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Signal-averaged electrocardiogram (SAECG)

Signal-averaged electrocardiogram (SAECG) testing is performed to identify low-amplitude “late-potentials”, typically at the end of the QRS complex. These late-potentials are associated with delayed activation of the ventricles, and can aid in the identification of a population of patients at an increased risk for ventricular tachycardia. This noninvasive outpatient technique has been used to identify patients with a history of coronary disease or left ventricular dysfunction who may be at increased risk for sudden cardiac death (SCD).


Figure 1.   Example of a processed signal-averaged ECG revealing a high-frequency low-amplitude late-potential, as seen labeled here.

The SAECG literally averages multiple QRS complexes that are then digitalized and filtered and further processed with spectral analysis to eliminate noise. The resultant late-potentials represent areas of delayed activation due to slowed conduction from either regions of scar or fibrosis; both of which are markers for the electrical substrate that initiates and perpetuates ventricular tachycardia.The SAECG can be useful to risk stratify the following populations for sudden cardiac death:

  • Post-myocardial infarction patients
  • Structural heart disease patients with depressed heart function
  • Arrhythmogenic right ventricular dysplasia (ARVD)
  • Brugada Syndrome

Video 2. Technique for cryoablation for atrial fibrillation