Uses and Fallacies of Intracardiac Electrograms at the Pulmonary Valve

Abstract

Intracardiac electrograms by cardiac catheterization were first recorded by Lenegre and Maurice (1945). The electrographic patterns in various chambers of the heart were studied by Hecht (1946), Battro and Bidoggia (1947), and Kossmann et al. (1950), and were mainly of value in studying the activation of the heart. Their importance during cardiac catheterization was first shown by Emslie-Smith (1955), who also suggested their usefulness in the exact localization of pulmonary stenosis (Emslie-Smith et al., 1956). Although various authors have studied the patterns of the intracardiac electrogram in the great vessels and in the different chambers of the heart, no systematic study of the changes occurring at the pulmonary valve has been presented except by Emslie-Smith et al. (1956) and Kossmann et al. (1950), who studied these changes in normal subjects without simultaneous pressure tracings.This study was therefore undertaken to analyse the variations in the intracardiac electrograms at the site of the pulmonary valve and in the outflow tract of the right ventricle, and to determine their value in the exact localization of obstruction in the outflow of the right ventricle. MATERIALS AND METHODSTwenty-seven cases of heart disease of different etiologies were studied. They were (1) acquired heart disease (11 cases), (2) pulmonary stenosis (simple or complicated) (4 cases), and (3) other congenital heart diseases (12 cases).Cardiac catheterization was carried out in the supine position under fluoroscopic control, a standard electrode catheter (U.S. Catheter Corporation-size 6 to 8 F, length 100 cm.) being used. The catheter was introduced through a medial antecubital vein and was negotiated into the pulmonary trunk. A withdrawal tracing across the pulmonary valve was recorded, with simultaneous registration of the pressures and of an intracardiac electrogram on a double channel direct-writing machine, at a paper speed of 25 or 100 mm./sec. The withdrawal was effected slowly under fluoroscopic control so as to be certain that the tip of the catheter moved very slowly across the pulmonary valve. In case of a sudden movement of the catheter tip the procedure was repeated. Usual precautions were taken to avoid AC interference, e.g. switching off other circuits in the room, manipulating lamp plugs, etc., but the catheter tip was not earthed in any of our cases.As the proximal end of the metal electrode was 2 mm. from the terminal opening, it was postulated that in the withdrawal tracings from the pulmonary trunk to the right ventricle, the change in the intracardiac electrogram might precede the pressure change. This, however, did not occur. In most cases the descending limb of the last pulmonary artery pressure pulse was continued to zero level and this was succeeded by a change in both tracings ( Fig. 1 and 2). For the purpose of this study, the intracardiac electrograms corresponding to the last pulmonary trunk and the first right ventricular pressure pulses were used for comparison. The last few beats from the pulmona...