Tetralogy of Fallot classically consists of the combination of ail except –
**Core Concept**
Tetralogy of Fallot (TOF) is a congenital heart defect characterized by a combination of four classic anatomical abnormalities. These defects result from abnormal development of the heart during embryonic life, leading to a reduction in pulmonary blood flow and subsequent cyanosis. TOF is a significant cause of cyanotic congenital heart disease.
**Why the Correct Answer is Right**
The correct answer is D. Left ventricular hypertrophy, because TOF is not typically associated with left ventricular hypertrophy. In TOF, the right ventricular outflow tract obstruction (pulmonary stenosis) leads to an increase in right ventricular pressure and volume, resulting in right ventricular hypertrophy, not left ventricular hypertrophy. The increased pressure and flow in the right ventricle also lead to right-to-left shunting through the ventricular septal defect (VSD), causing cyanosis.
**Why Each Wrong Option is Incorrect**
**Option A:** Obstruction to right ventricular outflow (pulmonary stenosis) is a classic feature of TOF, resulting from the narrowing of the pulmonary valve or right ventricular outflow tract.
**Option B:** Ventricular septal defect (VSD) is a key component of TOF, allowing blood to flow from the left ventricle to the right ventricle and contributing to the development of cyanosis.
**Option C:** Dextroposition of the aorta with septal override is a characteristic feature of TOF, where the aorta is positioned to the right of the ventricular septum and overrides the VSD, receiving blood from both ventricles.
**Clinical Pearl / High-Yield Fact**
TOF is often associated with a "boot-shaped" heart on chest X-ray due to the right ventricular hypertrophy and the dextroposition of the aorta.
**✓ Correct Answer: D. Left ventricular hypertrophy**