Abstract

Background: Acute myocardial infarction (AMI) is the leading cause of death in Chile. Since 1993, the Infarction Multicenter Study Group (GEMI) has studied the reality of AMI in Chilean hospitals using prospective registries. One of the factors studied is the drug prescription pattern, based on the benefits provided by drugs in terms of morbidity and mortality, as shown by clinical megatrials. Objective: To assess whether the dissemination of therapeutic guidelines allows an increase in the proportion of AMI patients treated with aspirin, beta-blockers, ACEIs and thrombolytics, and whether this change exerts an influence on the reduction of hospital mortality. Method: Two periods of prospective registry of patients admitted with the diagnosis of AMI to hospitals of Santiago de Chile and regional Chilean hospitals were compared. The first registry (R1) (1993-1995) included 2957 patients from 40 hospitals, and the second (R2) (1997-1998) included 1981 patients from 37 hospitals. Both collected information on demographic characteristics, treatment and in-hospital course of patients with AMI. Before the start of the second registry period, guidelines for AMI management were prepared and disseminated to all centers participating in the study. Results: There were no differences between R1 and R2 in mean age (62 ± 12 vs 62 ± 13 years) or the proportion of males (73.6 vs 75.5%). Significant increases were recorded in the use of beta-blockers 37 vs 55%; p < 0.01), ACEIs (32 vs 53%; p < 0.01), aspirin (93 vs 96.1%; p < 0.01), and i.v. nitrates (59 vs 67.6%; p < 0.05). A reduction was seen in the use of oral nitrates (56 vs 39%; p < 0.01), calcium channel blockers (23 vs 12.4%; p < 0.001) and antiarrhythmic agents (29 vs 24.6%; p < 0.001). There were no changes in the frequency of thrombolytic use. In the univariate analysis, R2 was associated to lesser hospital mortality (10.8 vs 13.4%; p < 0.007). In the multivariate analysis, the lesser mortality in R2 persisted after adjusting for the demographic characteristics (age, gender) and clinical presentation (Killip class, risk factors, AMI location) (odds ratio = 0.76; 95% CI: 0.62-0.94; p < 0.001). When the use of beta-blockers, ACEIs and aspirin was included in the model, the survival benefits associated to R2 weakened and lost statistical significance. Conclusion: The clinical characteristics of R1 and R2 patients were similar at the time of admission. The increased proportion of aspirin, beta-blocker and ACEI use in R2 largely explains the reduction in mortality.