Cardiopulmonary exercise parameters in relation to all-cause mortality in patients with chronic heart failure

In this study we analysed the all-cause mortality over a period of maximal 6 years in 60 male patients (age: 63.4+/-8.3 years, mean+/-S.D.), suffering from chronic heart failure with resting left ventricular ejection fraction and E-./(.)O2 slope as independent factors. We assessed functional NYHA class (II: n=36, III: n=24), radionuclide left ventricular ejection fraction (29.2+/-10.4%) and peak values of heart rate,(.)O2,(.)CO2,E-., anaerobic threshold and exercise duration with an incremental work load test on the treadmill. (.)O2 relative to E-. was based on the individual slopes of the regression of (.)O2 on E-. during the first 6 min of exercise. These slopes with other exercise-related variables and factors such as etiology, medication, and NYHA class were analysed with a Cox's Regression Method. A survival time analysis (Kaplan-Meier survival curve) was done to establish the influence of E-./(.)O2 slope and left ventricular ejection fraction (both split into above and below median values), as well as their interaction, on survival. From all investigated exercise-related variables,E-./(.)O2 slope is the most powerful variable regarding prediction of all-cause mortality in our group of chronic heart failure patients. Concerning risk stratification, the subgroup (n=18) with a relatively high left ventricular ejection fraction (>28%) and flat E-./(.)O2 slope (<27.6) had most survivors (77.8%) after about 3 years, while the subgroup (n=12) with a relatively high left ventricular ejection fraction (>28%), but a steep E-./(.)O2 slope (>27.6) had least survivors (33.3%). This difference in percentage is highly significant (P=0.0025). The fact that E-./(.)O2 slope and left ventricular ejection fraction show comparable main and interaction effects between measures of exercise tolerance (e.g., anaerobic threshold, peak (.)O2, exercise duration) on the one hand, and all-cause mortality on the other, suggests the existence of common sources of variance. Based on our analysis, it is unlikely that effects on all-cause mortality are mediated through phenomena related to exercise tolerance. Therefore, we hypothesize that the effects on exercise tolerance and all-cause mortality both depend on common factors, which cause both cardiac and peripheral organ (c.q. muscular) dysfunctions. Moreover, this study clearly shows that E-./(.)O2 slope during incremental exercise is an important prognostic marker for risk stratification in chronic heart failure patients, NYHA class II and III. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.