Anterior vs. Inferior MI

[miamiheatrn, BSN]

Hi guys, just wanted to refresh up on these.

What are the differences in clinical presentation between an Inferior vs. Anterior MI??

Also, how does treatment differ before cath lab?

Thanks!

[akulahawkRN, ADN, RN, EMT-P]

Caveat: I'm no cardiology expert. Remember that anterior and inferior MI's involve different areas of the heart and are supplied by different coronary arteries. Those coronary arteries also supply blood to other areas of the heart so if you see an Inferior MI, you might want to look for an MI in areas supplied by the RCA.

I worry most about RVI. The right side of the heart can be very sensitive to preload so giving nitroglycerin or morphine in RVI can be dangerous. Aside from being able to manage that, I haven't heard of any significant differences in management of MI regardless of location unless the SA or AV nodes are involved and in those cases, just be ready with TCP.

[diprifan]

Anterior MI (left side)

• LAD
  
• ST elevation in the precordial leads V1-V6 but mainly V3-V4
  
• Reciprocal ST depression III/aVF
  
• Tachycardia is common to compensate for decreased stroke volume/ cardiac output
  
• Low BP
  
• May need left sided mechanical support after reperfusion (impella/iabp)
  

Inferior MI (right side)

• RCA (if ST elevation II
• ST elevation in leads II, III, aVF
  
• ST elevation in the posterior leads (V7-8) can indicate posterior infarct
  
• Bradycardia, think conduction delays (Mobitz I, II, 3rd degree), might need transvenous pacer
  
• Vomiting due to vagal system stimulation
  
• Volume dependent infarct, so saline boluses are your friend before the cath lab
  
• May also need mechanical support
  

So anterior are tachy and hypotensive, probably need fluid and pressors. Inferior are brady and need fluid, atropine, potentially pacing, and pressors.

Hope this helps

[nurse2033, MSN, RN]

I would say Inferior MI is more of a structural problem if the infarct is large enough. This can be measured as "hypokinesis" on ECHO. The inferior wall is the largest pumping workhorse of the heart. Affecting the left ventricle, if enough of the muscle mass is affected it will not be able to squeeze effectively to meet the body's demands. This is called cardiogenic shock and dopamine (or another pressor) is used to stimulate the muscle to work better. This is at a cost of using more energy and oxygen of course so this patient still needs urgent cath lab. The anterior wall can include the septum, through which the conduction system runs. So you are more likely to see conduction defects such as blocks. Inferior infarcts show in leads II, III, and AVF, and anterior MIs show in leads V1-V4. Management does not really differ. You treat hypotension with fluids and pressers. Some blocks and bradycardias will respond to atropine, and external pacer can be used if atropine fails. Use MONA unless contraindicated by allergy or hypotension. You might be able to anticipate some issues based on location, but ultimately you will treat symptoms regardless of where the infarct is.

[Cowboyardee]

Some good advice above. I'll add that an inferior MI may or may not involve the right ventricle. Or in other words, you can't say the right ventricle is involved (or not) merely because the patient has an inferior MI.

An EKG with right sided leads can tell you more about whether the right ventricle is involved - look for elevation in leads V3R to V6R. Prior to obtaining a right sided EKG, ST elevation in lead V1 and greater ST elevation in lead III than lead II are both suggestive of right ventricular involvement. With all that said, none of the above have a 100% sensitivity, specificity, or accuracy in diagnosing right ventricular MI, so clinical correlation (or an echo) is important.

As mentioned above, one of the more important considerations with right ventricular MI is how dependent on preload the heart can be. Be careful with nitro.

for reference:

Right ventricular infarction - Life in the Fastlane ECG library