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Use of the signal-averaged electrocardiogram in arrhythmia evaluation and management

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


Sudden cardiac death affects over 300,000 individuals per year in the United States alone, with ventricular tachycardia (VT) or ventricular fibrillation (VF) being major causes [1,2]. The signal-averaged electrocardiogram (SAECG) is a noninvasive technique that enables detection of the substrate for reentrant arrhythmias, particularly VT.

In patients with the substrate for VT, slow conduction through myocardium disrupted by inflammation, edema, fibrosis, or scar tissue results in electrical potentials that extend beyond the activation time of normal surrounding myocardium, but which are too small for detection on the surface ECG [3,4]. 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). It is possible that the signals identified by the SAECG, which are related to late potentials identified in patients with structural heart disease and used to guide VT ablation, may also be identified by novel techniques [5,6]. (See "Technical aspects of the signal-averaged electrocardiogram".)

The potential clinical applications for the SAECG are diverse. An American College of Cardiology (ACC) consensus task force provided a guide to the settings in which the SAECG is of proven value, possible value, and not indicated [7].

This topic will review the use of the SAECG with an emphasis on the efficacy of antiarrhythmic medications, evaluation of the results of arrhythmia surgery, and identification of individuals with paroxysmal atrial fibrillation prone to frequent recurrences based upon abnormalities in the P-wave SAECG [8-10]. The use of the SAECG in other settings is discussed separately. (See "Clinical applications of the signal-averaged electrocardiogram: Overview" and "Use of the signal-averaged electrocardiogram in nonischemic heart disease and cardiac transplantation" and "Use of the signal-averaged electrocardiogram in ischemic heart disease".)


Although anti-arrhythmic drug efficacy is typically assessed by absence of recurrent arrhythmias, the SAECG offers an a priori method to assess drug efficacy. Several studies have tested the hypothesis that abnormalities on the SAECG evolve with the arrhythmogenic substrate, and thus diminish with successful antiarrhythmic therapy, in parallel with reduced risk for ventricular arrhythmias. As expected, changes in the SAECG correlate poorly with the clinical efficacy of anti-arrhythmic drugs that have not been shown to abolish late potentials [11]. (See "Pharmacologic therapy in survivors of sudden cardiac arrest".)

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Literature review current through: Sep 2017. | This topic last updated: Oct 20, 2017.
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