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]

SAQ 2 (10 marks) — Sinus venosus ASD with partial anomalous pulmonary venous return

Stem: A ten-year-old boy presents with exertional dyspnoea and recurrent respiratory infections. Echocardiography shows right ventricular dilation but no clear defect in the fossa ovalis; a defect is suspected near the superior vena cava orifice. Discuss the further imaging, the likely diagnosis, and the management. [5] [7]

Model answer

Likely diagnosis (2 marks). The likely diagnosis is a sinus venosus atrial septal defect with partial anomalous pulmonary venous return, in which the right upper pulmonary vein drains to the superior vena cava or right atrium. The defect sits near the cava orifice and is often missed on transthoracic echocardiography, presenting as unexplained right ventricular dilation. [5] [7]

Further imaging (3 marks). Cardiac computed tomography or magnetic resonance imaging is indicated to define the anatomy that the echo cannot see. The cross-sectional imaging maps the anomalous pulmonary vein, its drainage site, and the relationship to the superior vena cava, and it confirms the sinus venosus defect. This imaging is essential before surgery because the surgical plan depends on the precise venous anatomy. [7]

Management — surgical closure (3 marks). Sinus venosus defects are never closed with a device. Closure is surgical, via a median sternotomy with cardiopulmonary bypass, using a patch that closes the defect and redirects the anomalous pulmonary vein to the left atrium. Care is taken to avoid sinus node dysfunction from the patch near the superior vena cava, because the sinus node sits at the cavoatrial junction. [2] [5]

Follow-up and prognosis (2 marks). Post-operative echocardiography confirms closure and right ventricular remodelling. Lifelong follow-up continues for sinus node dysfunction, atrial arrhythmia, and pulmonary hypertension surveillance. The transition to adult congenital cardiology is structured, because arrhythmia remains more common than in the general population even after successful closure. [1] [2]