Help me understand S3 and S4 heart sounds

[Qester]

So this is my understanding

S3- Happens as a volume overload amount of blood passes through the AV valves. Typically seen with dilated ventricles.

S4- Happens in a pressure overload situation as the blood hits against a stiffened ventricular wall. Typically seen with hypertrophied ventricles.

My confusion is coming with the fact is why then is S3 seen in CHF, which typically has hypertrophied ventricles?

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[worldbeater]

CHF should present with dilated ventricles, the most common cause of heart failure is dilated cardiomyopathy (90%) of the time. This is occurring because the excess fluid physically stretches the fibers of the left ventricle, causing a loss of contractility, and the ventricle has more room to put extra volume in it. So it will present with an S3.

Maybe you thinking of "systolic dysfunction", which means the ventricle has a problem contracting, and that's why you thought of an S4?

 

[Qester]

CHF should present with dilated ventricles, the most common cause of heart failure is dilated cardiomyopathy (90%) of the time. This is occurring because the excess fluid physically stretches the fibers of the left ventricle, causing a loss of contractility, and the ventricle has more room to put extra volume in it. So it will present with an S3.

Maybe you thinking of "systolic dysfunction", which means the ventricle has a problem contracting, and that's why you thought of an S4?

Did some more research on my own and found this:

"The classic paradigm of hypertensive heart disease is that the left ventricular (LV) wall thickens in response to elevated blood pressure as a compensatory mechanism to minimize wall stress. Subsequently, after a series of poorly characterized events (“transition to failure”), the left ventricle dilates, and the LV ejection fraction (EF) declines (defined herein as “dilated cardiac failure”)."
http://circ.ahajournals.org/content/123/3/327.full

I was missing the fact that during the progression to failure you first hypertrophy, but later dilate, and once in failure you are dilated not hypertrophied.

 

[worldbeater]

I was missing the fact that during the progression to failure you first hypertrophy, but later dilate, and once in failure you are dilated not hypertrophied.

That's good we were able to figure it out. Makes sense, a patient would present with visible symptoms towards the end of the progression of the disease, where we would see the dilation present.