Preload & Afterload effects on heart murmurs

[BlondeCookie]

Having a difficult time trying to understand preload and afterload effects on heart murmurs. For ex:

• when preload increases/decreases, which murmurs are increased/decreased?
• when afterload increases/decreases, which murmurs are increased/decreased?

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[Xtrasystolic]

Most left sided heart murmurs increase in intensity with increased preload (more blood flow = more turbulence) and vice versa except:

HOCMP: the ASH and/or SAM are responsible for the murmur. Imagine increased preload causing increased EDV of the LV, the ASH moves away from the outflow tract and the mitral valve leaflet gets better approximated to the mitral ring. Thus, increased preload would decrease the murmur in HOCMP.

MVP: this one's easier to imagine. Again, increased preload = increased LVEDV = the floppy overgrown valve leaflet is now a better fit for the mitral annulus and thus no more prolapse and thus decreased murmur.

Hope this helps instead of confusing you even more 👍

 

[myhandsarecold]

HOCM murmur worst with decreased preload; you can make them do the valsalva and can hear the murmur more because there not enough volume to keep the LV outlet open during systole -> worst stenosis -> murmur; on the similar note, murmur decreased with increased afterload like hand grip or squatting.

there are others like worsening murmur caused by VSD and MVP, MI with increased afterload because the pressure increases and rather than going to the aorta, there is worsening of the shunting or regurgitation, yada yada

 

[OveractiveBrain]

Paraphrasing Conrad Fischer for this one.

Squatting increases the blood returning to the heart
Standing decreases the blood returning to the heart
Valsalva decreases the blood returning to the heart

More Blood in the Heart makes the murmur worse.
-Aortic Stenosis
-Aortic Regurgitation
-Mitral Stenosis
-Mitral Regurgitation
(Right sided lesions same deal)

More blood in the heart, more blood through a small hole (stenosis) more murmur. More blood in the heart, more blood through a regurgitant valve (regurgitation).

Less blood in the Heart makes the murmur better.

-Hypertrophic Cardiomyopathy
-Mitral Valve Prolapse

HCOM: Decreased blood makes the hypertrophied septum cover the aortic opening. Increased blood opens the ventricular space, moving the hypertrophied septum away from the aortic opening.

Mitral Valve Prolapse: Floppy mitral valves make the snapping sound. Increase the blood in the heart, stretch the ventricles open, pull the valves taught and prevent the murmur.