Value of Time- and Frequency-Domain Analysis of Signal-Averaged Electrocardiography for Arrhythmia Risk Prediction in Idiopathic Dilated Cardiomyopathy WOLFRAM GRIMM, JURGEN HOFFMANN, URSULA KNOP, JENS WINZENBURG, VOLKER MENZ, and BERNHARD MAISGH From the Cardiovascular Section of the Department of Medicine, Hospital of the Philipps-University of Marburg, Marburg, Germany GRIMM, W., ET AL.: Value of Time- and Frequency-Domain Analysis of Signal-Averaged Electrocardio- graphy for Arrhythmia Risk Prediction in Idiopathic Dilated Cardiomyopathy. Signal-averaged electro- cardiography (SAECG) was performed in 120 consecutive patients with idiopathic dilated cardiomyopa- thy (IDC), and in 60 healthy controls. Time-domain analysis of SAECGs revealed ventricular late potentials in 27 of 120 patients with IDC (23%) compared to 2 of 60 controls (3%; P < 0.05). Frequency- domain analysis of SAECGs showed ventricular late potentials in 9 of 120 patients with IDC (8%) com- pared to none of the 60 controls (0%, P < 0.05). During a prospective follow-up of 15 ± 7 months, serious arrhythmic events, defined as sustained ventricular tachyarrhythmias or sudden death, occurred in 17 of 120 patients with IDC (14%). The sensitivity, specificity, and positive and negative predictive values of ventricular late potentials for serious arrhythmic events were 35%, 80%, 22%, and 88% for the time-do- main analysis, and 18%, 94%, 33%, and 87% for the frequency-domain analysis of SAECG, respectively. Thus, neither the time- nor the frequency-domain analysis of SAECC appears to be useful for risk stratifi- cation in the setting of IDC in view of their low sensitivity and low positive predictive value for serious ar- rhythmic events during follow-up. (PACE 1996; 19(Pt. II].1923-1927) signal-averaged electrocardiography, idiopathic dilated cardiomyopathy, arrhythmic events Introduction Ventricular late potentials detected by signal- averaged electrocardiography (SAECG] after my- ocardial infarction indicate an increased risk for sustained ventricular arrhythmias and sudden death during follow-up.^~* In contrast to ischemic heart disease, only few studies, with relatively small numbers of patients have investigated the prognostic value of ventricular late potentials in idiopathic dilated cardiomyopathy (IDC).^~^° The purpose of the present prospective study was twofold: (1) to compare the incidence of ventricu- lar late potentials detected by time- and fre- quency-domain analysis of SAECC between pa- tients with IDC and healthy controls; and (2) to Address for reprints: Wolfram Grimm, M.D., Hospital of the Philipps-University Marburg, Department of Cardiology, Baldingerstraj3e, 35033 Marburg, Germany. Fax: 6421-28-8954. determine the value of ventricular late potentials in the prediction of serious arrhythmic events in the setting of IDC. Patients and Methods The study population consisted of 120 con- secutive patients with IDC, and a control group of 60 volunteers without structural heart disease. The clinical characteristics of the 120 study pa- tients with IDC are summarized in Table I. All pa- tients with IDC underwent noninvasive and inva- sive evaluation including physical examination, 12-lead ECC, M mode and two-dimensional echocardiography, 24-hour Holter monitoring, ex- ercise stress testing, and diagnostic cardiac catheterization with coronary angiography and left ventricular angiography. Of note, third-gener- ation implantable cardioverter defibrillators (ICDs), with electrogram storage capability of the electrical event leading to a shock, were im- PACE, Vol. 19 November 1996, Part II 1923