PA CME : Inferior MI
Ok, so we gave you an easy one! Clearly this is an ST-segment elevation myocardial infarction of the inferior wall (STEMI). Inferior wall MIs account for about 40-50% of all MIs and generally have a more favorable outcome as opposed to anterior MIs. Up to 40% of patients with an inferior STEMI will have a concomitant right ventricular infarction. These patients may develop severe hypotension in response to nitrates and generally have a worse prognosis. Inferior STEMI may also be associated with posterior infarction, which confers a worse prognosis due to increased area of myocardium at risk. Up to 20% of patients with inferior STEMI will develop significant bradycardia due to second- or third-degree AV block. This makes sense if you remember that the right coronary artery (RCA) supplies the inferior and posterior sides of the heart, and the AV node. Think about it for a minute; if the RCA was blocked it would weaken the pumping action of the right ventricle, which is dependent on preload. If the AV node isn’t getting blood, it’s not working well either![one_second]
We would diagnose this inferior MI with right-sided involvement with a 12-lead EKG. We would see ST elevation, ≥1mm or one small box, in leads II, III and aVF; progressive development of Q waves in II, III and aVF; lastly look for reciprocal ST depression in aVL (± lead I).
Now here comes the money; how do we fix this patient? Well we would need to get him to the cath lab (door to balloon time within 90 minutes), thrombolics (anti-platelet and anti-coagulant)and IV fluids, or surgery (CABG) is sometimes an option.[/one_second]