Congenital coronary anomalies and ALCAPA — formative SAQs

SAQ 1 (10 marks)

A ten-week-old boy is brought to the emergency department with a three-week history of pallor, sweating and irritability during feeds, poor weight gain, and increasing breathlessness. On examination he is tachypnoeic with a gallop rhythm, a pansystolic murmur at the apex, and hepatomegaly. His electrocardiogram shows deep Q waves in leads I, aVL and V5 to V7 with T-wave inversion, and his chest radiograph shows marked cardiomegaly with pulmonary venous congestion. [1] [2]

1. Give the most likely diagnosis, explain the pathophysiological mechanism that produces the symptoms at this age, and state the key investigations that confirm it. (4) [1] [2]
2. Outline the acute medical management while definitive treatment is arranged, and justify the role of mechanical circulatory support. (3) [3]
3. Describe the definitive surgical treatment and the determinants of long-term outcome. (3) [3] [6]

Model answer — SAQ 1

(1) Diagnosis, pathophysiology and investigations (4). The most likely diagnosis is anomalous left coronary artery from the pulmonary artery (ALCAPA, Bland-White-Garland syndrome), and the clues are the feeding-related pallor and diaphoresis (the anginal equivalents of infancy), the anterolateral Q waves on the electrocardiogram, and the dilated left ventricle with mitral regurgitation. The mechanism is the steal: in fetal and early neonatal life the high pulmonary vascular resistance drives forward flow from the pulmonary artery into the misoriginated left coronary artery, so the left ventricle is protected. As the pulmonary vascular resistance falls over the first weeks of life, the pressure gradient reverses, the left coronary artery drains into the low-pressure pulmonary artery, and the left ventricle is left perfused only by right coronary collaterals at low pressure, so the anterolateral myocardium infarcts, the ventricle dilates, and the ischaemic papillary muscles produce mitral regurgitation. The key investigation is echocardiography, which must show the left coronary artery arising from the pulmonary artery with retrograde colour-Doppler flow into the pulmonary artery, a dilated poorly contracting left ventricle, and mitral regurgitation; computed tomography coronary angiography confirms the anatomy when echo is equivocal. [1] [2]

(2) Acute management and mechanical support (3). Acute management is supportive and serves as a bridge to surgery. I would give oxygen and positive-pressure ventilation if the work of breathing is high, treat the heart failure with intravenous furosemide and an afterload-reducing agent such as an angiotensin-converting-enzyme inhibitor, and add inotropes such as milrinone and low-dose adrenaline for low cardiac output in a paediatric intensive care setting. Mechanical circulatory support with extracorporeal membrane oxygenation is justified for the infant who cannot be stabilised on inotropes, both as a bridge to surgery and as a bridge to recovery of the stunned ventricle after repair, because the infarcted left ventricle may need time to recover coronary flow before it can sustain the circulation alone. [3]

(3) Definitive surgery and long-term determinants (3). The definitive treatment is surgical re-establishment of a dual coronary system, most often by direct reimplantation of the left coronary artery into the aorta with a button of arterial wall, or by the Takeuchi intrapulmonary tunnel when the anatomy does not allow direct reimplantation. Severe mitral regurgitation is repaired at the index operation, but moderate regurgitation is often deferred because the ischaemic papillary muscles recover once coronary flow is restored. The determinants of long-term outcome are the timeliness of repair — earlier repair means better left ventricular recovery — together with the severity of residual mitral regurgitation and the burden of ventricular arrhythmia from scar; the ECHSA database and long-term follow-up show good left ventricular recovery and low late mortality when repair is timely, with lifelong surveillance and transition to adult congenital care. [3] [6]