Inferior myocardial infarction. High-risk subgroups.

I nferior myocardial infarctions account for 4050% of all acute myocardial infarctions1l2 and are generally viewed as having a more favorable prognosis than anterior wall infarctions. Data from a number of recent trials of thrombolytic therapy in acute infarction appear to support this view, with mortality rates of 2-9% reported among patients with inferior infarctions assigned to the "standard care" or control groups within these studies.1-3 It is, thus, not surprising that many of these trials have failed to demonstrate reduced mortality after thrombolytic therapy in the subset of patients with inferior infarction.1"3'4 It is important to note, however, that nearly 50% of patients suffering inferior infarction will have complications or distinguishing features associated with an increased mortality that will substantially alter an otherwise favorable prognosis. It is the purpose of this review to identify the complications most likely to occur during acute inferior infarction as defined electrocardiographically by STsegment elevation in leads II, III, and aVF. Specifically, heart block, concomitant precordial STsegment depression, and right ventricular infarction are discussed, their pathogenesis is reviewed, and their impact on prognosis is considered. Also, the data that exist on the impact of thrombolytic therapy on these high-risk subgroups are reviewed.