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This study was designed to establish and test guidelines for the prognostic use of the time domain signal-averaged ECG (SAECG) following MI. It was performed as a substudy in ten centers participating in the Cardiac Arrhythmia Suppression Trial (CAST).
In this study, 1158 patients with acute MI had SAECG within 30 days. Signal averaging was performed on 300 or more beats, and six variables were recorded: QRS duration, root-mean-square voltage in the last 40 ms, and duration of late potentials 40 mV or less at two filter settings. Holter 24-hour recordings were also performed. Patients were followed one year for the primary end point of sustained nonfatal V tach (120 or more beats/min for at least 30 seconds), arrhythmic cardiac arrest, or su…