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 β 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 β 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 β-blocker use ( P=0.004) on mortality, wherein risk of death was markedly higher among those with high discharge heart rate and not on β 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 β 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 β blockers at discharge. These findings highlight opportunities for risk stratification and intervention that will require further investigation.
Keywords: discharge; mortality; myocardial infarction; β blocker.