100+ Free Cert Cardiology(SA) Paed Practice Questions

Explanation: Perimembranous VSDs frequently undergo spontaneous closure or size reduction through the adherence of tricuspid valve tissue (specifically the septal leaflet and its chordae), forming a pseudo-aneurysm of the membranous septum. This tissue partially or completely occludes the defect over the first few years of life.

Explanation: In an ostium secundum ASD, left-to-right shunting causes chronic right ventricular volume overload. The increased right ventricular stroke volume delays closure of the pulmonary valve (P2). During inspiration, venous return to the RV increases while ASD shunting decreases; during expiration, venous return to the RV decreases while ASD shunting increases. This keeps RV stroke volume and P2 timing constant across respiration, producing a fixed, wide split S2.

Explanation: Cyclooxygenase inhibitors (indomethacin and ibuprofen) inhibit prostaglandin synthesis, which can decrease mesenteric and renal blood flow. Absolute contraindications include active necrotizing enterocolitis (NEC), active gastrointestinal bleeding, severe renal impairment (oliguria or elevated creatinine), active intracranial hemorrhage, and severe thrombocytopenia (<50,000/microL).

Explanation: Complete AVSD (endocardial cushion defect) is present in approximately 40-50% of infants with Down syndrome. The displacement of the conduction system (posterior and inferior displacement of the AV node and bundle of His) results in a characteristic superior QRS axis (left axis deviation or extreme axis deviation) with a counterclockwise frontal QRS loop on ECG.

Explanation: In duct-dependent systemic circulation (such as severe neonatal coarctation of the aorta, interrupted aortic arch, or HLHS), spontaneous closure of the ductus arteriosus leads to acute lower body hypoperfusion, severe metabolic acidosis, and cardiovascular collapse. Continuous PGE1 infusion reopens the ductus, restoring lower body systemic perfusion and stabilizing the infant prior to surgical intervention.

Explanation: Hypercyanotic spells in TOF occur when infundibular spasm or decreased SVR leads to increased right-to-left shunting across the VSD and reduced pulmonary blood flow. Knee-chest positioning kinks the femoral arteries, significantly increasing SVR. This higher systemic pressure reduces right-to-left VSD shunting and forces more blood across the obstructed RV outflow tract into the pulmonary circulation.

Explanation: In d-TGA with an intact ventricular septum, survival depends on adequate interatrial mixing between the parallel pulmonary and systemic circulations. If the atrial septum is intact or restrictive, severe hypoxemia occurs. Urgent bedside Rashkind balloon atrial septostomy tears the atrial septum, improving interatrial mixing and oxygenation until definitive arterial switch surgery is performed.

Explanation: Conotruncal anomalies (including Truncus Arteriosus, Tetralogy of Fallot, and Interrupted Aortic Arch Type B) are strongly associated with 22q11.2 deletion syndrome (DiGeorge / Velocardiofacial syndrome). Truncus arteriosus occurs due to failure of neural crest cell migration required for septation of the truncus arteriosus into the aorta and pulmonary artery.

Explanation: Infradiaphragmatic Total Anomalous Pulmonary Venous Connection (TAPVC Type III) is almost always obstructed because the anomalous conduit passes through the esophageal hiatus and hepatic parenchyma before joining the IVC. This causes severe pulmonary venous congestion, pulmonary hypertension, hypoxemia, and rapid mortality. Emergency surgical repair is required immediately.

Explanation: Most cyanotic congenital heart defects in newborns cause right ventricular hypertrophy and right axis deviation. Tricuspid Atresia is a classic exception: because the right ventricle is hypoplastic and the left ventricle is dominant, the ECG demonstrates left axis deviation (0 to -90 degrees), left ventricular hypertrophy, and tall P waves (p-tricuspidale) due to right atrial enlargement.