हृदय रोग एवं निदान

Degree of Beta-Blockade and Outcomes in Patients with Acute Coronary Syndrome

Abstract

Sachin Kumar Amruthlal Jain, Timothy R. Larsen DO, Charlotte Wiemann, Patrick Alexander, Michael Shaw, Peter A McCullough and Shukri David

Objective: We sought to determine if the outcome benefit of beta blockade in the ACS population is associated with baseline HR, discharge HR, or a reduction in HR.

Background: ACC guidelines recommend a resting HR goal of 50 to 60 bpm in ACS patients. This recommendation is not based on study outcomes, but rather on expert opinion. Evidence-based clinical trials investigating ideal target heart rate of beta blocker (BB) therapy in the ACS population are lacking.

Methods: A retrospective analysis was performed of all ACS patients who underwent coronary angiography (with or without percutaneous coronary intervention) at Providence Hospital from September 2006 to August 2011 excluding patients with any contraindication to BB therapy. Discharge HR was used as the predictor variable for outcomes in these patients.

Results: A total of 912 patients (403 ST elevation myocardial infarction MI (STEMI) and 509 Non STEMI patients were included. Discharge HR was divided into quintiles: quintile 1 (48 - 64 bpm), quintile 2 (65 - 70), quintile 3 (71 - 76), quintile 4 (77 - 83) and quintile 5 (84 - 119). There was a statistically significant difference seen between the quintile 1 composite endpoint and the other quintile endpoints. (p value <0.05) No differences were seen across quintiles in median TIMI risk index score at admission, systolic and diastolic blood pressure or beta-blocker dose at discharge. Patients in quintile 1 fared better overall with the observation of worse outcomes in patients with a discharge heart rate less than 55.

Conclusion: In those with ACS, particularly STEMI and NSTEMI, a lower discharge HR conferred a decreased composite endpoint at 24 months with the best outcomes seen at a resting HR between 55-65. Further studies are needed to investigate the clinical benefit of optimal HR reduction in this population beyond 2 years.