Heart rate: surrogate or target in the management of heart failure?

High heart rate is associated with longev-ity in many animal species including men.1 It has been shown in various car-diovascular diseases that high resting heart rate is a known marker of cardiovascular outcomes in hypertension,2 atheroscler-osis,3 myocardial infarction4 and heart failure.5 6 Among the different conditions the threshold from which risk is increased is different. More close correlations at low thresholds (≥70 bpm) to risk have been established in heart failure.5–8 One beat increase of baseline heart rate and five beats increase of resting heart rate is associated with an increase of cardiovas-cular death and heart failure hospitalisa-tion of 3 % and 16%, respectively.6 Therefore, it was tempting to speculate that heart rate reduction reverses risk, in particular in heart failure, where the asso-ciation of heart rate and risk is very close. Furthermore, the pathophysiology is plausible for heart failure, because the force-frequency relationship is reversed in the failing heart in vitro9 10 and in vivo.11 Shortening of diastole reduces oxygen supply to the myocardium. High heart rates are associated with atheroscler-osis12 13 potentially important in energy starvation of the failing heart.7 8 Finally, high heart rates are a reflection of neuro-hormonal activation and are associated with malignant arrhythmias.14–16 A reduc-tion of events by heart rate reduction only, would qualify heart rate as a target of treatment and risk factor beyond repre-senting just a surrogate or risk marker.