Heart rate and heart failure

Resting heart rate has long been thought to be a risk factor in cardiovascular disease and a prognostic factor in heart failure. β-Blockers were originally used in heart failure for their heart rate control abilities. However, they also have negative inotropic effects contributing to their overall benefit. The role of isolated heart rate modification is unclear in left ventricular systolic dysfunction.

Two recent studies looked at the heart rate-lowering effects of the If, or funny current inhibitor ivabradine and its potential role in heart failure therapy. At the doses chosen for the studies, ivabradine is presumed to have only effects on heart rate with no other cardiotropic effects. Thus, the cardiovascular outcome benefits are presumed to be secondary to heart rate modification.

The two recent trials showed both heart rate and cardiovascular events to be significantly lower in the ivabradine-treated group of patients with left ventricular systolic dysfunction and initial heart rate at least 70 beats/min. However, neither of these trials proved causality. Hence, the link between heart rate and improved cardiovascular outcomes still remains muddled.