Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic congestive cardiomyopathy.

BACKGROUND: An abnormal signal-averaged ECG (SAECG) has predictive value for arrhythmic events in patients with coronary artery disease. The purpose of this study was to investigate whether an abnormal SAECG could provide prognostic information in patients with nonischemic dilated cardiomyopathy. METHODS AND
RESULTS: We prospectively obtained SAECGs in 114 patients with dilated nonischemic cardiomyopathy. Twelve-lead ECGs, left ventricular ejection fractions, hemodynamic measurements, and peak exercise oxygen consumption (VO2) also were measured. An SAECG was defined as abnormal by any one of the three following criteria: filtered QRS duration > 120 msec, root-mean-square voltage in the last 40 msec < 20 microV, or duration < 40 microV > 38 msec at 40 Hz. Sixty-six patients had a normal SAECG, 20 patients had an abnormal SAECG, and 28 patients had bundle branch block (BBB). Mean follow-up was 10 +/- 5 months. Age, ejection fraction, peak VO2, pulmonary capillary wedge pressure, and cardiac index were not statistically different among the three groups. Use of antiarrhythmic drugs was similar among the three groups, although patients with BBB had more implantable defibrillators (p < 0.05). The incidence of previous atrial arrhythmias was similar for the three groups. Patients with abnormal SAECG or BBB had more past episodes of sustained ventricular tachycardia and/or sudden death episodes (n = 9) than patients with normal SAECG (n = 1) (p < 0.01). Prospectively, none of the 66 patients with normal SAECG died suddenly or had sustained ventricular arrhythmias. Two deaths occurred from progressive heart failure, and three patients required urgent transplant. In the 20 patients with an abnormal SAECG, four patients had sustained ventricular tachycardia, five patients died suddenly, two patients died from progressive heart failure, and one patient required urgent transplant. In the patients with BBB, four patients had sustained ventricular tachycardia, and four patients required urgent transplant. One-year event-free survival, i.e., absence of ventricular tachycardia and/or death, was 95% in patients with normal SAECG, 88% in patients with BBB, and only 39% in patients with an abnormal SAECG (p < 0.001). Multivariate analysis demonstrated that SAECG and New York Heart Association classification were independent predictors of survival.
CONCLUSIONS: Patients with an abnormal SAECG had a statistically significant increase in sustained ventricular arrhythmias and/or death than did patients with a normal SAECG or BBB. This study demonstrates that an abnormal SAECG is a marker of past and future arrhythmic events in patients with nonischemic dilated cardiomyopathy. In contrast, patients with a dilated cardiomyopathy with a normal SAECG have an excellent prognosis with adverse outcome only from progressive heart failure.