Use and adherence to beta-blockers for secondary prevention of myocardial infarction: who is not getting the treatment?

PURPOSE: To characterise those who receive beta-blocker therapy after MI and to estimate the effect of adherence to beta-blocker use on subsequent mortality and recurrent MI.

METHODS: A community-based observational cohort study was done using a record linkage database. Patients were those discharged from hospitals after their first MI between January 1994 and December 1995 and who also survived for at least 1 year. The outcome was all cause mortality and recurrent MI. Results were adjusted for age, sex, social deprivation, airways disease, peripheral vascular disease (PVD), diabetes mellitus, cardiovascular drug use, steroid use and hospitalisation for cardiovascular disease using a logistic regression model and a Cox regression model.

RESULTS: A total of 865 patients were included in this study. 386 (44.6%) were on beta-blocker treatment during the year after MI. Beta-blocker use was lower amongst high-risk patients (older patients, patients with obstructive airway disease, PVD and those with a previous hospitalisation for heart failure). Mortality was lower in patients treated with beta-blockers compared with those untreated. Good adherence (>or=80%) was associated with a lower adjusted relative risk of mortality compared with unexposed patients (0.49, 95%CI 0.30-0.80, p < 0.01). Within the high-risk subgroup of patients, the adjusted relative risk of mortality with good adherence was 0.40 (0.17-0.93, p = 0.03).

CONCLUSIONS: Beta-blocker use was lower in older patients, patients with airways disease, PVD and heart failure, but these patients appeared to have the greatest benefit from beta-blockers. Good adherence to beta-blocker treatment after MI was associated with a lower risk of mortality.