Background Vascular endothelial dysfunction is an underlying pathophysiological feature of chronic heart failure (CHF). Endothelial progenitor cells (EPCs) are also impaired. The purpose of the study was to assess the effect of a cardiac rehabilitation (CR) program on the increase of EPCs at rest and on the acute response after maximal exercise in patients with CHF and investigate whether there were differences between two exercise training protocols and patients of NYHA II and III classes. Methods Forty-four patients with stable CHF enrolled in a 36-session CR program and were randomized in one training protocol; either high-intensity interval training (HIIT) or HIIT combined with muscle strength (COM). All patients underwent maximum cardiopulmonary exercise testing (CPET) before and after the CR program and venous blood was drawn before and after each CPET. Five endothelial cellular populations, expressed as cells/10 6 enucleated cells, were quantified by flow cytometry. Results An increase in all endothelial cellular populations at rest was observed after the CR program (p < 0.01). The acute response after maximum exercise increased in 4 out of 5 endothelial cellular populations after rehabilitation. Although there was increase in EPCs at rest and the acute response after rehabilitation in each exercise training group and each NYHA class, there were no differences between HIIT and COM groups or NYHA II and NYHA III classes (p > 0.05). Conclusions A 36-session CR program increases the acute response after maximum CPET and stimulates the long-term mobilization of EPCs at rest in patients with CHF. These benefits seem to be similar between HIIT and COM exercise training protocols and between patients of different functional classes.

BACKGROUND Vascular endothelial dysfunction is an underlying pathophysiological feature of chronic heart failure (CHF). Patients with CHF are characterized by impaired vasodilation and inflammation of the vascular endothelium. They also have low levels of endothelial progenitor cells (EPCs). EPCs are bone marrow derived cells involved in endothelium regeneration, homeostasis, and neovascularization. Exercise has been shown to improve vasodilation and stimulate the mobilization of EPCs in healthy people and patients with cardiovascular comorbidities. However, the effects of exercise on EPCs in different stages of CHF remain under investigation. AIM To evaluate the effect of a symptom-limited maximal cardiopulmonary exercise testing (CPET) on EPCs in CHF patients of different severity. METHODS Forty-nine consecutive patients (41 males) with stable CHF [mean age (years): 56 ± 10, ejection fraction (EF, %): 32 ± 8, peak oxygen uptake (VO 2 , mL/kg/min): 18.1 ± 4.4] underwent a CPET on a cycle ergometer. Venous blood was sampled before and after CPET. Five circulating endothelial populations were quantified by flow cytometry: Three subgroups of EPCs [CD34 + /CD45 - /CD133 + , CD34 + /CD45 - /CD133 + /VEGFR 2 and CD34 + /CD133 + /vascular endothelial growth factor receptor 2 (VEGFR 2 )] and two subgroups of circulating endothelial cells (CD34 + /CD45 - /CD133 - and CD34 + /CD45 - /CD133 - /VEGFR 2 ). Patients were divided in two groups of severity according to the median value of peak VO 2 (18.0 mL/kg/min), predicted peak VO 2 (65.5%), ventilation/carbon dioxide output slope (32.5) and EF (reduced and mid-ranged EF). EPCs values are expressed as median (25th-75th percentiles) in cells/10 6 enucleated cells. RESULTS Patients with lower peak VO 2 increased the mobilization of CD34 + /CD45 - /CD133 + [pre CPET: 60 (25-76) vs post CPET: 90 (70-103) cells/10 6 enucleated cells, P < 0.001], CD34 + /CD45 - /CD133 + /VEGFR 2 [pre CPET: 1 (1-4) vs post CPET: 5 (3-8) cells/10 6 enucleated cells, P <...

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