence.
Other	Chronic kidney disease (accelerated calcific atherosclerosis), obesity, sedentary lifestyle, male sex

High Yield

Atherosclerosis is a systemic disease ^[1]. A patient presenting with PAD very likely also has coronary artery disease (CAD) and/or cerebrovascular disease. Always assess for IHD and carotid disease. Think of PAD as a "window" into the patient's overall vascular health.

4. Anatomy & Function of the Lower Limb Arterial System

Understanding the anatomy is essential because:

The site of occlusion determines the pattern of symptoms.
The availability of collaterals determines whether the disease is survivable for the limb.
The anatomy dictates surgical approach (where to bypass from and to).

Arterial System of the Lower Limbs ^[1]:

Key anatomical points:

External iliac artery passes through the inguinal ligament and becomes the femoral artery ^[3].
The common femoral artery bifurcates into:
- Profunda femoris (deep femoral): the "lifeline" collateral vessel. Gives off perforating branches that anastomose around the thigh. When the SFA is occluded (very common), the profunda keeps the distal limb alive via collaterals — this is why profundaplasty can be life-saving.
- Superficial femoral artery (SFA): the most commonly diseased segment. Enters Hunter's canal (adductor canal) to become the popliteal artery.
Popliteal artery gives off LAMP — mnemonic for its branches ^[3]:
- Lateral (superior & inferior genicular)
- Anterior tibial
- Peroneal (fibular)
- Posterior tibial
- Medial (superior & inferior genicular)

Why is the SFA so commonly affected? It runs through the adductor canal, where it is subject to repetitive mechanical stress (compression and flexion with every step). This chronic mechanical trauma to the arterial wall predisposes to intimal injury and atherosclerosis.

Layers of vessel wall ^[3]:

Tunica intima: innermost layer — endothelium + subendothelial connective tissue. This is where atherosclerosis begins (endothelial dysfunction → lipid infiltration).
Tunica media: smooth muscle + elastic fibres. Responsible for vasoconstriction/dilation. Calcification here (Mönckeberg's) makes vessels rigid and falsely elevates ABPI.
Tunica adventitia: outermost connective tissue layer. Contains vasa vasorum (vessels that supply the vessel wall itself) and nerves.

This is the key reason chronic ischaemia behaves differently from acute ischaemia:

Collateral Pathway	Bypasses Occlusion At
Internal iliac → gluteal aa. → profunda femoris	Aorto-iliac
Profunda femoris perforating branches → genicular aa.	Superficial femoral artery
Genicular network around knee	Popliteal artery
Peroneal artery collaterals	Tibial arteries

The profunda femoris is the most important collateral channel in lower limb PAD. Protecting and opening this vessel is a surgical priority.

5. Etiology & Pathophysiology

5.1 Causes of Chronic Arterial Occlusion

Chronic occlusion: Atherosclerosis, Vasculitis, Entrapment ^[1].

Pathophysiology — from first principles:

Endothelial injury: Smoking, hypertension, hyperglycaemia, dyslipidaemia, and turbulent flow at arterial bifurcations cause chronic damage to the endothelial lining.
Lipid infiltration: Damaged endothelium becomes permeable to LDL cholesterol, which accumulates in the subendothelial space (tunica intima).
Oxidation & inflammation: LDL is oxidised → triggers recruitment of monocytes → monocytes become macrophages → engulf oxidised LDL → become foam cells → form fatty streak (earliest lesion).
Smooth muscle migration: Cytokines cause smooth muscle cells from the media to migrate into the intima and proliferate, producing collagen → forms a fibrous cap over the lipid core.
Advanced plaque: The mature atherosclerotic plaque has a necrotic lipid core (cholesterol crystals, dead foam cells), a fibrous cap, and may calcify.
Progressive stenosis: The plaque gradually narrows the lumen → reduced distal perfusion → symptoms appear when blood supply cannot meet metabolic demand (first during exercise → eventually at rest).
Compensatory collateral formation: Over weeks to months, ischaemia stimulates angiogenesis via VEGF/HIF-1α → collateral vessels develop to bypass the stenosis. This is why chronic occlusion is more tolerable than acute — the body has time to build detours ^[2]^[3].
Multi-level disease: In advanced cases, atherosclerosis affects multiple arterial segments simultaneously → collaterals become insufficient → critical limb ischaemia ^[2].

Young (30–40s), Male, Smokers. Pan-arteriitis. Medium & small sized arteries & veins. Lower limb > upper limbs. Rest pain, digital ulcer, gangrene. Clinical diagnosis. Arteriogram: "tree trunk." Reconstruction seldom possible. Stop smoking is effective. ^[1]

"Thrombo" = clot, "angiitis" = vessel inflammation, "obliterans" = obliterating/blocking
Non-atherosclerotic, segmental, inflammatory disease
Almost exclusively in young male heavy smokers (age 20–45)
Pathology: pan-arteritis (inflammation of all 3 vessel wall layers) with highly cellular thrombus and preservation of internal elastic lamina (distinguishing it from other vasculitides)
Affects small and medium arteries AND veins of distal extremities (hands and feet)
Lower limb > upper limb involvement ^[1]
Clinical features: digit ischaemia, ischaemic ulcers, rest pain, Raynaud's phenomenon, superficial thrombophlebitis
Angiography shows characteristic "tree trunk" pattern — abrupt segmental occlusions with collaterals resembling tree roots ^[1]
Treatment: Absolute smoking cessation is the only effective treatment. Reconstruction is seldom possible because the disease affects small distal vessels where bypass is technically infeasible ^[1].

Buerger's vs Atherosclerosis

Key differentiators: Buerger's = young, heavy smoker, distal small vessels, involves veins too, no typical CV risk factors. Atherosclerosis = older, large and medium vessels, classic CV risk factors. If a 35-year-old smoker presents with toe gangrene and no DM/HT/HL — think Buerger's.

"Behçet" = named after Turkish dermatologist Hulusi Behçet
Rare systemic vasculitis characterised by recurrent oral aphthous ulcers + at least one of: genital ulcers, ocular inflammation (uveitis), skin lesions (erythema nodosum, pathergy)
Remarkable for ability to involve blood vessels of any size and both arteries and veins ^[2]
Can cause arterial aneurysms, thrombosis, and chronic ischaemia
More common along the ancient Silk Road (Turkey, Middle East, East Asia including China/HK)
Pathology: neutrophilic vasculitis

Typically affects young, athletic patients (often muscular males in 20s–30s)
Caused by anomalous musculoskeletal attachments (usually abnormal medial head of gastrocnemius) or an abnormal course of the popliteal artery → compression of the popliteal artery during activity (e.g., plantarflexion)
Key clue: presents with intermittent claudication but lacks atherosclerotic risk factors ^[2]^[3]
Diagnosis: provocation testing (plantarflexion), duplex ultrasound, MRA
Treatment: surgical release of compressing structure ± arterial reconstruction if damaged

Major Levels of Arterial Occlusion ^[1]:

Level	Vessels	Clinical Features
Aorto-iliac	Large vessels	Claudication (thigh AND calf), Impotence
Femoro-popliteal	Medium vessels	Claudication (calf), Tissue loss
Distal (infrapopliteal)	Small vessels	Tissue loss

Why does occlusion level matter?

The more proximal the occlusion, the larger the muscle groups deprived → bilateral thigh + buttock claudication (aorto-iliac).
The more distal the occlusion, the more likely it is to present with tissue loss (ulcers, gangrene) rather than claudication, because distal vessels have fewer collateral options.
Diabetic patients typically have distal disease → present late with tissue loss.

Leriche syndrome: gradual occlusion of terminal aorta ^[3], causing the classic triad:

Absent femoral pulses bilaterally
Intermittent claudication (bilateral buttock, thigh, calf)
Erectile dysfunction (impotence) — because the internal iliac arteries (which supply the internal pudendal artery → penile blood supply) are occluded

"Leriche" = named after French surgeon René Leriche. The syndrome is the archetypal aorto-iliac occlusive disease. Always ask about impotence in male PAD patients — it may be the presenting complaint!

6. Classification Systems

Stage	Description	Clinical Features
I	Asymptomatic	Subclinical disease, no symptoms
IIa	Mild claudication	Claudication distance > 200m
IIb	Moderate-severe claudication	Claudication distance < 200m
III	Ischaemic rest pain	Rest pain, especially nocturnal
IV	Tissue loss	Ulceration, necrosis, or gangrene

Grade	Category	Description
0	0	Asymptomatic
I	1	Mild claudication
I	2	Moderate claudication
I	3	Severe claudication
II	4	Ischaemic rest pain
III	5	Minor tissue loss (non-healing ulcer, focal gangrene with diffuse pedal ischaemia)
III	6	Major tissue loss (extending above transmetatarsal level, functional foot no longer salvageable)

Fontaine III + IV / Rutherford 4–6 = Critical Limb Ischaemia (CLI)

Critical Limb Ischaemia — Definition

CLI is defined as the presence of chronic ischaemic rest pain, ulcers, or gangrene attributable to objectively proven arterial occlusive disease ^[1]^[2]^[3]. It represents an absolute indication for intervention — without revascularisation, major amputation is highly likely within 6–12 months. Never confuse it with simple intermittent claudication, which is a relative indication.

The TransAtlantic Inter-Society Consensus (TASC II) classifies aorto-iliac and femoropopliteal lesions into Types A–D based on anatomical complexity:

Type A: Short, focal stenoses → best treated with endovascular approaches
Type B: Multiple stenoses or short occlusions → endovascular preferred
Type C: Long stenoses, multiple occlusions → surgery preferred
Type D: Complete occlusions of long segments → best treated with surgery ^[3]

7. Clinical Features

The Problems: A patient with LEG PAIN. A patient with ULCER or GANGRENE in the foot. ^[1]

7.1 Symptoms

Definition: Reproducible, cramping muscular pain in a defined muscle group, brought on by walking a consistent distance, and completely relieved by rest within a few minutes (typically ~5 min) ^[2]^[3].

Pathophysiology: During exercise, working muscles demand increased blood flow. In a stenosed artery, the flow cannot increase to meet demand → anaerobic metabolism in the muscle → lactic acid accumulates → pain. At rest, the demand drops back to baseline and the limited blood flow is sufficient again → pain resolves.

Localisation tells you the level of disease ^[1]^[3]:

Symptom Location	Level of Occlusion
Bilateral thigh + buttock claudication	Aorto-iliac (30%)
Unilateral buttock	Iliac artery
Calf claudication (most common)	Superficial femoral / femoropopliteal (70%)
Foot	Tibial / peroneal arteries

Why is calf claudication the most common? Because the SFA is the most commonly diseased artery. The SFA supplies the popliteal artery, which in turn supplies the calf muscles (gastrocnemius, soleus) via the tibial arteries.

Key claudication characteristics ^[3]:

Claudication distance (always ask on flat ground vs. slope — uphill is worse because muscles work harder)
How long they need to rest (usually ~5 minutes)
Whether they can then walk the same distance again (reproducibility is a hallmark)
Nature of pain: must be muscular pain (cramping, aching — NOT sharp, shooting, or burning) ^[3]

Definition: Persistent, severe pain in the forefoot and toes at rest, typically worst at night.

Pathophysiology: The arterial disease is now so severe that even the basal metabolic demands of resting tissue cannot be met. The pain is worst at night/when recumbent because:

Loss of gravity-assisted perfusion: When lying flat, the hydrostatic pressure column that assists blood flow to the feet (when standing/sitting) is lost → foot perfusion pressure drops further below the critical threshold.
Reduced cardiac output during sleep: HR and BP are lower at night → further reduction in already compromised perfusion.

Classical description ^[3]:

Patient wakes up due to pain
Swings legs out of bed to hang feet over the side → this restores the hydrostatic pressure column → perfusion improves → pain eases
May sleep in a chair with legs dependent

Why does hanging legs down help? Gravity adds ~60 cmH₂O of hydrostatic pressure to the foot arteries when the leg is dependent. In a critically ischaemic limb, this extra pressure may be just enough to push blood through to the tissue.

Consequences of chronic dependency:

Dependent rubor: chronic venous congestion and maximal arteriolar dilation give the foot a dusky red/purple colour when dependent
Peripheral oedema: chronic dependency → venous pooling → oedema → further compromises tissue perfusion (Starling forces)

Any tissue loss: ulcer, gangrene +/- infection ^[3]

Ischaemic ulcers:

Occur at pressure points (tips of toes, heel, malleoli, metatarsal heads)
Painful (unless concurrent neuropathy, as in diabetics)
Punched-out appearance, pale/grey base (poor blood supply = no granulation tissue)
Surrounded by pale/atrophic skin

Gangrene ("ganggraina" = Greek for "gnawing sore"):

Feature	Dry Gangrene	Wet Gangrene
Pathophysiology	Pure ischaemia → coagulative necrosis → tissue mummifies	Ischaemia + secondary bacterial infection → liquefactive necrosis
Appearance	Black, shrivelled, dry, well-demarcated	Swollen, discoloured, oedematous, blistered, pus, foul-smelling
Pain	Variable (may be painless once tissue is dead)	Very painful, systemically unwell
Management	May auto-amputate; revascularise first	Urgent — risk of sepsis, requires debridement/amputation + antibiotics
Systemic features	Minimal	Fever, tachycardia, sepsis

Never amputate digits before revascularization

Never amputate digits before revascularization ^[1]. If you amputate an ischaemic toe without restoring blood supply, the wound will not heal, and you'll need to amputate more proximally. Always restore inflow first, then let demarcation occur, then amputate the minimum necessary.

Specific to aorto-iliac disease (Leriche syndrome)
The internal iliac artery → internal pudendal artery → supplies the corpus cavernosum
Bilateral internal iliac artery occlusion → insufficient penile blood flow → inability to achieve/maintain erection ^[1]^[3]
Always ask about this in males — it may be the presenting complaint or a key clue to the level of disease

Because atherosclerosis is a systemic disease ^[1], always ask about:

Angina / chest pain / dyspnoea on exertion → coronary artery disease
TIA symptoms (amaurosis fugax, transient hemiparesis, dysarthria) → carotid/cerebrovascular disease
Abdominal angina (postprandial pain) → mesenteric ischaemia

7.2 Signs

Sign	Pathophysiology
Pallor (especially on elevation)	Reduced arterial inflow → insufficient blood to colour the skin
Dependent rubor	Chronic maximal arteriolar dilation (due to ischaemia) → when dependent, blood pools in dilated vessels → dusky red/purple colour
Trophic changes: hair loss, shiny atrophic skin, thickened nails	Chronic ischaemia → inadequate nutrition to skin appendages → atrophy
Muscle wasting (especially calf)	Chronic disuse (limited walking) + ischaemic myopathy
Ulceration / gangrene	As described above — tissue necrosis from inadequate perfusion
Amputation stumps (previous surgery)	Indication of severity/progression

Pulse assessment — systematically palpate from proximal to distal and compare both sides:

Common femoral (mid-inguinal point)
Popliteal (deep in popliteal fossa, flex knee slightly)
Posterior tibial (behind medial malleolus)
Dorsalis pedis (lateral to extensor hallucis longus tendon)

Finding	Interpretation
Absent femoral pulses bilaterally	Aorto-iliac disease (Leriche syndrome)
Present femoral, absent popliteal	SFA occlusion
Present popliteal, absent pedal pulses	Tibial artery disease
All pulses present but reduced	Proximal stenosis (not complete occlusion) or multilevel disease

Temperature: Compare both limbs. The ischaemic limb is cooler distally. The level at which temperature changes gives a rough indication of the occlusion level.

Capillary refill time: > 2 seconds is abnormal → suggests inadequate arterial perfusion.

Buerger's test: lift both legs slowly for pallor (Buerger's angle) → swing legs down for reactive hyperemia ^[3]

Technique:

Patient supine. Raise both legs to ~90° (or until pallor develops).
Buerger's angle = the angle at which the foot becomes pale.
- Normal: no pallor even at 90°
- Severe ischaemia: pallor at < 20°
- The lower the angle, the worse the ischaemia
Then sit the patient up and swing legs over the edge of the bed.
Reactive hyperaemia: In ischaemic limbs, the foot turns dusky red/purple (dependent rubor) due to maximally dilated arterioles filling slowly with deoxygenated blood. Normal limbs regain pink colour within seconds.

Why does this work? Raising the leg removes the hydrostatic pressure component. In normal circulation, arterial pressure is more than sufficient to perfuse the foot even when elevated. In PAD, the already-low perfusion pressure cannot overcome gravity → foot becomes pale at a threshold angle.

Listen for bruits over the femoral artery (groin), iliac arteries (lower abdomen), and aorta (epigastric).
A bruit indicates turbulent flow across a stenosis. Absence does not rule out disease (complete occlusion produces no flow, hence no bruit).

To complete: bedside Doppler for pulses, measure ABI on both sides, examine abdomen for AAA / RAS, cardiovascular examination for other CV risk factors (e.g., BP/P, AF), urine multistix for glucose ^[3]

Bedside handheld Doppler: to detect pedal pulses that may be impalpable manually
ABPI measurement: see diagnostic section (next session)
Abdominal examination: palpate for AAA (pulsatile expansile mass), listen for renal artery stenosis (RAS) bruits
Cardiovascular examination: BP, pulse rate and rhythm (AF → embolic risk), heart murmurs, carotid bruits
Urine dipstick for glucose: screen for diabetes
Neurological examination of lower limbs: differentiate from neurogenic claudication

This is a classic exam question and a critical clinical distinction ^[3]:

Feature	Vascular Claudication	Neurogenic Claudication (Spinal Stenosis)
Cause	Chronic limb ischaemia	Spinal stenosis
Nature of pain	Muscular cramping	Heaviness, weakness, tingling, burning
Radiation of pain	From distal to proximal	From proximal to distal (radiates down from back/buttock)
Claudication distance	Fixed, reproducible	Variable — may walk further some days than others
Exacerbating factor	Walking uphill (muscles work harder → more O₂ demand)	Walking downhill (spine extends → narrows spinal canal further)
Relieving factor	Rest — "Shop window to shop window"	Bending over, sitting — "Park bench to park bench" (flexion opens spinal canal)
Pulse	Absent	Present
Associations	Atherosclerotic risk factors, Atrophic changes	Only 10% SLR +ve, Back pain

Also differentiate from:

Sciatica ^[2]^[3]: Back pain with radiation, not relieved by resting — nerve root compression (usually L4-S1), dermatomal distribution, positive straight leg raise, not exercise-dependent.

Shop window vs Park bench

Vascular claudication: patient stops to rest (as if looking in a shop window), pain resolves, walks same distance again → "shop window to shop window". Neurogenic claudication: patient sits on a park bench (flexes spine), pain resolves → "park bench to park bench".

Feature	Arterial Ulcer	Venous Ulcer
Location	Pressure points: toes, heel, metatarsal heads, between toes	Gaiter area (medial malleolus, medial lower leg)
Appearance	Punched-out, pale/grey base, poor granulation	Shallow, irregular, sloughy base, may have granulation
Pain	Typically very painful	Usually less painful (may ache)
Surrounding skin	Pale, shiny, atrophic, hairless	Lipodermatosclerosis, haemosiderin staining (brown), varicose eczema
Pulses	Absent or reduced	Present
ABPI	Low (< 0.9)	Normal or high (unless mixed disease)

Assessment of Lower Limb Ischaemia ^[1]:

Two parallel assessments must happen simultaneously:

1. Assess the Patient (Systemic)

Risk factors: Elderly, Cardiac / pulmonary disease, Smoker ^[1]
Fitness for intervention (general anaesthetic risk, cardiac function, renal function)
Systemic atherosclerotic burden (IHD, cerebrovascular disease)

2. Assess the Limb

Limb at Risk: Rest Pain, Tissue Loss → Absolute indication for intervention ^[1]
Limb not threatened: Claudication → Relative indication for intervention ^[1]

High Yield Summary

Chronic arterial insufficiency = gradual (> 2 weeks) reduction in limb perfusion; most commonly due to atherosclerosis.
Acute and chronic occlusion are distinct entities — chronic allows collateral formation.
Risk factors: Smoking, DM, HT, HL, Family history — atherosclerosis is a systemic disease.
SFA is the most commonly affected vessel (~70%); aorto-iliac ~30%.
Fontaine: I (asymptomatic) → IIa (> 200m) → IIb (< 200m) → III (rest pain) → IV (tissue loss).
CLI (Fontaine III–IV) = absolute indication for intervention; claudication = relative.
Intermittent claudication: exercise-induced muscular pain, fixed distance, relieved by rest. Calf = SFA; thigh + buttock = aorto-iliac.
Rest pain: worst at night, relieved by dependency (hanging legs down restores hydrostatic pressure).
Leriche syndrome: aortic bifurcation occlusion → absent femoral pulses + bilateral claudication + impotence.
Buerger's disease: young male smokers, small distal vessels, "tree trunk" angiogram, stop smoking is the only effective treatment.
Never amputate digits before revascularization.
Buerger's test: elevation pallor (Buerger's angle) + dependent rubor (reactive hyperaemia).
Vascular vs neurogenic claudication: fixed distance vs variable; rest relieves vs bending forward; absent pulses vs present.

Active Recall - Chronic Arterial Insufficiency (Part 1)

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p1, p2, p8, p14, p22, p23) ^[2] Senior notes: felixlai.md (Chronic arterial insufficiency section) ^[3] Senior notes: maxim.md (Chronic limb ischaemia / Peripheral vascular disease section)

Differential Diagnosis of Chronic Arterial Insufficiency

The differential diagnosis (DDx) of chronic arterial insufficiency is really about answering two questions in sequence:

Is this truly vascular leg pain, or is something else mimicking it? (DDx of the symptom — especially intermittent claudication and rest pain)
If it is vascular, is it chronic or acute? (DDx within vascular pathology)

A very common exam pitfall highlighted on the lecture slides: Mis-diagnosis of claudication and Beware of "leg pain" ^[1]. Not all leg pain on walking is claudication. You must systematically consider and exclude the mimics.

The best way to organise the DDx is by the presenting complaint, because that is how you encounter patients in practice:

2. Differential Diagnosis of Intermittent Claudication

This is the most commonly tested DDx. The key principle: true vascular claudication is muscular pain with a fixed, reproducible claudication distance, relieved completely by rest within minutes, with absent pulses on examination. Any deviation from this pattern should make you think of alternatives ^[1]^[2]^[3].

Why does it mimic claudication? Lumbar spinal stenosis narrows the spinal canal → the cauda equina nerve roots become compressed, especially during walking when the spine is extended. This produces leg pain on walking that can look remarkably similar to vascular claudication.

How to tell them apart — this is a classic table from both lecture slides and senior notes ^[3]:

Feature	Vascular Claudication	Neurogenic Claudication
Cause	Chronic limb ischaemia	Spinal stenosis
Nature of pain	Cramping, muscular	Heaviness, weakness, tingling, burning, "jelly legs"
Radiation of pain	Distal → proximal (starts in calf, may extend to thigh)	Proximal → distal (starts in back/buttock, radiates down leg)
Claudication distance	Fixed, reproducible	Variable — better some days, worse others
Exacerbating factor	Walking uphill (muscles work harder, more O₂ demand)	Walking downhill (spine extends → canal narrows)
Relieving factor	Rest — "Shop window to shop window" (standing still is enough)	Bending over, sitting — "Park bench to park bench" (flexion widens spinal canal)
Pulse	Absent	Present
Skin changes	Atrophic changes (hairless, shiny, cool)	Normal skin
Associations	Atherosclerotic risk factors	Only 10% SLR +ve, Back pain

Why the different exacerbating factors?

Walking uphill in vascular disease: the calf muscles must generate more force against gravity → higher metabolic demand → ischaemic threshold reached sooner.
Walking downhill in spinal stenosis: going downhill forces the spine into extension → the ligamentum flavum buckles inward, the spinal canal narrows → nerve compression worsens. Conversely, going uphill tends to flex the spine slightly, which is why neurogenic claudication may paradoxically be better uphill.

Why "shop window" vs "park bench"?

Vascular: the patient only needs to stop moving (reducing muscle O₂ demand) → pain resolves in ~5 min → they can walk the same distance again before it recurs. They stop every 200m as if window-shopping.
Neurogenic: simply standing still doesn't help because the spine is still extended. The patient must sit down (flexes spine, opens canal) → finds a park bench. Alternatively they lean on a shopping trolley (the "shopping cart sign" — lumbar flexion while walking delays symptoms).

Sciatica: back pain with radiation, not relieved by resting ^[2]^[3]

"Sciatica" = "ischiadica" (Greek/Latin) = pain along the sciatic nerve (L4–S1 roots)
Caused by nerve root compression, most commonly from a herniated (prolapsed) intervertebral disc at L4/5 or L5/S1 ^[2]
Pain is sharp, burning, or shooting and radiates down the posterior or lateral aspect of the leg in a dermatomal distribution, often to the foot/ankle
Key distinguishing feature: pain is NOT exercise-dependent in the same reproducible way as claudication. It may be present at rest, worsened by coughing/sneezing/straining (Valsalva — increases intrathecal pressure), and is not relieved by simply stopping walking ^[2]^[3]
Positive straight leg raise (SLR) test (Lasègue sign)
Peripheral pulses are present

The crucial point: in sciatica, the pain pattern does not follow the exercise → rest → exercise cycle of true claudication. The patient may have pain while sitting, lying, or even at night — and standing still doesn't help.

Hip osteoarthritis: pain localised to the groin/hip, worsened by weight-bearing and movement (not specifically walking a fixed distance), stiffness after rest, reduced range of motion (especially internal rotation)
Knee osteoarthritis: pain over the joint, mechanical locking/giving way, stiffness
Foot arthritis (e.g., hallux rigidus, midfoot OA): localised joint pain on walking
Key difference: joint pain is localised to the joint, not a diffuse muscular cramping. Pain may be present even at first step (not after a fixed distance). Pulses are present.

Chronic compartment syndrome ^[2]:

Typically affects young heavy-muscled athletes — runners, footballers, military recruits
A reversible form of compartment syndrome: during exercise, muscle swelling within a tight fascial compartment raises intra-compartmental pressure → compromises local tissue perfusion → produces pain, tightness, and sometimes paraesthesia
Pathophysiology from first principles: Exercising muscle swells (increased blood flow + oedema). Normally the fascial compartment is compliant enough to accommodate this. In susceptible individuals, the fascia is abnormally tight or the muscle bulk is excessive → pressure rises above capillary perfusion pressure → ischaemic pain
Pain resolves within minutes of stopping exercise (similar to vascular claudication — this can be tricky!)
Key differences from vascular claudication: young, no CV risk factors, pulses present, pain is a tight/bursting sensation (not cramping), often bilateral, may have paraesthesia. Definitive diagnosis by intra-compartmental pressure measurement during and after exercise.

Baker's cyst ^[2]:

A popliteal synovial cyst arising from the gastrocnemius-semimembranosus bursa
Usually associated with underlying joint disease (OA, RA, meniscal tears) — synovial fluid from the knee joint tracks posteriorly into the bursa
Presents with posterior knee pain, stiffness, and a palpable swelling behind the knee
Can mimic claudication if it compresses the popliteal artery or causes posterior knee discomfort on walking
If the cyst ruptures, it can mimic DVT (acute calf pain, swelling — "pseudo-DVT")
Key difference: palpable posterior knee mass, pulses present, associated joint disease, USG confirms cyst

This is the second critical DDx axis — once you've confirmed the problem is vascular, you must determine the acuity ^[1]^[3]:

Acute & chronic occlusion are distinct entities ^[1].

Feature	Acute Limb Ischaemia	Chronic Arterial Insufficiency
Onset	Sudden (< 2 weeks) ^[4]	Gradual (> 2 weeks) ^[3]
Mechanism	Embolism, acute thrombosis, trauma ^[1]	Atherosclerosis, vasculitis, entrapment ^[1]
Collaterals	Absent → complete ischaemia	Present (had time to develop) → incomplete ischaemia
Clinical features	6 P's: Pain, Pallor, Pulseless, Perishingly cold, Paraesthesia, Paralysis ^[4]	Intermittent claudication → rest pain → tissue loss (gradual progression)
Contralateral limb	Often normal (if embolic)	Often also affected (systemic atherosclerosis)
Skin changes	Marble white → mottling (blanchable then fixed) ^[4]	Chronic trophic changes (hairless, shiny, thickened nails)
Urgency	Surgical emergency — irreversible damage in 4–6 hours without collaterals ^[4]	Elective workup in non-critical; urgent in CLI

Why is this distinction so critical? Because the management is completely different. Acute ischaemia = emergency embolectomy or thrombolysis. Chronic ischaemia = risk factor modification ± elective revascularisation. Missing acute ischaemia (Delay recognition of acute ischaemia ^[1]) leads to limb loss.

A specific scenario to watch for: Acute-on-chronic ischaemia — a patient with pre-existing PAD (chronic) who develops sudden worsening (acute thrombosis on top of a plaque). They may have some collaterals, so the presentation is not as catastrophic as a pure embolus, but they still need urgent assessment.

When a patient presents with a leg ulcer or tissue loss, the DDx extends beyond pure arterial disease:

Type	Arterial Ulcer	Venous Ulcer	Neuropathic Ulcer (Diabetic)	Mixed
Location	Pressure points: toes, heel, metatarsal heads	Gaiter area (medial malleolus)	Plantar surface, pressure points	Variable
Pain	Very painful	Mild aching	Painless (neuropathy)	Variable
Appearance	Punched-out, pale base	Shallow, irregular, sloughy	Deep, may probe to bone	Combination
Surrounding skin	Pale, atrophic, hairless	Haemosiderin staining, lipodermatosclerosis, eczema	Callus, warm foot, loss of sensation	Mixed features
Pulses	Absent/reduced	Present	May be present or absent	Reduced
ABPI	Low (< 0.9)	Normal (0.9–1.3)	May be falsely elevated (> 1.3 due to calcification) ^[5]	Low

Diabetic Foot Ulcers — ABPI Pitfall

In diabetic patients, ABPI may be falsely elevated (> 1.3) because medial arterial calcification (Mönckeberg's sclerosis) makes the vessels incompressible. The cuff cannot occlude the calcified vessel, so the measured ankle pressure is artefactually high. In such cases, use toe-brachial index (TBI) or transcutaneous oxygen pressure (TcPO₂) instead — digital arteries are usually spared from calcification ^[5].

Other causes of leg ulcers to consider:

Traumatic ulcers: history of injury, any location
Malignant ulcers: Marjolin's ulcer (SCC arising in a chronic wound/scar), BCC, melanoma — raised/rolled edges, bleeds easily, biopsy any non-healing ulcer
Infective ulcers: tropical ulcers, TB (Bazin's erythema induratum)
Vasculitic ulcers: e.g., rheumatoid vasculitis, pyoderma gangrenosum (IBD-associated)
Haematological: sickle cell disease (common cause of leg ulcers in young Afro-Caribbean patients)

Once you've confirmed chronic arterial ischaemia, you should consider the specific aetiology, because management differs:

Aetiology	Age/Demographics	Vessel Size	Key Features	Pulses	Angiographic Appearance
Atherosclerosis	Elderly, CV risk factors	Large/medium	Most common (> 95%), systemic	Absent at level of disease	Irregular stenoses, calcification
Buerger's disease	Young (30–40s), Male, Smokers ^[1]	Medium & small	Pan-arteriitis, lower limb > upper limb, digital ulcers, involves veins too	Absent distally	"Tree trunk" appearance ^[1]
Behçet's disease	Young adult, Silk Road populations	Any size	Oral/genital ulcers, uveitis, pathergy, involves arteries AND veins	Variable	Aneurysms, occlusions
Popliteal entrapment	Young, athletic, muscular	Popliteal artery	No CV risk factors, symptoms provoked by plantarflexion	Absent on provocation	Compression/occlusion of popliteal with provocative manoeuvres
Fibromuscular dysplasia	Young women	Medium (renal, carotid)	Non-atherosclerotic, "string of beads" on angiography	Variable	Alternating stenoses and dilations
Radiation arteritis	Any age with radiation hx	Field of radiation	History of radiotherapy, can present years later	Absent in field	Focal stenosis in radiation field

Arterial Diseases: Common Pitfalls ^[1]:

Mis-diagnosis of claudication — calling neurogenic or arthritic pain "claudication"

Toe amputation before revascularization — treating the end-organ (gangrene) without fixing the cause (arterial inflow)

Delay recognition of acute ischaemia — calling acute ischaemia "chronic" and not treating urgently

Beware of "leg pain" — not all leg pain is vascular; think systematically

"Treating the angiogram" — intervention for asymptomatic disease — finding a stenosis on imaging does not mean it needs fixing if the patient is asymptomatic (Fontaine I)

'Treating the Angiogram'

This is a critical concept: just because you see a narrowed artery on imaging does not mean you should intervene. Many patients have significant anatomical stenoses but adequate collateral circulation and no symptoms. Intervention carries risk (dissection, embolisation, restenosis). Only intervene for symptomatic disease — disabling claudication that fails conservative management, or critical limb ischaemia. Never treat the angiogram — treat the patient. ^[1]

When faced with a patient with leg pain or tissue loss, work through this checklist:

Step	Question	How to Answer
1	Is this vascular?	Pulses, ABPI, trophic changes, Buerger's test
2	Is it acute or chronic?	Onset < or > 2 weeks, presence of collaterals, chronicity of skin changes
3	If chronic vascular, what level?	Symptom location (buttock/thigh = aortoiliac; calf = femoropopliteal; foot = distal)
4	If chronic vascular, what aetiology?	Age, risk factors (atherosclerosis vs Buerger's vs entrapment)
5	If not clearly vascular, what mimic?	Neurogenic claudication, sciatica, arthritis, compartment syndrome, Baker's cyst
6	If tissue loss, what type of ulcer?	Location, pain, surrounding skin, pulses, ABPI

High Yield Summary

Most important DDx of intermittent claudication: neurogenic claudication (spinal stenosis), sciatica, hip/knee arthritis, chronic compartment syndrome, Baker's cyst.
Vascular vs neurogenic claudication: Fixed distance vs variable; rest relieves vs flexion relieves; absent pulses vs present; "shop window" vs "park bench"; uphill worse vs downhill worse.
Sciatica: back pain radiating down leg, dermatomal, NOT relieved by rest, positive SLR, pulses present.
Acute vs chronic: < 2 weeks = acute (emergency), > 2 weeks = chronic; acute lacks collaterals and presents with 6 P's.
Lecture slides pitfalls: mis-diagnosis of claudication, toe amputation before revascularisation, delay recognition of acute ischaemia, "treating the angiogram."
Leg ulcer DDx: arterial (painful, pressure points, absent pulses) vs venous (gaiter area, haemosiderin) vs neuropathic/diabetic (painless, plantar, may have falsely elevated ABPI).
Within chronic arterial causes: atherosclerosis (elderly, CV risk factors) vs Buerger's (young male smoker, small vessels, "tree trunk") vs popliteal entrapment (young athlete, no risk factors).

Active Recall - DDx of Chronic Arterial Insufficiency

References

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p2, p3, p7, p8, p22, p28) ^[2] Senior notes: felixlai.md (Chronic arterial insufficiency — Etiology, DDx of intermittent claudication) ^[3] Senior notes: maxim.md (Chronic limb ischaemia — DDx, History taking, Vascular vs neurogenic claudication table) ^[4] Senior notes: felixlai.md (Acute arterial insufficiency — 6 P's, clinical manifestation); maxim.md (Acute limb ischaemia) ^[5] Senior notes: maxim.md (Diabetic foot ulcers — ABPI pitfall, TcPO₂)

Diagnostic Criteria, Algorithm & Investigations for Chronic Arterial Insufficiency

Unlike conditions such as rheumatic fever or SLE, there is no formal point-based diagnostic criterion set for chronic arterial insufficiency. Instead, the diagnosis is made by combining three pillars:

Clinical history and examination — the foundation
Haemodynamic confirmation — primarily the Ankle-Brachial Index (ABI)
Anatomical localisation — imaging to define the level, length, and severity of disease for treatment planning

The lecture slides frame this beautifully as a systematic Clinical Evaluation checklist ^[1]:

Does the patient have arterial disease? Acute or chronic? How severe? Where is the obstruction? Why? ^[1]

Let's unpack each:

Question	How to Answer
Does the patient have arterial disease?	History (claudication, rest pain, tissue loss), examination (absent pulses, trophic changes, Buerger's test), confirmed by ABI
Acute or chronic?	Onset < 2 weeks = acute; > 2 weeks = chronic. Chronic has trophic changes and collaterals.
How severe?	Fontaine/Rutherford staging + ABI value + presence of tissue loss
Where is the obstruction?	Symptom localisation + pulse assessment + duplex USG + angiography
Why?	Risk factor profile (atherosclerosis vs Buerger's vs entrapment)

The ABI is the cornerstone objective test that both confirms the diagnosis and quantifies severity ^[1]^[2]^[3].

ABI Value	Interpretation	Pathophysiological Basis
> 1.3	Calcified (non-compressible) artery — falsely elevated ^[2]^[3]	Mönckeberg's medial calcification (especially in DM) makes the vessel rigid → cuff cannot compress it → artefactually high reading
> 0.9 – ≤ 1.3	Normal ^[2]^[3]	Ankle systolic pressure is normally equal to or slightly higher than brachial (pulse wave amplification in peripheral arteries)
0.4 – ≤ 0.9	Claudication — arterial obstruction associated with intermittent claudication ^[2]^[3]	Stenosis reduces distal perfusion pressure, but still sufficient at rest for tissue viability
< 0.4	Critical limb ischaemia — associated with rest pain, non-healing ulceration, gangrene ^[2]^[3]	Severe multi-level disease; perfusion pressure at rest is below the threshold needed to maintain tissue viability

ABI Does Not Rule Out Disease When Normal

Normal ABI values may present with intermittent claudication ^[3]. How? In early/mild disease, collaterals maintain resting perfusion pressure at near-normal levels. The stenosis only becomes haemodynamically significant during exercise when flow demand increases. This is why an exercise treadmill test is needed when the clinical suspicion is high but resting ABI is normal ^[2].

Criteria for a positive exercise ABI test ^[2]:

Patient walks on treadmill until symptoms reproduced
ABI is measured before and immediately after exercise
A decrease in ABI of ≥ 0.2 (or an absolute post-exercise ABI < 0.9) confirms exercise-induced ischaemia

Key logic points in this algorithm:

ABI first — it is cheap, bedside, non-invasive, and answers "does this patient have PAD?" for > 95% of cases.
Exercise ABI — for the borderline/normal resting ABI with convincing clinical history. Think of it as a "stress test for the legs."
Duplex USG — the first-line imaging investigation to localise the disease anatomically.
Arteriography is indicated ONLY when surgery is planned — NOT used for diagnosis ^[1]. This is a critical lecture slide point.
TBI/TcPO₂ — for diabetics with falsely elevated ABI.

4. Investigation Modalities — Detailed Breakdown

4.1 Non-Invasive Vascular Laboratory

The Non-invasive VASCULAR LABORATORY ^[1]:

Ultrasound based
Segmental pressure
Waveform analysis
Ankle-brachial index (ABI)
Exercise test ^[1]

What it is: The ratio of the highest ankle systolic pressure to the highest brachial systolic pressure.

ABI = Ankle systolic pressure ÷ Arm systolic pressure ^[1]

How to measure ^[2]^[3]:

Patient supine, rested for 10 minutes (eliminates exercise effect)
Brachial pressure: BP cuff on arm, handheld Doppler probe over brachial artery. Inflate cuff until signal is obliterated → slowly deflate → record pressure at which signal returns (systolic). Measure both arms — use the higher value as denominator (to account for possible subclavian stenosis)
Ankle pressure: BP cuff around the lower calf (NOT the ankle itself — common mistake). Doppler probe over the posterior tibial artery and then the dorsalis pedis artery. Measure both → use the higher value as numerator for that side
Calculate separately for left and right legs

Why does this work from first principles?

In a normal person, as blood travels from the aorta to the periphery, the systolic pressure actually increases slightly (pulse wave amplification due to progressive narrowing and wave reflection). So the ankle pressure should be ≥ brachial pressure → ABI ≥ 1.0.
A stenosis acts as a resistance → pressure drops across it (Poiseuille's law: ΔP ∝ resistance). The more severe the stenosis, the lower the downstream pressure → lower ABI.

Interpretation (as per table above):

ABI < 0.9 = diagnostic of PAD (sensitivity ~95%, specificity ~99% for angiographically confirmed > 50% stenosis) ^[6]

What: BP cuffs placed at multiple levels (upper thigh, above knee, below knee, ankle) to identify the level of occlusion.

A pressure drop of > 20 mmHg between adjacent segments indicates a significant stenosis in the intervening arterial segment.

Major Levels of Arterial Occlusion — Segmental pressures ^[1]:

Level	Aortoiliac	Femoropopliteal	Distal
Segmental pressures (example from slides)	140, 140	120, 60	50, 50

These numbers from the lecture slide ^[1] illustrate:

Aortoiliac: both thigh pressures ~140 (normal). No drop at this level.
Femoropopliteal: pressure drops from 120 (above knee) to 60 (below knee) — a huge > 20 mmHg drop → stenosis in the SFA/popliteal segment.
Distal: stays at ~50 at the ankle — no additional major drop below the knee, but the absolute pressure is critically low.

Doppler Velocity Waveforms ^[1]

Normal arterial flow is triphasic ^[2]^[3]:

Phase 1 (systolic forward flow): a tall, sharp peak — blood is pushed forward by ventricular systole
Phase 2 (early diastolic reversal): a brief period of retrograde flow — elastic recoil of the arterial wall plus high peripheral vascular resistance causes a transient reversal
Phase 3 (late diastolic forward flow): a small forward flow component — as the aortic valve closes and elastic recoil settles, there's a tiny antegrade blip before the next systole

Abnormal waveforms in PAD:

Biphasic: loss of phase 3 (early disease or moderate stenosis). The diastolic reversal is blunted.
Monophasic: loss of both phase 2 and 3 (severe stenosis/occlusion). Continuous forward flow — because the peripheral resistance downstream is so low (maximally dilated arterioles trying to compensate) that there is never any reversal.

Normal arterial flow waveform should be triphasic and either monophasic or biphasic waveforms are abnormal ^[2]

Why Does Severe Stenosis Produce Monophasic Flow?

Downstream of a critical stenosis, the arterioles are maximally vasodilated (autoregulatory compensation to maintain tissue perfusion). This dramatically reduces peripheral vascular resistance. With low resistance, there is continuous forward flow even in diastole — hence the monophasic "low resistance" pattern. The loss of the reversal phase tells you the vascular bed is "open" and begging for blood.

Used when ABI is unreliable (> 1.3 = calcified vessels, especially in DM) ^[3]^[5]:

Investigation	Method	Normal	Abnormal	Why It Works
TBI	Small cuff on great toe + photoplethysmography	> 0.7	< 0.7 = PAD; < 0.3 = CLI	Digital arteries are spared from medial calcification → compressible → accurate pressure measurement
TcPO₂	Electrode on dorsum of foot measures transcutaneous O₂	> 60 mmHg	> 30 mmHg = good wound healing potential; < 30 mmHg = poor healing ^[5]	Directly measures O₂ delivery to the skin, bypassing the problem of incompressible arteries altogether

Indication ^[2]:

Classical history of intermittent claudication or atypical extremity pain BUT normal ABI at rest

Protocol:

Patient walks on a treadmill at a standardised speed (usually 3.2 km/h) at 10–12% incline
ABI measured before and immediately after exercise
Positive = ABI drop ≥ 0.2 from baseline ^[2]

Why does exercise unmask disease?

At rest, collaterals are sufficient → normal ABI. During exercise, working muscles demand massively increased blood flow. The stenosed artery cannot increase flow to meet demand → pressure drops distal to the stenosis → ABI falls. It's the same principle as a cardiac exercise stress test for coronary artery disease.

4.2 Imaging Investigations

Duplex Ultrasound ^[1]

Duplex USG = B-mode USG + Doppler ^[2]^[3]:

B-mode (brightness mode): provides a real-time 2D anatomical image of the vessel — you can see plaque, thrombus, vessel diameter
Doppler: measures blood flow velocity. At a stenosis, velocity increases (Bernoulli principle — flow through a narrowing accelerates, like water through a garden hose nozzle). A peak systolic velocity ratio > 2 across a lesion indicates > 50% stenosis; > 4 indicates > 75% stenosis.

Advantages ^[3]:

Non-invasive, no radiation, no contrast, bedside, repeatable
Locates the level of obstruction and quantifies severity
Can assess both inflow (aortoiliac) and outflow (femoropopliteal, tibial) vessels

Limitations ^[3]:

Operator-dependent — quality varies with sonographer experience
Poor image for aortoiliac segment ^[3] — overlying bowel gas obscures deep abdominal vessels
Cannot easily image heavily calcified vessels
Limited for planning complex surgical procedures (insufficient anatomical road-mapping)

What: IV contrast injection with thin-cut helical CT → 3D reconstruction of the arterial tree
Less invasive alternative to DSA ^[3]
Advantages: rapid, widely available, excellent spatial resolution, shows vessel wall (calcification, plaque morphology), simultaneous assessment of surrounding anatomy
Limitations:
- Contrast allergy / nephropathy ^[3] — must check renal function (eGFR) and allergy history before contrast administration. Pre-hydration with IV saline ± N-acetylcysteine for renal protection if eGFR borderline.
- Radiation dose
- Heavy calcification can obscure lumen assessment (blooming artefact)
No significant difference in accuracy between CTA and MRA ^[2]

What: uses gadolinium contrast (or time-of-flight techniques without contrast) to image vessels
Avoids exposure to ionizing radiation and minimal risk of contrast nephropathy ^[2] — however, gadolinium is contraindicated in severe renal impairment (eGFR < 30) due to risk of nephrogenic systemic fibrosis (NSF)
Rarely done in routine PAD workup ^[3] — reserved for patients with iodinated contrast allergy, borderline renal function, or when CTA is equivocal
Limitations: overestimates degree of stenosis, cannot image calcification well, slow, expensive, contraindicated with certain metallic implants

Arteriography: Indicated ONLY when surgery is planned — NOT used for diagnosis ^[1]

Digital subtraction angiography (DSA): gold standard ^[2]^[3]

What it is: A catheter (usually inserted via the common femoral artery under local anaesthesia) is advanced to the target arterial segment. Radio-opaque contrast is injected while serial X-ray images are taken. The computer digitally "subtracts" the pre-contrast image (bone, soft tissue) from the post-contrast image, leaving only the contrast-filled arterial lumen visible ^[2].

Why is it the gold standard?

Highest spatial resolution of any imaging modality
Real-time assessment: you can see flow dynamics
Can be done intra-op: guides endovascular intervention ^[3] — this is the key advantage. The diagnostic study and the therapeutic intervention (angioplasty, stenting) can be done in the same session
Provides the definitive "road map" for surgical planning

Indications ^[1]^[2]^[3]:

Indicated ONLY in patients with planned intervention such as angioplasty and stenting ^[1]^[2]
Never performed "just to see" or to confirm a diagnosis — the ABI + duplex are sufficient for that
This is exactly the pitfall: "Treating the angiogram" — intervention for asymptomatic disease ^[1] — don't do a DSA unless you're ready to act on it

Complications ^[2]^[3]:

Contrast/drug allergy
Contrast nephropathy (iodinated contrast → direct tubular toxicity + renal vasoconstriction)
Arterial injury: dissection, pseudoaneurysm formation, haematoma at puncture site
Distal embolisation (dislodge plaque/thrombus during catheter manipulation)
Local infection at puncture site

Arteriography: Aortoiliac disease ^[1] — the slides show an angiogram demonstrating aortoiliac stenosis, illustrating the "road map" concept for surgical planning.

These are not specific to diagnosing PAD, but are essential in the workup because atherosclerosis is a systemic disease ^[1]:

Investigation	Rationale
CBC with differentials	Polycythaemia (↑ viscosity → worsens ischaemia), anaemia (reduces O₂ delivery), thrombocytosis
Clotting profile	Baseline before any anticoagulation or intervention
Renal function tests (RFT)	Baseline creatinine/eGFR before contrast administration (contrast nephropathy risk) ^[2]
Fasting glucose / HbA1c	Screen/monitor diabetes — major risk factor and affects prognosis
Fasting lipid profile	Assess dyslipidaemia — guides statin therapy
Arterial blood gas (ABG)	Look for lactic acidosis (in acute/severe ischaemia suggesting tissue hypoxia) ^[2]
Serum CK	Rhabdomyolysis screening (more relevant in acute ischaemia, but check if severe chronic disease with tissue necrosis) ^[2]
Cardiac enzymes (Troponin)	If suspecting concurrent AMI — remember systemic atherosclerosis ^[2]
ECG	Screen for AF (embolic source), LVH (hypertension), ischaemic changes ^[2]
Echocardiogram	If embolic source suspected (mural thrombus, valvular heart disease) ^[2]
CXR	Cardiac silhouette, mediastinal width (aortic dissection), pulmonary disease
Urine multistix	Screen for glycosuria (DM) and proteinuria (renal disease) ^[3]
XR foot & ankle	If tissue loss — assess for osteomyelitis (especially in diabetic foot) ^[5]

Tier	Investigation	Purpose	When
1st line	ABI (± exercise ABI)	Confirm diagnosis + severity	Every patient with suspected PAD
1st line	Segmental pressures + Doppler waveforms	Localise level + characterise flow	Part of vascular lab workup
2nd line	Duplex USG	Anatomical localisation, quantify stenosis	All confirmed PAD, initial imaging
2nd line	TBI / TcPO₂	When ABI unreliable (DM, calcified)	Diabetic patients, ABPI > 1.3
3rd line	CTA	Detailed anatomical road map	When intervention is being considered
3rd line (rarely)	MRA	Same as CTA, but avoid iodinated contrast	Contrast allergy, borderline renal function
Gold standard	DSA	Definitive road map + therapeutic in same session	ONLY when intervention is planned

Key Exam Points on Investigations

ABI < 0.9 confirms PAD. ABI < 0.4 = critical limb ischaemia.
ABI > 1.3 = calcified vessels → use TBI or TcPO₂ instead (especially in DM).
Normal resting ABI does NOT exclude PAD — use exercise treadmill test if clinical suspicion is high.
Duplex USG is the first-line imaging modality — non-invasive, locates obstruction, quantifies severity.
Arteriography (DSA) is indicated ONLY when surgery/intervention is planned — NOT for diagnosis ^[1].
Normal arterial Doppler flow is triphasic; monophasic = severe disease.

High Yield Summary

Diagnosis is clinical + haemodynamic (ABI) + anatomical (imaging).
Clinical Evaluation framework: Does the patient have arterial disease? Acute or chronic? How severe? Where? Why? ^[1]
ABI interpretation: > 1.3 = calcified; 0.9–1.3 = normal; 0.4–0.9 = claudication; < 0.4 = CLI.
Exercise ABI: drop ≥ 0.2 confirms exercise-induced ischaemia when resting ABI is normal.
Segmental pressures: > 20 mmHg drop between segments = significant stenosis at that level.
Doppler waveforms: triphasic = normal; biphasic = moderate disease; monophasic = severe.
Duplex USG: first-line imaging, non-invasive, operator-dependent, poor for aortoiliac.
CTA: for pre-intervention planning; watch for contrast nephropathy and allergy.
DSA: gold standard, ONLY for planned intervention, can be therapeutic (intra-op).
TBI/TcPO₂: essential in diabetics with falsely elevated ABI from vessel calcification.
Adjuncts: ECG (AF, ischaemia), bloods (renal function before contrast, glucose, lipids, CBC), CXR.

Active Recall - Diagnosis & Investigations of Chronic Arterial Insufficiency

References

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p7, p8, p9, p10, p12, p14) ^[2] Senior notes: felixlai.md (Chronic arterial insufficiency — Diagnosis: ABI, exercise treadmill, biochemical tests, radiological tests) ^[3] Senior notes: maxim.md (Chronic limb ischaemia — Investigations: ABPI, Duplex USG, CTA, MRA, DSA) ^[5] Senior notes: maxim.md (Diabetic foot ulcers — TcPO₂, ABPI pitfall in DM) ^[6] Lecture slides: GC 234. Common Foot and Ankle Conditions.pdf (p108 — ABI calculation and interpretation)

Management of Chronic Arterial Insufficiency

The management of chronic arterial insufficiency follows a logical, stepwise approach determined by two parallel assessments ^[1]:

How severe is the limb disease? (Fontaine/Rutherford stage → determines urgency)
How fit is the patient? (Systemic atherosclerotic burden, comorbidities → determines what intervention is safe)

Treatment of Lower Limb Ischemia ^[1]:

Presentation	Action
Asymptomatic	Do not treat (risk factor modification only)
Leg Pain (Claudication)	Conservative first → intervention if failed/disabling
Tissue Loss	Do not amputate (revascularise first) → then amputate minimum necessary

The lecture slide treatment framework for claudication specifically divides goals into two streams ^[1]:

Goal	Improve Survival	Improve Symptoms
Modality	Risk factor modification + Drugs	Exercise + Drugs + Endovascular + Surgery
Specifics	Smoking cessation, Diabetes control, Lipid lowering therapy, Hypertension control, Anti-platelet agents	Trental (Pentoxyphylline), Praxilene (Naftidrofuryl), Pletaal (Cilostazol)

This dual-stream concept is critical: you are treating the patient's survival (cardiovascular mortality is the biggest killer, not the leg itself) AND the limb symptoms simultaneously. Never lose sight of the systemic disease.

3. Conservative Management (The Foundation for ALL Patients)

Every patient with PAD — regardless of stage — receives conservative management. Even if they go on to have surgery, these measures are lifelong.

Improve Survival: Smoking cessation, Diabetes control, Lipid lowering therapy, Hypertension control ^[1]

Intervention	Mechanism & Rationale	Target
Smoking cessation	Single most important intervention. Smoking cessation slows disease progression, improves claudication distance, reduces cardiovascular mortality, and is essential for graft patency post-surgery. Continued smoking doubles graft failure rate.	Complete cessation — offer pharmacotherapy (NRT, varenicline, bupropion) + behavioural support
Diabetes control	Hyperglycaemia accelerates endothelial damage (AGEs), promotes microvascular disease, impairs wound healing. Tight control reduces microvascular complications.	HbA1c < 7% (individualised)
Lipid lowering therapy — Statin	Regardless of lipid level for overall CVS protection ^[3]. Statins reduce LDL, stabilise plaques (anti-inflammatory effect on endothelium), improve endothelial function, and reduce cardiovascular events by ~25%.	LDL < 1.8 mmol/L (or ≥ 50% reduction). High-intensity statin (atorvastatin 40–80 mg or rosuvastatin 20–40 mg)
Hypertension control	Reduces shear stress on arterial wall, slows plaque progression. Target BP < 130/80 in most PAD patients. ACE inhibitors have additional vascular protective effects (ramipril shown in HOPE trial to reduce CV events in PAD).	BP < 130/80 mmHg
Weight reduction	Reduces metabolic demand on lower limbs, improves insulin sensitivity, reduces BP.	BMI < 25

Anti-platelet agents ^[1]

Low dose aspirin (72–325 mg) ^[3]: secondary prevention of coronary heart disease and stroke — NOT primarily for improving claudication symptoms ^[2]
Aspirin inhibits cyclooxygenase-1 (COX-1) → reduces thromboxane A₂ production → decreases platelet aggregation → reduces thrombotic events
Clopidogrel 75 mg is an alternative if aspirin-intolerant (ADP receptor P2Y12 antagonist)
Note: antiplatelet therapy provides only modest or no improvement in claudication symptoms themselves — its main role is cardiovascular event prevention ^[2]

Exercise — listed under "Improve Symptoms" on the lecture slides ^[1]

Supervised exercise programme ^[3] — this is one of the most effective non-surgical interventions:

How it works (from first principles):

Increased collateral vessel formation: Repeated exercise → intermittent ischaemia → local release of VEGF and other angiogenic factors → stimulates new collateral vessels to bypass stenoses
Improved O₂ extraction: Training improves mitochondrial density and oxidative enzyme capacity in skeletal muscle → more efficient use of limited blood supply
Improved muscle metabolism: Aerobic conditioning shifts muscle from anaerobic to more efficient aerobic metabolism → delays lactic acid accumulation
Improved endothelial function: Exercise promotes nitric oxide (NO) release → vasodilation
Improved rheology: Reduced blood viscosity, improved RBC deformability

Protocol: typically 30–45 minutes of supervised walking, 3× per week, for ≥ 12 weeks. Walk until near-maximal claudication pain → rest → walk again. This "train through the pain" approach is key.

Evidence: increases claudication distance by 50–200% — comparable to or better than angioplasty for claudication alone.

Drugs to Improve Symptoms: Trental (Pentoxyphylline), Praxilene (Naftidrofuryl), Pletaal (Cilostazol) ^[1]

Drug	Mechanism	Efficacy	Key Side Effects / Contraindications
Cilostazol (Pletaal)	Phosphodiesterase III (PDE3) inhibitor → inhibits platelet aggregation + direct arterial vasodilation → ↑ blood flow to ischaemic muscle ^[2]^[3]	Only FDA-approved drug for claudication ^[2]. Increases walking distance by ~50%.	Contraindicated in heart failure of any severity ^[2]^[3] (PDE3 inhibitors ↑ mortality in HF — milrinone class effect). GI upset, headache, diarrhoea.
Naftidrofuryl (Praxilene)	5-HT₂ receptor antagonist → reduces platelet aggregation + improves aerobic muscle metabolism ^[2]^[3]	Fewer side effects than cilostazol. Moderate improvement in walking distance.	Well-tolerated; GI side effects
Pentoxifylline (Trental)	Rheologic modifier / PDE inhibitor → decreases blood viscosity, improves RBC deformability, reduces fibrinogen ^[2]^[3]	Benefits not firmly established ^[2]. Marginal benefit.	Nausea, dizziness. Largely superseded by cilostazol.
Prostaglandins (e.g., iloprost)	PGI₂ analogue → potent vasodilation + antiplatelet effects	Reserved for CLI when revascularisation not possible. IV infusion.	Hypotension, flushing, headache

Cilostazol — The Only FDA-Approved Drug

Cilostazol is the only drug specifically approved for improving claudication distance. However, its absolute contraindication in heart failure is a classic exam trap. Why? PDE3 inhibitors prevent the breakdown of cAMP in cardiac myocytes → increased contractility initially, BUT long-term ↑ cAMP in the heart → arrhythmias and increased mortality in HF patients. Remember the milrinone trials.

Surgery for Chronic Arterial Obstruction — INDICATIONS ^[1]:

Disabling claudication (failed 6 months of conservative management)
Limb salvage (critical ischaemia) — rest pain, tissue loss

Put another way from the assessment framework ^[1]:

Limb at Risk: Rest Pain, Tissue Loss → Absolute indication for intervention
Limb not threatened: Claudication → Relative indication for intervention

When to intervene for claudication ^[2]^[3]:

Failed conservative management (typically 6 months of supervised exercise + risk factor modification)
Claudication is "disabling" — significantly impacts quality of life, occupation, or independence
The decision is shared with the patient — unlike CLI, claudication intervention is not urgent

When to intervene for CLI:

Urgent — all patients with CLI (Fontaine III–IV) should be assessed for revascularisation
Without intervention, 1-year major amputation rate ~25%, 1-year mortality ~25%

The TransAtlantic Inter-Society Consensus II (TASC II) classification determines whether endovascular or open surgical revascularisation is preferred, based on the anatomical pattern of disease ^[2]:

TASC Type	Lesion Pattern	Preferred Treatment
TASC A	Short, focal stenoses (e.g., single stenosis ≤ 10 cm in SFA)	Endovascular — excellent result ^[2]
TASC B	Multiple stenoses or short occlusions (e.g., single occlusion ≤ 15 cm in SFA)	Endovascular — good result, preferred unless open surgery needed for another lesion ^[2]
TASC C	Long stenoses, multiple occlusions (e.g., total occlusion > 15 cm)	Open revascularisation preferred — better long-term results ^[2]
TASC D	Complete long-segment occlusions (e.g., CFA/SFA occlusion > 20 cm involving popliteal)	Open revascularisation primary treatment — endovascular associated with poor results ^[2]

Additional decision factors ^[2]:

For patients with estimated life expectancy ≤ 2 years or who do NOT have autogenous vein available as conduit → Balloon angioplasty (better short-term outcome, lower procedural risk)
For patients with estimated life expectancy > 2 years or who have autogenous vein available as conduit → Bypass surgery (better long-term durability)

7.1 Percutaneous Transluminal Angioplasty (PTA) ± Stenting

Percutaneous transluminal balloon angioplasty (PTA) +/- stenting ^[3]

Procedure from first principles:

Access via common femoral artery (Seldinger technique) under local anaesthesia + fluoroscopic guidance
Guidewire crossed through the stenosis/occlusion
Balloon catheter advanced over the wire to the lesion
Balloon inflated for ~30 seconds → mechanically compresses the plaque against the arterial wall, widening the lumen ^[3]
Dilation confirmed by angiogram ^[3]
If result suboptimal (residual stenosis ≥ 30%, flow-limiting dissection, elastic recoil): stent deployment ^[2]

Stenting ^[3]:

Stenting (+/- drug-elution): improve patency and reduce distal embolism
NOT used below knee ^[3] — below-knee stents have poor patency due to high mechanical stress (flexion at ankle), small vessel calibre, and worse run-off
Drug-eluting stents/balloons release antiproliferative agents (e.g., paclitaxel) to reduce neointimal hyperplasia and restenosis

Post-operative care ^[3]:

Post-op: antiplatelet + anticoagulation to prevent stent thrombosis
Typically: dual antiplatelet therapy (aspirin + clopidogrel) for a period, then lifelong single antiplatelet

Advantages ^[2]:

Lower procedural risk than open surgery
Repeatable (if restenosis occurs, can re-do PTA)
Shorter recovery time
Can be performed under local anaesthesia

Preferred for ^[3]:

TASC Types A and B
Aortoiliac diseases (iliac PTA has excellent results — primary patency > 90% at 5 years)
Short segment occlusion < 10 cm long
Life expectancy < 2 years

Complications ^[2]^[3]:

Arterial dissection
Arterial rupture
Distal embolisation
Restenosis of vessels (the most common late complication — neointimal hyperplasia)
Access site complications: haematoma, pseudoaneurysm, AV fistula

8. Surgical Revascularisation

LOCAL PROCEDURES: Endarterectomy ^[1]

Endarterectomy: Open the artery → evacuate the atheromatous plaque from the intima → close the artery ^[3]

Indications ^[1]:

Larger vessels
Short segments
Stenosis (not long occlusions)
e.g., Iliac, Carotid ^[1]
Also at femoral bifurcation — profundaplasty (endarterectomy of the profunda femoris origin) ^[3]

Why only for short segments? Removing plaque from a long segment is technically difficult, causes excessive vessel wall trauma, and has poor patency compared to bypass. For short focal lesions (e.g., common femoral bifurcation), direct removal is simple and effective.

Profundaplasty deserves special mention: opening up the origin of the profunda femoris can dramatically improve limb perfusion because the profunda is the key collateral channel when the SFA is occluded. Even without bypassing the SFA, restoring profunda inflow can upgrade a leg from CLI to stable claudication.

Arterial Bypass ^[1]: The principle is simple — take blood from a healthy artery proximal to the obstruction (inflow) and deliver it to a healthy artery distal to the obstruction (outflow/run-off) via a conduit.

Inflow -------- OBSTRUCTION -------- Outflow (runoff) ^[1]

Types of bypass ^[1]:

Type	Route	Indication
ANATOMICAL	Follows the native arterial pathway	Standard approach when patient can tolerate major surgery
Aorto-iliac	Aortic graft to iliac artery	Aorto-iliac occlusive disease
Aorto-bifemoral bypass	Aortic graft bifurcating to both femoral arteries ^[1]	Preferred method for symptomatic aortoiliac occlusion ^[2]
Femoro-popliteal bypass	Femoral artery to popliteal artery	SFA or proximal popliteal artery occlusion where the popliteal artery has luminal continuity with at least one tibial branch ^[2]
EXTRA-ANATOMICAL	Does NOT follow the native pathway	When standard approach is too risky or anatomy is hostile
Femoro-femoral bypass ^[1]	Graft from one femoral artery to the contralateral femoral artery	Unilateral iliac occlusion where aorta and contralateral iliac artery are disease-free ^[2]. Can be done under local anaesthesia.
Axillo-bifemoral bypass ^[1]	Axillary artery → subcutaneous tunnel → both femoral arteries	High-risk patients unfit for major aortic surgery; neither thoracic nor abdominal cavity is violated ^[2]. Poorer long-term patency than aorto-femoral bypass — reserved for limb-threatening ischaemia in high-risk patients ^[2].
Axillo-popliteal bypass	Axillary artery to popliteal artery	Last attempt to prevent amputation — when groin is hostile (infection, scarring) and iliac/femoral systems are involved ^[2]

Conduit	Details	Patency
Autologous vein (Best choice)	Great saphenous vein remains the conduit of choice ^[2]; alternatives: lesser saphenous vein, arm veins	Best long-term patency, especially for below-knee bypasses. Living endothelium = less thrombogenic.
Prosthetic graft (PTFE)	Polytetrafluoroethylene — synthetic	Patency comparable to vein grafts for above-knee bypasses; significantly lower patency for more distal (below-knee) procedures ^[2]. Higher infection risk.

Why is autologous vein superior below the knee? Below-knee arteries are smaller calibre, lower flow, and higher resistance. A venous conduit has a living endothelium that produces NO and prostacyclin (antithrombotic), making it more resistant to thrombosis in these challenging conditions. Prosthetic grafts lack this endothelial advantage and thrombose more readily in low-flow environments.

History-Taking for Surgery Planning

Always ask about: Contrast allergy (for DSA/CTA), Saphenous vein condition ^[3] — has the patient had vein stripping? Varicose vein surgery? Previous CABG harvesting the GSV? If the great saphenous vein is unavailable, you'll need an alternative conduit (lesser saphenous, arm vein) or prosthetic graft, which alters the surgical plan.

Bypass surgery is preferred for ^[2]^[3]:

TASC Types C and D
Failed angioplasty
Long-segment occlusion
Complete occlusion — no lumen for angioplasty guidewire to pass through ^[3]

Never amputate digits before revascularization ^[1]

Amputation after revascularization ^[1] — the slides make this sequence crystal clear: always try to restore blood flow first. Only then, once the limb has the best possible perfusion, amputate the minimum amount of non-viable tissue.

Indications (mnemonic: 3 D's) ^[3]:

Dead limb: Irreversible gangrene — delay in amputation results in infection, rhabdomyolysis, sepsis
Dangerous limb: Life-threatening infection (wet gangrene, necrotising fasciitis), malignancy
Damn nuisance: Un-reconstructable CLI, non-functional limb (contractures, paralysis), major trauma

Principles of amputation ^[3]:

Remove all infected/necrotic tissue
Preserve as much length as safely possible — functional outcome depends on preserving joints
Ensure adequate blood supply to heal the stump — revascularisation may be required before amputation

Levels of amputation ^[3]:

Level	When	Key Point
Toe / Ray amputation	Isolated toe gangrene with good proximal perfusion	Minimal functional loss
Transmetatarsal amputation	Forefoot gangrene	Preserves ankle function
Syme's amputation	Ankle joint level	End-bearing stump
Below-knee amputation (BKA)	Most common level. Aim to preserve the knee joint — much easier to walk on BKA prosthesis than AKA ^[3]	Contraindicated if fixed flexion deformity of knee ^[3]
Above-knee amputation (AKA) ^[1]	If femoral pulse is absent ^[3] — indicates insufficient blood supply to heal a BKA stump	Loss of knee joint → harder rehabilitation

Complications of amputation ^[3]:

Timing	Complication	Mechanism / Notes
Early	Wound haematoma, infection, dehiscence	Poor blood supply → delayed healing
Early	Stump gangrene	Inadequate perfusion to stump → higher amputation needed
Early	Phantom limb pain	Central sensitisation — the brain continues to "map" the amputated limb. Mx: reassurance, amitriptyline, gabapentin ^[3]
Early	DVT/PE	Immobility post-op. Mx: prophylactic heparin ^[3]
Late	Fixed flexion deformity of joint above	Muscle imbalance, inadequate rehabilitation
Late	Osteomyelitis, osteophyte formation	Exposed/infected bone
Late	Stump ulceration	Pressure from prosthesis
Late	Stump neuroma	Nerve regrowth into scar tissue → painful nodule

Rehabilitation ^[3]: Usually can bear weight on contralateral limb by 1 week, fit temporary prosthesis by 3 weeks.

10. Management of Specific Aetiologies

Reconstruction seldom possible. Stop smoking is effective. ^[1]

Small distal vessels → not amenable to bypass or angioplasty
Only effective treatment: absolute smoking cessation
Supportive: wound care, prostanoids (iloprost) for severe ischaemia, sympathectomy (limited evidence)
If smoking continues → progressive disease → eventual amputation

Dual pathology: neuropathy (insensate foot → unnoticed trauma → ulcers) + ischaemia (distal vessel disease)
Vascular component: angioplasty ^[5] (tibial/peroneal angioplasty — even though infrapopliteal, angioplasty is preferred over bypass in diabetic distal disease due to vessel size)
Neuropathic component: customised insole ^[5] — offloading to redistribute pressure
Surgical: debridement, below knee amputation ^[5] if unreconstructable

Clinical Scenario	Primary Management
Fontaine I (Asymptomatic)	Risk factor modification. Do not treat the artery ^[1].
Fontaine IIa (Mild claudication, > 200m)	Conservative: exercise + risk factor modification + antiplatelet + statin ± cilostazol
Fontaine IIb (Moderate claudication, < 200m)	Same conservative approach for 6 months → intervention if disabling
Fontaine III (Rest pain)	Urgent revascularisation (endovascular or surgical based on TASC)
Fontaine IV (Tissue loss)	Urgent revascularisation → amputation AFTER revascularisation ^[1]
Failed revascularisation / unreconstructable	Amputation (preserve maximum length)
Buerger's disease	Stop smoking → only effective treatment ^[1]

High Yield Summary

All patients get CV risk factor modification + antiplatelet + statin — this is for survival, not just the leg.
Improve Survival: Smoking cessation, DM control, lipid lowering (statin regardless of lipid level), HT control, antiplatelet agents.
Improve Symptoms: Supervised exercise programme + drugs (cilostazol, naftidrofuryl, pentoxifylline) + endovascular/surgery.
Cilostazol (PDE3 inhibitor) = only FDA-approved drug for claudication. Contraindicated in heart failure.
Aspirin = secondary CV prevention, NOT primarily for claudication improvement.
Supervised exercise increases claudication distance by 50–200% — comparable to angioplasty.
Indications for intervention: disabling claudication (failed 6 months conservative) + limb salvage (critical ischaemia).
TASC A-B → endovascular (PTA ± stent). TASC C-D → surgical bypass.
Endarterectomy: short segments, larger vessels (iliac, carotid, femoral bifurcation/profundaplasty).
Bypass: anatomical (aorto-bifemoral, fem-pop) vs extra-anatomical (fem-fem, axillo-bifemoral). Autologous vein = best conduit, especially below knee.
Never amputate digits before revascularisation.
Amputation indications (3 D's): Dead, Dangerous, Damn nuisance. BKA preferred to preserve knee joint.
"Treating the angiogram" = intervening on an asymptomatic stenosis — DON'T DO IT ^[1].

Active Recall - Management of Chronic Arterial Insufficiency

References

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p8, p14, p15, p16, p18, p22, p28, p29) ^[2] Senior notes: felixlai.md (Chronic arterial insufficiency — Treatment: TASC classification, medical treatment, endovascular, surgical revascularisation, amputation) ^[3] Senior notes: maxim.md (Chronic limb ischaemia — Management: conservative, endovascular, surgical, amputation; History taking — contrast allergy, saphenous vein condition) ^[5] Senior notes: maxim.md (Diabetic foot ulcers — Management)

Complications of Chronic Arterial Insufficiency

Complications of chronic arterial insufficiency can be broadly divided into three categories:

Complications of the disease itself (progressive ischaemia)
Complications of revascularisation (endovascular or surgical)
Complications of amputation

Understanding the pathophysiology behind each complication is what separates exam success from rote memorisation. Let's work through every complication from first principles.

1. Complications of the Disease Itself

Tissue Loss: Ulcers (painful), Gangrene (dry / wet), Pressure areas ^[1]

This is not really a "complication" in the traditional sense — it IS the natural history of untreated chronic arterial insufficiency. However, it is the complication of inadequately managed claudication.

Pathophysiology: Fontaine I → II → III → IV is a continuum. As atherosclerosis progresses and collaterals become insufficient, the limb transitions from compensated ischaemia (claudication) to decompensated ischaemia (rest pain) to tissue death (ulceration/gangrene). The transition can be accelerated by:

Acute thrombosis on a chronic plaque ("acute-on-chronic")
Progression of multi-level disease
Intercurrent illness reducing cardiac output (e.g., MI, sepsis, dehydration)
Minor trauma to the ischaemic foot (the tissue has no reserve to heal)

Gangrene progression:

Dry gangrene → coagulative necrosis, mummification. Relatively stable — can auto-amputate if left.
Dry → Wet gangrene → secondary bacterial infection of necrotic tissue → liquefactive necrosis → surgical emergency (risk of overwhelming sepsis, gas gangrene from Clostridium)

Delays in amputation of a non-viable extremity can result in infection, myoglobinuria, acute renal failure and hyperkalemia ^[2]. This is because dead muscle releases intracellular contents (K⁺, myoglobin, CK, H⁺) into the systemic circulation — effectively the same mechanism as crush syndrome/rhabdomyolysis.

A patient with stable chronic PAD may suddenly deteriorate if:

An atherosclerotic plaque ruptures → acute thrombosis
Dehydration or low cardiac output causes stasis → thrombosis on an existing stenosis
An embolic event (e.g., new-onset AF → embolus lodges at a bifurcation)

This converts a chronic picture (collateralised, tolerable) into an acute limb-threatening emergency. The presence of pre-existing collaterals may partially protect the limb, but the clinical deterioration can be dramatic.

Atherosclerosis is a systemic disease ^[1]

This is the single most important "complication" to understand: patients with PAD die from their hearts and brains, not their legs.

Event	Mechanism	Statistics
Myocardial infarction	Shared atherosclerotic disease in coronary arteries. PAD patients have 2–4× higher MI risk.	Leading cause of death in PAD patients
Stroke	Carotid/cerebrovascular atherosclerosis.	2nd leading cause of death
Cardiovascular death	Combined coronary + cerebrovascular + aortic events	5-year mortality ~30% in symptomatic PAD; up to 50% in CLI

This is exactly why the lecture slides emphasise Improve Survival: Smoking cessation, Diabetes control, Lipid lowering therapy, Hypertension control, Anti-platelet agents ^[1]. You are treating the patient's cardiovascular mortality risk just as much as (if not more than) their leg.

Specific complication of aorto-iliac disease
Bilateral internal iliac artery stenosis/occlusion → reduced blood supply to the corpus cavernosum via the internal pudendal arteries
Part of the Leriche syndrome triad: absent femoral pulses + bilateral claudication + impotence ^[3]

Chronic ischaemic ulcers and gangrenous tissue are highly susceptible to infection because:

Reduced blood flow → inadequate delivery of immune cells, antibodies, and antibiotics to the wound
Impaired wound healing → chronic open wounds serve as portals of entry
In diabetics: additional immune dysfunction (neutrophil chemotaxis and phagocytosis impaired by hyperglycaemia)

Infections can range from:

Cellulitis (superficial soft tissue)
Osteomyelitis (especially in diabetic foot — probe-to-bone test positive)
Necrotising fasciitis (surgical emergency — rapid tissue destruction along fascial planes)
Sepsis (systemic inflammatory response to uncontrolled local infection)

2. Complications of Revascularisation

These are divided by modality: endovascular and surgical.

Complication	Pathophysiology	Management
Arterial dissection	Balloon inflation tears the intima → blood enters the vessel wall → creates a false lumen → can obstruct true lumen	Stenting to tack down the intimal flap; rarely requires open surgical repair
Arterial rupture	Balloon over-inflation or vessel wall calcification → perforation	Covered stent-graft deployment; if massive → emergency open repair
Distal embolisation	Plaque/thrombus fragments dislodged during wire/balloon manipulation → travel distally → occlude small vessels	Aspiration thrombectomy, catheter-directed thrombolysis, or surgical embolectomy. Prevention: distal embolic protection devices
Restenosis	Most common late complication. Neointimal hyperplasia (smooth muscle proliferation in response to intimal injury) → progressive re-narrowing over weeks to months. More common in SFA than iliac stents.	Drug-eluting stents/balloons (paclitaxel) reduce restenosis; repeat PTA; surgical bypass if recurrent
Access site complications	Femoral artery puncture → haematoma, pseudoaneurysm, AV fistula, retroperitoneal haemorrhage	Manual compression, ultrasound-guided thrombin injection (for pseudoaneurysm), surgical repair if large
Contrast nephropathy	Iodinated contrast causes direct tubular toxicity + renal vasoconstriction → acute kidney injury (typically peaks at 48–72h post-procedure)	Prevention: pre-hydration with IV saline, minimise contrast volume, avoid nephrotoxic drugs. Treatment: supportive, dialysis if severe.
Contrast allergy	Type I hypersensitivity to iodinated contrast	Pre-medication with steroids + antihistamines if known allergy; use CO₂ angiography as alternative

Complication	Pathophysiology	Notes
Graft failure (early)	Technical error, graft kink, graft thrombosis (inadequate run-off, hypercoagulability) ^[3]	Occurs within 30 days. Requires urgent re-exploration.
Graft failure (intermediate)	Neointimal hyperplasia — smooth muscle proliferation at the anastomotic sites ^[3]	Occurs 1 month – 2 years. Detected by surveillance duplex. Treated with patch angioplasty or interposition graft.
Graft failure (late)	Atherosclerosis — progression of native disease in inflow/outflow vessels or within vein graft itself ^[3]	Occurs > 2 years. Managed with redo-bypass or endovascular intervention.
Graft infection	Especially with prosthetic grafts ^[3]. Bacteria colonise the graft → biofilm formation → chronic infection that is extremely difficult to eradicate	Devastating complication. May require graft explantation + extra-anatomical bypass through clean tissue planes + prolonged IV antibiotics.
Aortoenteric fistula	Erosion of an aortic graft (especially aorto-bifemoral) into the overlying duodenum ^[3]	Presents with "herald bleed" (small GI bleed) → then massive haematemesis. Surgical emergency.
Autonomic nerve damage	Dissection around the aortic bifurcation can damage the superior hypogastric plexus → retrograde ejaculation or erectile dysfunction ^[3]	Relevant in aorto-bifemoral bypass in males
Embolic complications	Manipulation of atheromatous aorta → cholesterol crystal embolisation → renal impairment, ischaemic bowel, spinal cord ischaemia (Adamkiewicz artery), blue toe syndrome ^[3]	"Trash foot" — microemboli cause patchy toe ischaemia despite palpable pulses
Ureter injury	Ureteral injury during retroperitoneal dissection for aortic procedures ^[3]	Prevent by careful identification; treat by repair over stent

Graft surveillance ^[3]:

Palpate for patency, auscultate for bruits, serial USG surveillance — typically duplex at 1 month, 3 months, 6 months, then annually
Peak systolic velocity ratio > 3 or absolute velocity > 300 cm/s at a focal point → suggests > 70% stenosis → needs re-intervention before graft thromboses

2.3 Reperfusion Injury

When blood flow is suddenly restored to ischaemic tissue (whether by endovascular or surgical means), a paradoxical cascade of injury occurs. This is one of the most important complications to understand from first principles.

Pathophysiology of reperfusion injury ^[2]:

During ischaemia: Cells switch to anaerobic metabolism → ATP depletion → failure of Na⁺/K⁺ ATPase pump → cellular swelling → membrane instability → accumulation of hypoxanthine (purine degradation product)
Upon reperfusion: Oxygen floods back in → xanthine oxidase converts accumulated hypoxanthine to xanthine and then uric acid, generating massive amounts of reactive oxygen species (ROS / oxygen free radicals)
ROS cause:
- Direct cell membrane damage (lipid peroxidation)
- Increased capillary permeability → fluid leaks into interstitium → oedema
- Neutrophil activation and sequestration in microcirculation → further inflammation and microvascular occlusion
Result: Reperfusion injury prolongs the ischaemic interval since it impairs adequate nutrient flow to the tissue despite restoration of axial blood flow ^[2]

This reperfusion injury can manifest as two major complications:

Compartment syndrome ^[1]^[2]^[3]:

Why does it happen after revascularisation?

Ischaemic muscle swells after reperfusion (capillary leak from ROS damage)
Muscle is enclosed within a non-distensible fascial envelope ^[2]
Swelling raises intra-compartmental pressure → when it exceeds capillary perfusion pressure (~30 mmHg) → microvascular blood flow is occluded → further ischaemia → more swelling → vicious cycle
Intracompartmental pressure > 30 mmHg is diagnostic ^[3]
Anterior compartment is most commonly affected whereas involvement of the posterior compartment is the most functionally devastating ^[2]

Clinical features ^[2]^[3]:

Pain out of proportion with clinical signs, worsening with time despite analgesia — this is the earliest and most sensitive sign
Numbness in the distribution of nerves running within the compartment — e.g., numbness in the web space between the 1st and 2nd toes suggests compression of the deep peroneal nerve in the anterior compartment ^[2]
Tense compartment on passive toe dorsiflexion and plantarflexion ^[3]
Pulses can be present — because systolic arterial pressure (SBP) >> intra-compartmental pressure; compartment syndrome is a microvascular problem, not a macrovascular one ^[3]

Pulses Present Does NOT Rule Out Compartment Syndrome

A common trap: students and junior doctors assume that palpable pedal pulses exclude compartment syndrome. They don't. SBP is typically 120 mmHg; compartment syndrome occurs at pressures as low as 30 mmHg. The large arteries easily transmit pulsatile flow through the compartment, but the capillaries within the compartment are compressed and cannot perfuse the muscle. Loss of pulse is a very late (and ominous) sign.

Management: Urgent fasciotomy (medial + lateral incisions) ^[3]

All compartments of the affected leg must be decompressed (the leg has 4 compartments: anterior, lateral, superficial posterior, deep posterior)
Skin incisions are left open for re-inspection at 48h
Delayed primary closure or skin grafting when swelling resolves
Prophylactic fasciotomy should be considered if ischaemia has lasted > 6 hours before revascularisation ^[2]

Rhabdomyolysis: Release of K⁺, H⁺ and myoglobin from damaged muscle cells ^[3]

Why does it happen?

Ischaemic and reperfusion-injured muscle undergoes necrosis → cell membranes rupture → intracellular contents flood into the systemic circulation

What is released?

Substance	Consequence
K⁺ (Potassium)	Hyperkalemia → cardiac arrhythmia ^[2] (peaked T waves, widened QRS, VF, cardiac arrest)
Myoglobin	Myoglobinuria → acute kidney injury (AKI) by acute tubular necrosis (ATN) ^[2]. Myoglobin precipitates in the renal tubules (especially in acidic urine), causing mechanical obstruction + direct tubular toxicity.
H⁺ (Hydrogen ions)	Metabolic acidosis — from lactic acid and cellular breakdown products
CK (Creatine kinase)	Marker of muscle injury — diagnostic, not directly harmful
Phosphate	Hyperphosphataemia → can bind calcium → hypocalcaemia → arrhythmias, tetany

Management ^[2]^[3]:

Post-op: monitor BP/P, UO, APTT, RFT, cardiac monitor ^[3]
Aggressive hydration (IV normal saline — aim UO > 200 mL/h initially) — to dilute myoglobin and maintain renal perfusion
Diuresis with mannitol — osmotic diuretic to flush myoglobin through tubules and reduce compartment pressure
IV bicarbonate to alkalinize the urine ^[2] — myoglobin is less nephrotoxic in alkaline urine (pH > 6.5) because it doesn't precipitate as readily
Treat hyperkalaemia urgently: calcium gluconate (cardioprotection), insulin-dextrose, salbutamol nebuliser, kayexalate, dialysis if refractory
ECG monitoring for arrhythmias

Complications: Compartment syndrome, Electrolytes / renal failure ^[1]

3. Complications of Amputation

When revascularisation fails or the limb is not salvageable, amputation becomes necessary. It carries its own set of complications ^[3]:

Complication	Pathophysiology	Management
Wound haematoma	Bleeding from cut surfaces, inadequate haemostasis	Evacuation if expanding; re-exploration if compromising flap
Wound infection / abscess	Contaminated field (especially if wet gangrene), poor tissue perfusion	Antibiotics, drainage, debridement
Wound dehiscence	Poor healing (ischaemic tissue), tension on sutures, infection	Revision — may need higher-level amputation
Stump gangrene	Inadequate perfusion to the stump (amputated too distally for the blood supply available)	Mx: higher amputation ^[3] — this is exactly why amputation after revascularization ^[1] is the correct sequence
Phantom limb pain	Central sensitisation — the brain's somatosensory cortex retains a "map" of the amputated limb. Peripheral nerve endings at the stump send aberrant signals that the brain interprets as pain from the missing limb.	Mx: reassurance, amitriptyline, gabapentin ^[3]. Mirror therapy, TENS.
DVT / PE	Post-operative immobility + hypercoagulable state (surgical stress response) + loss of calf muscle pump	Mx: prophylactic heparin ^[3], early mobilisation, compression stockings on remaining limb

Complication	Pathophysiology	Management
Fixed flexion deformity	Unopposed flexor tone (loss of distal extensors); patient tends to keep stump flexed for comfort → contracture develops	Prevention: physiotherapy, positioning. Treatment: difficult once established.
Osteomyelitis / Osteophyte formation	Residual infection in bone; bony overgrowth at stump end	Antibiotics (prolonged), debridement; revision amputation if refractory
Stump ulceration	Pressure from ill-fitting prosthesis, poor tissue quality, ongoing ischaemia	Prosthesis adjustment, wound care, assess for further revascularisation
Stump neuroma	Cut nerve endings attempt to regenerate → tangled mass of axons (neuroma) at the stump → painful on palpation or pressure	Desensitisation, nerve block, surgical excision with burial of nerve end into muscle/bone

Rehabilitation timeline ^[3]: Bear weight on contralateral limb by 1 week, temporary prosthesis by 3 weeks.

High Yield Summary

Disease complications:

Tissue loss (ulcers → gangrene → sepsis) is the natural history of untreated CLI.
Cardiovascular events (MI, stroke) are the leading cause of death — not the leg. Always manage systemic atherosclerosis.
Delay in amputating a non-viable limb → infection, myoglobinuria, AKI, hyperkalaemia.

Revascularisation complications: 4. Endovascular: dissection, rupture, distal embolisation, restenosis (most common late complication), contrast nephropathy. 5. Bypass surgery: graft failure (kink → neointimal hyperplasia → atherosclerosis), graft infection (prosthetic > autologous), aortoenteric fistula, autonomic nerve damage. 6. Reperfusion injury → compartment syndrome (pain out of proportion, tense compartment, pulses can be present, Mx: urgent fasciotomy) and rhabdomyolysis (K⁺/myoglobin release → arrhythmia/AKI, Mx: aggressive hydration, mannitol, IV bicarbonate).

Amputation complications: 7. Early: stump gangrene (→ higher amputation), phantom limb pain (Mx: amitriptyline/gabapentin), DVT/PE. 8. Late: fixed flexion deformity, stump neuroma, stump ulceration.

Active Recall - Complications of Chronic Arterial Insufficiency

References

^[1] Lecture slides: WCS 002 - Toe gangrene and leg ulcer - by Prof SWK Cheng.pdf (p2, p4, p14, p18, p27) ^[2] Senior notes: felixlai.md (Chronic/Acute arterial insufficiency — Complications: compartment syndrome, rhabdomyolysis, reperfusion injury, delayed amputation) ^[3] Senior notes: maxim.md (Chronic limb ischaemia — Complications of bypass surgery, reperfusion injury, compartment syndrome, rhabdomyolysis, amputation complications)

High Yield Summary

Chronic arterial insufficiency = gradual (> 2 weeks) reduction in limb perfusion; most commonly due to atherosclerosis.
Acute and chronic occlusion are distinct entities — chronic allows collateral formation.
Risk factors: Smoking, DM, HT, HL, Family history — atherosclerosis is a systemic disease.
SFA is the most commonly affected vessel (~70%); aorto-iliac ~30%.
Fontaine: I (asymptomatic) → IIa (> 200m) → IIb (< 200m) → III (rest pain) → IV (tissue loss).
CLI (Fontaine III–IV) = absolute indication for intervention; claudication = relative.
Intermittent claudication: exercise-induced muscular pain, fixed distance, relieved by rest. Calf = SFA; thigh + buttock = aorto-iliac.
Rest pain: worst at night, relieved by dependency (hanging legs down restores hydrostatic pressure).
Leriche syndrome: aortic bifurcation occlusion → absent femoral pulses + bilateral claudication + impotence.
Buerger's disease: young male smokers, small distal vessels, "tree trunk" angiogram, stop smoking is the only effective treatment.
Never amputate digits before revascularization.
Buerger's test: elevation pallor (Buerger's angle) + dependent rubor (reactive hyperaemia).
Vascular vs neurogenic claudication: fixed distance vs variable; rest relieves vs bending forward; absent pulses vs present.

High Yield Summary

Most important DDx of intermittent claudication: neurogenic claudication (spinal stenosis), sciatica, hip/knee arthritis, chronic compartment syndrome, Baker's cyst.
Vascular vs neurogenic claudication: Fixed distance vs variable; rest relieves vs flexion relieves; absent pulses vs present; "shop window" vs "park bench"; uphill worse vs downhill worse.
Sciatica: back pain radiating down leg, dermatomal, NOT relieved by rest, positive SLR, pulses present.
Acute vs chronic: < 2 weeks = acute (emergency), > 2 weeks = chronic; acute lacks collaterals and presents with 6 P's.
Lecture slides pitfalls: mis-diagnosis of claudication, toe amputation before revascularisation, delay recognition of acute ischaemia, "treating the angiogram."
Leg ulcer DDx: arterial (painful, pressure points, absent pulses) vs venous (gaiter area, haemosiderin) vs neuropathic/diabetic (painless, plantar, may have falsely elevated ABPI).
Within chronic arterial causes: atherosclerosis (elderly, CV risk factors) vs Buerger's (young male smoker, small vessels, "tree trunk") vs popliteal entrapment (young athlete, no risk factors).

High Yield Summary

Diagnosis is clinical + haemodynamic (ABI) + anatomical (imaging).
Clinical Evaluation framework: Does the patient have arterial disease? Acute or chronic? How severe? Where? Why? ^[1]
ABI interpretation: > 1.3 = calcified; 0.9–1.3 = normal; 0.4–0.9 = claudication; < 0.4 = CLI.
Exercise ABI: drop ≥ 0.2 confirms exercise-induced ischaemia when resting ABI is normal.
Segmental pressures: > 20 mmHg drop between segments = significant stenosis at that level.
Doppler waveforms: triphasic = normal; biphasic = moderate disease; monophasic = severe.
Duplex USG: first-line imaging, non-invasive, operator-dependent, poor for aortoiliac.
CTA: for pre-intervention planning; watch for contrast nephropathy and allergy.
DSA: gold standard, ONLY for planned intervention, can be therapeutic (intra-op).
TBI/TcPO₂: essential in diabetics with falsely elevated ABI from vessel calcification.
Adjuncts: ECG (AF, ischaemia), bloods (renal function before contrast, glucose, lipids, CBC), CXR.

High Yield Summary

All patients get CV risk factor modification + antiplatelet + statin — this is for survival, not just the leg.
Improve Survival: Smoking cessation, DM control, lipid lowering (statin regardless of lipid level), HT control, antiplatelet agents.
Improve Symptoms: Supervised exercise programme + drugs (cilostazol, naftidrofuryl, pentoxifylline) + endovascular/surgery.
Cilostazol (PDE3 inhibitor) = only FDA-approved drug for claudication. Contraindicated in heart failure.
Aspirin = secondary CV prevention, NOT primarily for claudication improvement.
Supervised exercise increases claudication distance by 50–200% — comparable to angioplasty.
Indications for intervention: disabling claudication (failed 6 months conservative) + limb salvage (critical ischaemia).
TASC A-B → endovascular (PTA ± stent). TASC C-D → surgical bypass.
Endarterectomy: short segments, larger vessels (iliac, carotid, femoral bifurcation/profundaplasty).
Bypass: anatomical (aorto-bifemoral, fem-pop) vs extra-anatomical (fem-fem, axillo-bifemoral). Autologous vein = best conduit, especially below knee.
Never amputate digits before revascularisation.
Amputation indications (3 D's): Dead, Dangerous, Damn nuisance. BKA preferred to preserve knee joint.
"Treating the angiogram" = intervening on an asymptomatic stenosis — DON'T DO IT ^[1].

High Yield Summary

Disease complications:

Tissue loss (ulcers → gangrene → sepsis) is the natural history of untreated CLI.
Cardiovascular events (MI, stroke) are the leading cause of death — not the leg. Always manage systemic atherosclerosis.
Delay in amputating a non-viable limb → infection, myoglobinuria, AKI, hyperkalaemia.

Sketchy memory palace for Chronic Arterial Insufficiency

Sketchy memory palace for Chronic Arterial Insufficiency

No.	Visual Cue	Meaning
1	A snail (slow >2 weeks) on a pipe (vessel) with many tiny branching tubes (collaterals).	- Chronic arterial insufficiency = gradual (> 2 weeks) reduction in limb perfusion; most commonly due to atherosclerosis. - Acute and chronic occlusion are distinct entities — chronic allows collateral formation. - Acute vs chronic: 2 weeks = chronic; acute lacks collaterals and presents with 6 P's.
2	A family tree surrounded by risk factors (smoking, DM, HT, HL) and a survival shield representing medical management (antiplatelets, statins, and risk modification).	- Risk factors: Smoking, DM, HT, HL, Family history — atherosclerosis is a systemic disease. - All patients get CV risk factor modification + antiplatelet + statin — this is for survival, not just the leg. - Improve Survival: Smoking cessation, DM control, lipid lowering (statin regardless of lipid level), HT control, antiplatelet agents. - Aspirin = secondary CV prevention, NOT primarily for claudication improvement.
3	A bridge labeled 70% SFA and 30% Aorto-Iliac.	- SFA is the most commonly affected vessel (~70%); aorto-iliac ~30%.
4	Fontaine steps: I (asymptomatic), IIa (>200m), IIb (<200m), III (rest pain), IV (tissue loss). Red glowing steps indicate absolute surgical need.	- Fontaine: I (asymptomatic) → IIa (> 200m) → IIb (< 200m) → III (rest pain) → IV (tissue loss). - CLI (Fontaine III–IV) = absolute indication for intervention; claudication = relative.
5	Fixed distance walk followed by rest on a bench; 'Shop window' stance contrasting with a 'Park bench' sitter flexing forward.	- Intermittent claudication: exercise-induced muscular pain, fixed distance, relieved by rest. Calf = SFA; thigh + buttock = aorto-iliac. - Vascular vs neurogenic claudication: fixed distance vs variable; rest relieves vs bending forward; absent pulses vs present. - Vascular vs neurogenic claudication: Fixed distance vs variable; rest relieves vs flexion relieves; absent pulses vs present; "shop window" vs "park bench"; uphill worse vs downhill worse.
6	Leg hanging down from a bed at night.	- Rest pain: worst at night, relieved by dependency (hanging legs down restores hydrostatic pressure).
7	Statue with absent femoral pulses and impotence.	- Leriche syndrome: aortic bifurcation occlusion → absent femoral pulses + bilateral claudication + impotence.
8	Young smoker with a 'tree trunk' (angiogram sign) vs. a young athlete (popliteal entrapment).	- Buerger's disease: young male smokers, small distal vessels, "tree trunk" angiogram, stop smoking is the only effective treatment. - Within chronic arterial causes: atherosclerosis (elderly, CV risk factors) vs Buerger's (young male smoker, small vessels, "tree trunk") vs popliteal entrapment (young athlete, no risk factors).
9	Elevation pallor followed by dependent rubor.	- Buerger's test: elevation pallor (Buerger's angle) + dependent rubor (reactive hyperaemia).
10	Spinal column (stenosis), lightning bolt (sciatica), and a Baker's sack (cyst).	- Most important DDx of intermittent claudication: neurogenic claudication (spinal stenosis), sciatica, hip/knee arthritis, chronic compartment syndrome, Baker's cyst. - Sciatica: back pain radiating down leg, dermatomal, NOT relieved by rest, positive SLR, pulses present.
11	Stopped toe amputation and 'treating the angiogram' (intervening on a non-symptom pipe).	- Never amputate digits before revascularization. - Lecture slides pitfalls: mis-diagnosis of claudication, toe amputation before revascularisation, delay recognition of acute ischaemia, "treating the angiogram." - Never amputate digits before revascularisation. - "Treating the angiogram" = intervening on an asymptomatic stenosis — DON'T DO IT .
12	Arterial ulcer (painful/pressure), Venous (hemosiderin/gaiter), and Neuropathic (painless/plantar). Untreated, these lead to a dark gangrene cliff.	- Leg ulcer DDx: arterial (painful, pressure points, absent pulses) vs venous (gaiter area, haemosiderin) vs neuropathic/diabetic (painless, plantar, may have falsely elevated ABPI). - Tissue loss (ulcers → gangrene → sepsis) is the natural history of untreated CLI.
13	The 'Evaluation Framework' containing clinical exam, hemodynamic (ABI), and anatomical (imaging) tools.	- Diagnosis is clinical + haemodynamic (ABI) + anatomical (imaging). - Clinical Evaluation framework: Does the patient have arterial disease? Acute or chronic? How severe? Where? Why? - Adjuncts: ECG (AF, ischaemia), bloods (renal function before contrast, glucose, lipids, CBC), CXR.
14	Pressure dial and a toe-specific cuff (TBI).	- ABI interpretation: > 1.3 = calcified; 0.9–1.3 = normal; 0.4–0.9 = claudication; < 0.4 = CLI. - TBI/TcPO₂: essential in diabetics with falsely elevated ABI from vessel calcification.
15	Treadmill ABI drop (0.2), segmental pressure drops (>20mmHg), and triphasic Doppler waves.	- Exercise ABI: drop ≥ 0.2 confirms exercise-induced ischaemia when resting ABI is normal. - Segmental pressures: > 20 mmHg drop between segments = significant stenosis at that level. - Doppler waveforms: triphasic = normal; biphasic = moderate disease; monophasic = severe.
16	Ultrasound (1st line), CTA (pre-op planning with contrast), and Gold-standard DSA (intervention only).	- Duplex USG: first-line imaging, non-invasive, operator-dependent, poor for aortoiliac. - CTA: for pre-intervention planning; watch for contrast nephropathy and allergy. - DSA: gold standard, ONLY for planned intervention, can be therapeutic (intra-op).
17	Supervised exercise and a Cilostazol pill bottle.	- Improve Symptoms: Supervised exercise programme + drugs (cilostazol, naftidrofuryl, pentoxifylline) + endovascular/surgery. - Cilostazol (PDE3 inhibitor) = only FDA-approved drug for claudication. Contraindicated in heart failure. - Supervised exercise increases claudication distance by 50–200% — comparable to angioplasty.
18	TASC A-B (endovascular) vs. TASC C-D (surgical bypass).	- Indications for intervention: disabling claudication (failed 6 months conservative) + limb salvage (critical ischaemia). - TASC A-B → endovascular (PTA ± stent). TASC C-D → surgical bypass.
19	Pipe scraper (endarterectomy) and a natural vine bypass hose (autologous vein).	- Endarterectomy: short segments, larger vessels (iliac, carotid, femoral bifurcation/profundaplasty). - Bypass: anatomical (aorto-bifemoral, fem-pop) vs extra-anatomical (fem-fem, axillo-bifemoral). Autologous vein = best conduit, especially below knee.
20	3 D's tombstone and a prosthetic leg showing a preserved knee joint (BKA).	- Amputation indications (3 D's): Dead, Dangerous, Damn nuisance. BKA preferred to preserve knee joint.
21	A heart clock representing the leading cause of death.	- Cardiovascular events (MI, stroke) are the leading cause of death — not the leg. Always manage systemic atherosclerosis.
22	Leaking ink (myoglobinuria), kidney damage (AKI), and a sliced muscle-box (fasciotomy for compartment syndrome).	- Delay in amputating a non-viable limb → infection, myoglobinuria, AKI, hyperkalaemia. - Endovascular: dissection, rupture, distal embolisation, restenosis (most common late complication), contrast nephropathy. - Reperfusion injury → compartment syndrome (pain out of proportion, tense compartment, pulses can be present, Mx: urgent fasciotomy) and rhabdomyolysis (K⁺/myoglobin release → arrhythmia/AKI, Mx: aggressive hydration, mannitol, IV bicarbonate).
23	Kinked, infected bypass hose leaking into a stomach-shaped sewer (aortoenteric fistula).	- Bypass surgery: graft failure (kink → neointimal hyperplasia → atherosclerosis), graft infection (prosthetic > autologous), aortoenteric fistula, autonomic nerve damage.
24	A phantom ghost limb, a fixed-flexed stump, and a nerve lump (neuroma).	- Early: stump gangrene (→ higher amputation), phantom limb pain (Mx: amitriptyline/gabapentin), DVT/PE. - Late: fixed flexion deformity, stump neuroma, stump ulceration.

Chronic Arterial Insufficiency

1. Definition

2. Epidemiology

Global & Hong Kong Context

Key Epidemiological Points

3. Risk Factors

4. Anatomy & Function of the Lower Limb Arterial System

4.1 Arterial Anatomy (Proximal → Distal)

4.2 Vessel Wall Layers

4.3 Collateral Circulation

5. Etiology & Pathophysiology

5.1 Causes of Chronic Arterial Occlusion

A. Atherosclerosis (Most Common Cause, > 95%)

B. Buerger's Disease (Thromboangiitis Obliterans)

C. Behçet's Disease

D. Popliteal Entrapment Syndrome

5.2 Levels of Arterial Occlusion and Clinical Correlation

5.3 Leriche Syndrome

6. Classification Systems

6.1 Fontaine Classification (European, Simpler)

6.2 Rutherford Classification (American, More Detailed)

6.3 TASC II Classification

7. Clinical Features

7.1 Symptoms

A. Intermittent Claudication (Non-Critical Ischaemia)

B. Rest Pain (Critical Limb Ischaemia)

C. Tissue Loss: Ulceration and Gangrene (Fontaine IV / Rutherford 5–6)

D. Impotence (Erectile Dysfunction)

E. Associated Symptoms of Systemic Atherosclerosis

7.2 Signs

A. Inspection

B. Palpation

C. Buerger's Test

D. Auscultation

E. Complete Examination

8. Differentiating Vascular from Neurogenic Claudication

9. Arterial vs Venous Ulcer Characteristics

10. Assessment Framework for Lower Limb Ischaemia

11. Summary of Pathophysiology Flow

Active Recall - Chronic Arterial Insufficiency (Part 1)

References

1. Framework for Differential Diagnosis

2. Differential Diagnosis of Intermittent Claudication

A. Neurogenic Claudication (Spinal Stenosis)

B. Sciatica (Lumbosacral Radiculopathy)

C. Arthritis of the Hip or Foot

D. Chronic Exertional Compartment Syndrome

E. Baker's Cyst (Popliteal Cyst)

3. Acute vs Chronic Limb Ischaemia

4. Differential Diagnosis of Leg Ulcers

5. Differential Diagnosis within "Chronic Arterial" Causes

6. Common Pitfalls in Differential Diagnosis

7. Summary of the Systematic DDx Approach

Active Recall - DDx of Chronic Arterial Insufficiency

1. Diagnostic Criteria — How Do We "Diagnose" Chronic Arterial Insufficiency?

2. Diagnostic Severity Criteria — ABI Thresholds

3. Diagnostic Algorithm

4. Investigation Modalities — Detailed Breakdown

4.1 Non-Invasive Vascular Laboratory

A. Ankle-Brachial Index (ABI / ABPI)

B. Segmental Pressures

C. Doppler Waveform Analysis

D. Toe-Brachial Index (TBI) & Transcutaneous Oxygen Pressure (TcPO₂)

E. Exercise Treadmill Test

4.2 Imaging Investigations

A. Duplex Ultrasound (First-Line Imaging)

B. CT Angiography (CTA)

C. MR Angiography (MRA)

D. Digital Subtraction Angiography (DSA) — The Gold Standard

4.3 Adjunctive / Baseline Investigations

5. Summary: Investigation Hierarchy

Active Recall - Diagnosis & Investigations of Chronic Arterial Insufficiency

1. Management Framework — The Big Picture

2. Overall Management Algorithm

3. Conservative Management (The Foundation for ALL Patients)

3.1 Cardiovascular Risk Factor Modification

3.2 Antiplatelet Therapy

3.3 Supervised Exercise Programme

4. Pharmacological Treatment for Claudication

5. Indications for Intervention (Revascularisation)