Atrial septal defect
Atrial septal defect is a communication in the interatrial septum causing a left-to-right shunt, often silent until adulthood. It classically produces a fixed split second heart sound and, over time, right heart volume overload, atrial arrhythmias, and pulmonary hypertension; hemodynamically significant defects are closed by device or surgery.
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What this article covers
- Overview
Definition: atrial septal defect (ASD) is a persistent communication in the interatrial septum allowing a shunt, usually left-to-right, between the atria.
- Epidemiology
A common congenital defect, frequently diagnosed in adulthood.
- Risk factors
Congenital malformation (often isolated).
- Pathophysiology
Left-to-right atrial shunt: the more compliant right heart receives shunted blood, causing right atrial and ventricular volume overload and pulmonary overcirculation.
- Clinical features
Often asymptomatic until adulthood. A fixed split second heart sound and a pulmonary flow (systolic ejection) murmur.
- Differential diagnosis
Patent foramen ovale: a flap-valve communication with no true septal tissue deficiency and usually no significant shunt, so right heart enlargement is absent, unlike ASD (Patent foramen ovale).
- Diagnosis
Establish and characterize with echocardiography and a bubble study, quantifying the shunt and right heart effect: the diagnostic basis is echocardiography (often transesophageal, with an…
- Management
First-line, close a hemodynamically significant defect: device closure (for suitable ostium secundum defects) or surgical repair is indicated for a significant shunt or right heart enlargement, before irreversible pulmonary hypertension.
- Complications
Right heart volume overload and failure. Atrial fibrillation and flutter.
- Prognosis
Excellent after timely closure, with reduced arrhythmia and improved function.
- Prevention
Timely closure of hemodynamically significant defects (pulmonary-to-systemic flow ratio, Qp:Qs, of 1.5:1 or more, or right heart enlargement) to prevent right heart and pulmonary complications.
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Related articles
- Patent foramen ovale
Patent foramen ovale is a persistent flap-like interatrial communication present in about a quarter of adults, usually benign. Its clinical importance is as a conduit for paradoxical embolism causing cryptogenic stroke; in selected younger patients with cryptogenic stroke, device closure plus antiplatelet therapy reduces recurrence.
- Ventricular septal defect
Ventricular septal defect is a hole in the interventricular septum causing a left-to-right shunt, the most common congenital heart defect. Small defects produce a loud murmur but close spontaneously, while large defects cause heart failure and pulmonary hypertension and require closure before irreversible pulmonary vascular disease (Eisenmenger physiology) develops.
- Eisenmenger syndrome
Eisenmenger syndrome is the end stage of a large uncorrected left-to-right cardiac shunt, in which chronic pulmonary overcirculation causes irreversible pulmonary vascular disease and shunt reversal to right-to-left with cyanosis. The defect can no longer be closed; management is specialized supportive care, pulmonary vasodilators, and avoidance of destabilizing insults.
- Pulmonic stenosis
Pulmonic stenosis is obstruction to right ventricular outflow from a narrowed pulmonary valve, usually congenital. It causes a systolic ejection murmur with an ejection click and, when severe, right ventricular hypertrophy and failure; severe or symptomatic disease is treated effectively with balloon valvuloplasty.
- Right heart failure
Right heart failure is inability of the right ventricle to maintain output at acceptable filling pressures, most often from left heart failure or pulmonary hypertension, and acutely from pulmonary embolism or right ventricular infarction. It causes systemic venous congestion, and management centers on the underlying cause, careful volume and afterload optimization, and preload-dependent support in acute disease.