Standards for Analysis of Ventricular Late

I mproved methods for detecting individual patients recovering from myocardial infarction who are at high risk for sudden cardiac death are essential for reducing mortality from ventricular arrhythmias. During the past decade, many investigators have recorded low-amplitude, high-frequency waveforms and altered frequency components in the terminal QRS complex in laboratory animalsl2 and patients prone to sustained ventricular tachycardia.3-16 These microvolt level waveforms are termed late potentials. The reported prevalence of abnormal signals has ranged from 60% to 90%, depending on the method of signal processing, the definition of late potentials, and the patient groups studied.6'8'10 Conversely, the incidence of abnormal signals in normal subjects is quite low and has been reported from 0% to 7% when essentially the same recording techniques were used.17'18 The technique for recording these abnormal signals is called high-resolution electrocardiography. Since the technical aspects of the available commercial systems differ considerably, standardization of re-