Prognostic implications of diagnostic Q waves after myocardial infarction

The long-term prognostic implications of the electrocardiographic location of a myocardial infarction and the subsequent retention or disappearance of diagnostic Q waves were examined in patients enrolled in the Aspirin Myocardial Infarction Study (AMIS). The 4524 participants, ages 30-69 years, had sustained a myocardial infarction 8 weeks to 60 months before randomization to aspirin and placebo groups. Subjects were followed for at least 3 years (average 38.2 months). Using the Minnesota Code, myocardial infarctions were classified according to three electrocardiographic locations: lateral, inferior and anterior, with further subdivision into major, moderate and minor criteria based on Q-wave duration and Q/R rations. Total mortality was not significantly different among patients with single infarct sites: lateral 11.8%, inferior 8.0% and anterior 9.4%. Patients with multiple electrocardiographic infarct locations had a significantly higher mortality (14.6%, p less than 0.0002). Participants with Minnesota Code major criteria of infarction also had a significantly higher mortality (10.6%) than those with moderate (7.2%) or minor (7.4%) criteria (p less than 0.01). Loss of a previously documented diagnostic Q wave occurred in 14.2% of participants. Mortality among patients who lost Q waves (6.5%) was not significantly different from that among those with persistent Q waves in a single infarct location (8.7%). No long-term prognostic significance can be attributed to the site of infarction or loss of Q wave on the resting ECG. However, major Q-wave criteria and extent of infarction based on multiple coded sites are associated with a higher 3-year mortality.