Exercise training increases oxygen uptake efficiency slope in chronic heart failure

Background and aim The oxygen uptake efficiency slope (OUES) is a novel measure of cardiopulmonary reserve. OUES is measured during an exercise test, but it is independent of the maximally achieved exercise intensity. It has a higher prognostic value in chronic heart failure (CHF) than other exercise test-derived variables such as <(V)over dot>(O2peak) or <(V)over dot>E/<(V)over dot>(CO2) slope. Exercise training improves <(V)over dot>(O2peak) and <(V)over dot>E/<(V)over dot>(CO2) in CHF patients. We hypothesized that exercise training also improves OUES. Methods and results We studied 34 New York Heart Association (NYHA) class II-III CHF patients who constituted an exercise training group T (N=20; 19 men/1 woman; age 60 9 years; left ventricular ejection fraction 34 +/- 5%) and a control group C (N= 14; 13 men/one woman; age 63 +/- 10 years; left ventricular ejection fraction 34 +/- 7%). A symptom-limited exercise test was performed at baseline and repeated after 4 weeks (C) or after completion of the training program (T). Exercise training increased NYHA class from 2.6 to 2.0 (P < 0.05), <(V)over dot>(O2peak) by 14% [P(TVsC)<0.01], and OUES by 19% [P(TvsC)< 0.01]. Exercise training decreased <(V)over dot>(O2peak) by 14% [P(TvsC)< 0.05]. Conclusion Exercise training improved NYHA class, <(V)over dot>E/<(V)over dot>(CO2) and also OUES. This finding is of great potential interest as OUES is insensitive for peak load. Follow-up studies are needed to demonstrate whether OUES improvements induced by exercise training are associated with improved prognosis.