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Canadian Journal of Cardiology

THE EFFECT OF BETA BLOCKAGE IN PATIENTS FOLLOWING ACUTE CORONARY SYNDROME - STRATIFIED ACCORDING TO LEFT VENTRICULAR EJECTION FRACTION.

      Background

      Beta blockers (BB) have been widely accepted as a standard of care in the post myocardial infarction (MI) period. The most recent AHA/ACC and ESC guidelines recommend BB use post-MI. However, the guidelines do admit to limited evidence, particularly in patients with preserved left ventricular ejection fraction (LVEF). There is also a paucity of data for BB use in patients with mild to moderate LV dysfunction. Our study aims to address the benefit of BB’s across LVEF subgroups in the post-MI period.

      Methods and Results

      We examined 7955 patients who underwent coronary angiography for a diagnosis of ACS between 2012-2016. Patients were categorized as follows: group 1 (LVEF >50%), group 2 (LVEF 35-50%), and group 3 (LVEF < 35%). LVEF was assessed by trans-thoracic echocardiography, if available, and if not left ventriculography. The primary outcome was all-cause mortality at 1-year. Incidence of the primary outcome was visualized with Kaplan-Meier survival curves. Associations were assessed using Cox proportional hazard modeling. These analyses were performed with and without propensity matching, to account for differences between patients who were or were not prescribed a BB. At index presentation, our cohort had a median age of 62, and 70% of patients were male. Patients who were prescribed beta-blockers were less likely to have a LVEF >50% (64% vs 77%, p< 0.001). Figure 1 shows Kaplan-Meier survival curves stratified by LVEF and BB usage. In patients with LVEF < 35%, BB usage was associated with a significantly reduced all-cause mortality at 1-year (unadjusted hazard ratio [HR] 0.30, p=0.044). Patients with a LVEF 35-50% were less likely to die if prescribed beta-blockers (unadjusted HR 0.42, p=0.001). However, this was not the case in propensity matched analyses (unadjusted HR 0.80, p=0.487). Lastly, there was no significant difference in all-cause mortality in patients with preserved LVEF (unadjusted HR 1.16, p = 0.626).