What resting heart rate should one aim for when treating patients with heart failure with a beta-blocker?: Experiences from the Metoprolol Controlled Release Extended Release Randomized Intervention Trial in Chronic Heart Failure (MERIT-HF)

OBJECTIVES The goal of this study was to explore the question: what resting heart rate (HR) should one aim for when treating patients with heart failure with a beta-blocker? BACKGROUND The interaction of pretreatment and achieved resting HR with the risk-reducing effect of beta-blocker treatment needs further evaluation. METHODS Cardiovascular risk and risk reduction were analyzed in five subgroups defined by quintiles (Q) of pretreatment resting HR in the Metoprolol Controlled Release/Extended Release Randomized Intervention Trial in Chronic Heart Failure (MERIT-HF). RESULTS Mean baseline HR in the 5 Qs were 71, 76, 81, 87, and 98 beats/min; achieved HR 63, 66, 68, 72, and 75 beats/min;, and net change -8, -10, -11, -13, and -14 beats/min, respectively. Baseline HR was related to a number of baseline characteristics. Cardiovascular risk was no different in Q1 to Q4 (placebo groups) but increased in Q5 (HR above 90 beats/min). No relationship was observed between the risk-reducing effect of metoprolol controlled release/extended release (CR/XL) and baseline HR in the five Qs of baseline HR, or achieved HR, or change in HR during follow-up, respectively. CONCLUSIONS Metoprolol CR/XL significantly reduced mortality and hospitalizations independent of resting baseline HR, achieved HR, and change in HR. Achieved HR and change in HR during follow-up were closely related to baseline HR; therefore, it was not possible to answer the question posed. Instead, one has to apply a very simple rule: aim for the target beta-blocker dose used in clinical trials, and strive for the highest tolerated dose in all patients with heart failure, regardless of baseline and achieved HR. (C) 2005 by the American College of Cardiology Foundation.