Tetralogy of Fallot results from anterosuperior displacement of the conotruncal septum. Which of the four features is the PRIMARY anomaly from which the other three are consequential?

• A Pulmonary stenosis
• B Right ventricular hypertrophy
• C Overriding aorta
• D Malalignment ventricular septal defect (subpulmonic outlet VSD) ✓

Explanation

The primary anomaly in TOF is the anterosuperior displacement of the conotruncal (infundibular) septum, which creates a malalignment VSD (the septum fails to align with the muscular septum). This displacement simultaneously narrows the right ventricular outflow tract (causing pulmonary stenosis) and causes the aorta to 'override' the VSD. Right ventricular hypertrophy develops secondarily as a consequence of the pulmonary outflow obstruction. Therefore the VSD is the embryological primary; RVH is purely a haemodynamic consequence.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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