Oscillatory Breathing and Exercise Gas Exchange Abnormalities Prognosticate Early Mortality and Morbidity in Heart Failure

ObjectivesThe 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.BackgroundThe prediction of early death in patients with CHF remains challenging.MethodsFive 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 (V̇o2), peak oxygen pulse, anaerobic threshold, ratio of ventilation to carbon dioxide output (V̇e/V̇co2), slope of V̇eversus V̇co2, 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.ResultsThe single best predictor of mortality was an elevated lowest V̇e/V̇co2(≥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 V̇eversus V̇co2slope, peak V̇o2, 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 V̇e/V̇co2and OB were superior. For morbidity, elevated lowest V̇e/V̇co2or lower peak V̇o2with OB were the best predictors. No nonexercise measurements discriminated mortality and morbidity.ConclusionsCardiopulmonary 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 V̇e/V̇co2and OB.