Impact of diabetes on muscle mass, muscle strength, and exercise tolerance in patients after coronary artery bypass grafting

Background: The impact of diabetes mellitus (DM) on muscle mass, muscle strength, and exercise tolerance in patients who had undergone coronary artery bypass grafting (CABG) has not been fully elucidated. Methods: We enrolled 329 consecutive patients who received cardiac rehabilitation (CR) after CABG (DM group, n= 178; non-DM group, n= 151) and measured lean body weight, mid-upper arm muscle area (MAMA), and handgrip power (HGP) at the beginning of CR. We also performed an isokinetic strength test of the knee extensor (Ext) and flexor (Flex) muscles and a cardiopulmonary exercise testing at the same time. Results: No significant differences in risk factors, including age, gender, number of diseased vessels, or ejection fraction were observed between the 2 groups. The levels of Ext muscle strength, peak oxygen uptake, and anaerobic threshold were significantly lower in the DM group than in the non-DM group (all p < 0.05). Both peak oxygen uptake and MAMA correlated with Ext and Flex muscle strength as well as HGP (all p < 0.005). The MAMA, HGP, and Ext muscle strength were lower in patients who received insulin therapy than in those who did not. Interestingly, fasting glucose levels significantly and negatively correlated with Ext muscle strength. Conclusions: These data suggest that DM patients had a lower muscle strength and exercise tolerance than non-DM patients. Moreover, a high glucose level may affect these deteriorations in DM patients after CABG. (C) 2011 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.