In Vitro Temperature Map of Cardiac Ablation Demonstrates the Effect of Flow on Lesion Development

Abstract

This paper presents an in vitro temperature mapping study of bovine cardiac tissue during radiofrequency ablation. The objectives were to: (i) develop a technique for measuring the spatial and temporal temperature distribution in the tissue and in the blood during ablation, and (ii) use the temperature measurements to characterize the effects of fluid flow on lesion dimensions, ablation efficiency, and temperature distributions. In vitro ablation (20 W, 60 s) of bovine cardiac tissue was performed. The tissue was placed in a saline-dextrose solution maintained at 37+/- 0.5 degrees C. The solution also irrigated the tissue surface and simulated blood flow velocities of (i) 30, (ii) 55, and (iii) 85 mm/s. Thermocouple measurements were recorded from 25 and 2 locations in the tissue and in the fluid, respectively. The lowest flow resulted in the largest lesion, the maximum tissue, fluid, and electrode temperature increases, and the highest ablation efficiency. The lesions were 5.8 +/- 0.81, 4.8 +/- 0.84, and 4.4 +/- 1.25 mm deep, and 9.3 +/- 1.07, 7.9 +/- 1.48, and 7.8 +/- 1.27 mm wide for flows (i)-(iii), respectively. The blood and tissue temperature distributions were asymmetric around the ablating electrode axis with higher temperatures on the outflow than on the inflow side. The experimental measurements were used to validate a numeric model of ablation in an accompanying paper.

Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

“…3). This is also in agreement with the experimental results obtained by Jain and Wolf [38] and Matsudaira et al [37], who found that the temperature reached in the cardiac tissue on the outflow side was greater than on the inflow side.…”

High Incidence of Thrombus Formation Without Impedance Rise During Radiofrequency Ablation Using Electrode Temperature Control

“…7). 22,23 These differences increased with increasing target electrode temperature and were greater for the 8‐mm electrode than the 4‐mm electrode (Fig. 7).…”

Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future

“…This was mainly achieved by using several small transducers (e.g. thermocouples) placed with precision around the ablation zone [ 31 , 47 , 105 ]. In this respect, small temperature sensors such as thermistors have also been proposed for measuring SAR distribution in the tissue [ 106 ].…”

“…The Duke University group [ 41 - 46 ] developed interesting three-dimensional RF cardiac ablation models to assess the effect of different factors on the temperature distributions in the tissue. This group focused mainly on increasing the realism of the modeling of blood flow [ 44 ], and conducted excellent experiments to validate their models [ 44 , 45 , 47 ]. The Valencia Polytechnic University group began their modeling studies on RF heating of the cornea [ 17 , 48 , 49 ], and later developed models for RF cardiac ablation, specifically studying the problem of thermal injury in the esophagus during RF ablation of the left atrium [ 50 - 53 ].…”