Radiofrequency lesion size reached maturity after 20 seconds of exposure and was determined solely by delivered power, with a maximum size of 8.5 mm due to coagulum formation at levels >7 W.
How do power and exposure duration affect lesion size during radiofrequency catheter ablation in a canine model?
In radiofrequency ablation, lesion size matures after 20 seconds and is subsequently determined by power level, though limited by coagulum formation at higher power.
The influence of power and exposure duration on lesion size in radiofrequency catheter ablation was investigated in 15 closed-chest dogs. Radiofrequency energy was delivered to the right ventricular endocardium between the tip of a standard 6F electrode catheter and a large W and durations of 5, 10, 20, 30, and 60 seconds. At necropsy 1 week later, well-demarcated homogeneous lesions were found when power had exceeded a threshold level that decreased from 1.8 W at 5 seconds to 0.7 W at 60 seconds. Lesion size ranged from 0 to 7.5 mm in depth and 0 to 9 mm in diameter. For the 5, 10, and 20 second ablations, lesion size was determined by exposure duration and power level. However, after a 20 second exposure, lesion size had reached maturity and was related to delivered power only. Therefore, a gradual, controlled growth of the lesion can be obtained by a stepwise increase of the radiofrequency power level with ample exposure duration at each level to allow for stabilization. At levels exceeding 7 W, the formation of a thin insulating layer of blood coagulum on the electrode surface caused an abrupt increase of impedance within approximately 30 seconds. Therefore, lesion size is limited to 8.5 mm in radiofrequency ablation with a standard 6F endocardial electrode catheter.
Wittkampf et al. (1989) studied Radiofrequency catheter ablation (n=15). Radiofrequency energy delivery was evaluated on Lesion size (depth and diameter). Radiofrequency lesion size reached maturity after 20 seconds of exposure and was determined solely by delivered power, with a maximum size of 8.5 mm due to coagulum formation at levels >7 W.