USEFULNESS OF SIGNAL-AVERAGED ELECTROCARDIOGRAM IN IDIOPATHIC DILATED CARDIOMYOPATHY FOR IDENTIFYING PATIENTS WITH VENTRICULAR ARRHYTHMIAS

In idiopathic dilated cardiomyopathy (IDC), the relation between the signal-averaged electrocardiogram and ventricular tachycardia (VT) remains unclear. In this study, conventional time domain and frequency domain analyses (2-dimensional, spectral temporal mapping and spectral turbulence analysis) of the signal-averaged electrocardiogram were performed in 64 patients with IDC. Eight patients had a history of symptomatic sustained VT and an additional 24 had nonsustained VT recorded during ambulatory electrocardiography. Conventional time domain analysis, using the 25 and 40 Hz filter, and spectral temporal map ping, detected late potentials within the terminal QRS in 8 (13%), 14 (22%) and 18 (28%) patients, respectively. Late potentials were seen more often in patients with than without VT, and in patients with sustained versus nonsustained VT, but these differences were not significant. The predictive accuracy of these techniques in detecting either form of VT were: sensitivity, 22, 25 and 31%; specificity, 97, 81 and 75%; and overall predictive value, 59, 53 and 50%, respectively. Two-dimensional frequency domain analysis of the signal-averaged electrocardiogram revealed a higher energy and area ratio in patients with than without VT (entire QRS), and in patients with sustained versus nonsustained VT (entire QRS and terminal QRS). Spectral turbulence analysis was abnormal in 24 patients (39%), but no differences were observed between patients with and without VT. During follow-up (mean duration 18 +/- 14 months) 5 patients had arrhythmic events (3 died suddenly, 1 had aborted sudden death and 1 developed sustained VT). The signal-averaged electrocardiogram was abnormal in 1 patient using time domain analysis and spectral temporal mapping, and in 3 using spectral turbulence analysis (score = 4) conclusion, time domain and spectral temporal mapping analysis of the signal-averaged electrocardiogram identifies IDC patients with VT with high specificity but low sensitivity. The application of the 2-dimensional frequency analysis improves identification of patients with sustained VT. Spectral turbulence analysis of the entire QRS complex is a promising technique for the identification of patients with IDC at high risk of sudden death.