Prediction of long-term outcomes by signal-averaged electrocardiography inpatients with unsustained ventricular tachycardia, coronary artery disease, and left ventricular dysfunction

Background-An abnormal signal-averaged ECG (SAF-CG) is a noninvasive marker of the substrate of sustained ventricular tachycardia after myocardial inf arction. We assessed its prognostic ability in patients with asymptomatic u nsustained ventricular tachycardia, coronary artery disease, and left ventr icular dysfunction. Methods and Results-A blinded core laboratory analyzed SAECG tracings from 1925 patients in a multicenter trial. Cox proportional hazards modeling was used to examine individual and joint relations between SAECG variables and arrhythmic, death or cardiac arrest (primary end point), cardiac death, an d total mortality. We also assessed the prognostic utility of SAECG at diff erent levels of ejection fraction (EF). A filtered QRS duration > 114 ins ( abnormal SAECG) independently predicted the primary end point and cardiac d eath, independent of clinical variables, cardioverter-defibrillator implant ation, and antiarrhythmic drug therapy. With an abnormal SAECG, the 5-year rates of the primary end point (28% versus 17%, P=0.0001), cardiac death (3 7% versus 25%, P=0.0001), and total mortality (43% versus 35%, P=0.0001) we re significantly higher. The combination of EF <30% and abnormal SAECG iden tified a particularly high-risk subset that constituted 21% of the total po pulation. Thirty-six percent and 44% of patients with this combination succ umbed to arrhythmic and cardiac death, respectively. Conclusions-SAECG is a powerful predictor of poor outcomes in this populati on. The noninvasive combination of an abnormal SAECG and reduced EF may hav e utility in selecting high-risk patients for intervention.