Effect of Initial Heart Rate on Cardiac Troponin and Ejection Fraction in Patients with Non-ST Segment Elevation Myocardial Infarction

Background: Increased heart rate has shown to be associated with adverse cardiovascular outcomes. This aim of this study was to find the association of troponin level and ejection fraction (EF) with triage heart rate in patients with non-ST elevation myocardial infarction (NSTEMI). It was hypothesized that heart rate at triage will be independently associated with higher troponin level and lower EF after NSTEMI. Methods: The association of maximum troponin level and left ventricular EF with triage heart rate after adjusting for other factors known to affect these variables was assessed. Results: Participants had a mean age of 68 +/- 10 years with 34% women. Unadjusted correlations using linear regression showed a correlation coefficient (r) of 0.21, P = 0.01, between heart rate and maximum troponin before cardiac catheterization and a correlation coefficient (r) of -0.26, P = 0.007, between heart rate and post-myocardial infarction EF. EF was divided into 4 categories, namely, <30%, 30% to 45%, 45% to 60% and >60%. Heart rate showed a progressive increase from higher EF to lower EF. A multivariate analysis was also performed for association of heart rate with troponin and EF separately after adjusting for other confounding factors (diabetes, hypertension, number of coronary vessels and previous myocardial infarction). All associations persisted at P <= 0.05. Conclusions: Triage heart rate is independently associated with higher troponin and lower EF in NSTEMI.