THE IMPACT OF CLINICAL-TRIALS ON THE USE OF MEDICATIONS FOR ACUTE MYOCARDIAL-INFARCTION - RESULTS OF A COMMUNITY-BASED STUDY

Background: The impact of clinical trials on medical practice remains controversial, in part because of weak study designs and nonrepresenta tive study samples. Objective: To assess changes in trends in medicati on use in the setting of acute myocardial infarction (AMI) before and after publication of two large clinical trials: the Second internation al Study of Infarct Survival (ISIS-2) trial that supported the use of aspirin after AMI and the Multicenter Diltiazem Postinfarction Trial t hat reported no overall benefit from the use of calcium antagonists af ter AMI. Methods: Study patients consisted of 2114 patients hospitaliz ed with AMI in 16 hospitals in metropolitan Worcester, Mass, during 19 86, 1988, and 1990. Data were obtained from medical records. We used m ultivariable logistic regression models to examine the rate of change in the use of selected medications before and after trial publication, controlling for medical history, characteristics and complications of AMI, medications taken, and procedures performed during hospitalizati on. The dependent variable was receipt of the specific medication unde r investigation. Results: Before publication of ISIS-2, 26% of patient s with AMI received aspirin while hospitalized compared with 66% after its publication. However, in-hospital aspirin use began to rise befor e ISIS-2 with an immediate increase in the level of use occurring afte r trial publication but with no significant change in the rate of incr ease. Before publication of the Multicenter Diltiazem Postinfarction T rial, 57% of patients with AMI were new recipients of calcium antagoni sts compared with 51% after trial publication. The decrease in calcium antagonist use began after trial publication (odds ratio, 0.79 per 6- month period; 95% confidence interval, 0.71 to 0.88). Conclusions: The published results of large trials of cardiovascular therapies have ha d variable impact on medication use, Efforts to assess the effects of publication of new scientific information on medical care need to cons ider prior trends in treatment patterns and the varying contexts of me dical care. They should consider both direct and indirect routes of in fluence.