Aortic Stenosis & Murmur: To Triple helx & All - ben

[ArchivalUser]

Pt has AS & is given Phenyepinephrine will the Murmur
-Increase or Decrease? & Why

[ArchivalUser]

Increase, as this drug will increase the cardiac contractility, and hence increase the murmur as well.

[ArchivalUser]

increase....more blood to da heart,more force of contraction...accentuation of da murmur

[ArchivalUser]

superdoc what is the Mechanism of Action of Phenylepin on Vasculature?
Once you know this you'll get a Logic Explanation. I posted this b/c I as well was confused about it when I saw it.

The Principle's that Triplehelix wrote about incr. & decr preload across Valves is correct but one has to be careful on how certain things (e.g drugs...) work and then see if there is an Incr. of Flow across the Vavles or not.

[ArchivalUser]

Well, phenylephrine causes contraction of vessels by alpha 1 receptors, so increase afterload, and its effect on heart also causes increased cardiac contractility, so logically it should accentuate that murmur.
Am I wrong, if yes, then please correct me

[ArchivalUser]

As Far as I remember Phenyepinephrine as you said directly affects the Peripheral vasculature by constriction. via Aplha 1 (I don't remeber that it has direct action on the Hearts Contractitlity via B Receptors)
It is used just as epi to maintain Vascular volume and therefor BP in Hypotensive Pts.

Since you already have a stenosed Valve the Incr. in Afterload actully causes less blood to travers and already stenosed Valve therfore the Murmur in AS w/ Phenyip will actually Decrease rather than Incr. (The Same Concept applies w/ Handgrip - Muscles squeezing and constriction Vessles, here as well the Murmur of AS will decrease..

I think a good way to look at this is
1. 1st Look at Actions on - Preload - Venous side
2. Actions on Peripheral Vasculature - Afterload
3. Relation to Actions above depenidng on the Valvular defect

Thanks to Goljan!!

[ArchivalUser]

good explanation, ben

[ArchivalUser]

thx Uterus I justed wanted to bring this up as this was actually a questiion I got on my exam. And it's an easy point to miss. Don't want Anyone to miss this if it shows up, we sure can use any easy points that come our way!!

[ArchivalUser]

another scenario came across my mind,

How amyl nitrite would affect in HOCM and AS?

[ArchivalUser]

Good one Uterus
- Amyl Nitrate causes Vasodilation - on Peripheral Vasculature & Venous side --therefore

--> In AS - Afterload will decrease and blood is able to traverse the Stenotic Valve much better thus the Murmur Increases

--> In HOCM - There is Decrease in Preload (in HOCM The Asymmetrical Hypertrophy Obstruct Blood Flow) to the Right side of the Heart theferore less Blood in the Heart overall which Increases the Murmur. If you have more Blood in the Left Ventricle then the Wall Strecht Out thus relieving the Obstruction and decreasing the Murmur