Prognostic significance of type and location of a first myocardial infarction

The prognostic significance of type (Q-wave versus non-Q-wave) and location of infarction (anterior versus infero-posterior) was assessed in 350 patients with a first myocardial infarction followed for 3 years. A baseline multivariate Cox model was constructed from variables assessable at entry of the index infarction. The prognostic significance of site and type of infarction was evaluated when added to this model. Both Q-wave infarction and anterior location were significant with a risk ratio of 1.91 (95% confidence interval 1.14-3.18) and 1.70 (95% confidence interval 1.11-2.61) respectively. However, when the model also included the size of infarction. Q-wave infarction was no longer formally significant, while anterior location still was associated with adverse outcome (risk ratio 1.56, 95% confidence interval 1.02-2.39). It is inferred from the results that this effect of anterior infarction is due to a larger damage to the left ventricle for identical infarct sizes compared to infero-posterior infarctions.