Ejection Fraction in Systolic dysfunction due to Aortic Regurgitation. - USMLE Forums
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#1
10-04-2015
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Ejection Fraction in Systolic dysfunction due to Aortic Regurgitation.

What will happen to LV stroke Volume and Ejection Fraction in Systolic Dysfunction due to Acute AR? And explain why?

#2
10-04-2015
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Ejection fraction decreases in all causes of systolic dysfunction.
EF= SV/EDV and in systolic dysfunction EDV increases.
SV from what I know reduces because stretch of muscle fibres exceeds the length upto which Starling's law is applicable.
#3
10-04-2015
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Quote:
 Originally Posted by datson Ejection fraction decreases in all causes of systolic dysfunction. EF= SV/EDV and in systolic dysfunction EDV increases. SV from what I know reduces because stretch of muscle fibres exceeds the length upto which Starling's law is applicable.
I just solved a question in UW that says in Acute AR due to volume overload LV stroke volume increases, which how I perceived is that due to increase in volume even though there is systolic dysfunction, but the amount of volume that's ejected exceeds the normal stroke volume. Let's say we normally have 500mL of blood and we are ejecting 300ml, and after acute AR our volume increases to 1000 and now we are ejecting 500ml, so our Stroke Volume increases and the "fraction" that we are "ejecting" decreases?
I was just confused cuz I saw two questions in UW which were contradicting the concept that SV is directly proportional to EF. QID's are 157 and 186.

#4
10-04-2015
 USMLE Forums Addict Steps History: 1 + CS Posts: 161 Threads: 18 Thanked 92 Times in 51 Posts Reputation: 102

I guess they are under pathophysiology. I have yet to answer those questions.
But stroke volume is not always directly proportional to EF. It depends on EDV too.
In acute AR, SV decreases because the LV cannot compensate for acute increase in volume.
In chronic AR, SV increases due to eccentric hypertrophy and chamber enlargement.
Ref: Uptodate

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