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Use of the signal-averaged electrocardiogram in nonischemic heart disease and cardiac transplantation

Sanjiv M Narayan, MD, PhD
Michael E Cain, MD
Section Editors
Ary L Goldberger, MD
Sharon A Hunt, MD
Deputy Editor
Brian C Downey, MD, FACC


Sudden cardiac death (SCD), predominantly from ventricular tachycardia (VT) or ventricular fibrillation (VF), remains a major public health problem. The signal-averaged electrocardiogram (SAECG) is a noninvasive technique to detect substrate for reentrant arrhythmias such as VT. It has been applied to identify individuals at risk for sudden cardiac death, particularly in the context of coronary artery disease, healed myocardial infarction, and left ventricular dysfunction [1-4]. (See "Clinical applications of the signal-averaged electrocardiogram: Overview".)

In patients with the substrates for VT, slow conduction through myocardium disrupted by inflammation, edema, fibrosis, or scar tissue continues throughout activation [5] but may also produce electrical potentials extending beyond the activation time of normal myocardium, but which are too small for detection on the surface ECG. Scar and fibrosis are important mechanistic determinants of VT in nonischemic as well as ischemic cardiomyopathy, as evidenced by magnetic resonance imaging [6] and other modalities, and scar may have a predilection for the epicardium in these patients [7]. The SAECG uses computerized averaging of ECG complexes, obtained during sinus rhythm, to facilitate the detection of these small microvolt level signals, recorded as ventricular late potentials (figure 1). Signals identified by the SAECG may reflect late potentials identified in patients with structural heart disease, and these signals may be identified by novel techniques [5,8]. (See "Technical aspects of the signal-averaged electrocardiogram".)

This topic will review the utility of the SAECG in patients with nonischemic heart disease and in cardiac transplant recipients. The use of the SAECG in patients with ischemic heart disease, arrhythmia, and syncope are discussed separately. (See "Use of the signal-averaged electrocardiogram in ischemic heart disease" and "Use of the signal-averaged electrocardiogram in arrhythmia evaluation and management" and "Syncope in adults: Clinical manifestations and diagnostic evaluation".)


Data are conflicting on the efficacy of the SAECG in predicting clinical outcomes or ventricular arrhythmias in patients with dilated nonischemic cardiomyopathy. Although the SAECG is predictive of total mortality, cardiac death, and/or arrhythmic events in some studies [9-11], it was not predictive in other series [12-14]. Mortality in patients with nonischemic cardiomyopathy is increased in patients with a widened QRS duration and with notching of the QRS complex, both of which are likely related to mechanisms indicated by the SAECG [15,16].

The predictive value of the SAECG has been suggested by a prospective study of 114 patients with nonischemic dilated cardiomyopathy [9]. Twenty of the 86 patients without bundle branch block had an abnormal SAECG. One-year survival free of ventricular tachycardia (VT) was much lower in those with late potentials on the SAECG (39 percent) as compared with those with a normal SAECG (95 percent) and those with bundle branch block (88 percent). Similarly, a study of 131 patients with dilated cardiomyopathy followed for 54 months found that those with late potentials had an increased risk of all-cause cardiac death (relative risk [RR] 3.3, 95% CI 1.5-7.5) and arrhythmic events (RR 7.2, 95% CI 2.6-19.4) [10].

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Literature review current through: Nov 2017. | This topic last updated: Nov 24, 2017.
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