Bipolar saline-enhanced electrode for radiofrequency ablation: results of experimental study of in vivo porcine liver.

Abstract

To evaluate whether a bipolar saline-enhanced radiofrequency (RF) ablation system embedded in one needle is able to consistently produce homogeneous and predictable areas of coagulation necrosis with or without the Pringle maneuver of vascular inflow occlusion. RF ablation (480 kHz) of the liver was performed in 24 healthy pigs by means of laparotomy: group A (n = 5), 4-cm distance between electrodes 1 and 2; group B (n = 7), 4-cm distance and the Pringle maneuver; group C (n = 5), 2-cm distance; and group D (n = 7), 2-cm distance with the Pringle maneuver. Twenty percent NaCl solution was infused continuously at a rate of 100 mL/h via each electrode during the procedure. The pigs were followed up, and they were euthanized on the 7th day. Livers were removed for histologic assessment. Time, impedance, current, power output, specific voltage of the contacts, energy output, temperatures in the liver, volume of the lesion, and energy delivered per lesion volume were determined and compared among groups. Predictability of lesion volume was evaluated with the coefficient of variability. Mean values of the variables were compared among the groups by means of one-way analysis of variance or Kruskall-Wallis test. Impedance at the end of the RF ablation procedure was almost twofold lower than the corresponding initial value in all groups. In Pringle groups B and D, regular ellipsoids of coagulation necrosis were created (mean lesion volume, 149.50 cm3 +/- 34.26 and 69.43 cm3 +/- 15.48, respectively). In non-Pringle groups A and C, the shape of coagulation necrosis was influenced by the vessels encountered, and mean lesion size was lower than that in the Pringle groups (P <.01). The coefficient of variability of lesion size was lower in the Pringle groups (23% and 22%, respectively) than that in the non-Pringle groups (75% and 30%, respectively). The bipolar saline-enhanced RF ablation method produces homogeneous and predictable areas of coagulation necrosis between two electrodes, regardless of the distance between them, preferably with vascular inflow occlusion.