Pyramid Electrode Location in a Cardiac Micropotential Study

There are several electrode systems dealing with low noise, body surface, and ECG recordings that have been suggested by various investigators. In the last few years, the most developed system for late potential detection has been related to the uncorrected Frank XYZ leads. However, for His bundle detection many different electrode networks have been used. A pyramid-type electrode system has been used previously for His-Purkinje signal measurement and, with some modifications, for late ventricular activity recordings. This pyramid-type system was used to evaluate 300 adult patients with coronary heart disease (CHD) or cardiomyopathy. In the proposed system, electrodes are located near the myocardium with their configuration consisting of three electrode pairs forming a pyramidal shape. Each electrode can also play the role of the top of the pyramid, with all measurement directions converging to a point. By changing the pyramidal top, signals can be detected in various chosen measurement directions. The pyramid system provides spatial averaging facility, allowing the whole measuring system (consisting of low noise multi-input amplifiers) to detect signals in the range of 1 microVp-p on a beat-to-beat basis. In the majority of cases in hospital environments, however, a number of digital averaging cycles is still necessary. Using this system, late potentials (LP) were found in 29% of the patients without myocardial infarction (MI) and in 86% of cases with remote MI and sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF). Waveforms suspected to be of His-Purkinje System (HPS) origin were detected in 71% of subjects with normal or prolonged P-R segment.