Discharge Heart Rate After Hospitalization for Myocardial Infarction and Long-Term Mortality in 2 US Registries

Background-Although admission heart rate predicts higher mortality after acute myocardial infarction (AMI), less is known about discharge heart rate. We tested the hypothesis that higher discharge heart rate after AMI is related to increased long-term mortality independent of admission heart rate, and assessed whether beta blockers modify this relationship. Methods and Results-In 2 prospective US multicenter registries of AMI, we evaluated the associations of discharge and admission heart rate with 3-year mortality using Cox models. Among 6576 patients with AMI, discharge heart rate was modestly associated with initial heart rate (r=0.28), comorbidities, and infarct severity. In this cohort, 10.7% did not receive beta blockers at discharge. After full adjustment for demographic, psychosocial, and clinical covariates, discharge heart rate (hazard ratio [HR]=1.14 per 10 beats per minute [bpm]; 95% CI=1.07-1.21 per 10 bpm) was more strongly associated with risk of death than admission heart rate (HR=1.05 per 10 bpm; 95% CI=1.02-1.09 per 10 bpm) when both were entered in the same model (P=0.043 for comparison). There was a significant interaction between discharge heart rate and beta-blocker use (P=0.004) on mortality, wherein risk of death was markedly higher among those with high discharge heart rate and not on beta blockers (HR=1.35 per 10 bpm; 95% CI=1.19-1.53 per 10 bpm) versus those with a high discharge heart rate and on beta blockers at discharge (HR=1.10 per 10 bpm; 95% CI=1.03-1.17 per 10 bpm). Conclusions-Higher discharge heart rate after AMI was more strongly associated with 3-year mortality than admission heart rate, and the risk associated with higher discharge heart rate was modified by b blockers at discharge. These findings highlight opportunities for risk stratification and intervention that will require further investigation.