A cutoff point for peak oxygen consumption in the prognosis of heart failure patients with β-blocker therapy.

PURPOSE: Beta-blockers (BB) have shown to improve outcomes among heart failure patients (HF). Adequate risk stratification is still a major concern for HF. The prognostic indexes have been detected, but only few parameters maintain consistently high power in predicting progression of disease and mortality. Peak oxygen consumption (VO(2) peak, ml kg(-1) min(-1)) is traditionally used for risk stratification in HF, however, there is limited evidence regarding predictive value of VO(2) peak in patients taking BB.
METHODS: Two hundred twenty nine patients, aged 49 ± 13 years with diagnosed HF for more than 6 months due to ischemic (n=73), idiopathic dilated (n=149) and Chagas disease (n=7) underwent a cardiopulmonary exercise test (CPX). The ejection fraction was 38 ± 10%; clinical stability was defined as no change in the NYHA class or absence of hospitalization for heart failure and stable medical treatment during 3 months prior to CPX. Subjects were tracked for cardiac-related mortality after CPX.
RESULTS: The mean follow-up period was 2.5 ± 1.1 years and means value for VO(2) peak was 16.3 ± 4. Current BB therapy included carvedilol (83.4%), metoprolol (7.8%), bisoprolol (3.9%) and others (4.8%). The area under the ROC curve for VO(2) peak was 0.80 (95% CI: 0.69-0.90, optimal threshold: 12.5 and 82% sensitivity/26% specificity, p<0.001). Kaplan-Meier analysis that revealed event-free survival for subjects in < and >12.5 was 28% and 2.8%, respectively (long-rank 34.8; p<0.001).
CONCLUSIONS: VO(2) peak seems to maintain prognostic value in HF patients BB therapy. The present study also provides new evidence that optimal threshold value for VO(2) peak in the BB era is 12.5 ml kg(-1) min(-1).