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Beta-Blockers and Mortality After AMI in Non-HF Patients
Study Questions:
Is there an association between beta-blocker use and mortality in patients with acute myocardial infarction (AMI) without heart failure (HF) or left ventricular systolic dysfunction (LVSD)?
Methods:
The authors conducted a nationwide observational study (English and Welsh registry data) to see if among survivors of AMI without LVSD or HF, the use of beta-blockers was associated with lower risk of death at up to 1 year. The analytical cohort (n = 179,810) was drawn from 531,282 patients with AMI admitted between January 1, 2007 and June 30, 2013, with final follow-up December 31, 2013. Patients were eligible if they were discharged with a final diagnosis of ST-segment elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI). Patients with other final diagnoses; those who died in the hospital; absent mortality data; >100 years of age, prior MI, angina, percutaneous coronary intervention and/or coronary artery bypass graft surgery; prior use of beta-blockers; contraindications to beta-blockers; HF; and loop diuretic use were excluded. Survival-time inverse-probability weighting propensity score analysis and instrumental variable analysis were used to evaluate the association between beta-blocker use and mortality. The models adjusted for sex; socioeconomic deprivation; year of hospitalization; diabetes, hypercholesterolemia, hypertension, smoking status, and family history of coronary heart disease; chronic obstructive pulmonary disease; cerebrovascular disease; peripheral vascular disease; statin, aspirin, P2Y12, angiotensin-converting enzyme inhibitor/angiotensin-receptor blocker use; adjusted mini-GRACE (Global Registry of Acute Coronary Events) risk score variables; care by cardiologist; and cardiac rehabilitation.
Results:
Of the 179,810 patients with AMI and no HF or LVSD, 91,895 had STEMI (51.1%) and 87,915 had NSTEMI (48.9%), and 141,097 (95.1%) received beta-blockers. Those patients who received beta-blockers were younger and male compared to those who did not receive beta-blockers (63.3 ± 13.4 years and 71.1% male, versus 68.6 ± 15.1 years and 61.7% male, respectively). Those who did not receive beta-blockers had more diabetes, chronic renal failure, asthma or chronic obstructive pulmonary disease, cerebrovascular disease, and intermediate or high GRACE score. In the entire cohort (maximum 1-year follow-up), there were 9,373 deaths (5.2%). Unadjusted 1-year mortality was lower in patients who received beta-blockers compared with those who did not (4.9% vs. 11.2%; p < 0.001). After balanced propensity score analysis, there were 16,683 patients (4,932 STEMI [29.6%] and 11,751 NSTEMI [70.4%]) remaining for analysis. Among this cohort, after weighting and adjustment, there were no survival differences between patients with AMI and without HF or LVSD who received beta-blockers and those who did not, at up to 1-year follow up (average treatment effect [ATE] coefficient, 0.07; 95% confidence interval [CI], -0.60 to 0.75; p = 0.827). Findings were similar for STEMI (ATE coefficient, 0.30; 95% CI, 0.98 to 1.58; p = 0.637) and NSTEMI (ATE coefficient, -0.07; 95% CI, -0.68 to 0.54; p = 0.819).
Conclusions:
In this prospective observational cohort study using nationwide registry data, the use of beta-blockers was not associated with a lower risk of death at up to 1 year among patients who suffered AMI and did not have HF or LVSD.
Perspective:
There is variation in guideline recommendations for the use of beta-blockers following AMI in patients without LVSD or HF. US guidelines recommend beta-blockers for all patients post-AMI regardless of HF or LVSD (Class I), while European guidelines have a Class IIa indication for beta-blocker use in patients without LVSD or HF. The current study adds to a body of evidence suggesting that the routine prescription of beta-blockers in patients with AMI and normal ejection fraction and without HF may not provide benefit. Being a registry-based study, one should keep in mind that there was no information regarding the rate of beta-blocker discontinuation after discharge or the development of HF or LVSD during the study period, nor was the role of in-hospital beta-blocker use investigated, all which are important variables that could possibly affect the study results. Nonetheless, a randomized controlled trial seems to be the next step for the evaluation of beta-blockers in AMI patients without HF or LVSD.
Keywords: Acute Coronary Syndrome, Adrenergic beta-Antagonists, Asthma, Cerebrovascular Disorders, Diabetes Mellitus, Geriatrics, Heart Failure, Kidney Failure, Chronic, Myocardial Infarction, Myocardial Ischemia, Primary Prevention, Pulmonary Disease, Chronic Obstructive, Survival, Ventricular Dysfunction, Left
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