[Localization of the optimal site for the detection of late potentials]

Late potentials (VLP) are high frequency-low amplitude electrical potentials that appear at late ventricular depolarization. A multilead method of detection (method M) was adopted in the present study. This study was designed to compare method M with composite XYZ lead method (method C) by analysis of signals recorded from the same hardware system. The purpose was to find out relations of the directions of MI Q vector and peri-infarction block to the recording lead axes of VLP. In 44 MI patients the results of VLP detection indicated that: (1) The positive incidence of VLP detection was 55% with method M which was significantly higher than that with method C (25%, P less than 0.01) especially in patients with ventricular tachycardia and/or ventricular fibrillation and ventricular premature contractions. The sensitivity of VLP with method M (75-88%) was apparently higher than that with method C (38%). (2) The direction of Q vector in MI was closely correlated with that of recording lead axes of VLP. (3) The positive VLP were found around peri-infarction block in patients with MI. The direction of peri-infarction block was mostly in line with that of lead axes with positive VLP, that is, the positive rate of VLP detection was the highest when ever the vector of MI and peri-infarction block were parallel to the recording lead axes of method M.