Cardiac Medicine Certification (CMC) Practice Exam

What clinical finding is typical of a posterior wall myocardial infarction?

1. ST elevations in V1-V6

2. ST depressions in V1-V6

3. New-onset holosystolic murmur

4. Elevated troponin levels within 3 hours

The correct answer is: ST depressions in V1-V6

In the context of a posterior wall myocardial infarction, the typical clinical finding would indeed include ST depressions in the precordial leads, especially in V1-V6. This phenomenon occurs because the electrical activity of the heart is altered due to the region of the heart involved in the infarction. In the case of a posterior wall infarction, the electrical changes manifest as ST segment depression in the anterior leads (V1-V6) as the heart's electrical activity is not conducted effectively from the infarcted posterior wall to these leads. In addition to this, the left ventricular wall may lead to compensatory mechanisms, and the reflections of posterior ischemia can also be observed in the anterior leads as depressed ST segments. This is a crucial diagnostic hallmark in recognizing a posterior wall myocardial infarction, particularly in patients presenting with chest pain or other ischemic symptoms. The other options do not align with the typical findings associated with a posterior wall myocardial infarction. For instance, ST elevations in V1-V6 would suggest anterior ischemia, which is not consistent with posterior wall involvement. A new-onset holosystolic murmur could indicate other cardiac conditions, such as mitral regurgitation, rather than being directly indicative of a posterior wall