Late potentials - a non-invasive marker of substrate of arrhythmia - recorded after acute myocardial infarction predict an increased likelihood of spontaneous ventricular tachycardia or sudden death. The effect of coronary artery bypass grafting (CABG) on ventricular arrhythmias remains controversial. In patients with recurrent ventricular monomorphic tachycardia this arrhythmia seems to be rarely controlled by coronary artery bypass grafting alone. The effect of revascularisation of the ischemic myocardium on substrate of arrhythmia identified by signal averaged electrocardiogram (SAECG) was evaluated in 38 patients with previous myocardial infarction. Late potentials (LP) were defined as the presence of 2 or 3 of the following criteria: 1) total QRS duration (QRSd) ; 2) low-amplitude terminal signal duration < 40 uV (LAS 40); 3) root-mean-square-voltage in terminal 40ms (RMS40). Before CABG late potentials on SAECG were recorded in 10 patients (26%). Late potentials after coronary surgery were observed in 16 patients (42%). This group comprised 8/10 patients (80%) who had abnormal SAECG before and remained late potentials-positive after CABG and 8/28 (29%) who had normal SAECG before and became late-potentials positive after bypass surgery. Among 22 patients without late potentials after CABG 2/10 (20%) patients lost their late potentials observed before CABG and 20/28 (71%) remained late-potentials negative. The results of this study suggest that in patients with remote myocardial infarction coronary artery bypass grafting has little effect on preexisting late patentials but some preoperatively LP negative patients may become LP positive after successful CABG.

Keywords: late potentials, signal averaged electrocardiogram, coronary artery bypass grafting