Impact of Diabetes Mellitus on the Improvement in Signal-Averaged Electrocardiography after Coronary Artery Bypass Grafting

Background: Although it has been reported that coronary artery bypass grafting (CABG) for multivessel disease markedly improves several parameters of signal-averaged electrocardiography (SAECG), its beneficial effect on SAECG is variable. The hypothesis of the present study was that the presence of diabetes mellitus (DM) affects the improvement in SAECG after CABG. Methods and Results: Pre- and post-operative SAECGs were recorded in 100 consecutive patients who underwent complete surgical revascularization. Changes in the following parameters were compared between the diabetic (n=43) and non-diabetic (n=57) patients: filtered QRS duration (dQRS), root mean square voltage in the terminal 40 s of the QRS complex (RMS40), and duration of the terminal low-amplitude signal lower than 40 μV (LAS40). Although baseline characteristics and the occurrence of late potentials were similar in both groups, quantitative improvements in the SAECG parameters after CABG were significantly greater in non-diabetic than in diabetic patients (dQRS: 109±22 ms vs 102±19 ms in diabetics and 106±21 ms vs 88±11 ms in non-diabetics; p=0.028, RMS40: 55±46 μV vs 65±38 μV in diabetics and 50±37 μV vs 76±37 μV in non-diabetics; p=0.037, LAS40: 31±20 ms vs 26±17 ms in diabetics and 32±12 ms vs 17±8 ms in non-diabetics; p=0.007, respectively). Conclusions: The presence of DM limits the CABG-induced improvement in SAECG. In diabetic patients, therefore, perioperative changes of the SAECG must be interpreted with caution.