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

Abstract

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.

Figure 1

Kaplan‐Meier analysis of 3‐year all‐cause mortality by discharge heart rate (A) and admission heart rate (B).

Figure 2

Forest plot showing results of multivariable analysis of discharge and admission heart rate and 3‐year mortality. Models are adjusted for age, sex, race, body mass index, hypertension, diabetes mellitus, hypercholesterolemia, smoking status, cancer, congestive heart failure, peripheral arterial disease, stroke, depressive symptoms, self‐report of monthly financial situation, avoidance of health care because of costs, lack of health insurance, education, marital status, glucose, hematocrit, estimated glomerular filtration rate, index ST‐segment–elevation myocardial infarction, left ventricular systolic function, Killip class, percutaneous coronary intervention during hospitalization, coronary artery bypass graft surgery during hospitalization, in‐hospital atrial fibrillation, provision of discharge instructions on smoking cessation, and discharge medications, including aspirin, β blockers, angiotensin‐converting enzyme inhibitors or angiotensin‐receptor blockers, statins, and thienopyridines. Bpm indicates beats per minute; HR, hazard ratio.

Figure 3

Forest plot showing interaction between discharge heart rate and β‐blocker (BBLK) therapy at discharge. Models adjusted for covariates in Figure 2. Bpm indicates beats per minute; HR, hazard ratio