USE OF THE HIS RVA ELECTRODE CATHETER IN CHILDREN/

Comprehensive electrophysiologic study with radiofrequency ablation re quires a number of intracardiac catheters. To reduce the number of cat heters placed in children, the authors evaluated a series of customize d catheters that combined the functions of two catheters. The customiz ed 6F catheter contains eight electrodes placed in pairs at 4, 5, 6, 7 , or 8 cm from the tip for recording the His electrogram and at the ti p for right ventricular pacing. The amplitude of the bundle of His pot ential recorded through the His right ventricular apex (RVA) catheter (n = 63) and the ventricular pacing threshold (in mA) (n = 48) were me asured and compared to the maximal bundle of His potential recorded wi th a 6F hexapolar catheter in 24 and 13 other patients, respectively. The relationship between the distance from the distal electrode pair a t the tip and the third electrode from the tip (the His/RVA distance) and patient size was analyzed in 42 patients. Following the initial st udy in the 90 patients, the selection of the optimal His/RVA catheter for 19 patients was determined by examining the regression plots deriv ed from the first group of 90 patients. The measured His/RVA distance was then determined by noting the His/RVA distance of the catheter use d. Regression analysis was then used to evaluate the fit between the p redicted His/RVA distance based on weight, height, or body surface are a (BSA) and the observed His/RVA distance. The maximal bundle of His e lectrogram measured in the two groups using the His/RVA catheter was c ompared. To evaluate catheter stability during the study, the amplitud e of the maximal His potential was measured in the 19 patients at the onset, midpoint, and end of the study. The maximal His potential recor ded through the octapolar catheter (0.21 mV) was significantly (P < .0 4) greater than that recorded through the hexapolar catheter (0.10 mV) . The mean ventricular threshold measured through the octapolar cathet er (0.44 mA) was significantly (P < .001) less than that measured thro ugh the hexapolar catheter (1.13 mA). There was a significant (P < .00 01) correlation between BSA, weight, and height and the His/RVA distan ce. There was no significant difference in the mean maximal amplitude of the His potential (0.21 +/- 0.31 mV vs 0.15 +/- 0.12 mV) recorded t hrough the His/RVA catheter between the two groups. The His/RVA distan ce estimated by weight, when plotted against the measured distance, de monstrated a good correlation (r = .84) between the expected His/RVA d istance based on the subject's weight and that actually observed. In 1 8 of 19 subjects, the first catheter based on the patient's weight (in kilograms) predicted the appropriate and only catheter used. There wa s no significant difference in the mean maximal bundle of His electrog ram recorded at the beginning of the study (0.15 +/- 0.12 mV), midway into the study (0.15 +/- 0.11 mV), and at the end (0.13 +/- 0.13 mV); however, there was extensive variation within individuals and over tim e. These data support the recording of a stable, high-quality bundle o f His electrogram and RVA pacing through a single catheter system and, hence, have important, practical implications for invasive electrophy siologic studies in children.