P5681Effects of exercise training on cardiovascular autonomic modulation and skeletal muscle tissue in chagasic cardiopathy patients and preserved systolic function

Abstract

Background: The benefits of aerobic exercise training (ET) in cardiovascular autonomic control and skeletal muscle of heart failure patients are well established. The study hypothesis was that ET improves cardiovascular autonomic function and structure, and muscle metabolism in chronic chagasic cardiopathy (CCC) patients even though they have preserved systolic function, considering that some of these patients develop the dilated form with ventricular dysfunction and its serious consequences. Purpose: To evaluate the effects of ET on cardiovascular autonomic control and skeletal muscle tissue in CCC patients and preserved systolic function. Methods: Patients with two positive serological reactions for Chagas disease, electrocardiographic alterations, left ventricular ejection fraction ≥55% and age between 30 and 60 years were included. Eight patients completed the ET protocol (ET, n=08) and ten patients completed clinical follow-up (NoET, n=10). Muscular sympathetic nerve activity (MSNA) was measured using microneurography technique and muscle blood flow (MBF) by the venous occlusion plethysmography technique. Cardiac baroreflex sensitivity was evaluated by infusion of vasoactive drugs. Functional capacity was determined by cardiopulmonary exercise test. Vastus lateralis muscle biopsy was performed for histological analysis of muscle fibers and for Atrogin-1 and MuRF-1 gene expression evaluation. The ET program consisted of three 60-minute exercise sessions per week for four months. Results: Regarding ET markers, there was a reduction in resting heart rate (66.1±2.6 vs 59.4±3.3 beats/min; p=0.003) and an increase in peak oxygen consumption (24.4±2.4 vs 28.1±1.7 ml/kg/min; p=0.03). ET reduced the sympathetic hyperactivity, contributing to an increase in MBF. ET reduced MSNA (31.9±3.8 vs 22.8±2.6 burst/min; p=0.008), as well as cardiac (68±4 vs 60±4 nu; p=0.004) and vasomotor sympathetic activity (46±5 vs 37±3 nu; p=0.04), and improved cardiac baroreflex sensitivity (-0.23±0.1 vs -0.46±0.1; p=0.04 for increases in BP and - 0.48±0.1 vs -1.00±0.3; p=0.04 for decreases in BP). A reduction of MSNA was associated to a reduction in cardiac (r=0.67; p=0.013) and vasomotor (r=0.81; p=0.003) hyperactivity, improved cardiac baroreflex sensitivity for increases (r=- 0.72; p=0.20) and decreases in BP (r=-0.82; p=0.001), and reduced Atrogin-1 (r=0.86; p=0.02) and MuRF-1 (r=0.64; p=0.06) gene expression. After the fourmonth period, the ET group presented lower Atrogin-1 gene expression than the NoET group (0.49±0.2 vs 2.27±0.4 u; p=0.001). Conclusion: ET significantly improved autonomic dysfunction, MBF and functional capacity of CCC patients and preserved systolic function. In addition, reduced ANSM was associated with improved cardiac baroreflex sensitivity, reduced sympathetic cardiovascular tone, and reduced Atrogin-1 and MuRF-1 gene expression, which are involved in muscle atrophy.