Oscillatory breathing and exercise gas exchange abnormalities prognosticate early mortality and morbidity in heart failure.

Abstract

The goal of this study was to identify better predictors of early death in patients with chronic left ventricular heart failure (CHF). Potential predictors, derived from cardiopulmonary exercise testing, were compared with other commonly used cardiovascular measurements. The prediction of early death in patients with CHF remains challenging. Five hundred eight patients with CHF due to systolic dysfunction underwent resting cardiovascular measurements, 6-min walking tests, and cardiopulmonary exercise testing. The peak oxygen uptake (.VO(2)), peak oxygen pulse, anaerobic threshold, ratio of ventilation to carbon dioxide output (.VE/.VCO(2)), slope of .VE versus .VCO(2), and presence or absence of a distinctive oscillatory breathing pattern (OB) were ascertained. Outcomes were 6-month mortality and morbidity, the latter a sum of cardiac hospitalizations and deaths. The single best predictor of mortality was an elevated lowest .VE/.VCO(2) (> or =155% predicted). Adding OB on the basis of stepwise regression (optimal 2-predictor model), the odds ratio for mortality increased from 9.4 to 38.9 (p < 0.001). The slope of .VE versus .VCO(2) slope, peak .VO(2), peak oxygen pulse, and anaerobic threshold combined with OB were also strong predictors. OB also increased the odds ratio 2- to 3-fold for each of these (p < 0.01). Kaplan-Meier survival curves and area under the receiver-operating characteristic curve confirmed that lowest .VE/.VCO(2) and OB were superior. For morbidity, elevated lowest .VE/.VCO(2) or lower peak .VO(2) with OB were the best predictors. No nonexercise measurements discriminated mortality and morbidity. Cardiopulmonary exercise testing parameters are powerful prognosticators of early mortality and morbidity in patients with CHF, especially the optimal 2-predictor model of a combination of elevated lowest .VE/.VCO(2) and OB.