Which one of the following is a cyanotic congenital hea disease?
**Core Concept**
Cyanotic congenital heart diseases are characterized by the presence of a right-to-left shunt, which allows deoxygenated blood to bypass the lungs and enter the systemic circulation, resulting in cyanosis. This class of heart diseases is often associated with a combination of structural anomalies that affect blood flow and oxygenation.
**Why the Correct Answer is Right**
Tricuspid atresia is a classic example of a cyanotic congenital heart disease. In this condition, the tricuspid valve is absent or abnormally developed, preventing blood from flowing from the right atrium to the right ventricle. As a result, the right ventricle is underdeveloped, and the blood is shunted from the right atrium to the left atrium through an atrial septal defect, bypassing the lungs and leading to cyanosis. The right-to-left shunt also results in decreased pulmonary blood flow and increased systemic venous pressure.
**Why Each Wrong Option is Incorrect**
**Option A:** Tetralogy of Fallot is a cyanotic congenital heart disease, but it is characterized by four specific anomalies: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. While it is a cyanotic heart disease, it is not the best example of a condition with a right-to-left shunt due to tricuspid atresia.
**Option B:** Ebstein's anomaly is a congenital heart disease characterized by an abnormal tricuspid valve and right ventricular hypoplasia. However, it is not typically associated with a right-to-left shunt and is not classified as a cyanotic congenital heart disease.
**Option D:** Hypoplastic left heart syndrome is a cyanotic congenital heart disease, but it is characterized by underdevelopment of the left heart structures, including the left ventricle, aortic valve, and aorta. This condition is not associated with tricuspid atresia.
**Clinical Pearl / High-Yield Fact**
Tricuspid atresia is often associated with other congenital anomalies, such as atrial septal defects, ventricular septal defects, and pulmonary stenosis. A high index of suspicion for tricuspid atresia should be maintained in infants with unexplained cyanosis and a normal or decreased pulmonary blood flow.
**Correct Answer: C. Tricuspid atresia**