MRCPCH FOP/TAS Question Bank

A ventricular septal defect (VSD) is the most likely diagnosis. VSD is the most common congenital heart defect, accounting for approximately 30% of all CHD. The classic presentation at 4-8 weeks (as pulmonary vascular resistance falls and left-to-right shunting increases) includes symptoms of heart failure - poor feeding, tachypnoea, sweating during feeds, and failure to thrive. The pansystolic murmur at the left lower sternal edge is characteristic.

An ASD (A) typically produces an ejection systolic murmur with fixed splitting of S2 and rarely causes heart failure in infancy. PDA (C) produces a continuous 'machinery' murmur below the left clavicle. Tetralogy of Fallot (D) presents with cyanosis, not heart failure, and has an ejection systolic murmur from the RVOT. Coarctation (E) presents with weak femoral pulses and upper/lower limb blood pressure discrepancy.

VSDs are classified by location: perimembranous (80%, adjacent to the tricuspid valve), muscular (5-20%, within the ventricular septum), outlet/supracristal (5%, near the aortic and pulmonary valves), and inlet (5%, near the AV valves). Small VSDs may close spontaneously (up to 80% of muscular VSDs close by age 10). Large VSDs causing heart failure require medical management (diuretics, ACE inhibitors, high-calorie feeds) and surgical closure, typically before 6 months.

Remember: VSD is the most common CHD - it presents at 4-8 weeks with heart failure symptoms as PVR falls, produces a pansystolic murmur at the LLSE, and small defects often close spontaneously.

Transposition of the great arteries (TGA) is the most likely diagnosis. The key features are: severe cyanosis unresponsive to oxygen (the hyperoxia test is failed), presentation in the first days of life, absent or minimal murmur, and the characteristic 'egg-on-a-string' CXR appearance (narrow mediastinum due to the anteroposterior relationship of the great arteries, with increased pulmonary vascularity due to unrestricted pulmonary blood flow).

Tetralogy of Fallot (A) typically presents later with progressive cyanosis and has a boot-shaped heart on CXR. TAPVD (C) presents with cyanosis but has a 'snowman' or 'figure-of-eight' CXR in the supracardiac type. Tricuspid atresia (D) shows reduced pulmonary vascularity on CXR. PPHN (E) would show clear lung fields and pre-post ductal saturation difference.

In TGA, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, creating two parallel circulations. Survival depends on mixing between the circulations through the PDA, foramen ovale, or a VSD. Emergency management includes prostaglandin E1 (alprostadil) infusion to maintain ductal patency, balloon atrial septostomy (Rashkind procedure) to improve atrial-level mixing, and definitive surgical correction with the arterial switch operation (Jatene procedure), ideally within the first 2 weeks.

Remember: Cyanosis unresponsive to oxygen in a newborn with 'egg-on-a-string' CXR is TGA - start prostaglandin immediately, arrange balloon septostomy for mixing, and plan arterial switch operation within 2 weeks.

Coarctation of the aorta is the most likely diagnosis based on the classic triad of weak femoral pulses, upper-lower limb blood pressure gradient (>20 mmHg systolic difference), and systolic murmur best heard posteriorly between the scapulae. Coarctation involves narrowing of the aorta, typically at the site of the ductus arteriosus insertion (juxtaductal).

PDA (A) would produce a continuous murmur and bounding pulses. Aortic stenosis (B) produces an ejection systolic murmur at the right upper sternal edge with a normal four-limb BP profile. Peripheral pulmonary stenosis (D) produces a murmur radiating to the axillae. Interrupted aortic arch (E) is a more severe variant presenting with cardiovascular collapse when the duct closes.

Coarctation is associated with Turner syndrome (45,X), bicuspid aortic valve (present in 50-80% of coarctation cases), and other left-sided obstructive lesions. In neonates, critical coarctation can present with cardiovascular collapse when the ductus arteriosus closes - prostaglandin E1 infusion should be started immediately to reopen the duct and restore distal perfusion. Older children with undiagnosed coarctation may present with hypertension, headaches, or leg claudication. Treatment is surgical repair or balloon angioplasty/stenting.

Remember: Four-limb BP measurement is essential in the newborn examination - weak femoral pulses with >20 mmHg upper-lower limb systolic gradient is coarctation until proven otherwise; start prostaglandin if critical.