Aortic Coarctation

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Aortic Coarctation

Definition and Prevalence

Coarctation of the aorta (CoA) is a localized or tubular narrowing of the aorta, almost always congenital in origin. First described by Morgagni in 1760, it accounts for approximately 5-8% of all congenital heart defects and represents a generalized arteriopathy - not merely a focal obstruction - with decreased aortic compliance that persists even after successful repair.

Braunwald's Heart Disease, p. 898

Anatomy and Location

The coarctation is typically juxtaductal - at the junction of the distal aortic arch and the descending aorta, just distal to the left subclavian artery origin, opposite or adjacent to the ductus arteriosus. It forms as a posterior/lateral shelf in the aortic wall.

Classification by position relative to the ductus:

Type	Location	Clinical significance
Preductal	Proximal to ductus arteriosus	Rarer; ductal-dependent circulation in neonates; differential cyanosis
Juxtaductal	At the level of the ductus	Most common
Postductal	Distal to ductus arteriosus	Often presents later in life with hypertension

The coarctation can also be classified by position relative to the left subclavian artery (proximal or distal).

Frameworks for Internal Medicine, p. 524
ROSEN's Emergency Medicine, p. 1357

Associated Anomalies

CoA is rarely an isolated lesion. Common associations include:

Bicuspid aortic valve (BAV): 50-85% of cases (most common association)
Ventricular septal defect (VSD)
Mitral valve abnormalities
Subaortic obstruction
Anomalous origin of the right subclavian artery
Intracranial (Berry) aneurysms in the Circle of Willis
Turner syndrome, Noonan syndrome, Williams-Beuren syndrome
Shone syndrome: CoA + parachute mitral valve + supramitral ring + multilevel left-sided LVOTO
Braunwald's Heart Disease, p. 898

Pathophysiology

Two main mechanisms underlie hemodynamic disturbance:

Mechanical obstruction: reduces flow to the lower body, causing lower extremity hypoperfusion.
Pressure overload proximal to the narrowing: causes upper-body hypertension and LV pressure overload.

Over time, collateral vessels develop (internal mammary, intercostal, posterior mediastinal arteries) to bypass the obstruction and maintain lower-body perfusion. The ductus arteriosus also acts as a bypass in neonates - its closure precipitates cardiovascular collapse in severe preductal coarctation.

In preductal coarctation with a patent ductus arteriosus: the lower body receives deoxygenated blood via right-to-left ductal shunting, producing differential cyanosis (pink upper body, cyanotic lower body).

Grainger & Allison's Diagnostic Radiology, p. 222
ROSEN's Emergency Medicine, p. 1360

Clinical Presentation

CoA follows a bimodal distribution:

Neonates and Infants (Severe Coarctation)

Cardiovascular collapse and shock when the ductus closes
Congestive heart failure, tachycardia, poor feeding
Differential cyanosis (preductal type)

Older Children and Adults (Milder Coarctation)

Asymptomatic hypertension - most common presentation
Headache
Leg claudication / cold legs
Discovered incidentally on murmur or hypertension workup

Key Physical Findings:

Brachial-femoral delay (palpate both pulses simultaneously)
BP differential: systolic BP right arm > lower extremities by ≥15-20 mmHg
Reduced femoral pulses
Systolic murmur best heard over the back / interscapular area
Continuous interscapular murmurs suggest collateral flow
S4 gallop from LV hypertrophy
Hypertensive retinopathy on fundoscopy

If the left subclavian artery is sacrificed during repair, left arm BP can be misleadingly low - always use the right arm for BP measurement.

Braunwald's Heart Disease, p. 898; Frameworks for Internal Medicine, p. 524

Investigations

Chest X-Ray

Rib notching: erosion of the inferior border of the posterior 3rd-9th ribs (from dilated intercostal collaterals) - typically bilateral, rarely seen before age 5
"Figure 3" sign: mediastinal silhouette showing pre-stenotic dilation of the aortic arch + post-stenotic dilation of the descending aorta

Chest radiograph showing rib notching (arrows) in the 3rd-5th ribs bilaterally. The "figure 3" mediastinal silhouette (blue dashed) is formed by the dilated distal aortic arch and the post-stenotic descending aorta (asterisks). CMR (B) confirms coarctation with large collateral vessels. - Braunwald's Heart Disease, Fig. 82.34

ECG

Left ventricular hypertrophy
Left atrial enlargement
Ischemic changes (in adults)

Echocardiography

Assesses coarctation site, aortic valve, LV function and mass
Continuous wave Doppler from suprasternal view: increased velocity at coarctation, diastolic tail in descending aorta, and continuous flow in abdominal aorta suggest significant stenosis

Cardiac MRI (CMR) - Primary imaging modality

Quantifies LV mass, arch hypoplasia, collateral flow, coarctation severity
Identifies post-repair complications (aneurysms, recoarctation, dissection)
Preferred over CT if no contraindications

Cardiac CT

Better for assessing stent lumen integrity, fracture, and coronary arteries

Cardiac Catheterization

Peak-to-peak gradient ≥20 mmHg across the coarctation (in the absence of well-developed collaterals) = hemodynamically significant
Braunwald's Heart Disease, p. 898; Grainger & Allison's Diagnostic Radiology, p. 228

Natural History (Untreated)

Without correction:

Mean life expectancy: 35 years
90% of patients die before age 50
Causes of death: coronary artery disease, stroke, aortic dissection, congestive heart failure, intracranial hemorrhage from aneurysm rupture
Frameworks for Internal Medicine, p. 524

Management

Neonates/Infants (Ductal-Dependent)

Prostaglandin E1 (PGE1) to maintain ductal patency until surgical repair
Primary surgical repair in infancy

Children

Surgery: resection + end-to-end anastomosis (preferred in infants/young children)
Balloon angioplasty may be considered for native or recurrent coarctation

Adults - Intervention Indications:

Intervention is indicated when:

Hypertensive patient with invasive peak-to-peak gradient ≥20 mmHg
Coarctation diameter ≤50% of aortic diameter at the diaphragm in a hypertensive patient (regardless of gradient)
Normotensive patient with gradient ≥20 mmHg

Adult Treatment of Choice:

Endovascular stenting - preferred over surgery in adults when technically feasible
Covered stents preferred to prevent/treat acute wall injury
Surgery reserved for complex anatomy (interrupted arch, long-segment coarctation, aneurysmal disease) - options include interposition graft, ascending-to-descending aorta bypass conduit

Medical Management:

Antihypertensives: beta-blockers, ACE inhibitors, ARBs (first-line)
Aggressive BP and lipid control to prevent atherosclerotic complications
Braunwald's Heart Disease, p. 898; Frameworks for Internal Medicine, p. 524

Post-Repair Complications and Follow-Up

Even after successful repair, CoA is NOT cured - it requires lifelong surveillance:

Complication	Details
Persistent/recurrent hypertension	>50% of adults, especially if repaired late; aortic compliance permanently reduced
Recoarctation	Up to 35% after balloon dilation; less with primary stenting
Aortic aneurysm	Especially after Dacron patch aortoplasty (opposite wall becomes aneurysmal)
Aortic dissection	Late risk, related to aortopathy
BAV complications	Aortic stenosis/regurgitation, ascending aortic dilation
Coronary artery disease	From chronic hypertension
Exercise-induced hypertension	Linked to adverse LV remodeling

Cross-sectional imaging (CMR) should be performed at intervals of at least 3-5 years lifelong.

Braunwald's Heart Disease, p. 898; Grainger & Allison's Diagnostic Radiology, p. 234

Key Summary Points

Feature	Detail
Most common site	Juxtaductal (distal to left subclavian artery)
Most common association	Bicuspid aortic valve (50-85%)
Classic CXR findings	Rib notching + "figure 3" sign
Classic physical exam	Brachial-femoral delay + upper > lower extremity BP
Significant gradient	≥20 mmHg peak-to-peak
Adult treatment of choice	Endovascular stenting
Untreated life expectancy	~35 years

Sources:

Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, Ch. 82
Frameworks for Internal Medicine, p. 524
ROSEN's Emergency Medicine, Ch. 165
Grainger & Allison's Diagnostic Radiology, Ch. 13

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