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  #1  
Old 06-09-2011
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Heart Cardiac output/venous return curves question

The change indicated by the dashed lines on the cardiac output/venous return curves shows:

Cardiac output/venous return curves question-co.jpg
click image to enlarge

A) Decrease blood volume
B) Increase cardiac output in the new steady state
C) Increase in total peripheral resistence
D) Decrease in total peripheral resistence
E) Decrease in venous compliance
F) Increase in venous compliance

Last edited by bebix; 06-09-2011 at 06:56 AM. Reason: typo
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  #2  
Old 06-09-2011
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Question

Decrease Contractility ==> Decrease Venous return ==> Increase TPR ( Sympathetic response)

Ans Increase TPR , TPR slope moves in anticlockwise direction
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I think is E) Decrease in venous compliance = decrease contractility
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A.
decrese blood volume
bcos there is decrese venous return and also decrese cardiac out put.and operating point is also decrese.so there is excessive blood loss..so answer is A.

Last edited by drmdshah; 06-09-2011 at 07:44 AM.
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I think A is the right answer
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I also think it's A
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C ,case hemorrahage
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i think is a...
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Quote:
Originally Posted by bebix View Post
The change indicated by the dashed lines on the cardiac output/venous return curves shows:

Attachment 1478
click image to enlarge

A) Decrease blood volume
B) Increase cardiac output in the new steady state
C) Increase in total peripheral resistence
D) Decrease in total peripheral resistence
E) Decrease in venous compliance
F) Increase in venous compliance
This is a tough one but i will do my best to reach to a reasonable answer
(Ansnwer is: Choice C)
Changing the point of interception between the CO curve and the VR curve vertically down to the point of interception of the dashed lines means acute loss of contractility (i.e. answer B is wrong), this should be normally compansated by shifting the whole VR curve to the right (i.e. increasing preload with increasing CVP) which is not the case in this curve.
if this case was actually because of loss of blood volume the CO curve would not shift to the right and the whole VR curve would have shifted to the left with decreasing CVP on a normal CO curve (i.e. Answer A is wrong).
The response of decreasing the TPR on the VR curve would be actually by inclining of the curve to the right on a normal cardiac curve without changing the CVP indicating an increased pumping of the heart ahead of a decreased after load, which is not the case here (i.e. Answer D is wrong)
Icreased venous compliance or decreased venous compliance is actually similar to increased and decreased blood volume (i.e. answers E and F are wrong)

This leaves us wit answer C which can be explained in clinical pratoce by acute hypertensive LV dysfunction (What is called afterload mis-match)
Systemic atrerial VC --> increased TPR --> increased afterload on an originally dysfunctioned heart --> decreased CO --> cannot be appropriately compansated by increased VR because of increased LVEDP created by hypertension
this is translated in the curve as the CO curve is shifted to the right (Decreased contractility) and inclination of the VR curve to the left without change in the CVP (i.e. increased TPR)

I hope this is right or else i will look like a joke
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Correct Answer correct answer

The right answer is C)Increase in total peripheral resistence

Here we have the possibles scenarios:

1.-Mean systemic pressure (MSP) is increased with not change in contractility (dashed lines):

Cardiac output/venous return curves question-3_12.jpg
click image to enlarge

- Increased blood volume or
- Decrease in venous compliance
*inverse scenario with a decrease in the MSP


2.- Increased contractility and increased cardiac outcome with the same MSP (dashed lines):

Cardiac output/venous return curves question-3_14.jpg
click image to enlarge

- Positive inotropic effect
*inverse scenario with a decrease in contractility


3.-Change in slope of the cardiac output curve and also change in the slope of the venous return curves: This is determined by the RESISTENCE OF THE ARTERIOLES

Cardiac output/venous return curves question-3_13.jpg
click image to enlarge

This case = INCREASED TRP
- COUNTERCLOCKWISE rotation of the venous return curve = increased TRP (decreased venous return as blood is retained on the arterial side)
- DOWNWARD shift of the cardiac output curve = increased TRP (increase afterload as the heart pumps againts a higher pressure)
RESULT = new equilibrium point which both cardiac output and venous return are decreased, but right atrial pressure is UNCHANGED.

Ref: Costanzo BRS Physiology

Last edited by bebix; 06-09-2011 at 07:34 PM. Reason: The last name is Costanzo...
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  #11  
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Thank you bebix!!!!!!!!!!!!!!!
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Quote:
Originally Posted by bebix View Post
The right answer is C)Increase in total peripheral resistence

Here we have the possibles scenarios:

1.-Mean systemic pressure (MSP) is increased with not change in contractility (dashed lines):

Attachment 1479

- Increased blood volume or
- Decrease in venous compliance
*inverse scenario with a decrease in the MSP



2.- Increased contractility and increased cardiac outcome with the same MSP (dashed lines):

Attachment 1481

- Positive inotropic effect
*inverse scenario with a decrease in contractility


3.-Change in slope of the cardiac output curve and also change in the slope of the venous return curves: This is determined by the RESISTENCE OF THE ARTERIOLES

Attachment 1480

This case = INCREASED TRP
- COUNTERCLOCKWISE rotation of the venous return curve = increased TRP (decreased venous return as blood is retained on the arterial side)
- DOWNWARD shift of the cardiac output curve = increased TRP (increase afterload as the heart pumps againts a higher pressure)
RESULT = new equilibrium point which both cardiac output and venous return are decreased, but right atrial pressure is UNCHANGED.

Ref: Constanzo BRS Physiology
hahahahaha
i was writing my answer while u were posting the result so i was too late, the answer i found with explanation before your post

however, i have to emphasize that this case is a case that we meet everyday in the cardiological practice and represents clinically a case of hypertensive induced LV dysfunction or what is called Afterload mismatch
great example of how physiology can represent clinical states
thank u man
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  #13  
Old 06-09-2011
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Quote:
Originally Posted by alaahoda2001 View Post


hahahahaha
i was writing my answer while u were posting the result so i was too late, the answer i found with explanation before your post

however, i have to imphasise that this case is a case that we meet everyday in the cardiological practice and represents clinically a case of hypertensive induced LV dysfunction or what is called Afterload mismatch
great example of how physiology can represent clinical states
thank u man
i'm a "sister" too
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  #14  
Old 06-09-2011
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Quote:
Originally Posted by bebix View Post
i'm a "sister" too
Shame on me
it appears that i have lost my decency as a gentle man
i am very sorry again my fair lady and please forgive my stupidness
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thank u
for the great question
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