Coarctation of the aorta is a congenital narrowing of the aorta, typically near the ductus arteriosus, that presents 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

Coarctation of the aorta (CoA) — from the Latin coarctare, meaning "to press together" or "to narrow" — is a congenital narrowing of the aorta, typically a discrete stenosis of the descending thoracic aorta at or just distal to the insertion of the ductus arteriosus (juxtaductal) ^[1]^[2]^[3]. Less commonly, it may present as a long-segment narrowing or diffuse tubular hypoplasia of the aortic arch ^[2]^[3].

The key concept: the narrowing creates a mechanical obstruction to left ventricular outflow, dividing the systemic circulation into a high-pressure proximal bed (head, upper limbs) and a low-pressure distal bed (lower body, kidneys, gut). The clinical consequences depend entirely on the severity of the narrowing and whether the ductus arteriosus remains patent.

Core Concept — Two Populations

Think of CoA as producing two distinct clinical phenotypes:

Neonates with severe/critical CoA → duct-dependent systemic circulation → presents with shock on ductal closure
Older children/adolescents with moderate CoA → presents with upper limb hypertension, murmur, or incidentally discovered femoral pulse deficit

Feature	Detail
Proportion of all CHD	~6–9% (some sources say 4–6%, others up to 9%; GC lecture and senior notes cite ~9%) ^[1]^[2]^[3]
Incidence	~4 per 10,000 live births ^[2]^[3]
Sex ratio	Male > Female (≈59:41%) ^[2]^[3]
Isolated vs. associated	Rarely truly isolated; most have at least one associated lesion
Age at presentation	Bimodal: neonatal period (critical CoA) or later childhood/adolescence (moderate CoA)

Hong Kong context: Congenital heart disease screening is performed in all newborns in Hong Kong public hospitals. CoA is one of the critical congenital heart diseases (CCHDs) targeted by pulse oximetry screening, although CoA is notoriously the lesion most likely to be missed by pulse oximetry alone (because pre-ductal saturations are normal) — hence the emphasis on four-limb blood pressure and femoral pulse palpation in the neonatal check.

Risk Factors and Associations

Turner syndrome (45,X) — CoA is the classic cardiac lesion of Turner syndrome ^[2]^[3]. Up to 10–15% of Turner syndrome patients have CoA. Always check for Turner features (short stature, webbed neck, lymphoedema, shield chest, wide-spaced nipples) in any girl with CoA.
Familial clustering — most cases are sporadic, but there is a small heritable component; first-degree relatives of CoA patients have a slightly increased risk of left-sided obstructive lesions ^[2]^[3].
Bicuspid aortic valve (BAV) — present in up to 50–85% of CoA patients. BAV is the single most common associated anomaly ^[2]^[3].

Association	Clinical Significance
Bicuspid aortic valve	Very common (~50–85%); may cause aortic stenosis or regurgitation later in life
Hypoplasia of the transverse aortic arch	Worsens the obstruction; may require more complex surgical repair
Ventricular septal defect (VSD)	Common association; large VSD + CoA = severe neonatal HF
Patent ductus arteriosus (PDA)	In neonates, the PDA is the lifeline; its closure precipitates crisis
Mitral valve anomalies	Parachute mitral valve, supramitral ring (Shone complex)

Shone Complex

Shone complex = the association of multiple left-sided obstructive lesions: (1) supramitral ring, (2) parachute mitral valve, (3) subaortic stenosis, and (4) coarctation of the aorta. Think of it as "serial obstruction" at every level of the left heart.

Berry (intracranial saccular) aneurysms — CoA patients have an increased prevalence of cerebral aneurysms, which predispose to subarachnoid haemorrhage, especially if hypertension persists ^[2]^[3]^[5].
This is the same association seen with adult polycystic kidney disease and connective tissue disorders — all share a vascular wall abnormality.

To understand CoA, you must know the normal aortic arch anatomy:

Ascending aorta → Aortic arch → (branches: brachiocephalic trunk, left common carotid, left subclavian) → Isthmus → Descending aorta

The aortic isthmus is the segment between the origin of the left subclavian artery and the insertion of the ductus arteriosus (ligamentum arteriosum after closure). This is the most common site of coarctation.
Why here? During fetal life, the isthmus carries relatively little blood (most right ventricular output bypasses the lungs via the ductus arteriosus to the descending aorta). The isthmus is therefore a naturally narrow segment. After birth, when the ductus closes and the entire cardiac output must pass through the isthmus, any additional narrowing at this site becomes haemodynamically significant.

Fetal Circulation Review (Essential for Understanding)

In the fetus:

RV output → pulmonary artery → ductus arteriosus → descending aorta (bypasses lungs)
LV output → ascending aorta → head/upper limbs + some flow across isthmus to descending aorta
The ductus arteriosus effectively provides a "bypass" around any aortic narrowing

At birth:

First breath → fall in pulmonary vascular resistance → increased pulmonary blood flow
Rise in PaO₂ + fall in circulating prostaglandins → ductus arteriosus closes (functional closure within hours, anatomical closure by 2–3 weeks)
Now ALL systemic blood flow must traverse the narrowed segment
If the coarctation is severe → catastrophic fall in distal perfusion

Aetiology and Pathophysiology

Two main theories explain why CoA occurs:

Ductal tissue theory (most widely accepted): Ectopic ductal (smooth muscle) tissue extends into the aortic wall at the isthmus. When the ductus closes after birth, this ectopic tissue also constricts, causing the aortic lumen to narrow. This explains why CoA often presents acutely when the duct closes (day 2–7 of life).
Flow theory (haemodynamic theory): Reduced antegrade flow through the aortic isthmus in utero (e.g., because of associated lesions like VSD that divert LV output, or left-sided obstructive lesions) leads to underdevelopment/hypoplasia of the isthmus. This theory better explains the long-segment/tubular hypoplasia variant.

In reality, both mechanisms likely contribute.

Pathophysiology — Two Clinical Scenarios

Key points from the lecture slides:

"Complete obstruction → no blood flow to descending aorta → bowel ischaemia / necrotizing enterocolitis, renal failure, poor perfusion resulting in metabolic acidosis" ^[1]

"Can guarantee baby will be dead in next few days if not discovered and treated" ^[1]

"Increased afterload, left ventricle extreme pressure overload, and fails" ^[1]

Why does the RV support systemic circulation before ductal closure?

Before the duct closes, the RV ejects blood through the pulmonary artery → ductus arteriosus → descending aorta, effectively bypassing the coarctation
That's why you feel an RV impulse (parasternal heave) rather than an LV impulse in duct-dependent CoA — the RV is doing the work of perfusing the lower body ^[2]^[3]
Once the duct closes, this bypass is lost, and the LV is suddenly faced with an impossible afterload

Why day 2?

The ductus arteriosus typically begins to functionally close within 12–24 hours of birth (triggered by rising PaO₂ and falling prostaglandin E₂ levels)
Day 2 neonatal HF with shock and oliguria is the classical presentation ^[2]^[3]
Death can occur within 1 week if the stenosis is tight and unrecognised ^[2]^[3]

When the narrowing is less severe, some blood can still pass through the isthmus even after ductal closure. The child survives the neonatal period but develops chronic consequences:

Why upper limb hypertension?

The coarctation sits distal to the branches supplying the head and upper limbs (brachiocephalic, left common carotid, left subclavian)
Blood proximal to the coarctation is at high pressure (the LV is generating more force to overcome the obstruction)
Blood distal to the coarctation is at low pressure (reduced flow)
This creates the classic upper limb hypertension with low lower limb pressures — the hallmark of CoA in older children

Why does RAAS activation occur?

The kidneys (supplied by the abdominal aorta, distal to the coarctation) "see" reduced renal perfusion pressure
This triggers the renin-angiotensin-aldosterone system, further raising systemic blood pressure
This is a major reason why systolic hypertension may persist even after successful repair — chronic RAAS activation and permanent alteration of arterial mechanics and physiology ^[2]^[3]

Why collateral circulation?

The body tries to bypass the obstruction by enlarging alternative pathways from the high-pressure proximal aorta to the low-pressure distal aorta
Main collaterals: internal mammary arteries → intercostal arteries → descending aorta
These dilated intercostal arteries erode the inferior margins of the ribs → rib notching (Roesler sign) on CXR, typically visible from age ~5 years onwards
A continuous murmur throughout the chest may be heard in older children with well-developed collaterals ^[2]^[3]

Persistent Hypertension After Repair

A very common exam point: Systolic hypertension may persist despite successful repair of CoA ^[2]^[3]. This is due to:

Chronic structural changes in the pre-coarctation arterial wall (reduced compliance, increased stiffness)
Resetting of baroreceptors
Persistent RAAS activation
Possible residual arch hypoplasia

This means all CoA patients need lifelong BP monitoring even after "successful" repair.

Classification

Type	Description
Discrete (juxtaductal)	Most common; focal shelf/ridge of tissue at the insertion of the ductus arteriosus ^[2]^[3]
Long-segment / tubular hypoplasia	Less common; diffuse narrowing of the aortic arch and/or isthmus ^[2]^[3]
Arch interruption	Most severe form (technically "interrupted aortic arch" rather than CoA proper); complete discontinuity of the arch

Type	Age	Mechanism
Duct-dependent (critical)	Neonate (typically day 2–7)	Severe narrowing; lower body perfusion depends entirely on PDA
Non-duct-dependent	Infant, child, adolescent	Moderate narrowing; some antegrade flow persists after ductal closure

Pre-ductal (infantile type): narrowing proximal to the ductus — often with tubular hypoplasia and associated intracardiac lesions
Post-ductal (adult type): narrowing distal to the ductus — typically discrete, well-developed collaterals
Juxtaductal: at the level of the ductus — most common

Modern practice prefers describing the anatomy (discrete vs. tubular hypoplasia, presence of arch hypoplasia) rather than using the pre/post-ductal terminology.

Clinical Features

A. Symptoms

The symptoms depend entirely on severity and timing:

Symptom	Pathophysiological Basis
Acute collapse / shock (day 2–7)	Ductal closure → sudden loss of lower body perfusion → cardiogenic + distributive shock ^[1]^[2]^[3]
Poor feeding / lethargy	Global hypoperfusion including CNS; also heart failure reduces feeding tolerance
Tachypnoea / respiratory distress	Pulmonary oedema from acute LV failure (LV cannot cope with sudden extreme afterload)
Oliguria / anuria	Renal hypoperfusion distal to coarctation → pre-renal AKI ^[1]^[2]
Abdominal distension	Bowel ischaemia → ileus; potential necrotising enterocolitis (NEC) ^[1]
Mottled / grey skin (lower body)	Poor perfusion to lower body; differential cyanosis may be present (pink upper body, grey/blue lower body)
Irritability / inconsolable crying	Visceral pain from bowel ischaemia; metabolic acidosis

Timeline is Everything

A well-appearing neonate who suddenly deteriorates on day 2–3 of life with shock, grey colour, absent femoral pulses, and metabolic acidosis → think critical CoA (or other duct-dependent lesions like interrupted aortic arch, critical aortic stenosis, HLHS). This is a paediatric emergency.

Symptom	Pathophysiological Basis
Asymptomatic (most common!)	Gradual adaptation; collateral circulation develops; often detected incidentally ^[2]^[3]
Headaches	Upper limb/cerebral hypertension
Epistaxis	Upper body hypertension → nasal mucosal vessel fragility
Leg pain / claudication with exercise	Lower limb hypoperfusion exacerbated by increased demand during exercise
Cold feet	Chronic lower limb hypoperfusion
Exertional dyspnoea	LV failure from chronic pressure overload; limited cardiac output increase during exercise

"Asymptomatic with incidental finding of murmur or systemic HTN (even if narrowing is moderate/severe)" ^[2]^[3] — CoA is a classic cause of secondary hypertension in children and young adults. Always check femoral pulses in any young patient with hypertension!

B. Signs

The Most Important Physical Sign

"Most important physical sign → absence of femoral pulse" ^[1]

This is the single most critical finding. In every neonatal examination, you MUST palpate the femoral pulses. A weak or absent femoral pulse is CoA until proven otherwise.

Sign	Mechanism
Weak or absent lower limb (LL) pulses	"Only reliable sign of this condition before ductus closes" ^[2]^[3]. No blood flow reaching descending aorta distal to coarctation while duct is closing
RV impulse (parasternal heave)	"Systemic circulation is supported by RV" ^[2]^[3] via the PDA; RV is doing the work of perfusing the lower body
Inaudible or soft ejection systolic murmur (ESM) at LUSB	Blood barely flowing through the tight narrowing; flow is too sluggish to generate a loud murmur ^[2]^[3]
Collapse, shock, oliguria after ductal closure	Complete loss of lower body blood supply ^[1]^[2]^[3]
Metabolic acidosis (on blood gas)	Tissue hypoperfusion → anaerobic metabolism → lactic acidosis ^[1]
Differential cyanosis	Lower body cyanosed (deoxygenated blood from RV via closing PDA); upper body pink. If there is an associated TGA, reverse differential cyanosis may occur (upper body cyanosed, lower body pink)
Hepatomegaly	Congestive heart failure → hepatic congestion
Gallop rhythm (S3)	Volume-overloaded, failing LV

Sign	Mechanism
Weak LL pulses with radiofemoral delay	Pulse wave must travel through collateral pathways (tortuous, longer) to reach femorals → delayed and dampened pulse ^[2]^[3]
Blood pressure discrepancy: upper > lower limbs	Normally, lower limb systolic BP is 10–20 mmHg higher than upper limb (due to amplification in longer vessel). In CoA, the lower limb BP is lower than upper limb. A gradient of > 20 mmHg is significant.
Upper limb hypertension	Proximal to obstruction → elevated pressure ^[2]^[3]
LV impulse (heaving apex beat)	Chronic LV pressure overload → compensatory LVH → forceful, sustained apex beat ^[2]^[3]
ESM at left upper sternal border (LUSB), radiating to left interscapular region	Turbulent flow across the narrowed segment; radiation to the back because the coarctation is posterior (descending aorta) ^[2]^[3]
± Soft continuous murmur throughout the chest	"In older children with well-developed collaterals" ^[2]^[3] — flow through dilated intercostal/internal mammary collateral arteries
± Ejection click	If associated bicuspid aortic valve (BAV)
Visible arterial pulsations	Pulsatile suprasternal notch, visible neck pulsations from hypertensive proximal aorta

How to check for radiofemoral delay:

Simultaneously palpate the right radial/brachial pulse and the right femoral pulse
In CoA, the femoral pulse is felt after the radial pulse (normally they are synchronous)
This delay reflects the longer, more tortuous path via collaterals

Four-limb blood pressure measurement:

Measure BP in both arms and one leg (or both legs)
Normal: leg systolic BP ≥ arm systolic BP (actually slightly higher due to pulse amplification)
CoA: arm systolic BP > leg systolic BP by > 20 mmHg
If the left subclavian artery origin is involved in or proximal to the coarctation, left arm BP may also be low → always compare right arm to legs

CoA is listed as a cardiovascular cause of secondary hypertension in the hypertension workup ^[4]^[6]. In any child or young adult with hypertension, palpate femoral pulses and measure four-limb BPs.

Feature	Duct-Dependent (Critical)	Non-Duct-Dependent
Age at presentation	Day 2–7 of life	Infancy to adulthood
Typical presentation	Shock, collapse, oliguria	Incidental murmur, HTN
Femoral pulses	Absent or very weak	Weak with radiofemoral delay
Precordial impulse	RV impulse	LV impulse (heaving apex)
Murmur	Soft/inaudible ESM	ESM at LUSB → back
Collateral murmurs	No (no time to develop)	± continuous murmur
CXR — rib notching	No	Yes (after ~5 years)
Urgency	LIFE-THREATENING EMERGENCY	Elective workup

Additional Pathophysiological Concepts

CoA is associated with berry (saccular) aneurysms of the circle of Willis ^[2]^[3]^[5]. The proposed mechanisms:

Haemodynamic stress: chronic upper body hypertension → increased wall stress on cerebral arteries → aneurysm formation at bifurcation points
Shared developmental vascular wall abnormality: some intrinsic weakness of the arterial wall may predispose to both CoA and aneurysm formation
Risk of subarachnoid haemorrhage if aneurysm ruptures — this is a late complication, more relevant in unrepaired or late-repaired CoA with persistent hypertension

In critical CoA, the gut is supplied by the superior and inferior mesenteric arteries (branches of the abdominal aorta, distal to the coarctation)
When the duct closes → sudden loss of mesenteric blood flow → bowel ischaemia → NEC ^[1]
This is different from classic NEC of prematurity (which is multifactorial), but the end result is similar: mucosal injury, bacterial translocation, pneumatosis intestinalis

CoA is a cardiovascular cause of secondary hypertension. In the workup of hypertension in a child or young adult:

Always palpate femoral pulses
Always measure four-limb blood pressures
Other causes to consider in the differential: renal artery stenosis, Conn syndrome (primary aldosteronism), phaeochromocytoma, Cushing syndrome, obesity/OSA ^[4]^[6]

High Yield Summary

Definition: Discrete narrowing of the descending aorta, usually at the site of the ductus arteriosus insertion (juxtaductal).

Epidemiology: ~6–9% of CHD; 4/10,000 live births; M > F (59:41%).

Key Associations: Turner syndrome, bicuspid aortic valve (~50–85%), VSD, transverse arch hypoplasia, berry aneurysms.

Two Presentations:

Critical/Duct-dependent (neonate): Day 2–7 collapse, shock, absent femoral pulses, metabolic acidosis, renal failure, bowel ischaemia → "Can guarantee baby will be dead in next few days if not discovered and treated"
Non-duct-dependent (older child): Asymptomatic HTN, incidental murmur, radiofemoral delay, weak femoral pulses, rib notching on CXR

Cardinal Sign: Absent or weak femoral pulses — the single most important finding.

BP Pattern: Upper limb BP > Lower limb BP (reversed from normal).

Murmur: ESM at LUSB radiating to left interscapular area (back); ± continuous murmur from collaterals.

Persistent HTN after repair is common — lifelong BP monitoring required.

CoA is a recognized cause of secondary hypertension in children and young adults — always check femoral pulses in any young hypertensive patient.

Active Recall - Coarctation of the Aorta

^[1] Lecture slides: Block C - Heart failure and cyanosis in children: acyanotic and cyanotic congenital heart disease.pdf (Coarctation of the aorta section) ^[2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p210, Coarctation of Aorta) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p190, Section 3.7.4 Coarctation of Aorta) ^[4] Senior notes: Block A - High blood pressure: hypertension.pdf (Secondary causes of hypertension) ^[5] Senior notes: Ryan Ho Neurology.pdf (p87, Cerebral Aneurysm — CoA as a risk factor) ^[6] Senior notes: Block A - Endocrine Data Interpretation.pdf (Cardiovascular causes of secondary hypertension including coarctation)

Differential Diagnosis of Coarctation of the Aorta in Paediatrics

The differential diagnosis of CoA is best approached by thinking about the presenting clinical scenario rather than memorising a disjointed list. CoA can present as two fundamentally different clinical pictures, and the DDx for each is different:

Neonatal collapse/shock (critical duct-dependent CoA)
Upper limb hypertension / pulse discrepancy / murmur in an older child or adolescent

We will systematically work through both.

The clinical signs of CoA — absent/weak femoral pulses, upper-lower limb BP discrepancy, shock in a neonate — are not pathognomonic. Several other conditions can mimic these findings, and some of them are even more immediately life-threatening. The key discriminating features are:

Four-limb BP and pulse assessment (the single most informative bedside manoeuvre)
Presence or absence of cyanosis (central vs. differential)
Echocardiographic anatomy
Response to prostaglandin E₁ (PGE₁)

A. Differential Diagnosis of Neonatal Collapse / Duct-Dependent Shock

When a neonate presents at day 2–7 of life with acute cardiovascular collapse, poor perfusion, metabolic acidosis, and weak/absent femoral pulses, think of the following:

Feature	Detail
What it is	Complete discontinuity of the aortic arch (contrast with CoA which is a narrowing). Classified by site: Type A (distal to left subclavian), Type B (between left carotid and left subclavian — most common, associated with DiGeorge/22q11 deletion), Type C (between innominate and left carotid — rarest)
Why it mimics CoA	Absent femoral pulses, neonatal shock on ductal closure, metabolic acidosis — virtually identical presentation to critical CoA
Key difference	IAA Type B has absent left brachial/radial pulse (because left subclavian arises distal to the interruption), whereas in typical CoA the left arm pulse is preserved. Associated with DiGeorge syndrome (22q11.2 deletion) — look for hypocalcaemia, thymic hypoplasia, cleft palate, characteristic facies
Mechanism	Same as critical CoA: duct-dependent systemic circulation. RV perfuses lower body via PDA; ductal closure → catastrophic lower body ischaemia ^[7]^[8]

"E.g. Coarctation of aorta + Interrupted aortic arch + Critical AS + HLHS" — these are all examples of duct-dependent systemic circulation ^[7]^[8].

Feature	Detail
What it is	Underdevelopment of the entire left heart — hypoplastic LV, aortic valve atresia/stenosis, mitral valve atresia/stenosis, hypoplastic ascending aorta and arch ^[8]
Why it mimics CoA	Neonatal shock on ductal closure; weak/absent pulses everywhere (not just lower limbs — the entire systemic circulation is duct-dependent)
Key difference	In HLHS, ALL peripheral pulses are weak (including upper limb), because the ascending aorta is also hypoplastic. In CoA, upper limb pulses are strong and lower limb pulses are weak. Also, HLHS typically has mild cyanosis from mixing at the atrial level. RV has to perfuse both pulmonary and systemic circulations ^[8]
Mechanism	"Survival depends on PDA to ensure adequate systemic perfusion from RV to aorta, and ASD to ensure adequate mixing of oxygenated and deoxygenated blood" ^[8]

CoA vs HLHS — The Pulse Pattern Matters

In CoA: strong upper limb pulses, weak/absent lower limb pulses (gradient across the coarctation). In HLHS: ALL pulses are weak (entire systemic output depends on the PDA and RV). This distinction is clinically critical and frequently examined.

Feature	Detail
What it is	Severe valvar aortic stenosis in a neonate, with duct-dependent systemic circulation
Why it mimics CoA	Neonatal HF, shock, metabolic acidosis, poor perfusion
Key difference	Typically has a harsh systolic murmur at RUSB with a palpable thrill; upper limb pulses are also weak (unlike CoA). Echo distinguishes easily. Associated with a dysplastic, thickened aortic valve rather than a discrete narrowing of the descending aorta
Mechanism	Severely stenotic aortic valve → LV cannot generate sufficient forward flow → duct-dependent systemic circulation, similar to HLHS/CoA

Feature	Detail
Why it mimics CoA	Neonatal sepsis can present with shock, poor perfusion, metabolic acidosis, mottled skin — very similar to duct-dependent cardiac lesion on initial assessment
Key difference	In sepsis, all pulses are equally weak (no upper-lower limb gradient). There is usually fever or hypothermia, raised inflammatory markers (CRP, procalcitonin), positive blood cultures. No structural cardiac abnormality on echo
Clinical pearl	Always consider both CoA AND sepsis simultaneously in a collapsed neonate. Start antibiotics AND prostaglandin E₁ until diagnosis is clear — "treat the treatable"

Feature	Detail
Why it mimics CoA	Acidosis, poor feeding, lethargy, collapse in a neonate
Key difference	No pulse discrepancy. Often associated with hyperammonaemia, hypoglycaemia, or specific organic acid profiles. Family history of consanguinity or neonatal deaths may be present

B. Differential Diagnosis of Upper Limb Hypertension / Unequal Pulses / Murmur in an Older Child

When CoA presents beyond the neonatal period, the clinical features are typically upper limb hypertension, radiofemoral delay, and/or an incidental murmur. The DDx here overlaps with causes of secondary hypertension in children and causes of unequal pulses/BPs.

From the lecture/senior notes, the differential for unequal BP and pulses includes: ^[7]^[8]

Diagnosis	Mechanism of Unequal Pulses	Key Distinguishing Features
Coarctation of aorta	Obstruction at aortic isthmus → high pressure proximal, low pressure distal	Upper > lower limb BP; radiofemoral delay; ESM at LUSB radiating to back
Aortic dissection	Intimal flap or haematoma compresses true lumen → variable obstruction of branch vessels	Tearing chest/back pain; asymmetric arm BPs (radial-radial delay in Type A); extremely rare in children unless connective tissue disorder (Marfan, Ehlers-Danlos) or Kawasaki vasculitis ^[9]
Supravalvular aortic stenosis	Narrowing of aorta above the aortic valve (at the sinotubular junction). The right brachiocephalic artery may receive preferential high-velocity flow (Coanda effect) → right arm BP > left arm BP	Associated with Williams syndrome (7q11.23 deletion — elfin facies, intellectual disability, hypercalcaemia, friendly personality, stellate iris). Right arm BP often > left arm BP (unlike CoA where both arms are high and legs are low)
Peripheral artery disease / arterial thrombosis	Atherosclerosis or embolism obstructing a peripheral vessel	Extremely rare in children unless secondary to umbilical artery catheterisation (femoral artery thrombosis in neonates), Takayasu arteritis, or chronic illness. Localised to specific limb
Takayasu arteritis ("pulseless disease")	Large-vessel vasculitis causing stenosis/occlusion of aorta and its branches	Adolescent females (especially Asian); constitutional symptoms; absent pulses in upper limbs; elevated ESR/CRP; characteristic angiographic findings
Subclavian steal syndrome	Stenosis of subclavian artery proximal to vertebral artery origin → retrograde flow in vertebral artery	Arm BP discrepancy (affected side lower); dizziness on arm exercise; very rare in paediatrics

CoA is a cardiovascular cause of secondary hypertension ^[10]^[11]. The mnemonic from the hypertension lecture is:

ABCDE mnemonic for identifiable causes of hypertension: ^[11]

A — Accuracy of diagnosis (is it genuine HT? white coat hypertension?); Apnoea (obstructive sleep apnoea)

B — Bruit (renal artery stenosis); Bad kidney (renal failure, polycystic kidney disease)

C — Catecholamines (phaeochromocytoma); Cushing's; Coarctation of aorta

D — Drugs (glucocorticoids, oral contraceptives, NSAIDs, stimulants, cocaine)

E — Endocrine (Conn syndrome / primary aldosteronism, thyrotoxicosis, acromegaly)

In paediatrics specifically, the causes of secondary hypertension shift compared to adults:

Age Group	Most Common Cause of HTN	Important Causes to Consider
Neonate	Renal artery thrombosis (post-UAC), CoA, congenital renal disease	Polycystic kidney disease, renal artery stenosis
Infant–6 years	Renal parenchymal disease (most common in young children)	CoA, renovascular disease, Wilms tumour, neuroblastoma
6–12 years	Renal parenchymal disease, renovascular	CoA, endocrine (phaeochromocytoma, CAH, Cushing's)
Adolescent	Essential (primary) HTN becoming more common	Renal, CoA, endocrine, drug-related

High Yield — CoA as a Cause of Secondary HTN in the Young

"Coarctation of aorta" is listed under the cardiovascular causes of secondary hypertension in the hypertension and endocrine data interpretation lectures ^[10]^[11]. Always check femoral pulses and four-limb BPs in any young patient presenting with hypertension — this is a classic exam scenario.

Physical exam clues for secondary HTN that point to CoA ^[11]:

"Auscultation of precordial or chest murmurs → aortic coarctation or aortic disease"
"Diminished and delayed femoral pulses and reduced femoral BP → aortic coarctation or aortic disease"

Since CoA can present with an ESM at the left upper sternal border, other causes of systolic murmur in this region enter the DDx:

Diagnosis	Murmur Characteristics	Distinguishing Features
Coarctation of aorta	ESM at LUSB, radiates to left interscapular region (back)	Radiofemoral delay, upper > lower limb BP
Pulmonary stenosis (PS)	ESM at LUSB, radiates to back and lung fields	Wide, fixed splitting of S2 (if ASD associated); no BP discrepancy; may have ejection click
Atrial septal defect (ASD)	ESM at LUSB (flow murmur across pulmonary valve due to increased RV volume)	Fixed splitting of S2; no pulse discrepancy; often asymptomatic
Patent ductus arteriosus (PDA)	Continuous "machinery" murmur at left infraclavicular area	Bounding pulses, wide pulse pressure
Innocent murmur	Soft, short ESM, varies with position	No associated signs (normal pulses, normal BP, no heave, normal S2)

C. Specific Conditions That Are Closely Associated and Enter the DDx

Both are genetic conditions associated with aortic pathology in paediatrics, but they produce different lesions:

Feature	Turner Syndrome (45,X)	Williams Syndrome (7q11.23 del)
Cardiac lesion	Coarctation of aorta, bicuspid aortic valve	Supravalvular aortic stenosis, peripheral pulmonary stenosis
Facies	No characteristic facies (may have webbed neck, low hairline)	Elfin facies (broad forehead, short nose, full lips, wide mouth)
Personality	Normal	Overly friendly, "cocktail party" personality
Other features	Short stature, streak gonads, lymphoedema, shield chest	Hypercalcaemia, intellectual disability, stellate iris pattern
BP pattern	Upper > lower limb (CoA)	Right arm > left arm (Coanda effect in supravalvular AS)

Marfan syndrome (FBN1 mutation → fibrillin-1 deficiency) predisposes to aortic root dilatation, aortic dissection, and aortic regurgitation ^[12], but not classically to CoA
However, Marfan patients can develop aortic dissection which may mimic CoA on presentation (unequal pulses, BP discrepancy)
Loeys-Dietz syndrome (TGFBR1/2 mutation) is another connective tissue disorder with aggressive aortic disease including CoA-like presentations
Key: CoA is a structural narrowing present from birth; aortic dissection is an acquired intimal tear — the mechanism of unequal pulses is fundamentally different

Clinical Feature	CoA	HLHS	IAA	Sepsis	Supravalvular AS
Upper limb pulses	Strong	Weak	Strong (unless Type B/C)	Weak	Strong (R > L)
Lower limb pulses	Weak/absent	Weak	Absent	Weak	May be normal
BP gradient (arm-leg)	>20 mmHg	No gradient (all low)	Present	No gradient	Variable
Central cyanosis	Absent (unless associated lesion)	Mild	Absent	Absent	Absent
Differential cyanosis	May be present (lower body cyanosed)	May be present	May be present	No	No
Syndrome association	Turner	None specific	DiGeorge (22q11)	None	Williams
Response to PGE₁	Improves lower body perfusion	Improves systemic perfusion	Improves lower body perfusion	No specific response	N/A
Echo findings	Discrete narrowing at isthmus	Hypoplastic LV, aortic and mitral atresia/stenosis	Complete arch discontinuity	Normal heart (usually)	Narrowing above aortic valve

Clinical Pearl — The 'Treat While You Investigate' Approach

In a collapsed neonate, you do NOT wait for echo before starting treatment. Start prostaglandin E₁ AND antibiotics simultaneously. The PGE₁ will re-open the ductus arteriosus and restore lower body perfusion if the cause is a duct-dependent cardiac lesion. The antibiotics cover for sepsis. You can then systematically investigate with echo, blood cultures, metabolic screen etc.

High Yield Summary — Differential Diagnosis of CoA

Neonatal collapse DDx (duct-dependent systemic circulation):

Coarctation of aorta — strong upper, weak lower limb pulses
Interrupted aortic arch — similar to CoA; Type B associated with DiGeorge/22q11
HLHS — ALL pulses weak (entire systemic circulation duct-dependent)
Critical aortic stenosis — harsh murmur at RUSB; all pulses weak
Sepsis — no pulse gradient; fever/hypothermia; raised inflammatory markers
Metabolic crisis — no pulse gradient; specific biochemical abnormalities

Unequal pulses/BP DDx in older children: ^[7]^[8]

CoA, aortic dissection, supravalvular aortic stenosis, peripheral artery disease

Secondary HTN DDx in children — remember ABCDE: ^[11]

A: Accuracy/Apnoea; B: Bruit/Bad kidney; C: Catecholamines/Cushing's/Coarctation; D: Drugs; E: Endocrine

Syndrome associations:

Turner syndrome → CoA + bicuspid aortic valve
Williams syndrome → supravalvular aortic stenosis
DiGeorge (22q11) → interrupted aortic arch (Type B)

Active Recall - Differential Diagnosis of CoA

References

^[7] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p259, p262 — CoA overview, differential diagnosis of unequal BP and pulses) ^[8] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p289 — HLHS, CoA, and interrupted aortic arch comparison in duct-dependent lesions) ^[9] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p905–906 — Aortic dissection differential diagnosis) ^[10] Senior notes: Block A - Endocrine Data Interpretation.pdf (p4 — Cardiovascular causes of secondary hypertension including coarctation of aorta) ^[11] Senior notes: Block A - High blood pressure: hypertension.pdf (p25, p26, p29 — ABCDE mnemonic, physical exam findings for secondary HTN including aortic coarctation) ^[12] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p869 — Marfan syndrome aortic disease)

Diagnostic Criteria, Algorithm, and Investigations for Coarctation of the Aorta in Paediatrics

Diagnostic Criteria

Unlike many medical conditions, CoA does not have a single standardised "diagnostic criteria" checklist like the Jones criteria for rheumatic fever or the Duke criteria for endocarditis. Instead, the diagnosis is made through a combination of clinical suspicion, physical findings, and confirmatory imaging. Let's build this from first principles.

The bedside diagnosis of CoA rests on three pillars:

Pillar	Finding	Significance
1. Pulse discrepancy	Absent or weak femoral pulses relative to brachial/radial pulses; radiofemoral delay in older children	The single most reliable clinical sign ^[1]^[2]^[3]
2. Blood pressure gradient	Upper limb systolic BP > lower limb systolic BP by > 20 mmHg	Normally leg BP is ≥ arm BP due to pulse amplification; reversal of this is pathological
3. Supporting evidence	Murmur (ESM at LUSB → back), LVH on examination, ± signs of HF in neonates	Adds specificity but may be absent in critical neonatal CoA

When is CoA 'Confirmed'?

Clinical suspicion (pulse discrepancy + BP gradient) must be confirmed by echocardiography as the first-line definitive investigation. Echo demonstrates the site, severity (Doppler gradient), and associated lesions. CT/MR angiography provides detailed anatomical delineation for surgical planning.

On imaging (echocardiography or catheterisation), CoA is considered haemodynamically significant when:

Peak systolic pressure gradient across the coarctation ≥ 20 mmHg on Doppler echocardiography or at catheterisation ^[2]^[13]
Diastolic run-off pattern ("diastolic tail") on continuous-wave Doppler — indicates severe obstruction where flow continues into diastole
Evidence of LV hypertrophy or LV dysfunction as a consequence of chronic pressure overload
Proximal hypertension with > 20 mmHg gradient on four-limb BP measurement ^[2]

Indications for repair include: proximal hypertension, > 20 mmHg gradient, severe CoA on imaging studies ^[2]

Diagnostic Algorithm

The approach differs between the collapsed neonate (emergency) and the older child with incidental findings (elective workup).

Do NOT Wait for Investigations in an Emergency

"Do not wait for investigations during emergency!" ^[14]

In a collapsed neonate, start PGE₁ and antibiotics BEFORE echo confirmation. The investigation confirms the diagnosis but must not delay life-saving treatment.

Investigation Modalities — Detailed Interpretation

"The aims of the investigations include confirming the diagnosis, delineating the underlying cause, assessing severity and complications, and obtaining essential information required for the successful management of the patient" ^[14]

"Investigations should be based on initial differential diagnoses after Hx and PE" ^[14]

1. Bedside Investigations

Aspect	Detail
Technique	Measure BP in right arm (always — as left subclavian may be involved in the coarctation) and either leg (ideally both). Use age-appropriate cuff size (width = 40% of mid-arm circumference; bladder should encircle ≥ 80% of limb). In neonates, use Dinamap or oscillometric device.
Normal	Lower limb systolic BP ≥ upper limb systolic BP (actually 10–20 mmHg higher in legs due to pulse wave amplification in longer, more muscular vessels)
CoA finding	Upper limb systolic BP > lower limb systolic BP. A gradient > 20 mmHg is significant ^[2]^[13]
Why right arm?	The right subclavian artery arises from the brachiocephalic trunk, which is proximal to any typical coarctation. The left subclavian may occasionally arise at or near the coarctation site, giving a falsely low left arm reading
Pitfall	If there is a right-sided aortic arch or aberrant right subclavian artery (rare), the right arm BP may also be low — always interpret in clinical context

Aspect	Detail
Technique	Right hand (pre-ductal) vs. either foot (post-ductal) SpO₂
CoA finding	In critical CoA with right-to-left PDA shunt, post-ductal SpO₂ may be lower than pre-ductal (differential cyanosis). However, many CoA neonates have normal saturations because the issue is flow obstruction, not desaturation — this is why CoA is the CCHD most likely to be missed by pulse oximetry screening
Utility	Better at detecting cyanotic heart disease; limited sensitivity for CoA

Simultaneously palpate right brachial/radial + right femoral pulse
Radiofemoral delay = femoral pulse arrives after radial pulse (pathological — pulse must travel via collaterals, which are longer and more tortuous)
In neonates: simply assess presence vs. absence of femoral pulses (delay is hard to appreciate in a tachycardic newborn)

"Bloods: severe metabolic acidosis due to ischemic colitis and AKI upon duct closure" ^[2]

Test	Findings in CoA	Rationale
VBG / ABG	Severe metabolic acidosis (↑ lactate, ↓ pH, ↓ HCO₃⁻, negative base excess)	Tissue hypoperfusion distal to coarctation → anaerobic metabolism → lactic acidosis. Particularly in critical neonatal CoA with ductal closure ^[2]
Lactate	Elevated (often > 5 mmol/L in shock)	Direct marker of tissue hypoxia; correlates with severity of distal hypoperfusion
Renal function (Cr, urea)	Elevated creatinine / rising urea	Renal failure from renal hypoperfusion (kidneys are distal to the coarctation). In neonates, remember that creatinine in the first 48h reflects maternal creatinine — a rising trend is more concerning than a single value
LFTs (ALT, AST)	May be elevated	Hepatic ischaemia ("shock liver") from poor splanchnic perfusion, or hepatic congestion from right heart failure
FBC	May show haemoconcentration or leukocytosis	Stress response; infection should be excluded (sepsis is in DDx)
Blood culture	Must be sent	To exclude sepsis, which presents similarly
BNP / NT-proBNP	Elevated	Marker of ventricular wall stress; reflects severity of heart failure. Useful for monitoring, not specific for CoA

ECG findings differ by age and severity: ^[2]

Age / Scenario	ECG Findings	Pathophysiological Explanation
Neonate with critical CoA	RVH pattern (dominant R wave in V1, right axis deviation)	The RV is supporting the systemic circulation via the PDA; RV is the dominant ventricle doing most of the work. Also, RV dominance is physiologically normal in neonates, so this finding may be subtle ^[2]^[3]
Older infant / child	LVH pattern (tall R waves in V5–V6, deep S waves in V1–V2, ± ST-T strain pattern)	Chronic LV pressure overload from pumping against the obstruction → compensatory LVH ^[2]^[3]
Older child / adolescent	LVH with possible LV strain pattern; may also see left atrial enlargement (P mitrale) if associated mitral valve disease	Progressive pressure overload; atrial dilatation if mitral involvement (Shone complex)

Paediatric ECG interpretation pearl:

Normal neonatal ECG shows RV dominance (right axis, dominant R in V1) — this is physiological
So in a neonate with critical CoA, the ECG may appear deceptively "normal" because the RVH pattern is expected for age
The key is to correlate with the clinical picture — an ECG alone will NOT diagnose CoA

CXR findings in CoA: ^[2]

Finding	Age Group	Explanation
Cardiomegaly	Neonates / infants with HF	Volume-overloaded, failing heart. Cardiothoracic ratio > 0.6 in neonates is abnormal (normal neonatal CTR is < 0.6) ^[2]
Increased pulmonary vascular markings	Neonates / infants with HF	Pulmonary congestion from left heart failure — elevated left atrial pressure transmitted retrogradely to pulmonary veins ^[2]
"Figure 3 sign" (or "reverse 3 sign" on barium swallow)	Older children / adolescents	The cardinal CXR sign: formed by (1) pre-stenotic dilatation of the left subclavian artery, (2) the indentation at the coarctation site, and (3) post-stenotic dilatation of the descending aorta. Looks like a "3" along the left mediastinal border ^[2]
Rib notching (Roesler sign)	Older children (typically > 5 years)	Notching of the undersurface of posterior ribs due to erosion by dilated intercostal collateral arteries ^[2]. Usually affects ribs 3–8 (rib 1–2 spared because the first two intercostals arise from the costocervical trunk, not the aorta; rib 9 onwards are too anterior)

Figure 3 Sign (schematic):

    Left subclavian (dilated) ——→  ⌒  (top bulge)
    Coarctation site ——————→  ∨  (indentation)  
    Post-stenotic aorta (dilated) →  ⌒  (bottom bulge)
    
    Together: looks like "3"

CXR Pearls for Exams

Rib notching is NOT seen in neonates or young infants — collaterals take years to develop enough to erode bone
The figure 3 sign is best seen on a PA CXR or with barium swallow (where it appears as a "reverse E" or "reverse 3" — the oesophageal impression)
In a neonate with CoA, the CXR may show only cardiomegaly and pulmonary plethora — non-specific findings that overlap with many other causes of neonatal heart failure

"Echo: demonstrate site and severity of coarctation and measure systolic pressure gradient" ^[2]

Echocardiography is the gold standard initial investigation for suspected CoA in paediatrics. It is non-invasive, radiation-free, and can be performed at the bedside — critical in a sick neonate.

Echo Modality	What It Shows	Key Findings in CoA
2D (B-mode)	Anatomical structure	Discrete shelf/narrowing at the aortic isthmus; assess arch anatomy (hypoplasia?); identify associated lesions (VSD, BAV, mitral valve anomalies)
Colour Doppler	Flow patterns	Turbulent, aliased flow at the coarctation site (colour mosaic pattern)
Continuous-wave Doppler	Pressure gradient	Peak systolic gradient across coarctation — significant if > 20 mmHg. A "diastolic tail" or diastolic run-off pattern (persistent forward flow into diastole) indicates severe obstruction
Pulsed-wave Doppler	Flow velocity profiles	Reduced pulsatility in the abdominal aorta (below the coarctation) — normally should show a biphasic/triphasic pattern; in CoA it becomes continuous, damped
M-mode / 2D function	LV function and dimensions	LVH, LV dilatation (if failing), reduced fractional shortening/ejection fraction in decompensated states

Associated lesions to actively look for on echo:

Bicuspid aortic valve (present in up to 85% — look for eccentric closure line, "fish mouth" opening)
VSD (size, location, shunt direction)
Mitral valve anomalies (parachute mitral valve, supramitral ring)
Transverse arch hypoplasia (measure arch dimensions indexed to body surface area)
PDA (size, shunt direction)

Suprasternal notch view is the key echocardiographic window for visualising the aortic arch and coarctation site. From this view, you can see the ascending aorta, arch branches, isthmus, and descending aorta in one sweep.

Limitations of echo:

Suprasternal window can be technically difficult in larger/older children
May underestimate the gradient if there are extensive collaterals (collaterals decompress the proximal aorta)
Cannot fully delineate complex arch anatomy in all cases → need cross-sectional imaging (CT/MRI)

"MRI: demonstrate length and severity of coarctation" ^[2]

Aspect	Detail
Role	Gold standard for detailed anatomical delineation of the coarctation, arch anatomy, and collateral vessels. Essential for surgical planning and post-operative surveillance
Advantages	No ionising radiation (critical in paediatrics — cumulative radiation dose matters in children); excellent soft tissue contrast; can assess LV mass, function, and flow quantification simultaneously
Gadolinium-enhanced MRA	Provides beautiful 3D reconstruction of the aortic arch, showing the exact site, length, and severity of narrowing, plus collateral vessel anatomy
Phase-contrast MRI	Allows quantification of flow and velocity → can calculate pressure gradient non-invasively and assess collateral flow volume
Limitations	Takes 20–60 minutes (sedation/general anaesthesia needed in young children); requires MRI-compatible monitoring equipment; cannot be performed on patients with certain metallic implants. Unsuitable in acutely unwell neonates due to duration and monitoring challenges
When to use	Pre-operative planning in stable patients; long-term post-repair surveillance (gold standard for detecting re-coarctation, aneurysm formation at repair site); assessment of LV mass regression after repair

Aspect	Detail
Role	Rapid, high-resolution anatomical delineation of the aortic arch. Increasingly used as an alternative to MRI for pre-operative planning
Advantages	Very fast (seconds); excellent spatial resolution; widely available; can be performed in unstable patients with appropriate monitoring
ECG-gated cardiac CT	Reduces motion artefact; allows assessment of coronary arteries (relevant if BAV with anomalous coronary anatomy)
Limitations	Ionising radiation — significant concern in paediatrics (aim ALARA: As Low As Reasonably Achievable). Iodinated contrast → risk of contrast allergy and nephrotoxicity (especially relevant if the child already has AKI from renal hypoperfusion). Not ideal for routine surveillance
When to use	When MRI is contraindicated or unavailable; when rapid anatomical information is needed urgently; in older children/adolescents where radiation concern is relatively lower

Aspect	Detail
Role	Previously the gold standard for diagnosis; now primarily therapeutic (balloon angioplasty ± stenting) rather than purely diagnostic
Diagnostic information	Direct measurement of pressure gradient across coarctation (most accurate); angiographic delineation of anatomy; assessment of collateral vessels; haemodynamic assessment of associated lesions
When used diagnostically	When non-invasive imaging is inconclusive; when haemodynamic data is needed for surgical decision-making; combined with planned intervention
Risks	Invasive; arterial access complications (especially in small infants — femoral artery thrombosis); contrast load; radiation

Investigation	Neonatal Critical CoA	Older Child CoA	Post-Repair Surveillance
Four-limb BP	✓ (immediate)	✓ (essential)	✓ (lifelong)
Pulse oximetry	✓ (pre + post-ductal)	± (less useful)	Not routine
Bloods (VBG, lactate, renal)	✓ (urgent)	Baseline	As needed
ECG	✓ (RVH)	✓ (LVH)	✓ (LVH regression)
CXR	✓ (cardiomegaly, plethora)	✓ (figure 3, rib notching)	±
Echocardiography	✓ (urgent, bedside)	✓ (first-line)	✓ (regular)
MRI / MRA	Not in acute setting	✓ (pre-op planning)	✓ (gold standard)
CT angiography	± (if MRI unavailable)	✓ (alternative to MRI)	± (radiation concern)
Catheterisation	± (usually therapeutic)	For intervention	For re-intervention

Common Diagnostic Pitfalls

Missed femoral pulse check: The neonatal examination MUST include femoral pulse palpation. CoA is missed if this step is omitted.
False reassurance from pulse oximetry: CoA often has normal saturations on newborn pulse oximetry screening because the problem is flow obstruction, not oxygen desaturation. CoA is the CCHD most commonly missed by pulse oximetry screening.
Normal neonatal ECG appearance: RVH is normal in the neonate — the ECG in critical CoA may look "normal for age." Never rely on ECG alone.
Gradient underestimation on echo: If extensive collateral vessels have developed (older children), they decompress the proximal aorta and reduce the measured Doppler gradient. A "low gradient" does NOT necessarily mean mild disease — assess the clinical picture and collateral flow.
Left arm BP may be falsely low: If the coarctation involves or is proximal to the left subclavian artery origin, left arm BP will be low. Always use the right arm as the reference for upper limb BP.
Post-repair surveillance complacency: After repair, patients need lifelong monitoring for re-coarctation, aneurysm at the repair site, persistent HTN, and associated BAV progression. MRI is the gold standard for post-repair surveillance.

High Yield Summary — Diagnosis of CoA

Clinical diagnosis: Pulse discrepancy (weak femorals) + arm-to-leg BP gradient > 20 mmHg + supporting signs.

First-line confirmatory test: Echocardiography — demonstrates site, severity (Doppler gradient), and associated lesions. Can be done at the bedside in a sick neonate.

Key CXR findings:

Neonate: cardiomegaly + increased pulmonary vascular markings ^[2]
Older child: figure 3 sign + rib notching (after age ~5) ^[2]

ECG: RVH in neonate (RV supports systemic circulation via PDA); LVH in older child (chronic LV pressure overload) ^[2]

Bloods in critical CoA: Severe metabolic acidosis, raised lactate, AKI ^[2]

MRI/MRA: Best for detailed anatomy and gold standard for post-repair surveillance.

Haemodynamic significance: Peak gradient > 20 mmHg across the coarctation on Doppler echo or catheterisation ^[2]^[13].

Golden rule: Do not wait for investigations during emergency ^[14]. Start PGE₁ + antibiotics in a collapsed neonate, then investigate.

Active Recall - Diagnosis and Investigations of CoA

References

^[1] Lecture slides: Block C - Heart failure and cyanosis in children: acyanotic and cyanotic congenital heart disease.pdf (Coarctation section) ^[2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p211, CoA investigations and management) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p190, Section 3.7.4 Coarctation of Aorta) ^[13] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p259, p262, p289 — CoA diagnostic criteria, haemodynamic significance, repair indications) ^[14] Lecture slides: General Clerkship Introduction to CVS Investigations 2026 Yiu.pdf (p2, p61 — aims of investigations, do not wait during emergency)

Management of Coarctation of the Aorta in Paediatrics

The management of CoA is fundamentally dictated by two clinical scenarios, each with a completely different urgency and approach:

Critical neonatal CoA (duct-dependent) → Medical emergency → stabilise → urgent surgical repair
Non-critical CoA in older children/adolescents → Elective assessment → intervention when indicated

The overarching goals are:

Restore adequate distal aortic perfusion (relieve the mechanical obstruction)
Treat and prevent heart failure
Address associated cardiac lesions
Lifelong surveillance for re-coarctation, persistent hypertension, aneurysm formation, and associated lesion progression

A. Emergency Management: Critical Neonatal CoA

This is a paediatric emergency. The neonate is in cardiogenic shock from ductal closure. Every minute counts.

Action	Rationale
Airway and breathing	Intubate and ventilate if in respiratory failure from severe pulmonary oedema or shock. Mechanical ventilation also reduces oxygen consumption and work of breathing.
IV access	Ideally two large-bore peripheral cannulae (for a neonate, 24G is fine). Consider umbilical venous catheter if peripheral access is difficult
Fluid resuscitation	Cautious — 10 mL/kg normal saline bolus if severely hypotensive. Avoid excessive fluid as the failing LV cannot handle volume overload
Correct metabolic acidosis	IV sodium bicarbonate (1–2 mEq/kg slowly) if pH < 7.1 and lactate is markedly elevated. Correcting acidosis improves myocardial contractility. Also correct any hypoglycaemia and hypocalcaemia (common in stressed neonates)

This is the single most important medical intervention in critical neonatal CoA.

"Urgent PGE1/2 infusion + inotropes (to maintain CO) in critical CoA followed by early surgical repair ( < 3m)" ^[2]^[3]

"IV Alprostadil — Prostaglandin E1 (PGE1) infusion — Indicated in infants younger than 4 months to maintain ductal patency and stabilize the patient prior to surgical repair" ^[13]^[15]

Aspect	Detail
Drug	Alprostadil (prostaglandin E₁ / PGE₁) — "alp-" from alprostadil, "prost-" from prostaglandin
Mechanism	PGE₁ acts on smooth muscle of the ductus arteriosus to maintain or re-open the PDA. This restores the bypass route: RV → pulmonary artery → PDA → descending aorta → lower body perfusion
Starting dose	5–10 nanograms/kg/min IV (some centres start at 50 ng/kg/min for rapid re-opening, then wean)
Maintenance dose	5 ng/kg/min once the duct is re-opened
Route	Continuous IV infusion via a dedicated line (ideally central, but peripheral is acceptable initially)
Monitoring	Continuous cardiorespiratory monitoring; SpO₂ (expect improvement in post-ductal saturations); HR; BP; urine output

Side effects of PGE₁ — Must Know:

Side Effect	Mechanism	Management
Apnoea (most important — ~12% of neonates)	PGE₁ acts on central respiratory centres, causing respiratory depression	Always have intubation equipment at the bedside before starting PGE₁. Elective intubation often performed prophylactically in very sick neonates
Fever / temperature instability	PGE₁ resets the hypothalamic thermostat	Supportive; monitor temperature
Hypotension	Vasodilatory effect of PGE₁	Volume support; adjust infusion rate; may need inotropes
Jitteriness / seizure-like activity	CNS effects	Usually mild; reduce dose if significant
Flushing, oedema	Peripheral vasodilatation, increased capillary permeability	Usually tolerated
Long-term (> 2 weeks): cortical hyperostosis	Periosteal bone proliferation — rarely relevant as most patients go to surgery quickly	Monitor if prolonged use needed

PGE₁ — The Lifeline

Think of PGE₁ as buying time. It does not fix the coarctation — it re-opens the ductus arteriosus to restore lower body perfusion while the surgical team prepares for definitive repair. The key complication to remember is apnoea — always have intubation equipment ready.

Drug	Mechanism	Paediatric Dose	Role
Dopamine	D₁ (renal vasodilation at low dose), β₁ (inotropy at moderate dose), α₁ (vasoconstriction at high dose)	5–10 mcg/kg/min for inotropy	First-line inotrope to support cardiac output
Dobutamine	β₁ agonist → increases contractility; mild β₂-mediated vasodilation	5–20 mcg/kg/min	If more pure inotropy needed without vasoconstriction
Milrinone	Phosphodiesterase-3 inhibitor → ↑ cAMP → inotropy + vasodilation ("inodilator")	0.25–0.75 mcg/kg/min	Useful after surgical repair to reduce afterload and improve LV function
Adrenaline	α₁ + β₁ agonist	0.05–0.3 mcg/kg/min	Rescue inotrope for refractory shock

"Inotropes to maintain CO" ^[2]^[3] — the failing LV needs pharmacological support until the mechanical obstruction is relieved surgically.

"Initial stabilization with IV infusion of PGE1 followed by early surgical repair" ^[13]^[15]

Surgery should be performed within the first few weeks of life (ideally within days of stabilisation, and certainly < 3 months ^[2]^[3]). The choice of surgical technique depends on the anatomy:

B. Surgical Treatment Options

"Resection with end-to-end anastomosis for discrete CoA" ^[2]^[3]

Aspect	Detail
Technique	The narrowed segment is excised, and the two cut ends of the aorta are sewn directly together
Indication	Discrete (short-segment) coarctation — the most common anatomy
Approach	Left posterolateral thoracotomy (between the ribs, no need for cardiopulmonary bypass)
Advantage	Removes all abnormal tissue (including ectopic ductal tissue); creates a "normal" anastomosis with growth potential
Limitation	Not suitable for long-segment narrowing (excessive tension on anastomosis if too much aorta is removed)

"Closed heart surgery only — correction of extra-cardiac abnormalities does not require opening of the heart or cardiopulmonary bypass" ^[13]^[15]

This is an important concept: CoA repair is off-bypass surgery. The coarctation is an extracardiac structure (descending aorta), so the heart does not need to be opened. The aorta is cross-clamped, the diseased segment excised, and the ends reanastomosed. However, the cross-clamp time must be limited (typically < 30 minutes) to minimise spinal cord ischaemia risk.

Aspect	Detail
Technique	The incision is extended along the underside of the aortic arch, allowing resection of more tissue and a wider anastomosis
Indication	Discrete CoA with associated transverse arch hypoplasia
Advantage	Addresses both the coarctation and the arch narrowing in one procedure

"Subclavian flap aortoplasty (obsolete) for long-segment CoA" ^[2]

Aspect	Detail
Technique	The left subclavian artery is divided and its tissue is turned down as a "flap" to widen the narrowed aortic segment
Indication	Historically used for long-segment CoA in neonates
Current status	Largely obsolete — sacrificing the left subclavian artery causes reduced left arm growth and BP measurement problems. Extended end-to-end anastomosis or bypass grafting is preferred ^[2]

"Bypass graft across coarctation for long-segment CoA too long for primary anastomosis" ^[2]^[3]

Aspect	Detail
Technique	A synthetic graft (e.g., Dacron or PTFE) is placed to bypass the coarctation, connecting the proximal and distal normal aorta
Indication	Long-segment CoA too long for primary anastomosis ^[2]^[3]; older children or adults where the aorta is less compliant
Limitation	Synthetic graft does not grow with the child — may need revision. Risk of infection. Generally reserved for older patients

Aspect	Detail
Technique	The narrowed segment is incised longitudinally and a patch (synthetic or autologous pericardium) is sewn in to widen the lumen
Current status	Largely abandoned — associated with high rates of late aneurysm formation at the patch site

C. Catheter-Based (Interventional) Treatment

"Balloon angioplasty in > 4 months with discrete coarctation or in re-coarctation" ^[2]^[3] "Balloon angioplasty is the procedure of choice for native coarctation of aorta in children beyond infancy and for recurrent coarctation after previous surgical repair" ^[13]^[15]

Aspect	Detail
Technique	A catheter with a balloon tip is advanced (usually via femoral artery) to the coarctation site. The balloon is inflated to dilate the narrowing by controlled tearing of the intima and media
Indication	Native discrete CoA in children > 4 months of age; re-coarctation after previous surgical repair (primary indication)
Contraindication	Generally not used in infants < 4 months — small vessel size leads to poor results and higher complication rates ^[2]^[3]; not ideal for long-segment or arch hypoplasia
Why > 4 months?	The femoral artery in a very young infant is tiny (risk of arterial injury, thrombosis); the aortic tissue is more fragile; and the restenosis rate in young infants is very high (~40%) compared to adolescents (~8%) ^[2]^[3]

"± stent placement: generally indicated after surgical repair or angioplasty for those ≥ 25 kg" ^[2]^[3] "Stent exerts a radial force to prevent elastic recoil of vessels after balloon dilation" ^[13]^[15]

Aspect	Detail
Technique	A metallic stent (balloon-expandable or self-expanding) is deployed at the coarctation site after balloon dilation
Mechanism	Stent exerts a radial force to prevent elastic recoil — the aortic wall tends to spring back after balloon dilation; the stent holds it open ^[13]^[15]
Indication	Children ≥ 25 kg (typically > 8–10 years); after surgical repair or balloon angioplasty with residual gradient; native CoA in larger children/adolescents
Why ≥ 25 kg?	Stents currently available are adult-sized; in small children, the stent would need to be re-dilated repeatedly as the child grows — this is a major limitation
Pros	Improved luminal diameter, reduced residual gradient ^[2]^[3]
Cons	Often require repeated planned re-intervention as the stent needs to be dilated as the child grows ^[2]^[3]; risk of stent fracture; aortic wall injury; limited MRI compatibility (depending on stent material)

"Indications for corrective intervention" ^[13]^[15]:

Patient Group	Indication	Modality
Neonates with critical CoA	Duct-dependent — depends on ductal patency for survival	PGE₁ → urgent surgical repair (end-to-end anastomosis) ^[2]^[3]^[13]^[15]
Children and adolescents	Hypertension proximal to coarctation + Resting peak gradient > 20 mmHg across narrowed segment + Severe CoA demonstrated by imaging	Balloon angioplasty ± stent (if > 4 months, ≥ 25 kg for stent) or surgical repair ^[2]^[3]^[13]^[15]
Re-coarctation (any age)	Recurrent gradient after previous repair	Balloon angioplasty is the procedure of choice for re-coarctation ^[13]^[15]

"Outcome: restenosis 5–15% in surgery, 40% (young infants) vs 8% (adolescents) in balloon" ^[2]^[3]

Modality	Restenosis Rate	Notes
Surgical repair	5–15%	Lower overall restenosis rate; gold standard for neonates
Balloon angioplasty — young infants	~40%	High rate — this is why balloon is generally avoided in < 4 months
Balloon angioplasty — adolescents	~8%	Much better outcomes in older children

"10-year survival generally > 90%" ^[2]^[3]

Hypertension Management

Even after successful repair, persistent hypertension is common (seen in 25–75% of patients depending on age at repair and follow-up duration). This requires lifelong management:

Drug Class	Paediatric Considerations	Rationale
ACE inhibitors (e.g., enalapril, captopril)	First-line for paediatric HTN. Captopril: 0.1–0.5 mg/kg/dose TDS (neonates), up to 1–2 mg/kg/dose TDS (children). Enalapril: 0.08–0.5 mg/kg/day OD-BD	Counteracts RAAS activation (which is a key driver of persistent HTN in CoA — kidneys "learned" to overproduce renin during chronic hypoperfusion)
Beta-blockers (e.g., propranolol, atenolol)	Useful if concurrent aortic root dilatation or BAV with regurgitation	Reduces cardiac contractility and heart rate; protects against aortic wall stress
Calcium channel blockers (e.g., amlodipine)	Commonly used if ACE inhibitor alone insufficient	Arterial vasodilation; fewer RAAS-related effects
Diuretics (e.g., furosemide)	Acute heart failure management, not first-line for chronic HTN	Volume reduction

Post-Repair HTN — A Lifelong Problem

"Systolic HTN may persist despite repair due to permanent alteration of arterial mechanics and physiology" ^[2]^[3]

Even after a "perfect" surgical result with no residual gradient, up to half of patients develop hypertension by adulthood. Mechanisms include:

Arterial wall stiffness and reduced compliance (structural remodelling)
Baroreceptor resetting
Chronic RAAS upregulation
Residual arch hypoplasia

All CoA patients need lifelong BP monitoring — at every clinic visit, ideally with four-limb BPs.

Cardiovascular follow-up includes: ^[13]^[15]

Surveillance	Modality	Frequency	Rationale
Blood pressure monitoring	Four-limb BP at every visit; consider ambulatory 24h BP monitoring	Every clinic visit (at least annually)	Monitoring and treatment of hypertension aggressively ^[13]^[15]
Echocardiography	TTE with Doppler	Annually or more frequently	Assess and follow-up dysfunctional bicuspid aortic valve; detect re-coarctation (increasing gradient); LV function ^[13]^[15]
Aortic imaging	MRI/MRA (gold standard) or CTA	Every 3–5 years, or more frequently if abnormalities detected	Detect potential complications such as re-coarctation or aneurysm formation at the repair site ^[13]^[15]
Cranial imaging	MRA of the circle of Willis	Consider in adolescence/adulthood; no universal consensus on timing	Evaluate for intracranial (berry) aneurysm ^[13]^[15] — particularly important if persistent HTN

Counselling points: ^[13]^[15]

Topic	Information
What is CoA?	A narrowing of the main blood vessel (aorta) that delivers blood to the body. Explain using simple diagrams. Age-appropriate language for the child
Frequency	5–7% of all congenital heart disease ^[13]^[15]
Recurrence risk	Siblings: ~2%. Offspring if mother affected: ~4%. Offspring if father affected: ~2% ^[13]^[15]
Need for lifelong follow-up	Even after "successful" repair, lifelong cardiology follow-up is essential for BP, valve, and aortic monitoring
Exercise	Generally permitted; avoid competitive isometric/strength sports (weightlifting) if residual HTN or aortic pathology. Encourage aerobic activity
Pregnancy counselling	Important for female adolescents — CoA (repaired or not) carries increased maternal cardiovascular risk during pregnancy. Pre-conception counselling recommended
SBE prophylaxis	Routine antibiotic prophylaxis for dental procedures is no longer recommended for isolated repaired CoA without prosthetic material (per current AHA/ESC guidelines). However, if prosthetic material (stent, graft) is present, prophylaxis may be indicated for the first 6 months after implantation
Turner syndrome screening	If the patient is female with CoA, consider karyotyping to exclude Turner syndrome if not already done

Feature	Surgical Repair	Balloon Angioplasty ± Stent
Best for neonates	Yes — gold standard	No (< 4 months: poor results, high restenosis)
Best for re-coarctation	Possible but technically more difficult (scar tissue)	Yes — procedure of choice for re-coarctation ^[13]^[15]
Approach	Left thoracotomy (off-bypass)	Percutaneous via femoral artery
Restenosis rate	5–15%	8% (adolescents) to 40% (young infants) ^[2]^[3]
Invasiveness	Open surgery (wound, chest tube, ICU stay)	Minimally invasive (day case or 1-night stay)
Addresses arch hypoplasia	Yes (extended end-to-end)	No (only treats focal stenosis)
Growth	Anastomosis grows with child	Stent requires re-dilation as child grows ^[2]^[3]
Scar / cosmesis	Left thoracotomy scar	Minimal (groin puncture site)

High Yield Summary — Management of CoA

Critical neonatal CoA (emergency):

PGE₁ infusion (alprostadil) — maintain ductal patency. Watch for apnoea — have intubation equipment ready.
Inotropes (dopamine/dobutamine) — maintain cardiac output
Correct metabolic acidosis, ventilatory support
Urgent surgical repair ( < 3 months) — resection with end-to-end anastomosis for discrete CoA ^[2]^[3]

Older child (elective):

Indications: proximal HTN, > 20 mmHg gradient, severe CoA on imaging ^[2]^[3]^[13]^[15]
Balloon angioplasty — procedure of choice for native CoA > 4 months and for re-coarctation ^[13]^[15]
Stent placement — for patients ≥ 25 kg; needs re-dilation as the child grows ^[2]^[3]
Surgical repair if complex anatomy or arch hypoplasia

Outcomes:

10-year survival > 90% ^[2]^[3]
Restenosis: 5–15% surgery; 8% balloon (adolescents); 40% balloon (young infants) ^[2]^[3]

Lifelong follow-up for ALL patients: BP monitoring, echocardiography, MRI/MRA, cranial imaging for berry aneurysms ^[13]^[15]

Persistent HTN after repair is common — treat with ACE inhibitors ± beta-blockers ± CCBs

Active Recall - Management of CoA

References

^[2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p211, CoA investigations and management) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p191, Section 3.7.4 CoA management and outcomes) ^[13] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p265 — CoA treatment: indications, surgical options, counselling, follow-up) ^[15] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p578–580 — CoA treatment: medical, surgical, interventional, follow-up)

Complications of Coarctation of the Aorta in Paediatrics

Complications of CoA can be divided into three temporal categories, each with a distinct pathophysiological basis:

Acute complications of the unrepaired lesion (neonatal presentation)
Procedure-related complications (peri- and post-operative)
Long-term complications (even after "successful" repair — the most commonly examined category)

Understanding why each complication occurs requires thinking about what the coarctation does to the circulation both before and after repair.

These occur when the ductus arteriosus closes in a neonate with severe CoA, cutting off lower body blood supply. They are effectively the consequences of acute lower body ischaemia and acute LV failure.

Complication	Pathophysiological Mechanism	Clinical Features
Cardiogenic shock	Ductal closure → sudden, extreme LV afterload → acute LV failure → inadequate cardiac output	Hypotension, tachycardia, poor capillary refill, mottled skin, altered consciousness
Acute kidney injury (AKI)	Renal arteries are distal to the coarctation → renal hypoperfusion → pre-renal AKI → oliguria/anuria	Rising creatinine, metabolic acidosis, oliguria. "Severe metabolic acidosis due to ischaemic colitis and AKI upon duct closure" ^[2]^[3]
Necrotising enterocolitis (NEC) / Ischaemic colitis	Mesenteric arteries (SMA, IMA) are distal to the coarctation → gut ischaemia → mucosal breakdown → bacterial translocation	Abdominal distension, bilious vomiting, bloody stools, pneumatosis intestinalis on AXR. A major cause of morbidity in neonatal CoA
Metabolic (lactic) acidosis	Global lower body hypoperfusion → anaerobic metabolism → lactate accumulation	Low pH, high lactate, negative base excess on VBG/ABG. May be refractory until perfusion is restored
Hepatic ischaemia ("shock liver")	Hepatic artery perfusion reduced (downstream of coarctation) + hepatic venous congestion from RHF	Markedly elevated transaminases (ALT, AST), coagulopathy (impaired synthetic function)
Death	Without intervention, tight CoA with ductal closure is fatal. Death ≤ 1 week if tight stenosis ^[2]^[3]	Refractory shock, multi-organ failure

NEC in CoA — Don't Forget the Gut

NEC in CoA is ischaemic in origin (not the classic NEC of prematurity which is multifactorial). Any neonate with CoA who develops abdominal distension, feeding intolerance, or bloody stools should have an AXR to look for pneumatosis intestinalis or portal venous gas. This complication can persist even after haemodynamic rescue with PGE₁ if gut injury has already occurred.

These can occur during or after surgical repair, balloon angioplasty, or stent placement.

Complication	Mechanism	Risk Factors / Notes
Re-coarctation (restenosis)	Scar tissue formation at the anastomotic site; residual ductal tissue constricting; inadequate resection; growth of the child with relative narrowing	Restenosis 5–15% after surgery; 40% in young infants vs. 8% in adolescents after balloon ^[2]^[3]. Most common long-term complication requiring re-intervention
Spinal cord ischaemia / paraplegia	During surgical repair, the descending aorta is cross-clamped. The spinal cord (particularly the anterior spinal artery and the artery of Adamkiewicz, which arises from a lower intercostal or lumbar artery) may be deprived of blood flow. If cross-clamp time exceeds ~30 minutes, risk increases substantially	Rare ( < 0.5%) with experienced surgical teams who limit cross-clamp time. Higher risk if collateral circulation is poorly developed (neonates)
Haemorrhage	Surgical bleeding from the anastomotic site, especially if aortic tissue is friable (common in neonates) or if there is tissue mismatch	May require re-exploration; ensure adequate blood products available
Recurrent laryngeal nerve injury	The left recurrent laryngeal nerve loops under the aortic arch near the ligamentum arteriosum — directly in the surgical field. Traction or transection → hoarseness, weak cry in neonates, aspiration risk	Left thoracotomy approach; identified by vocal cord paralysis on postoperative laryngoscopy
Phrenic nerve injury	Left phrenic nerve runs along the pericardium close to the surgical field	Diaphragmatic paralysis → respiratory compromise, especially in infants who are diaphragm-dependent breathers
Chylothorax	Damage to the thoracic duct (runs adjacent to the descending aorta on the left) → lymph leak into pleural space	Presents with milky pleural effusion; managed with drainage, medium-chain triglyceride (MCT) diet, and rarely surgical ligation
Wound infection / mediastinitis	Standard surgical risk	Prophylactic antibiotics; meticulous surgical technique

Complication	Mechanism	Notes
Femoral artery injury / thrombosis	Arterial catheter insertion in small paediatric vessels → intimal injury, dissection, or thrombosis	Higher risk in younger/smaller children — this is a major reason balloon angioplasty is avoided in infants < 4 months
Aortic wall dissection / rupture	Balloon inflation tears the intima and media (this is the intended mechanism for widening the lumen) — but if excessive, the tear extends through the adventitia → contained or free rupture	Rare but life-threatening; requires immediate surgical intervention
Aneurysm at dilation site	Over-dilation or weakening of the aortic wall → aneurysm formation at the site where the balloon tore the intima/media	Detected on follow-up imaging; may require covered stent or surgical repair if progressive
Stent-related: need for re-dilation	"Often require repeated planned re-intervention as the stent needs to be dilated as the child grows" ^[2]^[3]	Not a complication per se but a planned consequence of using a non-growing device in a growing child
Stent fracture / migration	Mechanical stress on stent from aortic pulsation and somatic growth	Follow-up imaging essential; may require re-stenting

C. Long-Term Complications (Post-Repair)

This is the most examined category. Even after "successful" repair with no residual gradient, patients remain at risk for significant morbidity throughout their lives.

"Long-term outcome: 10y survival generally > 90%" ^[2]^[3] "Cardiovascular complications: persistent HT, aortic aneurysm/dissection, IHD/stroke, arrhythmia" ^[2]^[3] "Systemic complications: berry aneurysms with rupture" ^[2]^[3]

This is the most important and most common long-term complication of CoA, even after anatomically successful repair.

Aspect	Detail
Prevalence	25–75% of patients develop HTN in long-term follow-up (higher if repair was performed later in childhood)
Mechanism	Multiple factors contribute: (1) Permanent alteration of arterial mechanics and physiology — the pre-coarctation arterial wall has been exposed to chronic high pressure, leading to reduced compliance, increased stiffness, and endothelial dysfunction ^[2]^[3]; (2) Baroreceptor resetting — aortic baroreceptors have been "reset" to accept a higher setpoint as normal; (3) Chronic RAAS upregulation — the kidneys were chronically underperfused, leading to persistent renin overproduction even after perfusion is restored; (4) Residual arch hypoplasia — even without discrete re-coarctation, a mildly hypoplastic arch can impose a subtle but persistent afterload on the LV
Clinical significance	Hypertension is the leading cause of cardiovascular morbidity in CoA patients long-term. It accelerates atherosclerosis, increases risk of LVH, heart failure, stroke, and aortic complications
Management	Aggressive antihypertensive therapy (ACE inhibitors, beta-blockers, CCBs); regular four-limb BP monitoring; 24-hour ambulatory BP monitoring recommended. "Monitoring and treatment of hypertension aggressively" ^[13]^[15]

Earlier Repair = Better BP Outcomes

Studies consistently show that repair in infancy/early childhood leads to lower rates of persistent HTN compared to repair in adolescence or adulthood. This is because the longer the proximal vasculature is exposed to high pressure, the more irreversible the arterial wall changes become. This is a key argument for early intervention.

Aspect	Detail
Definition	Recurrence of narrowing at or near the original coarctation/repair site
Mechanism	Scar tissue and fibrosis at the anastomotic site; neointimal hyperplasia; residual ductal tissue; inadequate initial repair; somatic growth outpacing the anastomosis
Incidence	5–15% after surgical repair; up to 40% in young infants after balloon angioplasty ^[2]^[3]
Detection	Recurrence of arm-leg BP gradient; increasing Doppler gradient on echo; confirmed by MRI/MRA
Management	Balloon angioplasty is the procedure of choice for re-coarctation ^[13]^[15] ± stent in larger children

Aspect	Detail
Site	At the repair site (anastomotic aneurysm or false aneurysm); at the site of previous balloon angioplasty; or in the ascending aorta (especially if associated bicuspid aortic valve with aortopathy)
Mechanism at repair site	Surgical anastomosis creates a weak point in the aortic wall; patch aortoplasty (now largely abandoned) was particularly associated with late aneurysm formation. Balloon angioplasty intentionally tears the intima/media — if healing is incomplete, the wall weakens
Mechanism in ascending aorta	Bicuspid aortic valve is associated with intrinsic aortic wall abnormality (cystic medial necrosis) → progressive ascending aortic dilatation → risk of dissection, similar to Marfan syndrome
Clinical significance	Aortic rupture or dissection is the leading cause of late death in CoA patients. Sudden tearing chest/back pain, haemodynamic collapse
Surveillance	"Periodic aortic imaging to detect potential complications such as re-coarctation or aneurysm formation" ^[13]^[15]. MRI/MRA is the gold standard for serial monitoring. CT angiography if MRI unavailable
Management	Surgical repair (graft interposition) or endovascular covered stent for enlarging aneurysms. Aggressive BP control to reduce wall stress

"Systemic complications: berry aneurysms with rupture" ^[2]^[3]

Aspect	Detail
Association	CoA is a well-recognised risk factor for cerebral (berry) aneurysms, typically at bifurcation points of the circle of Willis ^[2]^[3]^[5]
Mechanism	(1) Chronic upper body hypertension → increased haemodynamic stress on cerebral artery walls → aneurysm formation at weak points (bifurcations); (2) Possible intrinsic connective tissue abnormality affecting vessel walls (shared developmental mechanism with CoA)
Presentation	Most are asymptomatic until rupture → subarachnoid haemorrhage (SAH): sudden-onset "thunderclap" headache, meningism, vomiting, altered consciousness. In children, SAH is rare but devastating
Risk factors for rupture	Persistent hypertension (the most modifiable risk factor), aneurysm size > 7 mm, family history of SAH
Surveillance	"Periodic cranial imaging to evaluate for intracranial aneurysm" ^[13]^[15]. MRA of the circle of Willis is non-invasive and radiation-free. Timing: typically recommended in adolescence or early adulthood; no universal paediatric consensus on screening age
Aneurysm management	Microsurgical clipping (craniotomy, clip at aneurysm neck) or endovascular coiling (catheter-based placement of detachable coils into aneurysm) — both aim to prevent rupture ^[5]

Aspect	Detail
Mechanism	Persistent hypertension → accelerated atherosclerosis → coronary artery disease and cerebrovascular disease at a younger age than the general population. Also, BAV-associated aortopathy may affect coronary ostia
Implication	CoA patients (even repaired) have an increased lifetime risk of MI and stroke. Cardiovascular risk factor management (BP, lipids, exercise, no smoking) is essential from childhood onwards

Aspect	Detail
Mechanism	Chronic LV hypertrophy → myocardial fibrosis → substrate for ventricular arrhythmias (VT, VF). Atrial dilatation (from chronic pressure overload or associated mitral valve disease) → substrate for atrial arrhythmias (AF, atrial flutter)
Clinical significance	Palpitations, syncope, sudden cardiac death (rare). ECG monitoring recommended during follow-up

Aspect	Detail
Association	Present in 50–85% of CoA patients
Natural history	BAV can remain asymptomatic for decades but progressively develops: (1) Aortic stenosis (calcification and fibrosis of abnormal cusps) — typically presents in 4th–6th decade; (2) Aortic regurgitation (prolapse of one cusp); (3) Aortic root dilatation and aortopathy (risk of dissection)
Paediatric relevance	In childhood, most BAVs are haemodynamically insignificant. However, an ejection click may be heard. Serial echo is essential to track progression
Surveillance	"Periodic echocardiographic imaging to assess and follow-up of dysfunctional bicuspid aortic valve" ^[13]^[15]

Aspect	Detail
Mechanism	Turbulent flow at the coarctation site (if residual narrowing) or across a bicuspid aortic valve creates endothelial damage → nidus for bacterial adhesion → IE
Risk	Highest if there is residual CoA, prosthetic material (stent, graft), or a dysfunctional BAV. Risk is lower (but not zero) after successful native repair
Prophylaxis	Per current AHA/ESC guidelines, routine antibiotic prophylaxis before dental procedures is no longer recommended for isolated repaired CoA without prosthetic material. However, if prosthetic material (graft, stent, conduit) is present, IE prophylaxis is recommended for the first 6 months post-implantation (and lifelong if residual turbulence near the material). Patients with BAV generally do not require IE prophylaxis unless prior IE has occurred

A specific early postoperative complication worth mentioning separately:

Aspect	Detail
What it is	A clinical syndrome of abdominal pain, hypertension, nausea, vomiting, and sometimes intestinal haemorrhage occurring 2–3 days after surgical repair of CoA
Mechanism	After repair, blood flow to the previously hypoperfused mesenteric arteries suddenly increases. The gut vasculature has adapted to low flow and cannot autoregulate properly → mesenteric arteritis → bowel wall oedema, petechial haemorrhages, even transmural necrosis
Management	Supportive: IV fluids, NPO/bowel rest, antihypertensives (especially beta-blockers to reduce mesenteric perfusion pressure), careful monitoring. Usually self-limiting within days
Prevention	Gradual BP reduction post-repair; avoid sudden large drops in afterload; careful fluid management

Timeline	Complications
Acute (unrepaired neonatal)	Cardiogenic shock, AKI, NEC / ischaemic colitis, metabolic acidosis, hepatic ischaemia, death
Peri-/post-operative	Re-coarctation, spinal cord ischaemia, recurrent laryngeal nerve injury, phrenic nerve injury, chylothorax, post-coarctectomy syndrome, femoral artery thrombosis (catheter), aortic wall injury
Long-term (even post-repair)	Persistent hypertension, re-coarctation, aortic aneurysm/dissection, berry aneurysm with SAH, IHD/stroke, arrhythmia, BAV progression, infective endocarditis

High Yield Summary — Complications of CoA

Acute neonatal complications (untreated critical CoA):

Cardiogenic shock, AKI, NEC/ischaemic colitis, metabolic acidosis → death ≤ 1 week if tight stenosis ^[2]^[3]

Long-term complications (the exam favourites):

Persistent hypertension — most common, most important. Due to arterial wall remodelling, baroreceptor resetting, RAAS upregulation. "Monitoring and treatment of hypertension aggressively" ^[13]^[15]
Re-coarctation — 5–15% after surgery; 40% in infants after balloon ^[2]^[3]. Balloon angioplasty is the treatment of choice for re-coarctation
Aortic aneurysm/dissection — at repair site or ascending aorta (BAV aortopathy). Leading cause of late death. Needs MRI surveillance ^[13]^[15]
Berry aneurysms with rupture → SAH — due to chronic upper body HTN + intrinsic vessel wall abnormality ^[2]^[3]^[5]. Needs cranial imaging ^[13]^[15]
IHD and stroke — accelerated atherosclerosis from persistent HTN
Arrhythmia — from chronic LVH and myocardial fibrosis
BAV progression — aortic stenosis, regurgitation, aortopathy → needs serial echo ^[13]^[15]

Key principle: CoA is never "cured" — it is a lifelong condition requiring surveillance for re-coarctation, HTN, aneurysm, valve disease, and cerebrovascular complications.

Active Recall - Complications of CoA

References

^[2] Senior notes: Adrian Lui Pediatrics Notes.pdf (p211 — CoA long-term outcome: re-coarctation, cardiovascular complications, systemic complications) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p191 — CoA long-term outcome: persistent HTN, aortic aneurysm/dissection, IHD/stroke, arrhythmia, berry aneurysms) ^[5] Senior notes: Ryan Ho Neurology.pdf (p87 — Cerebral aneurysm: CoA as a risk factor, presentation with SAH, management with clipping/coiling) ^[13] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p265 — Cardiovascular follow-up: periodic cranial/aortic/echo imaging, aggressive HTN treatment) ^[15] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p578 — Cardiovascular follow-up: identical surveillance recommendations)

High Yield Summary

Definition: Discrete narrowing of the descending aorta, usually at the site of the ductus arteriosus insertion (juxtaductal).

Epidemiology: ~6–9% of CHD; 4/10,000 live births; M > F (59:41%).

Key Associations: Turner syndrome, bicuspid aortic valve (~50–85%), VSD, transverse arch hypoplasia, berry aneurysms.

Two Presentations:

Critical/Duct-dependent (neonate): Day 2–7 collapse, shock, absent femoral pulses, metabolic acidosis, renal failure, bowel ischaemia → "Can guarantee baby will be dead in next few days if not discovered and treated"
Non-duct-dependent (older child): Asymptomatic HTN, incidental murmur, radiofemoral delay, weak femoral pulses, rib notching on CXR

Cardinal Sign: Absent or weak femoral pulses — the single most important finding.

BP Pattern: Upper limb BP > Lower limb BP (reversed from normal).

Murmur: ESM at LUSB radiating to left interscapular area (back); ± continuous murmur from collaterals.

Persistent HTN after repair is common — lifelong BP monitoring required.

CoA is a recognized cause of secondary hypertension in children and young adults — always check femoral pulses in any young hypertensive patient.

High Yield Summary — Differential Diagnosis of CoA

Neonatal collapse DDx (duct-dependent systemic circulation):

Coarctation of aorta — strong upper, weak lower limb pulses
Interrupted aortic arch — similar to CoA; Type B associated with DiGeorge/22q11
HLHS — ALL pulses weak (entire systemic circulation duct-dependent)
Critical aortic stenosis — harsh murmur at RUSB; all pulses weak
Sepsis — no pulse gradient; fever/hypothermia; raised inflammatory markers
Metabolic crisis — no pulse gradient; specific biochemical abnormalities

Unequal pulses/BP DDx in older children: ^[7]^[8]

CoA, aortic dissection, supravalvular aortic stenosis, peripheral artery disease

Secondary HTN DDx in children — remember ABCDE: ^[11]

A: Accuracy/Apnoea; B: Bruit/Bad kidney; C: Catecholamines/Cushing's/Coarctation; D: Drugs; E: Endocrine

Syndrome associations:

Turner syndrome → CoA + bicuspid aortic valve
Williams syndrome → supravalvular aortic stenosis
DiGeorge (22q11) → interrupted aortic arch (Type B)

High Yield Summary — Diagnosis of CoA

Clinical diagnosis: Pulse discrepancy (weak femorals) + arm-to-leg BP gradient > 20 mmHg + supporting signs.

First-line confirmatory test: Echocardiography — demonstrates site, severity (Doppler gradient), and associated lesions. Can be done at the bedside in a sick neonate.

Key CXR findings:

Neonate: cardiomegaly + increased pulmonary vascular markings ^[2]
Older child: figure 3 sign + rib notching (after age ~5) ^[2]

ECG: RVH in neonate (RV supports systemic circulation via PDA); LVH in older child (chronic LV pressure overload) ^[2]

Bloods in critical CoA: Severe metabolic acidosis, raised lactate, AKI ^[2]

MRI/MRA: Best for detailed anatomy and gold standard for post-repair surveillance.

Haemodynamic significance: Peak gradient > 20 mmHg across the coarctation on Doppler echo or catheterisation ^[2]^[13].

Golden rule: Do not wait for investigations during emergency ^[14]. Start PGE₁ + antibiotics in a collapsed neonate, then investigate.

High Yield Summary — Management of CoA

Critical neonatal CoA (emergency):

PGE₁ infusion (alprostadil) — maintain ductal patency. Watch for apnoea — have intubation equipment ready.
Inotropes (dopamine/dobutamine) — maintain cardiac output
Correct metabolic acidosis, ventilatory support
Urgent surgical repair ( < 3 months) — resection with end-to-end anastomosis for discrete CoA ^[2]^[3]

Older child (elective):

Indications: proximal HTN, > 20 mmHg gradient, severe CoA on imaging ^[2]^[3]^[13]^[15]
Balloon angioplasty — procedure of choice for native CoA > 4 months and for re-coarctation ^[13]^[15]
Stent placement — for patients ≥ 25 kg; needs re-dilation as the child grows ^[2]^[3]
Surgical repair if complex anatomy or arch hypoplasia

Outcomes:

10-year survival > 90% ^[2]^[3]
Restenosis: 5–15% surgery; 8% balloon (adolescents); 40% balloon (young infants) ^[2]^[3]

Lifelong follow-up for ALL patients: BP monitoring, echocardiography, MRI/MRA, cranial imaging for berry aneurysms ^[13]^[15]

Persistent HTN after repair is common — treat with ACE inhibitors ± beta-blockers ± CCBs

High Yield Summary — Complications of CoA

Acute neonatal complications (untreated critical CoA):

Cardiogenic shock, AKI, NEC/ischaemic colitis, metabolic acidosis → death ≤ 1 week if tight stenosis ^[2]^[3]

Long-term complications (the exam favourites):

Persistent hypertension — most common, most important. Due to arterial wall remodelling, baroreceptor resetting, RAAS upregulation. "Monitoring and treatment of hypertension aggressively" ^[13]^[15]
Re-coarctation — 5–15% after surgery; 40% in infants after balloon ^[2]^[3]. Balloon angioplasty is the treatment of choice for re-coarctation
Aortic aneurysm/dissection — at repair site or ascending aorta (BAV aortopathy). Leading cause of late death. Needs MRI surveillance ^[13]^[15]
Berry aneurysms with rupture → SAH — due to chronic upper body HTN + intrinsic vessel wall abnormality ^[2]^[3]^[5]. Needs cranial imaging ^[13]^[15]
IHD and stroke — accelerated atherosclerosis from persistent HTN
Arrhythmia — from chronic LVH and myocardial fibrosis
BAV progression — aortic stenosis, regurgitation, aortopathy → needs serial echo ^[13]^[15]

Key principle: CoA is never "cured" — it is a lifelong condition requiring surveillance for re-coarctation, HTN, aneurysm, valve disease, and cerebrovascular complications.

Coarctation Of The Aorta

Coarctation of the Aorta (CoA) in Paediatrics

Risk Factors and Associations

Fetal Circulation Review (Essential for Understanding)

Aetiology and Pathophysiology

Pathophysiology — Two Clinical Scenarios

Classification

Clinical Features

A. Symptoms

B. Signs

Additional Pathophysiological Concepts

Active Recall - Coarctation of the Aorta

Differential Diagnosis of Coarctation of the Aorta in Paediatrics

A. Differential Diagnosis of Neonatal Collapse / Duct-Dependent Shock

B. Differential Diagnosis of Upper Limb Hypertension / Unequal Pulses / Murmur in an Older Child

C. Specific Conditions That Are Closely Associated and Enter the DDx

Active Recall - Differential Diagnosis of CoA

References

Diagnostic Criteria, Algorithm, and Investigations for Coarctation of the Aorta in Paediatrics

Diagnostic Criteria

Diagnostic Algorithm

Investigation Modalities — Detailed Interpretation

1. Bedside Investigations

Active Recall - Diagnosis and Investigations of CoA

References

Management of Coarctation of the Aorta in Paediatrics

A. Emergency Management: Critical Neonatal CoA

B. Surgical Treatment Options

C. Catheter-Based (Interventional) Treatment

Hypertension Management

Active Recall - Management of CoA

References

Complications of Coarctation of the Aorta in Paediatrics

C. Long-Term Complications (Post-Repair)

Active Recall - Complications of CoA

References

On this page

Coarctation Of The Aorta

Definition

Epidemiology

Risk Factors and Associations

Genetic / Syndromic

Associated Cardiac Lesions

Extra-Cardiac Associations

Anatomy and Normal Aortic Arch Function

Aetiology and Pathophysiology

Embryological Theories

Pathophysiology — Two Clinical Scenarios

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

Scenario 2: Moderate/Less Severe CoA — Non-Duct-Dependent [2][3]

Classification

By Anatomical Pattern

By Physiological Presentation

Historical Classification (Less Used Now)

Clinical Features

A. Symptoms

Neonatal / Critical CoA (Duct-Dependent)

Older Child / Non-Duct-Dependent CoA

B. Signs

Duct-Dependent CoA Signs [2][3]

Non-Duct-Dependent CoA Signs [2][3]

Comparison Table: Duct-Dependent vs. Non-Duct-Dependent CoA

Additional Pathophysiological Concepts

Why Berry Aneurysms?

Why Necrotising Enterocolitis (NEC) in Neonatal CoA?

CoA as a Cause of Secondary Hypertension [4][6]

Active Recall - Coarctation of the Aorta

References

Framework: Why a Differential Diagnosis is Needed

A. Differential Diagnosis of Neonatal Collapse / Duct-Dependent Shock

1. Interrupted Aortic Arch (IAA)

2. Hypoplastic Left Heart Syndrome (HLHS)

3. Critical Aortic Stenosis (Critical AS)

4. Sepsis / Neonatal Septicaemia

5. Metabolic Crisis (Inborn Errors of Metabolism)

B. Differential Diagnosis of Upper Limb Hypertension / Unequal Pulses / Murmur in an Older Child

Differential for Unequal BP and Pulses [7][8]

Differential for Secondary Hypertension in Children and Adolescents

Other Causes of Systolic Murmur at LUSB in a Child

C. Specific Conditions That Are Closely Associated and Enter the DDx

Williams Syndrome vs. Turner Syndrome

Marfan Syndrome and Connective Tissue Disorders

D. Summary: How to Differentiate CoA from its Mimics at the Bedside

E. Diagnostic Approach Flowchart for the Collapsed Neonate

Active Recall - Differential Diagnosis of CoA

Diagnostic Criteria

Clinical Diagnostic Triad (Bedside)

Haemodynamic Criteria for Significant CoA

Diagnostic Algorithm

Algorithm 1: Neonatal Collapse — Emergency Pathway

Algorithm 2: Older Child — Elective Workup Pathway

Investigation Modalities — Detailed Interpretation

1. Bedside Investigations

a. Four-Limb Blood Pressure Measurement

b. Pre-ductal and Post-ductal Pulse Oximetry

c. Pulse Assessment

2. Blood Tests

3. Electrocardiogram (ECG)

4. Chest X-Ray (CXR)

5. Echocardiography (First-Line Definitive Investigation)

6. MRI / MR Angiography (MRA)

7. CT Angiography (CTA)

8. Cardiac Catheterisation and Angiography

Summary Table: Investigations by Clinical Scenario

Diagnostic Pitfalls in Paediatrics

Active Recall - Diagnosis and Investigations of CoA

Principles of Management

Management Algorithm

A. Emergency Management: Critical Neonatal CoA

Step 1: Resuscitation (ABCs)

Step 2: Prostaglandin E₁ (PGE₁ / Alprostadil) Infusion

Step 3: Inotropic Support

Step 4: Urgent Surgical Repair

B. Surgical Treatment Options

1. Resection with End-to-End Anastomosis

2. Extended End-to-End Anastomosis

3. Subclavian Flap Aortoplasty