Critical overview of late potential recordings.

High resolution ECG (HRECG) techniques have been used for several years to quantify low level cardiac potentials which occur at the end of and after the normal registration of the QRS complex. These potentials have been recorded with endocardial catheter electrodes in man and epicardial electrodes in canine models of myocardial infarction. In order to record these small signals on the body surface, signal averaging is used to improve the signal-to-noise ratio. These so-called "late potentials" have been the focus of a few animal studies and an ever increasing number of clinical studies. The primary focus of the clinical studies has been in the patients with inducible ventricular tachycardias. Long-term follow-up of patients with myocardial infarction has also been reported. There is continual support for the conclusion that the presence of late potentials, measured with a variety of approaches, is an independent measure of vulnerability to life-threatening ventricular arrhythmias. Methods used for recording and analyzing the late potentials have varied widely among investigators. Four aspects of these various studies will be examined: lead selection, signal processing, parameter selection, and quality control. Specific data with regard to lead selection and high pass filtering will be presented.