2 weeks baby central cyanosis, grade II murmur, normal Sa single S2, plethoric lung ? diagnosis –
**Core Concept**
Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four classic features: ventricular septal defect (VSD), pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. This anomaly leads to cyanosis, due to reduced pulmonary blood flow and increased right-to-left shunting.
**Why the Correct Answer is Right**
In a 2-week-old baby presenting with central cyanosis, a grade II murmur, a normal S1 with a single S2, and plethoric lungs, the diagnosis is likely Tetralogy of Fallot (TOF). The absence of a palpable S2 (single S2) is a hallmark of TOF, resulting from the pulmonary stenosis. The plethoric lungs suggest that there is some left-to-right shunting, but the overall clinical picture is dominated by cyanosis and right ventricular outflow tract obstruction. The grade II murmur is consistent with the VSD.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not match the clinical presentation of TOF. Hypoplastic left heart syndrome (HLHS) typically presents with signs of left heart obstruction and may not have the characteristic single S2.
**Option B:** This choice is incorrect because it does not account for the cyanosis and single S2. Ebstein's anomaly is characterized by an abnormal tricuspid valve and right atrial enlargement, but it often presents with a characteristic "fixed" split S2.
**Option C:** This choice is incorrect because it does not match the clinical presentation of TOF. Total anomalous pulmonary venous return (TAPVR) typically presents with signs of pulmonary venous obstruction and may have a characteristic "supracardiac" murmur.
**Option D:** This choice is incorrect because it does not account for the cyanosis and single S2. Tricuspid atresia is characterized by an absent tricuspid valve and often presents with a characteristic "fixed" split S2.
**Clinical Pearl / High-Yield Fact**
Remember the "4Ts" of Tetralogy of Fallot: truncus arteriosus (overriding aorta), tumor (hypertrophied right ventricle), tricuspid (VSD), and tetralogy (the four classic features of TOF).
**Correct Answer:** C. Total Anomalous Pulmonary Venous Return (TAPVR)