Lesions produced by radiofrequency ablation of the cavotricuspid isthmus in an experimental model]

Experimental studies have shown that deeper and wider lesions (up to 10 mm long or deep) can be safely created using an 8 mm or irrigated tip catheter for ablation to treat atrial flutter. However, potential damage to the tricuspid valve or inferior cava vein has not been systematically evaluated.The cavotricuspid isthmus was ablated in 26 pigs (body weight 26-52 kg), with a total of 187 radiofrequency pulses. Standard 4 mm, 8 mm and irrigated tip catheters were used at random. For each ablation, energy, impedance and temperature were recorded continuously.The lesions were larger with irrigated tip and 8-mm catheters than with standard ones. In 7 animals (1 with an irrigated tip, 4 with an 8-mm, and 2 with a standard tip) the tricuspid valve was damaged. The tricuspid valve was severely damaged in 3 pigs and lesions were moderate in 4. In animals with tricuspid valve lesions, maximal energy was higher (59 +/- 27 vs. 51 +/- 24 W; p=0,03) and higher temperatures were reached (63 +/- 4 vs. 55 +/- 11 degrees C; p<0.001). Low energy pulses measured before ablation were also more intense in animals in which damage was produced (0.55 +/- 0.24 vs. 0.35 +/- 0.29; p=0.001), indicating greater contact pressure.The tricuspid valve may be severely damaged during the ablation of the cavotricuspid isthmus for atrial flutter: damage was seen most often with high energy pulses and with 8-mm catheters, but can also occur with usual energy levels and standard catheters. To minimize damage this technique should not be used from the inside of the right ventricle just above the tricuspid valve.