Signal-averaged electrocardiography.

Signal-averaged electrocardiography (SAECG) is a technique involving computerized analysis of segments of a standard surface electrocardiogram. It is used for detecting small electrical impulses, termed ventricular late potentials, that follow the QRS segment. They are embedded in the electrocardiogram but ordinarily obscured by skeletal muscle activity and other extraneous sources of "noise" encountered in recording a standard electrocardiogram. Ventricular late potentials in patients with cardiac abnormalities, especially coronary artery disease or following an acute myocardial infarction, are associated with an increased risk of ventricular tachyarrhythmias and sudden cardiac death. Proponents of SAECG claim that it can obviate the need for invasive techniques commonly used to identify high-risk patients for interventions that treat or prevent ventricular tachyarrhythmia and sudden death. No randomized clinical trials evaluating SAECG have been completed; data from an ongoing National Institutes of Health-sponsored clinical trial are expected to be available in 3-4 years. The current data on SAECG show relatively consistent high negative predictive values, poor positive predictive values, and variable sensitivity and specificity when the technique is used on patients with cardiomyopathy or following a myocardial infarction. The available evidence also indicates that combining SAECG with other tests of cardiac function is superior to using any single test for risk. The utility of SAECG alone as an indicator of risk remains to be proven. SAECG combined with other standard tests of risk has been demonstrated to have clinical utility in patients following an acute myocardial infarction. Other patient populations have not been conclusively shown to benefit from its use.