Tissue Temperatures and Lesion Size During Irrigated Tip Catheter Radiofrequency Ablation: An In Vitro Comparison of Temperature‐Controlled Irrigated Tip Ablation, Power‐Controlled Irrigated Tip Ablation, and Standard Temperature‐Controlled Ablation

Abstract

The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced in the power-controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature-controlled irrigated tip ablation, comparing it with standard temperature-controlled ablation and power-controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature-controlled irrigated tip ablation at target temperatures 60 degrees C, 70 degrees C, and 80 degrees C with infusion of 1 mL saline/min were compared with standard temperature-controlled ablation at 70 degrees C and power-controlled irrigated tip ablation at 40 W, and infusion of 20 mL/min. Lesion size and tissue temperatures were significantly higher during all modes of irrigated tip ablation compared with standard temperature-controlled ablation (P < 0.05). Lesion volume correlated positively with tissue temperature (r = 0.87). The maximum recorded tissue temperature was always 1 mm from the ablation electrode and was 67 +/- 4 degrees C for standard ablation and 93 +/- 6 degrees C, 99 +/- 6 degrees C, and 115 +/- 13 degrees C for temperature-controlled irrigated tip ablation at 60 degrees C, 70 degrees C, and 80 degrees C, respectively, and 112 +/- 12 degrees C for power-controlled irrigated tip ablation, which for irrigated tip ablation was significantly higher than tip temperature (P < 0.0001). Crater formation only occurred at tissue temperatures > 100 degrees C. We conclude that irrigated tip catheter ablation increases lesion size and tissue temperatures compared with standard ablation in the temperature-controlled mode at the same or higher target temperatures and in the power-controlled mode. Furthermore, tissue temperature and delivered power are the best indicators of lesion volume during temperature-controlled ablation.

Analysis of Catheter-Tip (8-mm) and Actual Tissue Temperatures Achieved During Radiofrequency Ablation at the Orifice of the Pulmonary Vein

“…In general, in non-PV tissue, tissue temperatures are correlated with lesion size. [13][14][15] With excessive temperatures, tissue charring, thrombus formation, and impedance rises occur, and the potential for collateral tissue injury is increased. 13 These surface changes may provide the substrate for embolic phenomena.…”

Target Indices for Clinical Ablation in Atrial Fibrillation

“…8 The maximal tissue temperatures can therefore reach higher levels in irrigated than in nonirrigated temperature-controlled radiofrequency ablation, although in both types of ablation a plateau occurs in the tissue temperature during the course of the ablation. 8 A linearly increasing fall in impedance with an increasing catheter tip temperature has been described for nonirrigated ablation. 4,9,10 This has been suggested to be because of increased conductivity of cardiac tissue with heating.…”

“…8 Catheter tip temperature is less reflective of this maximum temperature with irrigation as this cools the catheter tip. 8 The maximal tissue temperatures can therefore reach higher levels in irrigated than in nonirrigated temperature-controlled radiofrequency ablation, although in both types of ablation a plateau occurs in the tissue temperature during the course of the ablation. 8 A linearly increasing fall in impedance with an increasing catheter tip temperature has been described for nonirrigated ablation.…”

Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

“…The most frequently used RF delivery protocol is temperature control [2,3], which consists of modulating the applied RF voltage in order to keep the temperature measured in the active electrode approximately constant. The user sets the desired temperature value (target temperature) prior to ablation.…”