Normal split of S2 – MCQ – Answer
The normal inspiratory splitting of second heart sound (S2) is due to delay in occurrence of pulmonary component (P2) as a consequence of – Correct answer: a) Increase in capacitance of the pulmonary vascular bed
Capacitance of systemic vascular bed does not change significantly with respiration. A transient reduction in left ventricular volume during inspiration contributes slightly to the split in S2 by making aortic component (A2) slightly earlier. But the predominant component is the delay in P2 .
Increased capacitance of pulmonary vascular bed leads to a longer pulmonary hang out interval in inspiration. Hang out interval is the delay between the time of cross over of right ventricular and pulmonary artery pressure curves and the closure of the pulmonary valve.
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Reference: 1. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine, 10th Edition. Chapter 8: Physical Examination of the Heart and Circulation