Cardiac Medicine Certification (CMC) Practice Exam

What does an R wave greater than an S wave in leads V1 and V2 suggest in a case of a posterior wall myocardial infarction?

1. Possible occlusion of the left main artery

2. Possible occlusion in the RCA or circumflex artery

3. Normal variant with no clinical significance

4. Indication of a left ventricular hypertrophy

The correct answer is: Possible occlusion in the RCA or circumflex artery

When an R wave is greater than an S wave in leads V1 and V2, it suggests a specific change in the normal electrical activity of the heart. In the context of a posterior wall myocardial infarction, this finding is indicative of a right coronary artery (RCA) or circumflex artery occlusion. In a posterior wall myocardial infarction, the heart's electrical activity can be altered due to compromised blood flow to the heart muscle supplied by these arteries. The shifted R wave greater than the S wave in the anterior leads (V1 and V2) can signal that there is reflected electrical activity from the affected posterior wall. This alteration is typical when there is damage to the myocardial tissue supplied by the RCA or the circumflex artery, as they are mainly responsible for perfusing the inferior and posterior aspects of the heart. Understanding the implications of changes in the R and S waves in these leads is crucial for diagnosing the type and location of myocardial infarctions accurately, which can guide treatment approaches. The finding helps clinicians identify an underlying RCA or circumflex artery issue that could be causing the posterior wall ischemia.