Magnitude of muscle wasting early after on-pump coronary artery bypass graft surgery and exploration of aetiology.

NEW FINDINGS: What is the central question of this study? It remains uncertain whether significant fat-free mass wasting occurs early after coronary artery bypass graft surgery, and the aetiology of this wasting in these particular conditions is unexplored. What is the main finding and its importance? Significant fat-free mass wasting is present after coronary artery bypass graft surgery, and this wasting effect is greater in younger patients and in patients with greater increments in blood cortisol-to-testosterone ratios after surgery. The magnitude and aetiology of muscle wasting early after coronary artery bypass graft (CABG) surgery remains unknown. In the present study, we assessed changes in fat-free mass early after CABG surgery and explored the possible aetiology (relationships with postsurgical changes in blood hormones, insulin resistance, subject characteristics and inflammation) for these changes. Fat-free mass was assessed before and 23 (range: 25) days after CABG surgery in 25 subjects. Blood testosterone, cortisol, insulin-like growth factor-1, growth hormone, sex hormone-binding globulin, glucose, insulin, C-peptide and C-reactive protein concentrations were determined, and free androgen index, cortisol-to-testosterone ratio and HOMA-IR index were all calculated before surgery, during the first 3 days after surgery and at reassessment of body composition. Relationships between changes in fat-free mass and changes in blood parameters after surgery or subject characteristics were studied. After surgery, free androgen index and blood sex hormone-binding globulin, testosterone and insulin-like growth factor-1 concentrations decreased significantly, while HOMA-IR index, cortisol-to-testosterone ratio, blood growth hormone, insulin and C-reactive protein concentrations increased significantly (P < 0.0025, observed α > 0.80). Whole-body fat-free mass decreased significantly [by -1.9 (range: 9.1) kg, P < 0.0025, observed α = 0.99] after surgery. According to regression analysis, greater absolute loss of fat-free mass was observed after CABG surgery in subjects who were younger, who experienced a greater increase in blood cortisol-to-testosterone ratio after surgery and/or who underwent earlier reassessment of body composition (P < 0.05). Significant decrements in fat-free mass were observed early after CABG surgery, especially in younger subjects and/or subjects with elevated blood cortisol-to-testosterone ratios after surgery. Interventions to preserve fat-free mass soon after CABG surgery are thus warranted.

Clinical benefits of the addition of lower extremity low-intensity resistance muscle training to early aerobic endurance training intervention in patients with coronary artery disease: a randomized controlled trial.

OBJECTIVE: Muscle resistance training is often combined with aerobic endurance training during rehabilitation of patients with coronary artery disease. However, the clinical effects of additional lower-extremity low-intensity muscle resistance training during early rehabilitation (within the first month after coronary revascularization) in patients with coronary artery disease remain unclear. DESIGN: Prospective randomized controlled trial. SUBJECTS: Sixty patients with coronary artery disease. METHODS: Subjects were randomly assigned to early aerobic endurance training (n = 30) or combined aerobic endurance and resistance muscle training (n = 30). Subjects performed 18 (standard deviation 2) exercise sessions (at 65% VO(2peak), for 40 mins/session). In resistance muscle training, additional low-intensity (12-20 repetition maximum) resistance muscle exercises were performed. The following parameters were evaluated: exercise capacity, body composition, blood lipid profile, glycaemic control, blood endothelial progenitor cell and cytokine content, and muscle performance. RESULTS: A total of 47 patients with coronary artery disease completed the intervention. Total body lean tissue mass tended to increase with greater magnitude (p = 0.07), and blood high-density lipid cholesterol content increased with significantly greater magnitude in resistance muscle training (p < 0.05), compared with aerobic endurance training. Maximal exercise capacity, ventilatory threshold, and muscle performance increased, and steady-state exercise respiratory exchange ratio, and adipose tissue mass reduced significantly (p < 0.05), without differences between groups (p < 0.05). CONCLUSION: In early aerobic endurance training intervention in patients with coronary artery disease, additional low-intensity resistance muscle training contributes to a greater increase in blood high-density lipid cholesterol content, and tends to affect lean tissue mass.