β-blockers after myocardial infarction and 1-year clinical outcome - a retrospective study

Background Long term beta-blocker therapy after myocardial infarction (MI) reduces mortality and recurrent MI but evidence for this treatment predates contemporary acute coronary care. beta-blocker treatment is a key quality of care indicator in the Swedish national quality register for acute coronary care, Riks-HIA. Between 2011 and 2015 a declining number of MI-patients discharged with a beta-blocker from the coronary care unit (CCU) at Helsingborg and other hospitals was reported. This retrospective observational study aimed to investigate the causes for discharge without a beta-blocker and relate it to outcome, compared to patients discharged with a beta-blocker. Methods MI-patients registered in Riks-HIA discharged without beta-blocker during 2011-2015 (no-beta-group) and a control group (beta-group) comprised of patients discharged with beta-blocker treatment between January 1 to December 31, 2013, were matched by RIKS-HIA criteria for beta-blocker use. Clinical characteristics, date of death, readmission for MI, other cardiovascular events were collected from Riks-HIA and medical records. Results The no-beta-group included 141 patients, where 65.2% had a justified reason for non-beta-blocker use. The beta-group included 206 patients. There was no difference in cardiovascular risk factor profile. There were a trend towards a higher number of readmissions for MI in the no-beta-group was (n = 8 (5.7%) vs n = 2 (1.0%), p = 0.02), but not mortality (6 (4.3%) vs 2 (1.0%), p = 0.07) and combined readmission for angina pectoris, heart failure, arrhythmias or stroke/TIA (n = 23 (16.3%) vs n = 25 (12.1%), p = 0.27). Conclusion A majority of the patients in the no-beta-group had a justified absence of a beta-blocker. beta-blocker treatment post-MI showed a trend towards fewer readmissions for MI. But important quality information is lacking to make a firm conclusion of the effect on outcome.