MI and vomiting

[boréale]

Does anyone know WHY nausea and vomiting are commonly associated with myocardial infractions? That is to say what is the physiological mechanism of vomiting being a symptom of MI?

[Microbiodude]

Well I'm not 100% sure but here's my theory:

 

During an MI, the GI tract experiences decreased perfusion resulting in the activation of an ischemic cascade. The falling pH/ ischemia experienced may be interpreted by the GI system as an acute poisoning episode. This would then result in activation of the appropriate pathways to expel the toxin.

 

Here's a link briefly explaining the pathophys behind nausea/vomitting:

 

http://www.mywhatever.com/cifwriter/library/70/4936.html

 

This link mentions some triggers being "acute rises in chemicals"

 

During an MI, if there is infarction we can see acute rises in Troponin. This may serve as a trigger for nausea/vomitting.

 

Let me know what you think/ find out.

 

CHeers!

[leviathan]

There's a couple good explanations, the first being simply sympathetic discharge during an MI. It's not going to usually be the MI itself that causes decreased perfusion like I think micro was getting at (unless it's a massive infarct with cardiogenic shock), but just a high level of sympathetic discharge which itself leads to a decrease in GI perfusion. Just think of times in the past when you've been really scared/startled by something and your heart starts pounding and you get knots in your stomach.

 

The second explanation may have to do with the fact that certain parts of the heart share visceral innervation at the same spinal level as parts of the GI tract. That actually correlates well with the fact that inferior MIs are more commonly associated with nausea and vomiting than infarcts in other vascular territories.

[j8848]

Usually I think of inferior MI's as being associated with bradycardia and barfing.

 

In most inferior MI's the RCA is affected. )I say most, because in only 85% of people the RCA supplies the inferior wall/ventricular septum). The ECG will show ST elevation in II, III and aVF with reciprocal ST depression in V1 and V2.

 

The inferior aspect of the heart has rich innervation of vagal nerve terminals (While the sympathetic adrenergic system is concentrated in the anterior surface). When an infero-posterior MI occurs it stimualtes the vagus nerve and results in a bradycardic response. Vagal nerve stimulation is also known to cause nasuea and vomiting.