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.

Cardiac rehabilitation in patients with pacemakers and implantable cardioverter defibrillators.

Large subsets of patients admitted in cardiac rehabilitation centers are having a pacemaker, cardiac resynchronization (CRT) or implantable cardiac defibrillator (ICD). Cardiac rehabilitation for patients, mostly with heart failure, with implanted electronic devices as pacemakers or ICD is a unique opportunity not only to optimize the medical treatment, to increase their exercise capacity and improves their clinical condition but also to supervise the correct functioning of the device. CRT reduces clinical symptoms and increases slightly the exercise capacity. But in these patients, the clinical improvements are likely to be explained by both the enhancement of cardiac function induced by the device and by the improved peripheral (muscular and vascular) and cardiac effects of exercise. The additional expected gain by exercise in this population is between 14 to 25%. In patients implanted with an ICD, exercise training is safe, without increasing shocks or anti-tachycardia pacing therapy. The comprehensive cardiac rehabilitation combining exercise training and a psycho-educational intervention improves exercise capacity, quality of life, general and mental health. Nevertheless, further large scale studies was needed to evaluate the most appropriate management and demonstrate definitively the role of cardiac rehabilitation in this particular group of patients.