End Diastolic Volume in Exercise?

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Up or down?

EF goes up, ESV goes down, SV goes up, TPR goes down (despite sympathetic activithy, due to metabolites); what about EDV?

lord_jeebus

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If EF goes up and ESV goes down, EDV must decrease.

EDIT: ignore this I mixed things up

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On further thought: It seems EDV goes up a bit. SV definitely goes up a bit. Then EF can either go up, go down, or stay the same. If EF goes up, then SV must increase more than EDV has, in which case, does it follow that ESV necessarily decreased?

ScubaStarved

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If EF goes up and ESV goes down, EDV must decrease.
Is this some rule of adaptation to exercise not made obvious by the math, EF=SV/EDV? A decrease in ESV alone (decreased afterload) could raise your SV and thus raise your EF.

For what it's worth OP, I looked this up in First Aid 2010 pg252 on the graph of cardiac and vascular function curve. It shows exercise as an example of decreased TPR which shifts the venous return curve to the right. The x-intercept of the venous return curve = EDV.

Unless I'm misunderstanding it, exercise increases EDV (at least up to a point). I guess your heart rate could increase to the point that you have insufficient filling time.

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Thanx. What about EF and ESV? EDV and SV go up, I think that's a given, but what about EF and ESV? According to EF=SV/EDV, EF will only go up if ESV goes down. So....?

Not an NBME. Realizing that I hate these kind of questions makes me realize that I must be uncomfortable with them.

lord_jeebus

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Is this some rule of adaptation to exercise not made obvious by the math, EF=SV/EDV? A decrease in ESV alone (decreased afterload) could raise your SV and thus raise your EF.

For what it's worth OP, I looked this up in First Aid 2010 pg252 on the graph of cardiac and vascular function curve. It shows exercise as an example of increased TPR which shifts the venous return curve to the right. The x-intercept of the venous return curve = EDV.

Unless I'm misunderstanding it, exercise increases EDV (at least up to a point). I guess your heart rate could increase to the point that you have insufficient filling time.

You're right, I mixed EDV and ESV up when I was reasoning through this.

I agree, EDV should increase unless HR gets excessively fast. Without doing my reading, I'd say it's due to increased venous return and lusitropic effects of catecholamines.

rem6775

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Is this some rule of adaptation to exercise not made obvious by the math, EF=SV/EDV? A decrease in ESV alone (decreased afterload) could raise your SV and thus raise your EF.

For what it's worth OP, I looked this up in First Aid 2010 pg252 on the graph of cardiac and vascular function curve. It shows exercise as an example of increased TPR which shifts the venous return curve to the right. The x-intercept of the venous return curve = EDV.

Unless I'm misunderstanding it, exercise increases EDV (at least up to a point). I guess your heart rate could increase to the point that you have insufficient filling time.

I don't have the 2010 version of FA and I don't think that was in the 2009 version, but for what it's worth: a change in TPR does not shift the venous return curve, it simply changes its slope with its x-intercept remaining the same and the y-intercept falling (i.e., mean systemic pressure does not change).

Anyway, from what I understand, exercise should lead to a drop in TPR, not a rise, due to arteriolar dilation in skeletal muscle. There is also venoconstriction, which would increase blood return to the heart for stroke volume, which obviously increases.

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Ef? Esv?

ScubaStarved

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Thanx. What about EF and ESV? EDV and SV go up, I think that's a given, but what about EF and ESV? According to EF=SV/EDV, EF will only go up if ESV goes down. So....?

Not an NBME. Realizing that I hate these kind of questions makes me realize that I must be uncomfortable with them.
Were you not given decreased ESV in the question stem?

Look at page 255 of 2010 FA, at the cardiac cycle tracing at the top. That's how I understand high output / high contractility states. Increased EDV, decreased ESV.

ScubaStarved

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I don't have the 2010 version of FA and I don't think that was in the 2009 version, but for what it's worth: a change in TPR does not shift the venous return curve, it simply changes its slope with its x-intercept remaining the same and the y-intercept falling (i.e., mean systemic pressure does not change).

Anyway, from what I understand, exercise should lead to a drop in TPR, not a rise, due to arteriolar dilation in skeletal muscle. There is also venoconstriction, which would increase blood return to the heart for stroke volume, which obviously increases.

You're right on the first point, I mistyped and meant decreased TPR and have edited the previous post to reflect that.

I cross-checked BRS Phys and you are correct that it shows changed TPR as not shifting the x-intercept whereas First Aid does. Without remembering this in detail, I'd give points to Costanzo and say that FA is in error here. I did 2-3 minutes of reading and it seems FA strays from Costanzo's explanations in quite a few points.

BRS Phys got moved up in my schedule. Thanks.

IMGUSMLEStep1

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I think this is what happens to the heart during exercise:

EF = SV/EDV

+++ sympathetic activity --> +++ SV
+ venous return --> + preload --> + EDV

So the EF would still increase.

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You're right on the first point, I mistyped and meant decreased TPR and have edited the previous post to reflect that.

I cross-checked BRS Phys and you are correct that it shows changed TPR as not shifting the x-intercept whereas First Aid does. Without remembering this in detail, I'd give points to Costanzo and say that FA is in error here. I did 2-3 minutes of reading and it seems FA strays from Costanzo's explanations in quite a few points.

BRS Phys got moved up in my schedule. Thanks.

Yeah, that curve in FA isn't entirely accurate from what I recall.

HTxFrog

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ha I asked this same question a few months ago on the allo forum, still don't get that first aid graph