A patient with severe aortic stenosis shows a paradoxically split second heart sound (S2). The physiological basis of this paradoxical splitting is:

• A Premature closure of the pulmonary valve relative to the aortic valve
• B Increased right ventricular afterload causing delayed P2 component
• C Delayed closure of the aortic valve due to prolonged left ventricular ejection time, making A2 follow P2 ✓
• D Left bundle branch block shortening the electromechanical delay of the left ventricle

Explanation

Normally A2 precedes P2. In aortic stenosis (and LBBB), prolonged LV ejection time delays A2, so A2 moves to follow P2, creating paradoxical (reversed) splitting. This split narrows or disappears on inspiration (opposite of normal splitting) because inspiration-induced increased venous return further delays P2 to align with the already-late A2. Pulmonary hypertension causes loud but not paradoxically split P2; RBBB delays P2 causing wide normal splitting.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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