What type of myocardial infarction is characterized by V1-3 ST depression, V1-4 tall R waves, and upright T waves in anterior precordial leads?

The characteristics described in the question—V1-3 ST depression, V1-4 tall R waves, and upright T waves in the anterior precordial leads—are indicative of a posterior myocardial infarction.

In a standard 12-lead ECG, the anterior leads (V1-V4) typically show ST elevation during an anterior MI. However, in the case of a posterior MI, the electrical activity altered due to the infarction can manifest as reciprocal changes in the anterior leads. Here, the ST depression observed in leads V1-3 suggests that while the posterior wall is affected, the anterior leads are not showing classic signs of an anterior MI. The presence of tall R waves in these leads, along with upright T waves, further supports the diagnosis, as these changes occur due to a shift in the repolarization sequence when there is a posterior wall involvement.

This pattern can sometimes lead to confusion, as the presentation deviates from typical anterior MI findings. However, recognizing these subtle signs is crucial for accurately diagnosing the type of myocardial infarction. Therefore, the combination of these ECG findings provides a strong indication of a posterior myocardial infarction.