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can any1 explain the mechanism of premature closure of aortic valve in mitral regurgitation which would b the reason for wide splitting of s2?
the way I think of it is:
during MR, less blood flows through the aortic valve (because some of it regurgitates into left atrium), so the decreased volume flowing through the aortic valve means the aortic valve closes earlier,
normal splitting is A2 then P2, since aortic valve has closed earlier in MR, the difference between A2 and P2 widens--- wide split of S2
The rapid fall in the left ventricular pressure during systole due to regurgitation of blood into the left atrium causes an early/ premature closure of the aortic valve. hence the wide split.
In addition you should also note that wide splitting of S2 is caused by pulmonary stenosis and right bundle branch block. This can lead to premature closure of aortic valve.
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