Increased SVR and MVP/HCM murmurs

[loveoforganic2]

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Does anyone have a conceptual explanation for why increased SVR (hand grip) leads to increased intensity of MVP and decreased intensity of HCM? Most of these make sense to me, but I'm having trouble with this one.

Thanks in advance and sorry for all the Q's - making my last pass through FA

Edit: So for MVP, it's just increased back pressure on mitral valve --> more forceful snap of the chordae. For HCM, the backpressure decreases outflow, and since it's an outflow tract obstruct, that would decrease HCM murmur. This work?

 

[Myxedema]

Technically, handgrip also increases preload (by pressing against the capacitance vessels), but to simply, let's start with the basis that handgrip increases afterload. Now, for both MVP and HOCM, the murmur has to do with the volume of the LV: More volume in LV --> Less murmur. Thus, both increased preload and increased afterload with decrease the murmur of both MVP and HOCM.

 

[loveoforganic2]

Technically, handgrip also increases preload (by pressing against the capacitance vessels), but to simply, let's start with the basis that handgrip increases afterload. Now, for both MVP and HOCM, the murmur has to do with the volume of the LV: More volume in LV --> Less murmur. Thus, both increased preload and increased afterload with decrease the murmur of both MVP and HOCM.

FA 2013 has the opposite listed for MVP (increased murmur with hand grip). So MVP and HCM would present w/the same trends for each physical exam maneuver? Obviously they wouldn't sound the same, but as far as alterations of intensity

 

[Myxedema]

Errata (found here) adds new information, but I think it still makes it a bit confusing. In short, the duration of the murmur of MVP and HOCM depends on the volume of LV. Less volume --> longer duration; more volume --> shorter duration. As for the intensity, some books say it decreases the intensity (here), and some say it increases the intensity (here). I tend to think the latter is more correct. So, if we sum it up, handgrip shortens the duration, but increases the intensity of the murmur of MVP.

 

[loveoforganic2]

Errata (found here) adds new information, but I think it still makes it a bit confusing. In short, the duration of the murmur of MVP and HOCM depends on the volume of LV. Less volume --> longer duration; more volume --> shorter duration. As for the intensity, some books say it decreases the intensity (here), and some say it increases the intensity (here). I tend to think the latter is more correct. So, if we sum it up, handgrip shortens the duration, but increases the intensity of the murmur of MVP.

Interesting, thanks for the info. I think I had learned in class that decreased preload increases the murmur intensity (because I just remembered my memory trick for it), but it looks debated, so I have a feeling that won't be terribly testable (at least not as much as the changes in duration and timing with maneuver). Also, I completely forgot to recheck errata since they first came out, so thanks again!

 

[21385]

For HCM, it increased intensity with decreased preload (because less volume in the LV causes it to have larger obstruction), and decreases intensity with increased afterload (because less volume is being ejected out (so more stays behind in the LV=>smaller obstruction).

For MVP, whenever the murmur sound decreases, the midsystolic click occurs earlier. Most people just simplify this and say that the murmur "increases" since the duration of the murmur is longer. However, the sound is quieter. This occurs with decreased preload.

Whenever the murmur sound increases, the midsystolic click occurs later. Most people just say that this "overall" decreases the MVP murmur since the duration of the murmur decreases. However, note that the murmur itself increases in sound while the duration of the murmur decreases. This occurs with increased afterload.

 

[loveoforganic2]

For HCM, it increased intensity with decreased preload (because less volume in the LV causes it to have larger obstruction), and decreases intensity with increased afterload (because less volume is being ejected out (so more stays behind in the LV=>smaller obstruction).

For MVP, whenever the murmur sound decreases, the midsystolic click occurs earlier. Most people just simplify this and say that the murmur "increases" since the duration of the murmur is longer. However, the sound is quieter. This occurs with decreased preload.

Whenever the murmur sound increases, the midsystolic click occurs later. Most people just say that this "overall" decreases the MVP murmur since the duration of the murmur decreases. However, note that the murmur itself increases in sound while the duration of the murmur decreases. This occurs with increased afterload.

That was a great summary, thanks! I think you hit what was really confusing for me (the increased duration vs increased intensity)