Acute vs. chronic valvular pathologies

[Apoplexy__]

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Just had a UWorld question that required you to know that the morphological changes in the left atrium are different in mitral regurgitation depending whether the regurg is an acute vs. chronic onset. They wanted you to know that the adaptive changes in the left atrium influence the compliance of the chamber, and only occur in chronic onset of regurgitation. The difference in high or normal compliance predisposes to different sequelae.

My question: Can this be said for every valvular pathology? And is the difference in remodeling in acute vs. chronic seen only in atria or also a notable difference in ventricles as well?

 

[MudPhud20XX]

So the compliance should be decreased in chronic onset as the chamber gets enlarged right?

I think a similar explanation can be applied to aortic regurgitation. This one explains the compliance of the Lt ventricle in aortic regurgitation. Hope this helps.

I had to look for Kaplan step 2 CK to get this and here is what it says:

"Aortic regurgitation results in a volume overload of the left ventricle.
- The ventricle compensates by increasing its end-diastolic volume according to the Frank-Starling mechanism.
- The left ventricular dilation is thought to overstretch the myofibrils, leading to less actin-myosin interaction and decreased contractility.
- In acute severe aortic regurgitation, the left ventricle has not had the opportunity to dilate, its compliance is relatively high, and the aortic regurgitation therefore leads to very high left ventricular end-diastolic pressure.

If mitral regurgitation ensues, the elevated left ventricular diastolic pressure is reflected back to the pulmonary vasculature, and acute pulmonary edema may occur.

Acute aortic regurgitation results in a lower cardiac output, narrower aortic pulse pressure, and a smaller left ventricle than does chronic aortic regurgitation.

Aortic diastolic pressure decreases in chronic aortic regurgitation because of both the regurgitation of blood into the left ventricle and a compensatory decrease in systemic vascular resistance to maintain forward cardiac flow to the periphery. The increased pulse pressure in chronic aortic regurgitation is due to the large stroke volume, causing increased systolic and decreased diastolic pressure."

 

[Apoplexy__]

So the compliance should be decreased in chronic onset as the chamber gets enlarged right?

Particularly for the atria, the compliance would actually increase in chronic onset due to dilation. In the case of a ventricle pushing against a stenotic valve, you'd be right, that would produce hypertrophy and decreased compliance, but it's different with dilation.

The atria in particular have a greater capacity for dilation than hypertrophy. Therefore, I would have been hesitant to say that ventricles could get increased compliance due to significant dilation (instead of the main response being hypertrophy), but your source appears to also say that chronic onset --> more significant dilation than hypertrophy --> Increased compliance.

I think a similar explanation can be applied to aortic regurgitation. This one explains the compliance of the Lt ventricle in aortic regurgitation. Hope this helps.

Yeah, that was a great excerpt, thanks a ton for that. So the answer then is
1. Yes, the difference between chronic and acute onset regurgitation is important not only in AV valves but also ventricular output valves.
2. Yes, this is an important distinction that occurs in ventricles, not just atria.

I appreciate you taking the time to dig through your resources to bring that up.