Atrial septal defect and partial anomalous pulmonary venous return — formative SAQs

SAQ 1 (10 marks) — The incidental murmur at the preschool check

Stem: A four-year-old girl is referred after a preschool medical examination picks up a heart murmur. She is asymptomatic, grows normally, and has had two episodes of bronchitis in the past year. On examination, there is a soft systolic ejection murmur at the upper left sternal edge and a widely split second heart sound that does not vary with respiration. Outline your diagnosis, investigations, and management. ^{[5] [1]}

Model answer

Diagnosis and auscultatory signature (2 marks). The most likely diagnosis is a secundum atrial septal defect. The wide, fixed, split second heart sound is the auscultatory signature of an atrial-level shunt, caused by delayed right ventricular emptying against the increased pulmonary flow. The soft systolic ejection murmur is the sound of increased right ventricular stroke volume crossing a normal pulmonary valve, not blood crossing the defect. ^[5]

Confirm with echocardiography (3 marks). Echocardiography is the single diagnostic investigation. Two-dimensional imaging shows the defect, its location, size, and the surrounding rims of atrial septal tissue. Colour Doppler confirms the left-to-right shunt. The right ventricular size is dilated, and the pulmonary artery pressure is estimated from the tricuspid regurgitation jet. The Qp to Qs ratio quantifies the shunt, with a ratio above 1.5 to 1 meeting the closure threshold. ^{[5] [1]}

Management — device closure (3 marks). A secundum defect with adequate rims exceeding five millimetres, except the retro-aortic rim, and a stretched diameter under thirty-eight millimetres, is closed with a transcatheter device such as the Amplatzer septal occluder. Aspirin is given for three to six months for antiplatelet protection until the device endothelialises. Endocarditis prophylaxis is not needed beyond the early period. ^{[3] [1]}

Timing and prognosis (2 marks). Closure in childhood preserves the right ventricle and prevents the adult complications of heart failure, atrial arrhythmia, paradoxical embolism, and pulmonary vascular disease. The right ventricle remodels back to normal within months, and the life expectancy approaches the normal population. Lifelong follow-up continues for arrhythmia and pulmonary hypertension surveillance. ^{[1] [2]}