Exercise Anaerobic Threshold and Ventilatory Efficiency Identify Heart Failure Patients for High Risk of Early Death

Background: The maximal oxygen uptake (peak VO2) is used in risk stratification of patients with chronic heart failure (CHF). Peak VO2 might be lower than maximally possible if exercise is stopped early because of lack of patient motivation or premature cessation by the investigator. In contrast, the anaerobic threshold (VO2AT) and the ventilatory efficiency (VE versus VCO2 slope) are less subject to these influences. Thus, we compared these parameters with peak VO2 in identifying patients with CHF at increased risk for death within 6 months after evaluation.

Methods And Results: We performed cardiopulmonary exercise tests with gas exchange measurements in 223 consecutive patients with CHF (114 coronary artery disease, 92 dilated cardiomyopathy, 17 others) at the Herzzentrum Ludwigshafen between 1995 and 1998. We measured peak VO2, VO2AT and VE versus VCO2 slope. We selected peak VO2 of < or =14 mL/kg per minute, VO2AT of <11 mL/kg per minute, and VE versus VCO2 slope of >34 as threshold values for high risk of death. The median follow-up time was 644 days. Patients with peak VO2 of < or =14 mL/kg per minute had a >3-fold-increased risk (OR=3.4; CI, 1.3 to 9.1), with VO2AT <11 mL/min per kg or VE versus VCO2 slope >34 a 5-fold increased risk for early death (OR=5.3; CI, 1.5 to 19.0; OR=4.8; CI, 1.7 to 13.8, respectively). In patients with both VO2AT <11 mL/kg per minute and VE versus VCO2 slope >34, the risk of early death was 10-fold higher (OR=9.6; CI, 2.1 to 44.7). After correction for age, sex, left ventricular ejection fraction, and New York Heart Association class in a multivariate analysis, the combination of VO2AT <11 mL/kg per minute and VE versus VCO2 slope >34 was the best predictor of 6-month mortality (RR=5.1, P=0.001).

Conclusions: VO2AT of <11 mL/kg per minute and slope of VE versus VCO2 >34, combined, better identified patients at high risk for early death from CHF than did peak VO2 and should therefore be considered when prioritizing patients for heart transplantation.