1.11 Adult Congenital Heart Disease & Coarctation of the Aorta

1. Why Adult Congenital Disease Appears on an Internal Medicine Exam

More adults than children now live with congenital heart disease, and most are cared for by internists between specialist visits. ABIM lists Congenital heart disease in adults as a named subsection under Cardiovascular Disease, enumerating atrial septal defect and patent foramen ovale, bicuspid aortic valve, and other congenital heart disease (patent ductus arteriosus, ventricular septal defect, pulmonic stenosis). Coarctation of the aorta is listed separately, under the hypertension subsection.

These items are usually recognition questions built on a physical finding, an ECG pattern or an incidental imaging result — not management questions requiring surgical judgment.

2. Atrial Septal Defect and Patent Foramen Ovale

A patent foramen ovale (PFO) is a normal fetal structure that fails to seal; it is present in roughly a quarter of adults and is not a defect in the anatomic sense. An atrial septal defect (ASD) is a true deficiency of the septum. The distinction matters because it drives both physiology and management.

The fixed split S2 is the single highest-yield finding. In normal physiology, inspiration delays pulmonic valve closure and widens the split; expiration narrows it. A large left-to-right atrial shunt keeps right ventricular volume loaded throughout the respiratory cycle, so the split no longer varies. A systolic murmur may be present, but it arises from increased flow across the pulmonic valve, not from flow across the defect itself — the interatrial pressure gradient is too small to generate a murmur.

The ECG helps localize the defect: secundum defects typically show right axis deviation with an incomplete right bundle branch pattern, whereas primum defects show left axis deviation and are associated with atrioventricular valve clefts and with Down syndrome.

Closure of an ASD is considered when there is right-sided chamber enlargement, generally with a shunt fraction (Qp:Qs) above 1.5:1, provided pulmonary vascular resistance has not risen prohibitively. PFO closure is a different question entirely and is considered chiefly in younger patients after cryptogenic stroke when no other mechanism is found.

3. Bicuspid Aortic Valve

A bicuspid aortic valve is the most common congenital cardiac malformation. Two exam points dominate:

1. It stenoses early. Turbulent flow across two rather than three cusps accelerates calcific degeneration, so bicuspid patients present with severe aortic stenosis one to two decades earlier than patients with trileaflet valves. An ejection click followed by a systolic murmur in a patient in their fifties should raise the possibility.
2. The aortopathy is independent of the valve lesion. Bicuspid valve disease is associated with an intrinsic abnormality of the aortic media, so ascending aortic dilation, aneurysm and dissection occur even when the valve works normally. The ascending aorta must therefore be imaged and followed regardless of valve function, and first-degree relatives should be screened.

4. Ventricular Septal Defect, Patent Ductus Arteriosus and Pulmonic Stenosis

A counterintuitive rule worth memorizing: in ventricular septal defect, murmur intensity is inversely related to defect size. A small restrictive defect generates a high-velocity jet and a loud murmur; a large defect equalizes ventricular pressures and may be nearly silent while causing far more physiologic harm.

Right-sided murmurs — pulmonic stenosis, tricuspid regurgitation — increase with inspiration as venous return to the right heart rises. Left-sided murmurs do not. This is the fastest bedside discriminator on the exam.

5. Coarctation of the Aorta

Coarctation is listed by ABIM under Hypertension, and that placement is the clinical clue: it is a surgically correctable cause of secondary hypertension in a young patient.

The triad to recognize:

• Upper-extremity hypertension with lower-extremity hypotension. A systolic gradient between arm and leg is the defining finding.
• Radiofemoral delay. The femoral pulse is delayed and diminished relative to the radial pulse.
• Rib notching on chest radiograph. Dilated intercostal collateral arteries erode the inferior rib margins, and the dilated aorta above and below the narrowing can produce a "figure 3" contour.

Coarctation is strongly associated with bicuspid aortic valve (present in a majority of cases) and with intracranial berry aneurysms; it is also a recognized feature of Turner syndrome. Any young hypertensive patient should have blood pressure measured in an arm and a leg at least once — it is a two-minute test that occasionally reveals a curable cause.

6. Eisenmenger Physiology

A long-standing, uncorrected left-to-right shunt drives pulmonary vascular remodeling. When pulmonary vascular resistance rises above systemic resistance, the shunt reverses and the patient becomes cyanotic — Eisenmenger syndrome.

The critical management consequence: once Eisenmenger physiology is established, defect closure is contraindicated. The shunt has become the right ventricle's only pressure-relief pathway; closing it converts a cyanotic but compensated circulation into acute right ventricular failure.

Other management principles in Eisenmenger physiology:

• Avoid systemic vasodilation and volume depletion, both of which increase right-to-left shunting and worsen hypoxemia.
• Avoid routine phlebotomy for erythrocytosis; the elevated hematocrit is a compensatory response to hypoxemia, and phlebotomy causes iron deficiency and increases stroke risk.
• Use meticulous air-filter precautions on intravenous lines, because a right-to-left shunt allows paradoxical air embolism.
• Pregnancy carries very high maternal mortality and is generally advised against.

Differential cyanosis — pink fingers with blue toes — is the signature of a reversed patent ductus arteriosus, because the deoxygenated shunt enters the aorta distal to the vessels supplying the upper extremities.