Cardiac Medicine Certification (CMC) Practice Exam

During a posterior wall myocardial infarction, what condition is NOT typically seen?

1. Reciprocal changes in V2-V3

2. ST elevation in inferior leads

3. Positive R-wave progression

4. Increased R wave in V1

The correct answer is: Positive R-wave progression

In the context of a posterior wall myocardial infarction, understanding the electrocardiogram (ECG) changes is crucial for diagnosis and management. When analyzing the typical characteristics noted during a posterior infarction, we recognize that others manifest differently, thus providing a clearer picture. Reciprocal changes in V2-V3 are often observed in posterior wall infarctions. These changes occur due to electrical activity discrepancies between leads that are positioned to capture the heart’s electrical signals from different perspectives. In particular, when the posterior wall begins to fail, areas designated for other walls (like V2 and V3) may reflect these shifting signals. Therefore, reciprocal changes in these leads are a common finding. ST elevation in the inferior leads is another characteristic that can occur during a posterior wall myocardial infarction, primarily because of the anatomical connections within the heart. As the inferior wall (primarily supplied by the right coronary artery in right-dominant systems) may also experience ischemic changes, this can lead to notable ST elevation, as the ischemia can affect the electrical conduction through these regions. Increased R wave in V1 could be indicative of posterior infarction, and here’s why: as the infarction extends, the electrical axis may shift, leading to