Beta-blocker efficacy according to heart rate and rhythm in patients with heart failure. Commentary on the Cardiac Insufficiency Bisoprolol Study II analysis.

Large randomized trials have demonstrated that beta-blocker treatment reduces morbidity and mortality in patients in chronic heart failure. Questions remain about the influence of individual characteristics on the magnitude of the benefit of beta-blockers in patients with heart failure including the influence of heart rate and cardiac rhythm. In the Cardiac Insufficiency Bisoprolol Study II, baseline heart rate and heart rate change over time had prognostic value but treatment with bisoprolol was associated with a benefit at all levels of baseline heart rate and additional benefit related to heart rate slowing was observed. In the subgroup of patients with atrial fibrillation, morbidity and mortality rates were similar in placebo and bisoprolol treated patients. It is possible that patients with atrial fibrillation had a higher level of sympathetic stimulation that would have required higher doses of bisoprolol to achieve a similar level of beta-blockade. Alternatively, the failure to observe improved outcome in the subgroup with atrial fibrillation may have been due to chance. However, because this finding was not observed in other large trials, and because there was no clear explanation, it should not be concluded that patients with chronic heart failure and atrial fibrillation do not benefit from beta-blockade.