Responses to exercise training in patients with heart failure. Analysis by oxygen transport steps.

BACKGROUND

Exercise training (ET) increases exercise tolerance, improves quality of life and likely the prognosis in heart failure patients with reduced ejection fraction (HFrEF). However, some patients do not improve, whereas exercise training response is still poorly understood. Measurement of cardiac output during cardiopulmonary exercise test might allow ET response assessment according to the different steps of oxygen transport.

METHODS

Fifty-three patients with HFrEF (24 with ischemic cardiomyopathy (ICM) and 29 with dilated cardiomyopathy (DCM) had an aerobic ET. Before and after ET program, peak oxygen consumption (VO2peak) and cardiac output using thoracic impedancemetry were measured. Oxygen convection (QO2peak) and diffusion (DO2) were calculated using Fick's principle and Fick's simplified law. Patients were considered as responders if the gain was superior to 10%.

RESULTS

We found 55% VO2peak responders, 62% QO2peak responders and 56% DO2 responders. Four patients did not have any response. None baseline predictive factor for VO2peak response was found. QO2peak response was related to exercise stroke volume (r = 0.84), cardiac power (r = 0.83) and systemic vascular resistance (SVRpeak) (r = -0.42) responses. Cardiac power response was higher in patients with ICM than in those with DCM (p < 0.05). Predictors of QO2peak response were low baseline exercise stroke volume and ICM etiology. Predictors of DO2 response were higher baseline blood creatinine and prolonged training.

CONCLUSION

The analysis of the response to training in patients with HFrEF according to the different steps of oxygen transport revealed different phenotypes on VO2peak responses, namely responses in either oxygen convection and/or diffusion.