BACKGROUND: Elevated resting heart rate is associated with increased cardiovascular risk, particularly in patients with left ventricular systolic dysfunction. Heart rate is not routinely monitored in these patients. We hypothesized that routine monitoring of heart rate would increase its prognostic value in patients with left ventricular systolic dysfunction. METHODS: We analyzed the relationship between heart rate measurements and a range of adverse cardiovascular outcomes, including hospitalization for worsening heart failure, in the pooled placebo-treated patients from BEAUTIFUL and SHIFT, using standard and time-varying covariate Cox proportional hazards models. Adjusting for other prognostic factors, models were fitted for baseline heart rate alone or for time-updated heart rate (latest heart rate) alone or corrected for baseline heart rate or for immediate previous time-updated heart rate. RESULTS: Baseline heart rate was strongly associated with all outcomes apart from hospitalization for myocardial infarction. Time-updated heart rate increased the strengths of associations for all outcomes. Adjustment for baseline heart rate or immediate previous time-updated heart rate modestly reduced the prognostic importance of time-updated heart rate. For hospitalization for worsening heart failure, each 5 beats per minute increase in baseline heart rate and time-updated heart rate was associated with a 15% (95% CI 12%-18%) and 22% (19%-40%) increase in risk, respectively. Even after correction, the prognostic value of time-updated heart rate remained greater. CONCLUSIONS: In patients with LVSD, time-updated heart rate is more strongly related with adverse cardiovascular outcomes than baseline heart rate. Heart rate should be measured to assess cardiovascular risk at all assessments of patients with left ventricular systolic dysfunction.