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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Widely fixed split S2

  • Midsystolic murmur

  • Diastolic flow rumble at the lower left sternal border if the shunt is large

  • Incomplete right bundle branch block (RBBB) with vertical QRS axis (ostium secundum ASD) and superior axis (ostium primum ASD) on ECG

  • Prominent pulmonary arteries and right ventricular (RV) enlargement

  • RV dilatation, increased pulmonary artery flow velocity, and left-to-right atrial shunt by Doppler echocardiography

  • Oxygen step-up within the right atrium; right-sided catheter can pass into the left atrium across the defect

GENERAL CONSIDERATIONS

  • Most common congenital lesion in adults (after bicuspid aortic valve)

  • Classification is according to location

  • Secundum ASD (most common) is a defect involving the septum secundum in the region of the fossa ovalis

  • Primum ASD (also called atrioventricular [AV] canal defect) involves the ostium primum in the lower portion of the atrial septum

  • Sinus venosus ASD is a defect that can be located either superiorly near the superior vena cava or inferiorly near the inferior vena cava.

  • ASD is often asymptomatic and undiagnosed until adulthood

  • The pathophysiologic consequences depend on the quantity of blood shunted from the systemic to pulmonary circulation

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Usually no symptoms in the young adult with an ASD and normal pulmonary artery pressures unless the defect is very large

  • Symptoms more common in the fourth or fifth decade

  • Dyspnea

  • Diminished exercise tolerance

  • Atrial arrhythmia increases with age and may be the most common presenting symptom in patients over 50

  • Signs and symptoms of RV failure due to pulmonary hypertension or longstanding volume overload

PHYSICAL EXAM FINDINGS

  • Prominent RV impulse

  • Palpable pulmonary artery

  • Systolic ejection murmur that does not vary with respiration

  • Wide, fixed split S2

  • Right-sided diastolic flow rumble

  • Right-sided S3 gallop

  • Holosystolic murmur of mitral regurgitation with ostium primum ASD

  • With pulmonary hypertension, the P2 is usually increased and a diastolic murmur of pulmonic insufficiency may be audible (Graham Steell murmur)

  • Signs of RV failure with elevated jugular venous pressure and venous congestion in late stages

  • Cyanosis in patients with Eisenmenger physiology

DIFFERENTIAL DIAGNOSIS

  • Other causes of exertional dyspnea, of atrial arrhythmias, of RV failure, and of a midsystolic murmur (eg, pulmonic stenosis)

  • The wide fixed split S2 can be mimicked by complete RBBB, pericardial knock, and a late systolic click

  • Other causes of pulmonary hypertension

DIAGNOSTIC EVALUATION

ELECTROCARDIOGRAPHY

  • Incomplete RBBB in 90% of cases

  • Right axis deviation with ostium secundum and sinus venosus ASDs

  • First-degree AV block, complete RBBB, and left anterior fascicular block with superior and leftward axis with primum ASDs

  • Ectopic atrial rhythm with superior P-wave axis occasionally with sinus venosus ASD

  • RV hypertrophy

  • Notch on the R wave ("crochetage" pattern) in ...

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