beetles
Forum Newbie
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Anybody help explain why A-V fistula will increase cardiac output? I can't figure out. Thanks a lot.
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| Tiff
Forum Guru
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Found this. Should help explain. http://en.wikipedia.org/wiki/Arteriovenous_fistul...
"When an arteriovenous fistula is formed involving a major artery like the abdominal aorta, it can lead to a large decrease in peripheral resistance. This lowered peripheral resistance causes the heart to increase cardiac output in order to maintain proper blood flow to all tissues. The physical manifestations of this would be a relatively normal systolic blood pressure with a decreased diastolic blood pressure resulting in a wide (large) pulse pressure."
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| Cave.Canem
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Like the previous poster said, large AV fistulas reduce systemic resistance and bypass the microcirculation, hence increasing venous return to the heart, leading to a wide pulse pressure and high-output cardiac failure. Compression on an artery proximal to the fistula causes the swelling to diminish and the pulse slow down (i.e., less return to the heart).
Hope this helps as well.
Edited by Cave.Canem on 01/27/08 - 04:37 PM
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| Ig F
Forum Elite
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increased venous return to the heart due to the AV-fistula lead to the increased cardiac output
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| maoudoody
Forum Elite
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marys law states that cardiac output is inversely proportional to the total peripheral resistance
now wat happens in av fistula is that u connect a new resistance but in parallel to the arterial circuit
so tpr decreases
and thus co increases to maintain mean arterial pressure
in fact there is a clinical test depending on this physiological fact to differentate between av fistula and anuerysm
compressing the suspected swelling will cause bradycardia" branham bradycardia"
if it was av fistula
when u compress the av fistula u eliminate the resistance added in parallel and thus tpr increases so cop decreases and u experience that the heart rate decreases
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