Beta-blockers in acute coronary syndrome: does rhythm matter?
Authors: Carvalho C , Monteiro J , Carvalho P , Baptista A , Moreira J 
Published: October 2022

Abstract

Introduction
Beta-blockers (BB) are recommended in patients with previous acute myocardial infarction (AMI), aiming to reduce morbidity and mortality. Their benefit is greater in patients with associated left ventricular dysfunction. However, in patients with atrial fibrillation (AF) its prognostic benefit is controversial.

Purpose
To assess and compare the in-hospital and 1-year prognostic impact of BB prescription after acute coronary syndrome (ACS), in patients with previous or de novo AF, and in patients with sinus rhythm (SR).

Methods
This was a national multicentre retrospective study of patients hospitalized for ACS between October 2010 and December 2021. A total of 35279 patients was included, and divided in two groups according to the prescription or not of BB. Patients with previous history of ischemic heart disease (myocardial angina, AMI or coronary revascularization) or heart failure, as well as presenting in Killip class IV or submitted to coronary artery bypass graft during admission were excluded. The impact of BB prescription on in-hospital and 1 year mortality rates, in patients with AF versus SR, was compared.

Results
A total of 14906 patients was selected, 82.5% with and 17.5% without BB prescription. Most patients were in SR (90.2%), with 9.8% presenting previous or new-onset AF.
Patients without BB prescription were older (67±14 vs. 63±13 years) and had more comorbidities, namely valvular disease (2.3% vs. 1.2%, p&lt;0.001) and chronic pulmonary obstructive disease (7.1% vs. 3.1%). The mean left ventricular ejection fraction was 53±13% in patients without BB prescription and 52±11 in the group with BB prescription (p&lt;0.001). In-hospital and after discharge BB prescription was less frequent in AF patients (80.2% vs. 82.5% and 74.7% vs. 78.8%, respectively).
The in-hospital mortality rate was 2.2%, 1.3% in the BB group and 6.6% in patients without BB prescription (p&lt;0.001). At 1 year, mortality rate increased to 5.1%.
BB prescription was associated with lower in-hospital mortality rate regardless of the rhythm, with an 81% risk reduction in SR (OR = 0.19, 95% CI 0.14–0.24) and 79% in AF patients (OR = 0.21, 95% CI 0.13–0.35). In a multivariate regression analysis, after adjusting for all the possible confounders, in-hospital BB prescription was associated with 70% of mortality risk (OR = 0.30, 95% CI 0.23–0.35).
Overall, after discharge BB prescription was associated with reduced 1-year mortality risk (HR = 0.57, 95% CI 0.44–0.73), although it didn't reach statistical significance in AF patients (p=0.413). Nevertheless, in a bivariate Cox regression, rhythm showed no impact on BB protective effect (p-interaction = 0.335). As expected, AF had a negative prognostic impact (HR = 3.85, 95% CI 2.66–5.02).

Conclusion
BB prescription was associated with reduced in-hospital and 1 year mortality rates. The prognostic benefit of BB therapy was equivalent in ACS patients in sinus rhythm and with previous or new-onset AF.

Funding Acknowledgement
Type of funding sources: None.