Long-term adherence to secondary preventive medications after myocardial infarction: a post-hoc analysis of the BETAMI trial

Introduction The combined BETAMI-DANBLOCK trial demonstrated that long-term beta-blocker therapy after myocardial infarction (MI) reduced the risk of recurrent cardiovascular events. Detailed knowledge of long-term adherence to allocated treatment and other secondary preventive therapies is important for appropriate interpretation of the trial results. Purpose To describe the long-term adherence to the assigned treatment strategy and other secondary preventive drug use patterns in post-MI patients in a contemporary pragmatic trial setting. Methods In BETAMI-DANBLOCK patients hospitalised with MI without heart failure and a left ventricular ejection fraction (LVEF) ≥40% were randomised to beta-blocker therapy or no beta-blocker (PROBE design). For this sub-study of the BETAMI cohort, data on dispensed secondary preventive drugs were obtained from the Norwegian Prescribed Drug Registry from 6 months prior to inclusion until 3 years post-inclusion or end of follow-up (April 1, 2025), whichever occurred first. Patients were classified as “on treatment” if previously dispensed tablets, when taken according to standard treatment practice (1 or 2 tablets/day), would still have been available at the assessment date. Otherwise, they were classified as “off treatment”. Results All patients included in this substudy were revascularized for their index MI. Among the 2,867 included patients, only a minority had been treated with cardiovascular drugs during the six months period prior to their index-MI (Table). Within seven days after inclusion, 1300/1431 (91%) of patients randomised to beta-blocker therapy had dispensed a beta-blocker, compared to 71/1436 (5%) randomised to no beta-blockers (Table). Metoprolol was prescribed in 98% of patients dispensing beta-blocker in the beta-blocker arm, at a median dose of 50 mg/day (IQR: 25-50). In addition, most patients in both groups were discharged with acetylsalicylic acid (ASA, 86%) at a median dose of 75 mg/day (IQR: 75-75), statins (88%) with a median atorvastatin dose of 80 mg/day (IQR: 40-80), and P2Y12 inhibitors (85%). During follow-up, the median doses remained unchanged, and adherence to other cardiovascular drugs was high in both treatment arms (Figure). For patients randomised to beta-blocker therapy, the proportion on beta-blockers was 88% at 6 months, 82% at 12 months, decreasing to 71% at 3 years. In the no beta-blocker arm, 10% were on a beta-blocker at 6 months, 11% at 12 months, and 14% at three years follow-up. Conclusions In the BETAMI trial, long-term adherence to the allocated beta-blocker strategy was high, although a gradual decline in beta-blocker use was observed over time in the active treatment arm. In this pragmatic clinical trial, an even higher adherence to beta-blockers would be expected to yield an even stronger favourable effect on MACE. Adherence to other guideline-recommended secondary preventive therapies after AMI was consistently high in both groups.ESC_Adherence_TableESC_Adherence_Figure