Effect of squatting on TOF murmurs? - USMLE Forums
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Old 06-01-2011
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Stethoscope Effect of squatting on TOF murmurs?

TOF (tetralogy of Fallot) has a right to left shunt and the child squats to relieve the symptoms. Squatting increases PVR and decreases the R-L shunt, lessening the degree of cyanosis.

In Valvular heart disease some murmurs increase by squatting/leg raising, and decrease by standing /valsalva.
Squatting/leg raising increases pre-load and therefore more blood in the heart. Left sided murmurs increase with squatting/leg raising.

So my question is how can squatting increase pre-load, and does it have any effect on afterload?
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Old 06-02-2011
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squatting increase pre-load and after-load
from kaplan notes there is table of preload and afterload
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Old 06-02-2011
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Default Squatting

Yes Important area for discussion! Thanks for posting.

Squatting is a useful bedside test particularly useful for HCOM!

Squatting acutely increases venous return, effective filling pressure, stroke output and systemic arterial pressure. Systolic murmurs in HCOM can be abolished, softer or shorten in intensity with squatting!

The opposite effect is found in majority of valvular lesion except MVP.
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I found out this thread and all the hemodynamic effects of squatting are explained superbly!

Quote:
Originally Posted by Rich View Post
"When squatting is done as a P/E maneuver..we r looking for its ability to INCREASE PRELOAD n bring about a change in murmur" (a high yield point...ALL murmurs-AS/AR/MR/MS n their Pulm n Tricusp equivalents have INCREASED INTENSITY of murmur when preload increases, EXCEPT MVP and HCM).

"When children with TOF Squat..they do so b/c they r looking for the ability of the Squat to increase Systemic vascular Resistance (increase afterload)"

"If we wanted to check the effect of increased afterload on a murmur through a P/E maneuver...we wud ask the patient to do a handgrip exercise"

Cheers!!


Effect of Squatting on Preload???
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Old 08-02-2011
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But how does preload increase with squatting ? what is the pathophysiology ?
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Old 08-02-2011
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From the thread linked above-
....
It is assumed that due to INCREASED SKELETAL MUSCLE TENSION in squatting position, venous blood is pumped back to the heart. This leads to INCREASED VENOUS RETURN IN SECOND PHASE (REASON B), leading to INCREASED CARDIAC OUTPUT, which relives the child of cyanotic spell.
-please note that the increased cardiac output in second phase is only during the time when the child is in squatting position. Once the child resumes to standing position, the cardiac output and vascular resistance return to the baseline level

Therefore, there is,
Decrease in venous return during EARLY PHASE OF SQUATTING.
Increase in venous return during LATE PHASE.

and ofcourse as we all know venous return is the preload
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Old 08-03-2011
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Quote:
Originally Posted by 1TA2B View Post
Squatting is a useful bedside test particularly useful for HCOM!

Squatting acutely increases venous return, effective filling pressure, stroke output and systemic arterial pressure. Systolic murmurs in HCOM can be abolished, softer or shorten in intensity with squatting!

The opposite effect is found in majority of valvular lesion except MVP.
Does increasing afterload decrease or increase murmur intensity of MVP ?
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Old 08-03-2011
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A manuever to inc afterload is the handgrip its effects are

1) AS = dec nmumur
2) AR = Inc
3) MVP = Dec
4) HOCM = Dec

think of it this way inc afterload = harder to push forward so that means a decease in its emptying = left ventricle increases in size causing a decrease in the murmum intensity of MVP
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