Evaluation of the contributors of generator impedance during radiofrequency catheter ablation

Abstract

This study aimed to clarify the contributions of dispersive electrode configuration, extracardiac impedance, and blood pool impedance to generator impedance (GI). Forty-five patients who underwent catheter ablation with Intellanav Stablepoint™ catheter were included. Four dispersive electrode positions were tested: the left hip, lower back, middle back, and upper back. For each dispersive electrode position, GI in the blood pool (BP-GI) and GI during contact with the myocardium of the left atrial anterior wall (Myo-GI) were measured at 46 kHz in standby mode. Body mass index (BMI) and hematocrit served as surrogates for extracardiac and blood pool impedance, respectively. The lowest BP-GI and Myo-GI were observed with the middle back dispersive electrode (BP-GI: 119 ± 13 Ω; Myo-GI: 123 ± 13 Ω), followed by the upper back (122 ± 13 Ω; 126 ± 13 Ω), lower back (126 ± 14 Ω; 129 ± 14 Ω), and the left hip dispersive electrode (153 ± 15 Ω; 156 ± 14 Ω). With the middle back dispersive electrode, BMI and hematocrit predicted BP-GI and Myo-GI with acceptable accuracy (adjusted R2 = 0.78 and 0.55, respectively). The standardized beta coefficients of BMI and hematocrit were 0.38 and 0.70 for BP-GI and 0.37 and 0.54 for Myo-GI, respectively. The middle back dispersive electrode yielded the lowest GI. GI differences among the back positions were small. BMI and hematocrit accurately predicted GI under the optimal (middle back) dispersive electrode position, and the effect of hematocrit was greater than that of BMI.