Mitral Regurg and narrow pulse pressure

[Guest thatgirlonabike]

Can someone explain why pulse pressure is narrowed in mitral regurg.  I've found some contradicting information and I'm having trouble wrapping my head around the physiology of it.

 

Thanks!

[LT_Oneal_PAC]

Ventricle goes to eject, but loss of forward pressure to the leaky back valve. So a decrease in the systolic. Diastolic should remain unchanged. That’s the only physiologic reason I can think of and would have to be severe for it to be enough to notice.

[Guest thatgirlonabike]

1 minute ago, LT_Oneal_PAC said:

Ventricle goes to eject, but loss of forward pressure to the leaky back valve. So a decrease in the systolic. Diastolic should remain unchanged. That’s the only physiologic reason I can think of and would have to be severe for it to be enough to notice.

Ok.  Makes sense we kept talking as I posted this and this was the conclusion we came up with.  Glad to see it validated.  

[UGoLong]

Here's a good description from cvphysiology (https://www.cvphysiology.com/Heart Disease/HD005). The narrowed pulse pressure is for severe MR:

 

 

Mitral valve regurgitation occurs when the mitral valve fails to close completely during ventricular systole, which causes blood to flow back (regurgitate) into the left atrium (LA) as the left ventricle (LV) contracts (see figure at right). This causes the left atrium to be become engorged with blood because blood is entering the LA from the LV during ventricular systole as well as from the pulmonary veins. This causes LA pressure to increase (25 mmHg in this example). During LV filling, the higher pressure and volume of the LA leads to an increase in LV end-diastolic pressure (25 mmHg in this example) and LV end-diastolic volume. This increase in LV preload causes the LV to contract more forcefully (Frank-Starling mechanism), which enables it to increase its stroke volume. Although the LV stroke volume (end-diastolic minus end-systolic volume) is increased, the net amount of blood ejected into the aorta is reduced because part of the LV stroke volume (regurgitant fraction) is also ejected into the LA. If the volume of blood ejected into the aorta is sufficiently reduced, then aortic pressure may fall (110/75 mmHg in this example). In acute mitral regurgitation (e.g., after sudden rupture of the chordae tendineae), the atrial pressure can become very elevated.  In long-standing or chronic mitral regurgitation, the left atrium adapts to the larger volume by dilating, which increases its compliance. The LV also undergoes anatomic dilation. This remodeling helps to limit the increases in LA and LV pressures. The backward flow of blood into the LA during ventricular systole results in a holosystolic murmur.