USEFULNESS OF LATE POTENTIALS ON THE IMMEDIATE POSTOPERATIVE SIGNAL-AVERAGED ELECTROCARDIOGRAM IN PREDICTING VENTRICULAR TACHYARRHYTHMIAS EARLY AFTER ISOLATED CORONARY-ARTERY BYPASS-GRAFTING

The present study was undertaken to determine the value of abnormal la te ventricular potentials on signal-averaged electrocardiograms (ECG) in Identifying patients at risk of developing ventricular tachycardia Or ventricular fibrillation in the early postoperative period after co ronary artery bypass grafting. Signal-averaged ECGs were recorded imme diately after operation in 72 patients Abnormal late potentials were d efined as the presence of 2 or 3 of the following: (1) root-mean-squar e amplitude of the last 40 ms of the QRS <20 mu V; (2) duration of the terminal QRS potentials (after 40 mu V) greater than or equal to 39 m s; and (3) high-frequency QRS duration >120 ms (in patients with condu ction defects, only the first 2 criteria were used). Abnormal late ven tricular potentials were present on the immediate postoperative signal -averaged ECG in 26 of the 72 patients (36%). Life-threatening ventric ular tackyarrhythmias occurred in 6 patients. Late potentials were pre sent in all 6 patients, but only in 20 of 66 (36%) who did not develop ventricular tachyarrhythmias (p <0.005) (sensitivity 100%, specificit y 70%, predictive accuracy 72%). Of 12 pre- and perioperative variable s examined by univariate and multi-variate regression analysis, the pr esence of late potentials on the signal-averaged ECG and low cardiac o utput postoperatively were found to he independent predictors of life- threatening tachyarrhythmias.