Coarctation of the aorta is a congenital narrowing of the aorta, typically near the ductus arteriosus, presenting in neonates with heart failure or in older children and adolescents with upper extremity hypertension, diminished femoral pulses, and a blood pressure gradient between the arms and legs.

Coarctation of the Aorta (CoA) in Paediatrics

Feature	Detail
Proportion of all CHD	~4–9% of congenital heart disease ^[2]^[3]
Incidence	~4 per 10,000 live births ^[2]^[3]
Sex ratio	M > F (approximately 59:41, i.e., ~1.5:1 male predominance) ^[2]^[3]
Familial recurrence	Majority sporadic; may display familial clustering ^[2]^[3]
Geographic note (HK)	No specific ethnic predilection; incidence consistent with global figures. Turner syndrome screening relevant in any female with CoA in Hong Kong

Key Associations

Turner syndrome (45,X) — CoA is the most characteristic cardiac lesion of Turner syndrome (~10–15% of Turner patients). Any girl or adolescent diagnosed with CoA should be evaluated for Turner syndrome ^[2]^[3].
Bicuspid aortic valve (BAV) — present in up to 50–80% of patients with CoA. The embryological link is defective neural crest cell migration, which contributes to both the aortic valve and the aortic isthmus ^[2]^[3].
Hypoplasia of the transverse aortic arch ^[2]^[3]
Ventricular septal defect (VSD) ^[2]^[3]
Berry (intracranial) aneurysms — increased risk of subarachnoid haemorrhage in later life, relevant even in adolescents ^[2]^[3]^[4]
Other: mitral valve abnormalities (parachute mitral valve), subaortic stenosis → these can coexist in the Shone complex (multilevel left heart obstruction)

High Yield – Turner Syndrome Link

Every female neonate/child/adolescent diagnosed with CoA should be karyotyped to exclude Turner syndrome (45,X). Conversely, every girl with Turner syndrome should have echocardiographic screening for CoA and BAV.

Anatomy and Normal Function

Aetiology (Focus on Hong Kong Context)

Risk Factor	Mechanism
Turner syndrome	Defective lymphatic/vascular development; haploinsufficiency of X-chromosome genes involved in vascular development
Male sex	~1.5× more common in males; reason unclear but may relate to hormonal influence on ductal tissue
Family history of CHD	Polygenic inheritance pattern
Maternal factors	Less well-defined than for some other CHDs; some association with maternal diabetes and teratogen exposure

In Hong Kong, CoA diagnosis may be made:

Prenatally via fetal echocardiography (increasingly detected at the anomaly scan at 18–22 weeks, though isolated CoA can be difficult to detect antenatally)
Postnatally in the neonatal period (critical CoA) or incidentally in childhood (non-critical CoA with hypertension)

Pathophysiology

This is the heart of understanding CoA. Let's build it from first principles.

In milder coarctation, the DA closes normally and the LV can generate enough pressure to push blood past the narrowing. Over time:

Chronic pressure overload of LV → compensatory LVH ^[2]^[3]
- The LV faces increased afterload (like chronically squeezing against a narrowed pipe)
- Concentric LVH develops as an adaptive response
- Eventually can lead to LV diastolic dysfunction and heart failure
Systolic hypertension in the upper limbs due to outflow obstruction ^[2]^[3]
- Blood pressure proximal to the coarctation is elevated
- BP in the upper limbs is high; BP in the lower limbs is low → upper-lower limb BP gradient > 20 mmHg is a classic finding
Systemic arterial insufficiency → enlargement of intercostal arteries as collaterals with rib notching ^[2]^[3]
- The body tries to bypass the obstruction by developing collateral vessels
- Internal mammary arteries → intercostal arteries → descending aorta (below the CoA)
- Enlarged, pulsatile intercostal arteries erode the undersurface of the ribs → rib notching on CXR (typically ribs 3–8; NOT ribs 1–2 because the first two intercostal arteries arise above the coarctation)
- Rib notching is not seen in neonates/infants — it takes years to develop and is typically a finding in older children and adolescents
Systolic HTN may persist despite repair due to permanent alteration of arterial mechanics and physiology ^[2]^[3]
- Even after successful repair, ~25–30% of patients develop late/recurrent hypertension
- Mechanisms: abnormal aortic wall compliance, resetting of baroreceptors, activation of the renin-angiotensin-aldosterone system (RAAS) due to chronic renal hypoperfusion, endothelial dysfunction
- This is why long-term cardiovascular follow-up is essential

Why Does CoA Cause Hypertension?

Two mechanisms:

Mechanical: Obstruction increases resistance → pressure builds up proximal to the narrowing (simple physics: Pressure = Flow × Resistance)
Neurohormonal: Chronic renal hypoperfusion (kidneys are distal to the coarctation) activates RAAS → angiotensin II → vasoconstriction + aldosterone → sodium/water retention → hypertension. This is why hypertension can persist even after surgical repair.

Classification

Classification	Description	Notes
Preductal (Infantile type)	Narrowing proximal to the DA insertion	Historically associated with long-segment hypoplasia; often severe; presents in neonatal period
Juxtaductal	Narrowing at the level of the DA	Most common type; the discrete shelf of posterior aortic wall tissue
Postductal (Adult type)	Narrowing distal to the DA	Historically described as the "adult" form with collateral development

Modern understanding: The preductal/postductal classification is somewhat outdated. Most CoA is juxtaductal, and the clinical presentation depends more on the severity of narrowing and the presence of associated lesions than on exact anatomical position relative to the ductus.

Type	Presentation	Age Group
Critical/Severe (Duct-dependent)	Neonatal shock, HF, oliguria upon DA closure	Neonate (day 1–14 of life)
Non-critical (Non-duct-dependent)	Asymptomatic hypertension, murmur, weak femoral pulses	Infant, child, adolescent

Clinical Features

Symptoms

The symptoms depend entirely on severity and timing of presentation.

Symptom	Pathophysiological Basis
Initially appears well (day 0–1)	DA is still open, allowing RV to supply lower body via the ductus
Acute deterioration on day 2–3	DA closure → sudden obstruction to lower-body blood flow and acute LV pressure overload
Poor feeding / lethargy	Reduced cardiac output and tissue perfusion; metabolic acidosis
Tachypnoea / respiratory distress	Pulmonary oedema from acute LV failure (increased LV end-diastolic pressure → increased LA pressure → increased pulmonary venous pressure → fluid transudation into alveoli)
Oliguria/anuria	Renal hypoperfusion distal to CoA → acute kidney injury ^[2]^[3]
Pallor / mottling / grey appearance	Peripheral vasoconstriction due to poor cardiac output and shock
Cardiovascular collapse / shock	Cardiogenic shock from acute LV failure + obstructive shock from CoA itself ^[2]^[3]

Classical Presentation – Don't Miss This!

Day 2 neonatal HF with shock and oliguria in severe CoA with duct-dependent systemic circulation → death ≤1 week if tight stenosis ^[2]^[3]. This is the classic exam scenario: a neonate who was well at birth and then collapses on day 2–3 when the ductus closes. Always check femoral pulses in any collapsed neonate!

Symptom	Pathophysiological Basis
Asymptomatic (most common presentation!)	Gradual LVH compensates for the pressure load; collaterals develop
Incidental finding of murmur or systemic HTN	Even if narrowing is moderate/severe ^[2]^[3]
Headache	Upper-body hypertension
Epistaxis	Upper-body hypertension → capillary fragility in nasal mucosa
Leg cramps / claudication on exercise	Lower-body hypoperfusion during exertion when demand exceeds collateral supply
Exercise intolerance	LV cannot increase output sufficiently to meet demand across the obstruction
Cold feet	Reduced lower-limb perfusion

Important: Many children with non-critical CoA are completely asymptomatic, and the diagnosis is made incidentally when hypertension or a murmur is detected during a routine check-up. This is why checking four-limb blood pressures and femoral pulses is a fundamental part of the paediatric cardiovascular examination.

Signs

Sign	Pathophysiological Basis
Weak lower-limb (LL) pulses: only reliable sign of this condition before ductus closes	Reduced flow to the descending aorta. This is the SINGLE most important clinical clue ^[2]^[3]
RV impulse (parasternal heave)	Systemic circulation is supported by RV pumping through the DA ^[2]^[3]
Inaudible or soft ejection systolic murmur (ESM) at LUSB	The narrowing is so tight that minimal flow crosses it → little turbulence → quiet murmur ^[2]^[3]
Collapse, shock, oliguria after ductal closure	Acute loss of lower-body perfusion + acute LV failure ^[2]^[3]
Hepatomegaly	Right heart failure secondary to LV failure (back-pressure transmitted to pulmonary veins → pulmonary arteries → RV)
Metabolic acidosis (on blood gas)	Lactic acidosis from poor tissue perfusion
Differential cyanosis (if DA has R→L shunt)	Desaturated blood from RV through DA reaches lower body; oxygenated blood from LV reaches upper body

Weak Femoral Pulses – The Key Sign

Weak LL pulses is the only reliable sign of CoA before the ductus closes ^[2]^[3]. ALWAYS palpate femoral pulses in every newborn examination. If femoral pulses are absent or weak, think CoA until proven otherwise. This is a lifesaving clinical skill.

Sign	Pathophysiological Basis
Weak LL pulse with radiofemoral delay	Blood reaches the femoral arteries late (via collaterals or through the narrow segment) compared to the radial pulse ^[2]^[3]
LV impulse (heaving apex beat)	Compensatory LVH from chronic pressure overload ^[2]^[3]
ESM at LUSB radiating to left interscapular region at the back	Turbulent flow across the narrowed aortic segment; the jet radiates posteriorly because the CoA is at the posterior aortic wall near the spine ^[2]^[3]
± Soft continuous murmur throughout chest in older children with well-developed collaterals	Continuous flow through tortuous, dilated collateral vessels (intercostal arteries). The murmur is continuous because flow is present in both systole and diastole through these low-resistance collateral channels ^[2]^[3]
Upper limb hypertension	Mechanical obstruction raises pressure proximal to CoA
Upper-lower limb BP gradient > 20 mmHg	Direct consequence of the obstruction
Palpable collateral vessels (intercostal/scapular)	Dilated intercostal and internal mammary arteries can sometimes be felt along the chest wall, especially over the back
Systolic thrill at suprasternal notch	Turbulent flow in the aortic arch
Apical ejection click ± ESM (if associated BAV)	BAV produces a click from restricted leaflet opening; flow across a stenotic bicuspid valve creates an ESM

Measurement	Expected Finding in CoA
Right arm BP	HIGH (proximal to CoA)
Left arm BP	Usually HIGH (left subclavian usually arises proximal to CoA) but may be low if CoA involves left subclavian origin
Lower limb BP	LOW (distal to CoA)
Gradient	> 20 mmHg upper-to-lower limb systolic BP difference is diagnostic

Normal in children: Lower-limb systolic BP should be equal to or slightly higher (by ~10 mmHg) than upper-limb BP (due to pulse wave amplification). If the lower-limb BP is lower, this is abnormal and suggests CoA.

Important paediatric note: Use age-appropriate BP cuff sizes. In neonates, measure BP in the right arm (pre-ductal) and either leg. In older children, measure in both arms and one leg.

Key teaching point from lecture slides: Coarctation of the aorta is classified as an acyanotic congenital heart disease with left-to-right shunt dynamics or obstructive lesion. It is a cause of heart failure and shock in the neonatal period (duct-dependent systemic circulation) and of systemic hypertension in older children ^[1].

High Yield Summary

Definition: Discrete narrowing of the descending aorta at the aortic isthmus (juxtaductal), near the ductus arteriosus insertion.

Epidemiology: 4–9% of CHD, 4/10,000 live births, M > F (59:41) ^[2]^[3].

Associations: Turner syndrome, bicuspid aortic valve, VSD, aortic arch hypoplasia, berry aneurysms ^[2]^[3].

Pathophysiology:

Severe: duct-dependent systemic circulation → DA closure → acute LV failure, shock, oliguria, death within 1 week ^[2]^[3]
Less severe: chronic LV pressure overload → LVH, upper-body HTN, collateral formation (rib notching) ^[2]^[3]
HTN may persist post-repair due to altered arterial mechanics and RAAS activation ^[2]^[3]

Clinical Features:

Critical (neonate): weak LL pulses (only reliable sign before ductus closes), RV impulse, soft/absent ESM at LUSB, collapse after DA closure ^[2]^[3]
Non-critical (older child): weak LL pulses with radiofemoral delay, heaving apex (LVH), ESM at LUSB → left interscapular back, continuous murmur from collaterals, upper-lower limb BP gradient > 20 mmHg ^[2]^[3]

Must-do in every newborn exam: Palpate femoral pulses!

Active Recall - Coarctation of the Aorta (Clinical Features & Pathophysiology)

Differential Diagnosis of Coarctation of the Aorta in Paediatrics

The differential diagnosis of CoA depends on the clinical presentation. Because CoA can present in two fundamentally different ways — (1) a collapsed neonate (critical/duct-dependent CoA) or (2) an older child with hypertension and/or weak femoral pulses — the differential diagnosis must be structured around each presentation separately. Let's work through this systematically from first principles.

Part A: Differential Diagnosis in the Neonate with Shock/Collapse

When a neonate presents with collapse, shock, and oliguria after ductal closure ^[2]^[3], the critical question is: is this a duct-dependent cardiac lesion, or is there another cause of neonatal shock?

1. Other Duct-Dependent Systemic Circulation Lesions

These are the conditions that, like critical CoA, depend on the ductus arteriosus to maintain lower-body (systemic) blood flow. When the duct closes, they present with the same picture of acute cardiovascular collapse.

Feature	Detail
Definition	Complete discontinuity (not just narrowing) of the aortic arch
Pathophysiology	Duct-dependent systemic circulation → neonatal HF with shock on day 2 — identical mechanism to critical CoA. The descending aorta is supplied entirely through the PDA from the RV ^[2]
Associations	DiGeorge syndrome (22q11.2 deletion) — especially Type B, VSD ^[2]
Key distinguishing features	- Absence of thymus on CXR (suggestive of DiGeorge → Type B) ^[2] — this is a critical radiological clue - Differential cyanosis: SpO₂ in RUL higher than lower limbs ^[2] - Type classification differs from CoA (Type A/B/C based on site of interruption) ^[2] - Weak/absent femoral pulses with changes to UL/carotid pulses depending on type ^[2]: • Type A (distal to left subclavian): equally strong UL pulses • Type B (between left common carotid and left subclavian): weak LEFT upper limb pulse • Type C (between innominate and left common carotid): weak LEFT upper limb + LEFT carotid pulses
How to differentiate from CoA	Echocardiography shows complete absence of a segment of the arch (vs. narrowing in CoA). IAA + DiGeorge features (hypocalcaemia, lymphopenia, absent thymus) strongly favours IAA Type B

Why is this the closest mimic? Because IAA is essentially "the most extreme form of CoA" — instead of a narrowing, there is a complete interruption. The clinical presentation is virtually identical. Only echocardiography can reliably distinguish them.

IAA Type B and DiGeorge – High Yield

Absence of thymus on CXR should prompt investigation for DiGeorge syndrome (CBC for lymphopenia, calcium/phosphate for hypocalcaemia, chromosomal study for 22q11.2 deletion) ^[2]. DiGeorge syndrome is remembered by the mnemonic CATCH-22:

Cardiac abnormalities (conotruncal: IAA, truncus arteriosus, TOF)
Abnormal facies
Thymic hypo/aplasia
Cleft palate
Hypocalcaemia
Chromosome 22q11.2 deletion

Feature	Detail
Definition	Severe obstruction at the aortic valve level in the neonate
Pathophysiology	Severe AS → LV cannot generate enough forward flow → duct-dependent systemic circulation (similar to CoA but the obstruction is at the valve, not the aorta)
Key distinguishing features	- Harsh ESM at RUSB (aortic area), not LUSB/back - Thrill at suprasternal notch and RUSB - LV is often dilated and poorly functioning (vs. CoA where LV function may be relatively preserved initially) - Echocardiography shows thickened, restricted aortic valve leaflets with a small valve orifice
How to differentiate from CoA	Murmur location (RUSB vs. LUSB/back), echocardiography shows valve-level obstruction with post-stenotic dilation of ascending aorta

Feature	Detail
Definition	Spectrum of underdevelopment of left-sided cardiac structures: small LV, hypoplastic/atretic mitral valve, hypoplastic/atretic aortic valve, hypoplastic ascending aorta and arch
Pathophysiology	The LV is essentially non-functional. ALL systemic blood flow depends on: (1) R→L shunt at atrial level (foramen ovale), (2) RV pumping through PA → PDA → descending aorta AND retrograde flow through the hypoplastic arch to supply coronaries and brain. When the duct closes → complete circulatory collapse
Key distinguishing features	- More severe presentation than CoA — often profound cyanosis, shock, and acidosis - Single S2 (absent aortic component) - Often no murmur at all (no flow through the aortic valve) - Echocardiography diagnostic: tiny LV cavity, atretic/severely hypoplastic mitral and aortic valves
How to differentiate from CoA	HLHS presents more severely and earlier. Echocardiography is definitive — the LV cavity is hypoplastic in HLHS (vs. relatively normal-sized in CoA)

2. Cardiogenic Shock from Non-Structural Causes

These present with neonatal shock but without duct-dependence — the shock is from myocardial dysfunction rather than obstruction.

Feature	Detail
Cause	Viral (Coxsackie B, enterovirus, adenovirus) — can be acquired transplacentally or perinatally
Pathophysiology	Viral invasion of myocardium → inflammation → myocyte necrosis → pump failure → cardiogenic shock
Key distinguishing features	- History of maternal viral illness, PROM, or neonatal infection - Features of cardiogenic shock: diffuse lung crackles, hepatomegaly, gallop rhythm ^[5] - Femoral pulses equally weak (all pulses diminished, not just lower limbs) - ECG: diffuse ST/T changes, low voltages, arrhythmias - Echocardiography: globally dilated, poorly contracting LV with NO structural obstruction
How to differentiate from CoA	In CoA, femoral pulses are selectively weak compared to upper-limb pulses. In myocarditis, all pulses are equally weak. Echocardiography distinguishes definitively

Feature	Detail
Pathophysiology	Sustained rapid heart rate (typically > 220 bpm in neonates) → inadequate diastolic filling → reduced cardiac output → heart failure and shock
Key distinguishing features	- Heart rate very high (> 220 bpm), often > 250 bpm - Regular, narrow-complex tachycardia on ECG - May present with irritability, poor feeding, then acute collapse - Femoral pulses equally weak
How to differentiate from CoA	ECG is diagnostic: fixed, very rapid HR with narrow QRS. CoA does not cause extreme tachycardia as a primary feature

3. Non-Cardiac Causes of Neonatal Shock

Feature	Detail
Pathophysiology	Bacterial infection → systemic inflammatory response → distributive shock (vasodilatation, capillary leak, myocardial depression)
Key distinguishing features	- Risk factors: PROM, maternal GBS, prematurity, chorioamnionitis - Fever or hypothermia, poor feeding, lethargy - Warm peripheries initially (distributive shock) → then cold shock - Raised inflammatory markers (CRP, procalcitonin, WCC) - Femoral pulses equally diminished - No upper-lower limb BP gradient
How to differentiate from CoA	Femoral pulses are not selectively weak. Blood cultures positive. No structural heart lesion on echo. However, sepsis and critical CoA can coexist — a collapsed neonate with presumed sepsis who does not respond to antibiotics and fluid resuscitation should have femoral pulses checked and an urgent echocardiogram

Critical Teaching Point – Sepsis vs. CoA

A collapsed neonate initially treated for sepsis who fails to improve should ALWAYS have femoral pulses palpated and an echocardiogram performed to rule out critical CoA or other duct-dependent lesions ^[2]^[3]. These two conditions can look almost identical in the first hours, and delayed diagnosis of CoA is catastrophic. Remember: weak femoral pulses is the only reliable sign of CoA before the ductus closes ^[2]^[3].

Feature	Detail
Examples	Organic acidaemias (methylmalonic, propionic), urea cycle defects, fatty acid oxidation defects
Pathophysiology	Accumulation of toxic metabolites → encephalopathy, metabolic acidosis, myocardial depression → shock
Key distinguishing features	- Often presents after initiation of feeds (protein load) - Severe metabolic acidosis with elevated ammonia and/or lactate - Encephalopathy (seizures, lethargy, hypotonia) - No selective femoral pulse weakness
How to differentiate from CoA	Blood gas shows severe metabolic acidosis (can also occur in CoA), but ammonia/organic acids/acylcarnitine profile is abnormal. No structural heart lesion on echo

Feature	Detail
Relevance	A collapsed infant may have suffered abusive head trauma
Key distinguishing features	Unexplained encephalopathy, retinal haemorrhages, subdural haematoma, bruising in non-mobile infant
How to differentiate from CoA	Neuroimaging findings, ophthalmological examination, skeletal survey. No cardiac structural lesion

Part B: Differential Diagnosis in the Older Child/Adolescent

In an older child, CoA typically presents with asymptomatic hypertension, incidental murmur, weak femoral pulses, or upper-lower limb BP gradient ^[2]^[3]. The differential here centres on causes of secondary hypertension in children and conditions mimicking the vascular signs of CoA.

1. Vascular Causes (Mimicking CoA's Vascular Findings)

Feature	Detail
Definition	Narrowing of the abdominal aorta (suprarenal or infrarenal), rather than the thoracic aorta
Causes	Takayasu arteritis, neurofibromatosis type 1 (NF1), Williams syndrome, fibromuscular dysplasia, or idiopathic
Pathophysiology	Abdominal aortic narrowing → upper-body hypertension, reduced lower-limb perfusion (identical haemodynamic principle to thoracic CoA)
Key distinguishing features	- Abdominal bruit (vs. interscapular murmur in CoA) - Echocardiography of the thoracic aorta is normal - CT/MR angiography shows abdominal aortic narrowing
How to differentiate from CoA	Echocardiography of thoracic aorta is normal; cross-sectional imaging (CTA/MRA) localises the narrowing to the abdominal aorta

Feature	Detail
Definition	Large-vessel vasculitis causing stenosis of the aorta and its branches
Epidemiology	Uncommon, usually affects females of reproductive age (10–40 years), especially in Asians ^[6] — but can rarely present in older paediatric patients
Pathophysiology	Granulomatous inflammation of aortic arch and abdominal aorta → stenosis ^[6]
Key distinguishing features	- Constitutional symptoms: weight loss, low-grade fever, fatigue ^[6] - Bruits (80%), limb claudication (70%), absent/weak pulses (60%) ^[6] - Asymmetric BP (50%), HTN (> 50%) ^[6] - Raised ESR/CRP - Vascular imaging (MRA/CTA) shows vessel wall thickening and stenoses in a pattern not typical of congenital CoA
How to differentiate from CoA	Takayasu is acquired (not congenital), presents with systemic inflammation, and typically involves multiple aortic branch vessels (not just the isthmus). CTA/MRA pattern is diffuse, not discrete

Feature	Detail
Definition	Williams syndrome (7q11.23 deletion including elastin gene) causes stenosis of the arterial system ^[2]
Cardiac lesions	Supravalvular aortic stenosis (most characteristic), peripheral pulmonary artery stenosis, renal artery stenosis, coronary artery ostial stenosis ^[2]
Clinical features	Intellectual disability, elfin facies (full cheeks, flat nasal bridge, anteverted nostrils, long philtrum, prominent lips with open mouth), hypercalcaemia ^[2]
How to differentiate from CoA	The stenosis in Williams syndrome is supravalvular (above the aortic valve, in the ascending aorta) rather than at the isthmus. The dysmorphic features and hypercalcaemia are distinctive. Echocardiography localises the obstruction

Feature	Detail
Definition	Posterior fossa malformations, Haemangiomas, Arterial anomalies, Coarctation of aorta/Cardiac anomalies, Eye abnormalities ^[7]
Relevance	CoA can occur as part of PHACE syndrome — large facial/cervical haemangiomas should prompt cardiac screening including assessment for CoA ^[7]
How to differentiate	Not truly a "differential" but rather an associated syndrome. The presence of a large segmental facial haemangioma in an infant should trigger echocardiographic screening for CoA

2. Renal Causes of Paediatric Hypertension

Renal disease is the most common cause of secondary hypertension in children. These conditions cause hypertension but do NOT cause selective femoral pulse weakness or upper-lower limb BP gradient (unless renal artery stenosis is bilateral and severe enough to mimic aortic disease).

Feature	Detail
Examples	Glomerulonephritis (post-streptococcal, IgA nephropathy, lupus nephritis), reflux nephropathy, polycystic kidney disease, chronic kidney disease
Pathophysiology	Reduced renal function → sodium/water retention + RAAS activation → hypertension
How to differentiate from CoA	Normal femoral pulses, no upper-lower limb BP gradient, abnormal urinalysis (haematuria, proteinuria), abnormal renal function, abnormal renal ultrasound

Feature	Detail
Causes in children	Fibromuscular dysplasia (most common paediatric cause), NF1, Williams syndrome, Takayasu arteritis, post-umbilical artery catheterisation (neonatal)
Pathophysiology	Stenosis of one or both renal arteries → renal hypoperfusion → RAAS activation → renovascular hypertension
How to differentiate from CoA	Femoral pulses are NORMAL (the aorta itself is not narrowed). Renal Doppler ultrasound shows asymmetric renal size and abnormal renal artery flow. CTA/MRA confirms renal artery stenosis

3. Endocrine Causes of Paediatric Hypertension

Feature	Detail
Definition	Catecholamine-secreting tumour from adrenal medulla chromaffin cells (phaeochromocytoma) or extra-adrenal sympathetic chain (paraganglioma)
Clinical features	Paroxysmal hypertension, classical triad of headache + sweating + palpitation ^[8]^[9]
Paediatric context	Rare in children but included in differential of secondary HTN; 10% occur in children ^[9]
How to differentiate from CoA	Paroxysmal nature, normal femoral pulses, no BP gradient. Diagnosed by 24h urine or plasma fractionated metanephrines ^[8]^[9]

Condition	Key Feature	How to Differentiate
Cushing syndrome	Moon face, central obesity, striae, growth failure	Normal femoral pulses, elevated cortisol, no BP gradient
Hyperthyroidism	Tachycardia, tremor, weight loss, exophthalmos	Normal femoral pulses, elevated fT4/suppressed TSH
Congenital adrenal hyperplasia (11β-hydroxylase deficiency)	Virilisation + hypertension	Elevated 11-deoxycortisol, normal femoral pulses
Primary hyperaldosteronism	Hypertension + hypokalaemia	Normal femoral pulses, elevated aldosterone:renin ratio

4. Other Cardiac Causes

Feature	Detail
Pathophysiology	Obstruction at the valve level → LV pressure overload → LVH → systolic HTN
Key distinguishing features	ESM at RUSB (not LUSB/back), radiates to carotids, ejection click if bicuspid valve. Femoral pulses may be low-volume but NOT selectively weaker than upper-limb pulses
How to differentiate from CoA	No upper-lower limb BP gradient. Echocardiography localises the obstruction to the valve

Feature	Detail
Relevance	Turner syndrome is associated with left-sided cardiac lesions: CoA, bicuspid aortic valve, valvular AS, idiopathic aortic dilatation (risk of dissection/aneurysm), MVP, hypoplastic left heart syndrome ^[2]
Clinical implication	In any girl with one left-sided cardiac lesion, screen for others. CoA may coexist with AS, and the clinical picture may be mixed

Condition	Femoral Pulses	UL-LL BP Gradient	Murmur Location	Key Distinguishing Feature
Coarctation of aorta	Weak/absent	Present ( > 20 mmHg)	LUSB → back	Discrete narrowing at isthmus on echo
Interrupted aortic arch	Weak/absent	Present	Variable	Complete discontinuity on echo; DiGeorge features
Critical aortic stenosis	Equally weak	Absent	RUSB → carotids	Valve-level obstruction on echo
HLHS	Equally weak	Absent	Often no murmur	Hypoplastic LV on echo
Neonatal sepsis	Equally weak	Absent	None	Positive blood cultures, raised inflammatory markers
Myocarditis	Equally weak	Absent	Gallop rhythm	Global LV dysfunction on echo, raised troponin
Mid-aortic syndrome	Weak	Present	Abdominal bruit	Abdominal aortic narrowing on CTA/MRA
Takayasu arteritis	Asymmetric	May be present	Bruits over multiple vessels	Raised ESR/CRP, diffuse arterial involvement on CTA
Renal artery stenosis	Normal	Absent	Renal bruit	Abnormal renal Doppler, CTA confirms
Phaeochromocytoma	Normal	Absent	None	Paroxysmal HTN, elevated metanephrines

ALWAYS check femoral pulses in:

Every newborn examination

Any collapsed neonate (especially day 2–7)

Any child with unexplained hypertension

Any child with a murmur

MUST be palpated as it is the ONLY sign of coarctation ^[2]

Delay (radiofemoral delay) is usually NOT detectable in neonates due to (1) short aorta length and (2) rapid HR ^[2] — rely on pulse volume comparison, not timing.

High Yield Summary – Differential Diagnosis of CoA

In the collapsed neonate (duct-dependent presentation):

Closest mimics: Interrupted aortic arch (especially Type B with DiGeorge), critical aortic stenosis, HLHS
Non-structural cardiac: myocarditis, SVT with HF
Non-cardiac: sepsis (most important to exclude concurrently), metabolic crisis, NAI
Key differentiator: Selective femoral pulse weakness (present in CoA and IAA; absent in myocarditis, sepsis, and metabolic crises)

In the older child with hypertension:

Vascular: mid-aortic syndrome, Takayasu arteritis, Williams syndrome arteriopathy
Renal (most common paediatric HTN cause): renal parenchymal disease, renal artery stenosis
Endocrine: phaeochromocytoma, Cushing, CAH (11β-hydroxylase), primary hyperaldosteronism
Key differentiator: Upper-lower limb BP gradient > 20 mmHg is virtually pathognomonic of aortic obstruction (CoA or mid-aortic syndrome)

Golden rule: A neonate treated for sepsis who fails to improve → check femoral pulses and get an echocardiogram!

Active Recall - Differential Diagnosis of CoA

Diagnosis of Coarctation of the Aorta in Paediatrics

Diagnostic Criteria

There is no single universally agreed "diagnostic criteria" checklist for CoA (unlike, say, Kawasaki disease or rheumatic fever). Instead, diagnosis is made by combining clinical suspicion with confirmatory imaging. Let's break this down from first principles.

The diagnosis requires demonstration of a discrete narrowing of the aorta (usually at the isthmus) on imaging, in a clinical context consistent with the haemodynamic consequences of that narrowing.

In practice, the "diagnostic standard" depends on the clinical setting:

Setting	Diagnostic Standard
Fetal/Antenatal	Fetal echocardiography showing size discrepancy between right and left heart structures, small aortic isthmus, or direct visualisation of narrowing (sensitivity is limited — ~50% detection rate antenatally for isolated CoA)
Neonate (critical CoA)	Clinical findings (weak LL pulses, shock on day 2, oliguria ^[2]^[3]) + transthoracic echocardiography confirming the site and severity of narrowing and measuring the pressure gradient
Older child/adolescent	Clinical findings (weak femoral pulses, radiofemoral delay, upper-lower limb BP gradient > 20 mmHg, ESM at LUSB/back ^[2]^[3]) + echocardiography ± MRI/CT angiography for definitive anatomical assessment

Investigation Modalities: Detailed Findings and Interpretation

1. Bedside Investigations

This is the single most important bedside diagnostic manoeuvre in the older child and should be performed in any neonate with weak femoral pulses.

Detail	Explanation
Technique	Measure systolic BP in the right arm (pre-ductal — always above the CoA) and either leg (post-ductal — below the CoA). In older children, measure both arms and one leg
Normal finding	Lower-limb systolic BP should be equal to or 10–20 mmHg higher than upper-limb BP (due to pulse wave amplification in the longer arterial tree to the legs)
Abnormal finding in CoA	Upper-limb systolic BP > lower-limb systolic BP, with gradient > 20 mmHg ^[2]^[3]
Why right arm?	The right subclavian artery arises from the brachiocephalic trunk, which is always proximal to any coarctation. The left subclavian may occasionally arise at or near the CoA, giving a falsely low left-arm reading
Paediatric cuff size	Must use age-appropriate cuff (bladder width = 40% of arm circumference). An undersized cuff overestimates BP; an oversized cuff underestimates it

Teaching point: In a neonate in whom you cannot easily measure leg BP, simply comparing the volume of the femoral pulse with the brachial pulse is the clinical equivalent. Weak LL pulses is the only reliable sign of this condition before the ductus closes ^[2]^[3].

Detail	Explanation
Technique	Right hand (pre-ductal) vs. either foot (post-ductal)
Finding in critical CoA with R→L PDA shunt	Post-ductal SpO₂ (foot) may be lower than pre-ductal SpO₂ (right hand) by ≥ 3%
Limitation	CoA may NOT show a SpO₂ difference if there is no significant R→L shunting through the PDA (e.g., if PDA flow is predominantly L→R or the PDA is already closed). Pulse oximetry screening misses a significant proportion of CoA cases

MUST be palpated as it is the ONLY sign of coarctation ^[2].

Detail	Explanation
In neonates	Radiofemoral delay is usually NOT detectable due to (1) short aorta length and (2) rapid heart rate ^[2]. Rely on pulse volume — compare the "strength" of the brachial and femoral pulse simultaneously
In older children	Radiofemoral delay becomes detectable (the longer aorta allows the time difference to be appreciated, and the slower heart rate gives more time per cardiac cycle)

Exam Tip – Femoral Pulse Palpation

Many students and even junior doctors forget to palpate femoral pulses in the newborn examination. This is the most commonly missed sign leading to delayed diagnosis of CoA. In neonates, delay is NOT detectable — compare pulse VOLUME, not timing ^[2]. Practice this skill on every newborn you examine.

2. Blood Investigations

Test	Finding in Critical CoA	Pathophysiological Basis
Arterial/venous blood gas	Severe metabolic acidosis (low pH, low HCO₃⁻, raised lactate)	Due to ischaemic colitis and AKI upon duct closure ^[2]^[3] — gut and kidneys are distal to the CoA and become acutely ischaemic when the PDA closes
Lactate	Raised (often > 5 mmol/L)	Tissue hypoperfusion → anaerobic metabolism → lactic acid accumulation
Urea and creatinine	Raised	Acute kidney injury from renal hypoperfusion
Electrolytes	May show hyperkalaemia	AKI → reduced renal K⁺ excretion
Glucose	May be low or high	Stress response; neonates have limited glycogen stores
CBC	Non-specific; may show leucocytosis	Stress response. Important to rule out sepsis as a concurrent or alternative diagnosis

Test	Indication	Why
Karyotype (or FISH/microarray)	Any female with CoA	Screen for Turner syndrome (45,X) ^[2]^[3]
22q11.2 deletion study	If thymus absent on CXR, or if IAA suspected	DiGeorge syndrome ^[2]
Calcium, phosphate	If DiGeorge suspected	Hypoparathyroidism → hypocalcaemia ^[2]
Lymphocyte subsets	If DiGeorge suspected	Thymic aplasia/hypoplasia → lymphopenia (T-cell deficiency) ^[2]

The CXR is a first-line investigation that provides indirect evidence of CoA and its haemodynamic consequences. It is NOT diagnostic on its own but provides important clues.

CXR Findings by Clinical Scenario

In neonates/infants with heart failure [2][3]:

Finding	Pathophysiological Basis
Cardiomegaly	LV failure → LV dilatation; or RV dilatation if RV is supporting systemic circulation via PDA
Increased pulmonary vascular markings	Pulmonary venous congestion from elevated LA pressure (back-pressure from LV failure) ^[2]^[3]

In older children (non-duct-dependent) [2][3]:

Finding	Pathophysiological Basis
'Figure 3 sign' (or 'reverse E sign')	The aortic knob shows a characteristic indentation at the site of coarctation, with pre-stenotic dilatation of the left subclavian artery above and post-stenotic dilatation of the descending aorta below ^[2]^[3]. On barium swallow, this produces an 'E sign' (mirror image = figure 3 on plain CXR)
Rib notching (undersurface of posterior ribs)	Erosion by enlarged, pulsatile intercostal arteries serving as collaterals ^[2]^[3]. Affects ribs 3–8 (ribs 1–2 spared because their intercostals arise proximal to the CoA). Takes years to develop — NOT seen in neonates or infants

High Yield – CXR 'Figure 3 Sign'

The 'figure 3 sign' is the classic CXR appearance of CoA in older children ^[2]^[3]. Imagine the number "3" lying on its side along the left mediastinal border:

Top curve = dilated left subclavian artery or proximal aortic arch
Indentation = the coarctation site itself
Bottom curve = post-stenotic dilatation of the descending aorta

When barium is given, the oesophagus is indented by the aorta in a mirror-image pattern → 'reverse 3' or 'E sign' on barium swallow.

The ECG reflects the haemodynamic burden on the ventricles and differs by age of presentation.

Clinical Scenario	ECG Finding	Pathophysiological Basis
Neonatal HF (critical CoA)	RVH (right axis deviation, dominant R waves in V1, upright T in V1 beyond day 7) ^[2]^[3]	The RV is supporting the systemic circulation via the PDA → RV pressure overload. Also, the LV has not yet developed compensatory hypertrophy
Older child (non-duct-dependent)	LVH (tall R waves in V5–V6, deep S waves in V1, ± LV strain pattern with ST depression/T inversion in lateral leads) ^[2]^[3]	Chronic LV pressure overload from pumping against the obstruction → compensatory concentric LVH

Why RVH in neonates but LVH in older children? In critical neonatal CoA, the ductus is still open (or has just closed) and the RV has been supporting systemic circulation. The LV has not had time to hypertrophy. In chronic non-critical CoA, the LV has been working against the obstruction for months to years, so LVH develops.

Normal neonatal ECG considerations:

Right axis deviation and RV dominance are NORMAL in the first days of life (due to fetal RV dominance)
RVH is suggested if the pattern persists beyond the expected neonatal transition or is exaggerated
Always use age-appropriate ECG reference values when interpreting paediatric ECGs

5. Echocardiography (Echo)

Echocardiography is the primary diagnostic imaging modality for CoA ^[2]^[3]. It is non-invasive, widely available, radiation-free, and can be performed at the bedside — ideal for both the critically ill neonate and the ambulatory child.

Feature	Detail
Site of coarctation	Direct visualisation of the narrowing at the aortic isthmus from the suprasternal notch view ^[2]^[3]
Severity of coarctation	Measured by: (1) anatomical narrowing (luminal diameter), (2) systolic pressure gradient across the coarctation by continuous-wave Doppler ^[2]^[3]
Doppler pattern	Elevated peak systolic velocity at the coarctation site (typically > 3 m/s). In severe CoA, there is diastolic flow continuation ("diastolic tail") — flow persists through the narrowing even in diastole because the pressure gradient is maintained throughout the cardiac cycle
Associated lesions	Bicuspid aortic valve, VSD, aortic arch hypoplasia, mitral valve abnormalities ^[2]^[3] — all must be systematically assessed
LV function	LV contractility (fractional shortening, ejection fraction), LV wall thickness (to document LVH), LV dimensions
Aortic arch anatomy	Whether the arch is hypoplastic, presence of tubular narrowing, transverse arch dimensions (Z-scores)
PDA status	Is the ductus still open? Direction and size of PDA flow

Finding	Interpretation
Peak gradient > 20 mmHg	Haemodynamically significant CoA
Peak gradient > 40 mmHg	Severe CoA
Low gradient with LV dysfunction	Does NOT mean mild CoA — the LV cannot generate sufficient pressure
Low gradient with extensive collaterals	Collaterals bypass the coarctation, reducing the measured gradient despite significant narrowing

Echo Limitations in CoA

Echocardiography has limitations:

Acoustic windows may be suboptimal in older/larger children and adolescents
The suprasternal notch view can be technically difficult
Transverse arch hypoplasia may be underestimated
Collateral vessels are not well visualised by echo
Post-operative anatomy can be challenging to assess

When echo is equivocal or anatomy is complex → proceed to MRI or CT angiography.

MRI demonstrates the length and severity of coarctation ^[2]^[3] and is considered the gold standard for anatomical delineation in older children, adolescents, and for pre-operative/post-operative assessment.

Feature	Detail
Advantages	No ionising radiation (critical in paediatrics), excellent soft tissue contrast, 3D reconstruction of arch anatomy, can assess collaterals, can measure flow and gradients using phase-contrast MRI
What it shows	- Precise site, length, and degree of narrowing - Transverse arch dimensions - Collateral vessel development - Post-repair assessment (re-coarctation, aneurysm at repair site) - LV mass and function (superior to echo for quantification)
Limitations	- Requires general anaesthesia or deep sedation in young children (long acquisition time, patient must stay still) - Not suitable for haemodynamically unstable neonates - Contraindicated with certain metallic implants
When to use	- Complex anatomy not fully delineated by echo - Pre-operative planning for surgical or catheter-based intervention - Post-operative surveillance (preferred modality for long-term follow-up)

Feature	Detail
Advantages	Very fast acquisition (no sedation needed in many cases), excellent spatial resolution, 3D reconstruction
What it shows	Same anatomical information as MRI — site, length, severity of narrowing, arch anatomy, collaterals
Limitations	- Ionising radiation — significant concern in children (cumulative lifetime cancer risk). Use only when MRI is not feasible or in emergency situations - IV contrast required (risk of contrast reaction, nephrotoxicity — particularly concerning if there is AKI from the CoA itself) - Less information about flow haemodynamics compared to MRI
When to use	- Emergency situations where rapid anatomical delineation is needed and echo is equivocal - Patients with contraindications to MRI - Post-operative assessment when MRI is not feasible

Feature	Detail
Role	Historically the gold standard for diagnosis; now primarily used as a therapeutic (interventional) tool rather than purely diagnostic
What it provides	- Direct measurement of pressure gradient across CoA (most accurate haemodynamic assessment) - Angiographic visualisation of the coarctation and arch - Simultaneous intervention (balloon angioplasty ± stenting)
When used diagnostically	- When non-invasive imaging is inconclusive - Pre-intervention assessment combined with planned catheter-based intervention
Limitations	Invasive, requires sedation/GA, radiation exposure, vascular access complications (especially in neonates/small children), risk of vessel injury

These are not for diagnosing the CoA itself, but for detecting the well-known associated conditions that impact management.

Investigation	Condition Screened	Rationale
Karyotype / chromosomal microarray	Turner syndrome (45,X)	Any female with CoA ^[2]^[3]
Echocardiographic assessment of aortic valve	Bicuspid aortic valve	Present in up to 50–80% of CoA ^[2]^[3]
Echo assessment of interventricular septum	VSD	Common association ^[2]^[3]
Echo assessment of transverse arch	Aortic arch hypoplasia	Affects surgical planning ^[2]^[3]
MRA of head (in older children/adolescents)	Berry aneurysms	Associated with CoA; risk of subarachnoid haemorrhage, especially with longstanding hypertension ^[2]^[3]^[4]
Renal ultrasound	Renal anomalies	Horseshoe kidney and other renal anomalies are associated with CoA
Thyroid function, calcium	Turner syndrome endocrine complications	If Turner confirmed

Investigation	Neonate (Critical CoA)	Older Child (Non-Critical CoA)
4-limb BP	May not be feasible in shock; focus on pulse volume	UL-LL gradient > 20 mmHg
Pulse oximetry	Pre-post ductal SpO₂ difference possible	Usually normal
Bloods	Severe metabolic acidosis, raised lactate, AKI ^[2]^[3]	Usually normal
CXR	Cardiomegaly + ↑pulmonary vascular markings ^[2]^[3]	Figure 3 sign, rib notching ^[2]^[3]
ECG	RVH ^[2]^[3]	LVH ^[2]^[3]
Echo	Site and severity of CoA, pressure gradient, PDA status, associated lesions ^[2]^[3]	Same + assess LVH, collaterals
MRI	Not in acute setting (too unstable)	Gold standard for anatomy: length and severity ^[2]^[3]
CTA	Only if echo equivocal and MRI not feasible	Alternative to MRI
Catheterisation	Rarely purely diagnostic; therapeutic role	Combined diagnostic + therapeutic

High Yield Summary – Diagnosis of CoA

Diagnostic approach:

Clinical suspicion → weak femoral pulses, upper-lower limb BP gradient > 20 mmHg, murmur at LUSB/back
First-line investigation → Transthoracic echocardiography (demonstrates site, severity, gradient, associated lesions) ^[2]^[3]
Second-line/definitive anatomy → Cardiac MRI (gold standard for length and severity, especially pre-operative and for follow-up) ^[2]^[3]

Key investigation findings:

Bloods (critical CoA): Severe metabolic acidosis from ischaemic colitis and AKI ^[2]^[3]
CXR: Cardiomegaly + ↑pulmonary vascular markings (neonate); Figure 3 sign + rib notching (older child) ^[2]^[3]
ECG: RVH in neonatal HF; LVH in older children ^[2]^[3]
Echo: Primary diagnostic modality — site, severity, gradient, associated lesions
MRI: Demonstrates length and severity of coarctation ^[2]^[3]

Don't forget associations: Screen for Turner syndrome (karyotype in females), BAV, VSD, arch hypoplasia, berry aneurysms.

Haemodynamic significance: Gradient > 20 mmHg, proximal HTN, or severe narrowing on imaging ^[2]^[3]

Active Recall - Diagnosis of Coarctation of the Aorta

Management of Coarctation of the Aorta in Paediatrics

A. Emergency Management of Critical Neonatal CoA

This is a paediatric cardiac emergency. The neonate presents in shock when the ductus arteriosus closes (typically day 2–3 of life). Without intervention, death occurs within ≤1 week if tight stenosis ^[2]^[3].

Step	Action	Rationale
Airway	Secure airway; intubate if needed	A shocked neonate may have reduced consciousness and inadequate airway protection
Breathing	High-flow O₂ initially; mechanical ventilation if respiratory failure	Pulmonary oedema from acute LV failure impairs gas exchange. However, see O₂ caveat below
Circulation	IV access (consider umbilical venous catheter in neonates), judicious fluid bolus (10 mL/kg 0.9% NaCl)	Restore preload — but be cautious as the LV is failing; excessive fluid worsens pulmonary oedema

Oxygen Caveat in CoA

While O₂ is given for immediate resuscitation, be aware that supplemental O₂ can accelerate ductal closure (the ductus constricts in response to rising PaO₂). In a duct-dependent lesion, this could worsen the obstruction. Once PGE1 infusion is started, titrate O₂ to maintain SpO₂ in the low-to-mid 90s rather than aiming for 100%. The priority is to re-open the ductus with PGE1 rather than to maximise oxygen delivery ^[2].

This is the single most important intervention in the acute management of critical CoA.

Feature	Detail
Drug	Prostaglandin E1 (alprostadil) IV infusion ^[1]^[2]^[3]. Some centres use PGE2 (dinoprostone) — both work ^[2]
Mechanism	PGE1 acts on smooth muscle in the ductus arteriosus wall → relaxes ductal smooth muscle → re-opens (or maintains patency of) the ductus arteriosus → restores blood flow from PA via PDA to the descending aorta → rescues lower-body perfusion
Dose	Start at 0.05 μg/kg/min IV (some protocols: 0.01–0.1 μg/kg/min). Can increase to 0.1 μg/kg/min if no response. Once duct is open, titrate down to the lowest effective dose (typically 0.01–0.03 μg/kg/min) to minimise side effects
Route	Continuous IV infusion via central or peripheral line. Must NEVER be given as a bolus
When to start	Immediately upon clinical suspicion — do NOT wait for echocardiographic confirmation ^[1]^[2]^[3]
Monitoring	Continuous cardiorespiratory monitoring in NICU/PICU. Monitor SpO₂, heart rate, BP, temperature, respiratory status

Why PGE1 works from first principles: The ductus arteriosus closes postnatally because (1) rising PaO₂ causes smooth muscle constriction and (2) falling circulating PGE₂ (which was produced by the placenta) removes the tonic vasodilatory stimulus. PGE1 infusion replaces this lost prostaglandin → reverses ductal constriction → the ductus re-opens. Simple.

PGE1 Side Effects — Must Know for Exams

Side Effect	Mechanism	Clinical Implication
Apnoea (up to 12%)	PGE1 acts on brainstem respiratory centres → respiratory depression	Must have intubation equipment at bedside. Many centres electively intubate before starting PGE1, especially for inter-hospital transfer
Hypotension	Systemic vasodilatation (PGE1 is a vasodilator)	Monitor BP closely; may need concurrent inotrope support
Fever	Prostaglandin-mediated pyrexia (PGE acts on hypothalamic thermoregulation)	Can mimic sepsis — important to distinguish
Flushing	Cutaneous vasodilatation	Usually benign
Jitteriness / seizure-like activity	CNS effects (rare at standard doses)	Reduce dose if occurs
Cortical periosteal hyperostosis	Prolonged use (> 2 weeks) → periosteal new bone formation	Relevant only for long-term use awaiting surgery

PGE1 = Apnoea Risk → Prepare for Intubation

PGE1 infusion causes apnoea in up to 12% of neonates. ALWAYS have intubation equipment immediately available before starting the infusion. In practice, many transport teams intubate the neonate prophylactically before transfer to a surgical centre. This is a favourite exam question.

Feature	Detail
Indication	To maintain cardiac output ^[2]^[3] in the setting of acute LV failure
Drug of choice	Dopamine (5–10 μg/kg/min) or dobutamine (5–20 μg/kg/min) IV infusion
Mechanism	Dopamine: dose-dependent β₁-adrenergic stimulation → ↑contractility and ↑heart rate. Dobutamine: β₁-selective → ↑contractility with less tachycardia and less vasoconstriction than dopamine
Milrinone	Phosphodiesterase-3 inhibitor (= "inodilator": ↑contractility + vasodilation). Useful as adjunct, especially if high afterload is an issue

Derangement	Treatment	Rationale
Severe metabolic acidosis	Sodium bicarbonate IV (only if pH < 7.1 and not improving with resuscitation)	Acidosis impairs myocardial contractility and reduces response to catecholamines. However, NaHCO₃ has risks (hyperosmolality, paradoxical intracellular acidosis) — correct the underlying cause (restore perfusion) first
Hypoglycaemia	IV dextrose (2 mL/kg of 10% dextrose bolus, then 10% dextrose maintenance)	Neonates have limited glycogen stores; hypoglycaemia worsens neurological injury
Hyperkalaemia	If K⁺ > 6.5 mmol/L: calcium gluconate (cardioprotection), salbutamol nebuliser, insulin-dextrose	AKI from renal hypoperfusion → reduced K⁺ excretion
AKI	Fluid management, diuretics if fluid overloaded after duct is reopened	Restoring renal perfusion via PGE1 is the primary treatment

Feature	Detail
Timing	Early surgical repair, ideally within the first 3 months of life ^[2]^[3]. In practice, surgery is performed once the neonate is stabilised (often within days of presentation)
Procedure	Resection with end-to-end anastomosis for discrete CoA ^[2]^[3] — see Surgical Repair section below

From the lecture slides: Management of severe left ventricular outflow obstruction: (1) initial stabilisation by PGE1/E2, (2) corrective surgery or catheter intervention, (3) surgical repair of aortic coarctation/interruption ^[1].

B. Planned Management of Non-Critical CoA (Older Infant/Child/Adolescent)

Repair is indicated in selected patients with ^[2]^[3]:

Indication	Explanation
Proximal (upper-limb) hypertension	Evidence that the CoA is causing clinically significant haemodynamic compromise ^[2]^[3]
Pressure gradient > 20 mmHg across the coarctation (measured by echo Doppler or catheterisation) ^[2]^[3]	Indicates haemodynamically significant obstruction
Severe CoA on imaging studies (significant anatomical narrowing) ^[2]^[3]	Even if the gradient is not impressively high (may be due to collaterals or LV dysfunction)

If none of these criteria are met (mild CoA), the child is managed with surveillance: regular BP monitoring, periodic echocardiography, and exercise testing.

Modality 1: Surgical Repair [2][3]

Surgery is the gold standard for treatment of CoA, especially in neonates and infants.

Technique	Indication	How It Works
Resection with end-to-end anastomosis	Discrete CoA (most common) ^[2]^[3]	The narrowed segment is excised and the two free ends of the aorta are directly sutured together. This is the simplest and most widely used technique. It removes the abnormal ductal tissue completely
Extended end-to-end anastomosis	Discrete CoA with some isthmus/arch hypoplasia	Similar to above but the incision is extended along the underside of the aortic arch, allowing a wider anastomosis. Preferred when there is mild associated arch hypoplasia
Subclavian flap aortoplasty	Long-segment CoA ^[2]^[3]	The left subclavian artery is divided, opened longitudinally, and folded down as a patch to widen the narrow aortic segment. Now largely obsolete ^[2] because it sacrifices the left subclavian artery → risk of left arm growth discrepancy and ischaemia
Bypass graft across coarctation	Long-segment CoA too long for primary anastomosis ^[2]^[3]	A prosthetic or homograft conduit is placed to bypass the narrowed segment. Used when the coarctation is too extensive for resection
Patch aortoplasty	Historical technique	The narrowed segment is opened longitudinally and a patch (synthetic or pericardial) is sewn in to widen it. Largely abandoned due to high rate of late aneurysm formation at the patch site

Age Group	Timing
Neonate (critical CoA)	Urgent, within days of presentation, certainly < 3 months ^[2]^[3]
Older infant/child	Elective repair, ideally before school age (3–5 years) if criteria for intervention are met. Earlier if significant HTN or symptoms

Outcome	Detail
Restenosis rate	5–15% after surgery ^[2]^[3]
Operative mortality	Very low (< 1–2% in experienced centres) for isolated CoA
Complications	Recurrent laryngeal nerve palsy (hoarseness), phrenic nerve injury, chylothorax, wound infection, paradoxical hypertension (see below), spinal cord ischaemia (rare — < 0.5%)

Why is spinal cord ischaemia a risk? During surgical repair, the aorta is cross-clamped proximal and distal to the coarctation. This interrupts blood flow to the intercostal arteries that supply the anterior spinal artery (artery of Adamkiewicz). In children with well-developed collaterals, this risk is very low because collaterals maintain spinal cord perfusion. In neonates without collaterals, the cross-clamp time must be kept short.

What is paradoxical hypertension? After successful CoA repair, some children develop acute severe hypertension in the first 24–72 hours postoperatively, even though the obstruction has been relieved. This is caused by: (1) acute increase in blood flow to a previously underperfused vascular bed → mesenteric arteritis, (2) activation of sympathetic nervous system and RAAS (baroreceptor resetting), (3) catecholamine surge. It can cause abdominal pain (mesenteric arteritis — "post-coarctectomy syndrome") and is treated with short-acting antihypertensives (e.g., IV esmolol, sodium nitroprusside).

Balloon angioplasty is a catheter-based (interventional cardiology) approach — less invasive than surgery.

Feature	Detail
Technique	A balloon catheter is advanced (usually via the femoral artery) to the coarctation site, and the balloon is inflated to dilate the narrowed segment. The mechanism involves controlled tearing of the intima and media of the aortic wall at the coarctation
Indication	In children > 4 months old with discrete coarctation ^[2]^[3]. Also indicated for re-coarctation (recurrence after previous surgical repair) — where it is the preferred first-line approach ^[2]^[3]
Age restriction	Generally not used for those < 4 months due to small vessel size → poor results ^[2]^[3]
Contraindications	Long-segment coarctation (poor response), very young neonates (vessel too small), associated arch hypoplasia requiring surgical reconstruction
Outcomes	Restenosis rate: 40% in young infants vs. 8% in adolescents ^[2]^[3] — this is why balloon angioplasty is preferred in older children and for re-coarctation rather than for native CoA in neonates
Complications	Femoral artery injury (especially in small children), aortic wall dissection, aneurysm formation at the dilatation site, residual gradient, re-coarctation

Why does balloon angioplasty have higher restenosis in young infants? Several reasons: (1) The ductal tissue that forms the coarctation is elastic and tends to recoil after balloon dilatation. (2) Small vessel calibre means less effective dilatation. (3) Growth of the child may outpace the dilated segment. (4) Intimal proliferation and fibrosis at the site of controlled tear.

Native CoA vs. Re-Coarctation — Different Preferred Approaches

Native CoA in neonates/young infants: Surgery is preferred (balloon angioplasty has high restenosis)
Re-coarctation after previous surgery: Balloon angioplasty is preferred ^[2]^[3] — the scar tissue at the surgical site responds better to balloon dilatation and has lower recoil than native ductal tissue
Native CoA in older children/adolescents: Either surgery or balloon angioplasty ± stent can be offered

Feature	Detail
Technique	A metallic stent (expandable mesh tube) is deployed at the coarctation site during catheterisation, holding the vessel open
Indication	Generally indicated after surgical repair or angioplasty for those ≥ 25 kg ^[2]^[3]. Also increasingly used as a primary intervention in adolescents and larger children
Weight threshold	≥ 25 kg ^[2]^[3] — this is because the stent needs to be large enough to accommodate future growth to adult aortic dimensions. In smaller children, the stent would need to be re-dilated or exchanged multiple times
Pros	Improve luminal diameter, ↓residual gradient ^[2]^[3]
Cons	Often require repeated planned re-intervention as the stent needs to be dilated as the child grows ^[2]^[3]. Stent fracture, in-stent restenosis, need for lifelong imaging follow-up
Types	Bare metal stents (most common); covered stents (useful if there is risk of aortic wall injury or aneurysm)
Contraindications	Small children < 25 kg (stent cannot accommodate growth to adult size), very young infants, long-segment CoA, associated arch hypoplasia requiring reconstruction

Why the ≥ 25 kg threshold? An adult descending aorta is approximately 20–25 mm in diameter. A stent placed in a small child would need to be dilated multiple times as the child grows, eventually reaching adult dimensions. If the initial stent is too small, it may not be expandable to the required final diameter. At ≥ 25 kg, the aorta is large enough that a stent can be placed at near-adult dimensions, minimising future re-interventions.

From the lecture slides, the management of paediatric heart failure follows a stepwise approach ^[1]:

Identification of the cause and precipitating factors → Tackling of precipitating factors → General supportive management → Medical therapy of heart failure (diuretics, digoxin, ACEI, carvedilol) → Treatment of underlying cause by surgical or catheter intervention → Mechanical circulatory support and heart transplantation ^[1]

In the context of CoA, medical therapy is used as a bridge — to stabilise the child before definitive repair — not as a long-term solution, because the underlying problem is mechanical obstruction.

Drug Class	Drug	Mechanism	Role in CoA
PGE1	Alprostadil	Relaxes ductal smooth muscle → reopens PDA	Lifesaving bridge in critical neonatal CoA ^[1]^[2]^[3]
Inotropes	Dopamine, dobutamine	β₁-agonist → ↑contractility	Maintain cardiac output in acute LV failure ^[2]^[3]
Diuretics	Furosemide (1 mg/kg IV)	Loop diuretic → ↓preload by promoting natriuresis	Relieve pulmonary congestion from acute LV failure
ACE inhibitors	Captopril, enalapril	Block RAAS → ↓afterload + ↓aldosterone	Useful in chronic HF management; also used for post-repair hypertension
Beta-blockers	Carvedilol	β-blockade + α-blockade → ↓HR, ↓afterload	Chronic HF management; NOT in acute decompensated HF
Digoxin	Digoxin	Na⁺/K⁺-ATPase inhibition → ↑intracellular Ca²⁺ → ↑contractility	Seldom used due to narrow therapeutic index ^[2]; role is limited in CoA

Medical Therapy ≠ Definitive Treatment in CoA

Unlike dilated cardiomyopathy where medical therapy (ACEI + BB + diuretics) is the mainstay, in CoA the problem is a fixed mechanical obstruction. No drug will "open up" the narrowing. Medical therapy is a bridge to surgery/intervention. Prolonged medical management without definitive repair is inappropriate and dangerous.

D. Antihypertensive Therapy (Pre- and Post-Repair)

In older children with non-critical CoA and significant hypertension awaiting intervention:

Drug	Paediatric Dose	Notes
ACE inhibitor (enalapril)	0.08–0.5 mg/kg/day in 1–2 doses	First-line; reduces afterload and counteracts RAAS activation
Beta-blocker (atenolol)	0.5–2 mg/kg/day	If ACEI insufficient; reduces cardiac output and renin secretion
Amlodipine (Ca²⁺ channel blocker)	0.1–0.3 mg/kg/day	Alternative or add-on if BP not controlled

E. Long-Term Follow-Up and Surveillance

ALL patients with CoA — whether repaired or not — require lifelong cardiovascular follow-up. This is a key concept that distinguishes CoA from many other surgical conditions.

Long-term Outcome: 10-year survival generally > 90% [2][3]

Surveillance Component	Frequency	What to Look For
Clinical examination	Every 6–12 months (more frequent initially post-repair)	BP in both arms and one leg, femoral pulses, cardiac auscultation
Blood pressure monitoring	Every visit; consider ABPM	Persistent HTN (even after repair) ^[2]^[3]
Echocardiography	Annually (or more frequently if concerns)	Re-coarctation (peak gradient at repair site), arch hypoplasia, LV function, LVH regression, BAV progression
Cardiac MRI	Every 3–5 years (or as clinically indicated)	Repair site anatomy, aneurysm formation at repair site, arch dimensions
Exercise testing	In older children/adolescents	Exaggerated hypertensive response to exercise (may unmask haemodynamically significant re-CoA not apparent at rest)
MRA of head	Consider in older patients with longstanding HTN	Berry aneurysm screening ^[2]^[3]^[4]

Clinical Scenario	First-Line Treatment	Alternative	Key Points
Critical neonatal CoA	PGE1 infusion → surgical repair (resection + end-to-end anastomosis) within first 3 months ^[1]^[2]^[3]	—	Start PGE1 immediately; don't wait for echo
Non-critical CoA, infant < 4 months	Surgical repair ^[2]^[3]	—	Balloon angioplasty has poor results at this age
Non-critical CoA, child > 4 months, discrete	Surgical repair or balloon angioplasty ^[2]^[3]	Stent if ≥ 25 kg	Surgery and balloon are both reasonable; individualise
Non-critical CoA, long-segment	Surgical repair (bypass graft) ^[2]^[3]	—	Balloon/stent inappropriate for long-segment disease
Re-coarctation	Balloon angioplasty ± stent ^[2]^[3]	Re-do surgery	Balloon is preferred first-line for re-CoA
Residual HTN post-repair	Antihypertensives (ACEI/ARB ± BB) ^[2]^[3]	—	Lifelong monitoring; HTN may persist despite successful repair

High Yield Summary – Management of CoA

Emergency (Critical Neonatal CoA) ^[1]^[2]^[3]:

ABC resuscitation
PGE1/E2 infusion immediately — reopens ductus, restores lower-body perfusion. Watch for apnoea.
Inotropes to maintain cardiac output
Early surgical repair < 3 months — resection with end-to-end anastomosis for discrete CoA

Planned (Non-Critical CoA) ^[2]^[3]:

Indications for intervention: proximal HTN, gradient > 20 mmHg, severe CoA on imaging
Surgical repair: gold standard; restenosis 5–15%
Balloon angioplasty: for > 4 months, discrete CoA or re-coarctation; restenosis 40% in young infants vs. 8% in adolescents
Stent placement: for ≥ 25 kg; improves lumen but requires re-intervention as child grows

Key Lecture Slide Points ^[1]:

Management of paediatric HF: identify cause → tackle precipitating factors → general supportive → medical therapy → surgical/catheter intervention → mechanical support/transplant
Management of severe LVOT obstruction: PGE1/E2 stabilisation → corrective surgery or catheter intervention → surgical repair of aortic coarctation/interruption

Long-Term ^[2]^[3]:

10-year survival > 90%
Lifelong follow-up for re-CoA, persistent HTN, aneurysm, berry aneurysms
HTN may persist post-repair due to altered arterial mechanics

Active Recall - Management of Coarctation of the Aorta

Complications of Coarctation of the Aorta in Paediatrics

Complications of CoA can be divided into three main categories:

Acute complications of the untreated/unrepaired CoA (including complications of critical neonatal CoA)
Complications of surgical or catheter-based intervention (perioperative)
Long-term complications (even after successful repair)

Understanding these requires revisiting the pathophysiology: CoA is a mechanical obstruction that creates proximal hypertension and distal hypoperfusion. Even after the obstruction is relieved, the vascular damage from years of abnormal haemodynamics may be irreversible. This is why 10-year survival is generally > 90% ^[2]^[3] but patients are never truly "cured" — they require lifelong cardiovascular surveillance.

A. Acute Complications of Untreated/Unrepaired CoA

These arise from the direct haemodynamic consequences of the obstruction and are most dramatic in the neonatal period when the ductus closes.

Feature	Pathophysiological Basis
Duct closure → acute ↑LV pressure → acute HF with shock + renal failure ^[2]^[3]	When the PDA closes, the LV suddenly faces an enormous afterload increase (the entire lower-body vascular resistance is concentrated at the coarctation). The neonatal LV, which has not had time to hypertrophy, cannot cope → acute decompensation with biventricular failure
Pulmonary oedema	Acute LV failure → elevated LV end-diastolic pressure → elevated LA pressure → elevated pulmonary venous pressure → fluid transudation into alveoli
Hepatomegaly	Back-pressure from LV failure → RV failure → hepatic venous congestion

Death within ≤1 week if tight stenosis and untreated ^[2]^[3]. This is the most feared acute complication and the reason critical CoA is a paediatric emergency.

Feature	Pathophysiological Basis
Oliguria/anuria and rising creatinine	Kidneys lie distal to the CoA → acute renal hypoperfusion upon duct closure → pre-renal AKI → if prolonged, intrinsic renal injury (acute tubular necrosis)
Severe metabolic acidosis	Due to ischaemic colitis and AKI upon duct closure ^[2]^[3]. Both the gut and kidneys are hypoperfused → lactic acidosis from anaerobic metabolism in ischaemic tissues + impaired renal acid excretion

Feature	Pathophysiological Basis
Abdominal distension, bloody stools, feeding intolerance	The mesenteric circulation is distal to the CoA → gut ischaemia upon duct closure. In severe cases this can progress to NEC (mucosal necrosis, pneumatosis intestinalis, perforation). This is a recognised neonatal complication of critical CoA

B. Complications of Intervention (Perioperative)

Complication	Mechanism	Incidence / Notes
Paradoxical (post-coarctectomy) hypertension	After relief of the obstruction, blood flow to the previously underperfused mesenteric vascular bed increases acutely → mesenteric arteritis. Simultaneously, baroreceptor resetting and sympathetic/RAAS activation cause a catecholamine surge → acute severe hypertension in the first 24–72 hours post-operatively	Common (seen in up to 50–80% in the immediate post-op period). Treated with short-acting IV antihypertensives (esmolol, nitroprusside). Can cause abdominal pain ("post-coarctectomy syndrome")
Post-coarctectomy syndrome	A specific manifestation of paradoxical HTN → acute mesenteric arteritis from sudden reperfusion of the mesenteric bed → abdominal pain, ileus, bowel wall oedema. Rarely progresses to bowel infarction	Typically resolves with BP control and bowel rest. More common after repair of severe, long-standing coarctation
Recurrent laryngeal nerve palsy	The left recurrent laryngeal nerve loops around the aortic arch/ligamentum arteriosum — it is at risk of injury during dissection of the coarctation site	Presents with hoarseness, weak cry in neonates, risk of aspiration. Usually temporary; permanent injury is rare
Phrenic nerve injury	The phrenic nerve runs along the mediastinum and can be injured during surgical dissection	Ipsilateral diaphragmatic paralysis → respiratory compromise, especially significant in neonates who are diaphragm-dependent breathers
Chylothorax	Injury to the thoracic duct (which runs in the posterior mediastinum near the aortic arch) during surgery → lymphatic fluid leaks into the pleural space	Presents as milky pleural effusion post-operatively. Managed with chest drainage, medium-chain triglyceride diet (bypasses lymphatic absorption), and rarely surgical thoracic duct ligation
Spinal cord ischaemia (paraplegia)	During aortic cross-clamping, the intercostal arteries that feed the anterior spinal artery (artery of Adamkiewicz, typically T9–T12) are temporarily occluded → spinal cord ischaemia	Very rare (< 0.5%) in paediatric CoA repair. Risk increases with prolonged cross-clamp time. Lower risk in neonates (shorter aorta, shorter clamp time). Patients with well-developed collaterals are relatively protected
Wound infection / bleeding	Standard surgical risks	Low incidence in experienced centres

Complication	Mechanism
Femoral artery injury	Vascular access complications — the femoral artery in children is small and prone to spasm, dissection, or thrombosis. More common in younger/smaller patients
Aortic wall dissection	Balloon inflation may extend beyond the intima/media → aortic dissection at the intervention site
Aneurysm formation at dilatation site	Controlled tearing of the aortic wall by the balloon can weaken the wall → pseudoaneurysm or true aneurysm. Reported in 5–10% after balloon angioplasty. Requires long-term imaging surveillance
Stent migration or fracture	Mechanical failure of the stent over time, especially with growth and repeated dilatation
In-stent restenosis	Neointimal hyperplasia within the stent → recurrent narrowing

C. Long-Term Complications (Even After Successful Repair)

This is the most important section for clinical practice and exams. Even after "successful" repair with no residual gradient, patients with CoA are not cured. They carry lifelong risks that necessitate ongoing surveillance.

Long-term outcome: 10-year survival generally > 90% [2][3]

Feature	Detail
Definition	Recurrence of haemodynamically significant narrowing at or near the original coarctation/repair site
Incidence	Restenosis 5–15% after surgery; 40% (young infants) vs 8% (adolescents) after balloon angioplasty ^[2]^[3]
Mechanism	Scar tissue formation and fibrosis at the anastomotic site; residual ductal tissue; growth mismatch (the repaired segment may not grow proportionally with the child)
Detection	Regular echo follow-up; exercise testing may unmask a gradient not apparent at rest; MRI for definitive assessment
Treatment	Balloon angioplasty ± stent is the preferred first-line for re-coarctation ^[2]^[3]. Re-do surgery is reserved for failed catheter intervention or complex anatomy

Why is re-coarctation more common in young infants? (1) The aortic tissue in neonates is immature and more prone to elastic recoil and fibrosis. (2) Small vessel calibre means proportionally greater scar formation relative to lumen size. (3) Growth may outpace the repaired segment. (4) If repair involved ductal tissue, residual ductal tissue may constrict.

Feature	Detail
Definition	Systemic hypertension persisting or developing de novo after successful repair with no residual gradient
Incidence	Up to 25–30% of patients develop late/recurrent hypertension ^[2]^[3]
Mechanism	Systolic HTN may persist despite repair due to permanent alteration of arterial mechanics and physiology ^[2]^[3]. Specifically:

The mechanisms of persistent hypertension deserve detailed explanation because they are commonly tested:

Mechanism Category	Explanation
Arterial wall stiffness	The ascending aorta and arch were exposed to chronic supranormal pressures before repair → structural remodelling with increased collagen deposition and reduced elastin → permanent reduction in compliance. This increases pulse wave velocity and augments systolic pressure
Baroreceptor resetting	The carotid and aortic baroreceptors were chronically exposed to high BP → their "set point" for triggering sympatholytic responses shifts upward. Even after the mechanical obstruction is relieved, the baroreceptors continue to "accept" a higher BP as normal
RAAS activation	Chronic renal hypoperfusion (kidneys are distal to the CoA) → juxtaglomerular apparatus upregulation → sustained renin-angiotensin-aldosterone system activation. This may not fully reverse after repair
Endothelial dysfunction	Abnormal shear stress patterns both proximal and distal to the CoA cause chronic endothelial damage → impaired production of nitric oxide (the key endothelium-derived vasodilator) → impaired vasodilatory reserve

Clinical implication: Persistent hypertension is the single biggest long-term risk factor for cardiovascular morbidity and mortality in repaired CoA patients. It drives the development of premature atherosclerosis, LVH, heart failure, stroke, and aortic complications. Aggressive BP management is essential.

Feature	Detail
Sites	(1) At the repair site (especially after patch aortoplasty — now largely abandoned for this reason). (2) Ascending aorta (due to intrinsic aortopathy — the same connective tissue abnormality that caused the CoA affects the entire aortic wall)
Mechanism	- At repair site: weakening of the aortic wall from surgery or balloon dilatation → progressive dilatation → aneurysm → risk of dissection/rupture - Ascending aorta: the aortic wall has abnormal structure (deficient elastic fibres, increased collagen) → cystic medial necrosis-like changes → dilatation and dissection risk. This is worsened by chronic hypertension
Detection	Cardiac MRI is the gold standard for surveillance; should be performed every 3–5 years lifelong
Risk is higher in	Patients with bicuspid aortic valve (shared aortopathy), those with persistent hypertension, and those who had patch aortoplasty

Aortopathy in CoA – An Intrinsic Problem

CoA is not just a "local narrowing" — it is a manifestation of a generalised aortopathy. The entire aortic wall has abnormal histology (similar to that seen in bicuspid aortic valve aortopathy). This is why:

Aneurysms can form even in segments of the aorta that were never narrowed or surgically touched
The risk persists lifelong regardless of the quality of repair
Patients with CoA + BAV have additive risk This concept is critical for understanding why lifelong surveillance is mandatory.

Feature	Detail
Mechanism	Persistent hypertension → accelerated atherosclerosis → premature coronary artery disease and cerebrovascular disease. The chronic endothelial dysfunction and arterial stiffness in CoA patients further accelerate this process
Clinical relevance	Patients with repaired CoA have a significantly higher risk of cardiovascular events compared to the general population, even decades after repair. This is one of the leading causes of late mortality
Prevention	Aggressive BP control, lipid management, healthy lifestyle counselling (important even in adolescence)

Feature	Detail
Association	CoA is a known risk factor for intracranial (berry) aneurysms ^[2]^[3]^[4]
Mechanism	The same connective tissue/vascular wall abnormality that causes CoA predisposes to aneurysm formation at arterial bifurcations within the circle of Willis. Additionally, chronic upper-body hypertension increases haemodynamic stress on intracranial vessels → promotes aneurysm growth and rupture
Presentation	Subarachnoid haemorrhage (SAH) when ruptured ^[4] — sudden-onset severe headache ("thunderclap headache"), meningism, reduced consciousness
Screening	MRA of the head should be considered in older children, adolescents, and adults with CoA, particularly those with longstanding or poorly controlled hypertension

Berry aneurysms are usually at arterial bifurcations, majority along the circle of Willis, 90% in the anterior circulation ^[4]. Risk of rupture is related to aneurysm size and hypertension.

Feature	Detail
Types	Atrial fibrillation, atrial flutter, ventricular arrhythmias
Mechanism	(1) LVH from chronic pressure overload → myocardial fibrosis → arrhythmogenic substrate. (2) Surgical scarring in the aortic region may disrupt conduction pathways. (3) Persistent HTN → atrial dilatation → predisposes to atrial arrhythmias
Clinical relevance	May present with palpitations, syncope, or sudden cardiac death in extreme cases

Feature	Detail
Mechanism	Turbulent blood flow at the coarctation site (or residual jet post-repair) damages the endothelium → nidus for bacterial adhesion and vegetation formation. Associated bicuspid aortic valve further increases IE risk
Clinical relevance	Antibiotic prophylaxis is no longer routinely recommended for isolated CoA (per current AHA/ESC guidelines) unless there is a prosthetic valve, prior IE, or unrepaired cyanotic CHD. However, good dental hygiene should be emphasised

Feature	Detail
Association	Present in up to 50–80% of CoA patients ^[2]^[3]
Complications	The BAV may progressively develop: (1) Aortic stenosis (fibrocalcific degeneration — though this is usually an adult complication, it can begin in adolescence), (2) Aortic regurgitation (prolapse of a bicuspid leaflet), (3) Ascending aortic dilatation (BAV aortopathy)
Surveillance	Echo assessment of the aortic valve at every follow-up

Category	Complications	Key Mechanism
Acute (untreated neonatal CoA)	HF with cardiogenic shock, AKI, ischaemic colitis/NEC, metabolic acidosis, multi-organ failure, death	Duct closure → acute lower-body hypoperfusion
Perioperative (surgical)	Paradoxical HTN, post-coarctectomy syndrome, recurrent laryngeal nerve palsy, phrenic nerve injury, chylothorax, spinal cord ischaemia (rare)	Surgical manipulation of aortic arch structures; reperfusion injury
Perioperative (catheter)	Femoral artery injury, aortic dissection, aneurysm at dilatation site, stent complications	Mechanical disruption of vessel wall
Long-term	Re-coarctation (5–15% surgery, 40%/8% balloon), persistent HTN, aortic aneurysm/dissection, IHD/stroke, berry aneurysm rupture, arrhythmia ^[2]^[3]	Residual aortopathy, vascular remodelling, RAAS activation, endothelial dysfunction

Aspect	Detail
Growth	Neonates with critical CoA and prolonged shock may have growth faltering. After successful repair, catch-up growth is expected. Persistent HTN and heart failure impair growth
Exercise	Children with successfully repaired CoA and no residual obstruction or significant HTN can generally participate in most physical activities. Those with residual gradient, HTN, or aneurysm may need exercise restriction (avoid heavy isometric exercise which acutely raises systemic BP)
Neurodevelopment	Neonates who experienced prolonged shock or required prolonged NICU stay may have neurodevelopmental sequelae. Developmental follow-up is recommended
Psychosocial	Living with a lifelong cardiac condition requires ongoing family-centred support, age-appropriate education about the condition, and transition planning to adult cardiology services
Pregnancy counselling (adolescents)	Female adolescents with repaired CoA should receive pre-conception counselling — pregnancy increases cardiovascular demands; risk of aortic dissection during pregnancy, especially if there is residual CoA, aneurysm, or uncontrolled HTN. Contraception counselling is also appropriate

Lifelong Disease – Not a One-Time Fix

A common misconception among families (and sometimes clinicians) is that surgical repair of CoA is a "cure." CoA is a lifelong cardiovascular condition. Even after technically perfect repair with no residual gradient:

25–30% develop persistent hypertension
5–15% develop re-coarctation
Risk of aneurysm, dissection, premature atherosclerosis, and berry aneurysm rupture persists lifelong
All patients need lifelong cardiology follow-up with regular BP monitoring, echo, and periodic MRI

Communicate this clearly to families in an age-appropriate and supportive manner.

High Yield Summary – Complications of CoA

Acute complications of untreated critical CoA:

HF with cardiogenic shock upon duct closure (day 2) → death within ≤1 week ^[2]^[3]
Severe metabolic acidosis from ischaemic colitis and AKI ^[2]^[3]

Perioperative complications:

Paradoxical hypertension and post-coarctectomy syndrome (mesenteric arteritis)
Recurrent laryngeal nerve palsy, phrenic nerve injury, chylothorax
Spinal cord ischaemia (rare, < 0.5%)
Balloon/stent: femoral artery injury, aortic dissection, aneurysm at site

Long-term complications (even after successful repair) ^[2]^[3]:

Re-coarctation: 5–15% surgery; 40% young infants vs 8% adolescents after balloon
Persistent hypertension: ~25–30%; due to altered arterial mechanics, baroreceptor resetting, RAAS activation, endothelial dysfunction
Aortic aneurysm/dissection: at repair site or ascending aorta (generalised aortopathy)
IHD and stroke: from premature atherosclerosis driven by persistent HTN
Berry aneurysm rupture (SAH): intrinsic association + chronic upper-body HTN
Arrhythmia: from LVH, fibrosis, surgical scarring

Key message: CoA is a lifelong cardiovascular condition requiring lifelong surveillance even after successful repair.

Coarctation Of The Aorta

Definition

Epidemiology

Anatomy and Normal Function

Normal Aortic Arch Anatomy (Paediatric Context)

The Ductus Arteriosus — Why It Matters

Why the Isthmus?

Aetiology (Focus on Hong Kong Context)

Cause

Risk Factors

Pathophysiology

The Fundamental Problem

Presentation Pattern 1: Severe/Critical CoA — Duct-Dependent Systemic Circulation [1][2][3]

Presentation Pattern 2: Less Severe (Non-Duct-Dependent) CoA [2][3]

Associated Lesion Pathophysiology

Classification

By Anatomy (Historical vs. Modern)

By Clinical Presentation (More Clinically Useful)

By Associated Lesions

Clinical Features

Symptoms

A. Severe/Critical CoA (Duct-Dependent) — Neonatal Presentation [2][3]

B. Non-Critical CoA (Non-Duct-Dependent) — Older Infant/Child/Adolescent [2][3]

Signs

A. Duct-Dependent (Critical CoA) Signs [2][3]

B. Non-Duct-Dependent (Older Child/Adolescent) Signs [2][3]

Four-Limb Blood Pressure — The Diagnostic Manoeuvre

Pulse Oximetry Screening

Summary of Pathophysiology → Clinical Features Connection

Active Recall - Coarctation of the Aorta (Clinical Features & Pathophysiology)

References

Conceptual Framework: What Are We Actually Differentiating?

Differential Diagnosis Mermaid Diagram

Part A: Differential Diagnosis in the Neonate with Shock/Collapse

1. Other Duct-Dependent Systemic Circulation Lesions

a) Interrupted Aortic Arch (IAA) [2]

b) Critical Aortic Stenosis (Critical AS)

c) Hypoplastic Left Heart Syndrome (HLHS)

2. Cardiogenic Shock from Non-Structural Causes

a) Neonatal Myocarditis

b) Supraventricular Tachycardia (SVT) with Heart Failure

3. Non-Cardiac Causes of Neonatal Shock

a) Neonatal Sepsis

b) Inborn Errors of Metabolism (Metabolic Crisis)

c) Non-Accidental Injury (NAI) / Abusive Head Trauma

Part B: Differential Diagnosis in the Older Child/Adolescent

1. Vascular Causes (Mimicking CoA's Vascular Findings)

a) Mid-Aortic Syndrome (MAS)

b) Takayasu Arteritis [6]

c) Williams Syndrome Arteriopathy [2]

d) PHACE Syndrome [7]

2. Renal Causes of Paediatric Hypertension

a) Renal Parenchymal Disease

b) Renal Artery Stenosis (RAS)

3. Endocrine Causes of Paediatric Hypertension

a) Phaeochromocytoma / Paraganglioma [8][9]

b) Other Endocrine Causes

4. Other Cardiac Causes

a) Aortic Stenosis (Valvular)

b) Turner Syndrome with Multiple Cardiac Lesions [2]

Summary Table: Key Differentiating Features

The "Can't-Miss" Approach: When to Think CoA

Active Recall - Differential Diagnosis of CoA

References

Diagnostic Criteria

What Constitutes a Diagnosis of CoA?

Haemodynamic Criteria for Significance

Diagnostic Algorithm

Investigation Modalities: Detailed Findings and Interpretation

1. Bedside Investigations

a) Four-Limb Blood Pressure Measurement

b) Pulse Oximetry (Pre-ductal vs. Post-ductal)

c) Femoral Pulse Palpation

2. Blood Investigations

a) Bloods: Severe Metabolic Acidosis [2][3]

b) Additional Bloods (Association Screening)

3. Chest X-Ray (CXR)

4. Electrocardiogram (ECG)

5. Echocardiography (Echo)

What Echo Demonstrates