Pediatric Cardiology: Congenital Lesions and Murmurs
This domain tests the differentiation of acyanotic from cyanotic congenital heart disease, the hyperoxia test, ductal-dependent lesions and the management of heart failure in infancy.
Acyanotic lesions
- Ventricular septal defect: holosystolic murmur at the left lower sternal border, heart failure at 4-8 weeks as pulmonary vascular resistance falls; many close spontaneously.
- Patent ductus arteriosus: continuous machinery murmur, bounding pulses, wide pulse pressure.
- Atrial septal defect: fixed split second heart sound, pulmonary flow murmur.
Cyanotic lesions
- Tetralogy of Fallot: ventricular septal defect, overriding aorta, right ventricular outflow obstruction and right ventricular hypertrophy; boot-shaped heart, squatting, right aortic arch in about 25%.
- Transposition of the great arteries: profound cyanosis in the first hours with an unremarkable examination and an "egg on its side" silhouette.
- Ductal-dependent lesions (transposition, critical coarctation, interrupted arch, pulmonary atresia) require prostaglandin E1 infusion.
Hypercyanotic spell in tetralogy
Place the child knee-chest, give oxygen, morphine, intravenous fluid and phenylephrine; a beta-blocker prevents recurrence. Avoid isoproterenol, which worsens outflow obstruction.
Congestive heart failure in infants
Tachypnea, feeding difficulty, sweating with feeds, poor weight gain and hepatomegaly. Treat with diuretics and an ACE inhibitor, ensure adequate calories, and refer for surgery if growth fails.
Worked example
A 6-week-old has poor feeding, tachypnea, hepatomegaly and a grade 3 holosystolic murmur at the left lower sternal border. Reasoning: the age, murmur and heart failure signs fit a large ventricular septal defect. Start furosemide, add an ACE inhibitor, increase caloric density, and plan surgical closure if symptoms persist.
Traps
Attributing cyanosis to lung disease without a hyperoxia test (PaO2 above 150 mmHg suggests cardiac disease); giving prostaglandin in unobstructed total anomalous pulmonary venous return, which can be harmful; and reassuring a family that a murmur is innocent without checking pulses and blood pressure.