Background: The overall rate of mortality due to ischemic heart disease is known to increase progressively with age. We evaluated the relation between the mortality rate and age in patients with first myocardial infarctions treated with thrombolytic therapy.
Methods: We studied 9720 patients with first infarctions who had been enrolled in the GISSI-2 trial. (This trial compared the efficacy of tissue plasminogen activator with that of streptokinase in patients with myocardial infarction.) Of these, only 35 percent had a history of angina. The relation between age and mortality during hospitalization and during the six months after discharge was determined by unadjusted and adjusted analyses.
Results: The in-hospital mortality rate was 1.9 percent among patients 40 years old or younger, but it increased to 31.9 percent among those more than 80 years old; however, values for indicators of infarct size did not increase with age. Autopsies were performed in 20 percent of the 772 patients who died in the hospital; the findings showed that the frequency of cardiac rupture increased from 19 percent among patients 60 years old or younger to 86 percent among those more than 70 years old. The mortality rate for the first six months after hospital discharge also increased significantly with age. After adjustment for confounding variables, older age continued to be significantly associated with a higher risk of in-hospital and post-discharge death. When age was introduced into a multivariate model as a continuous variable, the risk of death was estimated to increase by about 6 percent per year for both in-hospital and six-month mortality rates.
Conclusions: In patients with first myocardial infarctions who received thrombolytic therapy, age was a powerful independent predictor of both in-hospital and post-discharge mortality rates. The exponential, age-related increase in the mortality rate did not appear to be explained by larger infarcts.