questions on murmurs

[soxman]

So I have been getting confused on these basic concepts on what extenuates murmurs. Like for MR, I get how doing a valsalva decreases the murmur intensity because it decreases venous return (or does it?) and how standing and nitrates and exercise also decrease the intensity BUT why on earth does standing make the murmur for aortic stenosis worse? Doesnt the venous return drop when you stand quickly so applying the same concept to MR, shouldnt the murmur intensity drop?
And another issue which is driving me crazy is TPR....when you squat the TPR increases which means that the venous return increases, right? But then I'm reading the as the TPR decreases venous return increases. If someone could straighten this out for me, I'd really appreciate it.

Sox

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[ijn]

Think of TPR like arterial resistance. As you drop arterial resistance, then the heart pumps against less afterload, so cardiac output increases given the same amount of work.

For cardiovascular physiology a fundamental rule you should burn into your brain is that as cardiac output increases, venous return increases. And vice versa. It's basically a closed system. If you up the output, the input increases. If you up the input, the output increases.

 

[soxman]

Think of TPR like arterial resistance. As you drop arterial resistance, then the heart pumps against less afterload, so cardiac output increases given the same amount of work.

For cardiovascular physiology a fundamental rule you should burn into your brain is that as cardiac output increases, venous return increases. And vice versa. It's basically a closed system. If you up the output, the input increases. If you up the input, the output increases.

Thanks for the response. The TPR issue makes more sense now. Whats still bothering me is the the thing with Aortic stenosis murmurs getting worse when the patient stands up. I thought that it would get worse when the preload increased so when you stand quickly wont that drop the preload and decrease the aortic stenosis murmur?

 

[OveractiveBrain]

So I have been getting confused on these basic concepts on what extenuates murmurs. Like for MR, I get how doing a valsalva decreases the murmur intensity because it decreases venous return (or does it?) and how standing and nitrates and exercise also decrease the intensity BUT why on earth does standing make the murmur for aortic stenosis worse? Doesnt the venous return drop when you stand quickly so applying the same concept to MR, shouldnt the murmur intensity drop?
And another issue which is driving me crazy is TPR....when you squat the TPR increases which means that the venous return increases, right? But then I'm reading the as the TPR decreases venous return increases. If someone could straighten this out for me, I'd really appreciate it.

Sox

www.onlinemeded.org

watch this video. Its not step 1, but it it will likely explain, in simple terms, the difference of manuvers, heart murmurs, and the treatment of the underlying condition. Its a free website, designed for clinical clerkships and step 2. But hey, if it gets you to understand...

"more blood in the heart, more murmur" - AR, AS, MR, MS

"less blood in the heart, more murmur" - HCOM, Mitral Prolapse

 

[soxman]

www.onlinemeded.org

watch this video. Its not step 1, but it it will likely explain, in simple terms, the difference of manuvers, heart murmurs, and the treatment of the underlying condition. Its a free website, designed for clinical clerkships and step 2. But hey, if it gets you to understand...

"more blood in the heart, more murmur" - AR, AS, MR, MS

"less blood in the heart, more murmur" - HCOM, Mitral Prolapse

nice! thanks!