Radiofrequency current produced smaller, more homogeneous lesions with fewer inexcitable cells between 2 and 5 mm from the ablation site compared to direct current (2.6% vs 36.4%, P<0.05).
Does radiofrequency energy produce different cellular electrophysiological changes compared to direct current energy in an in vitro canine epicardial preparation?
Radiofrequency ablation produces smaller, more homogeneous lesions with a smaller border zone of partially depolarized but viable myocardium compared to direct current ablation.
Absolute Event Rate: 2.6% vs 36.4%
p-value: p=< 0.05
The purpose of this study was to examine the cellular electrophysiological effects of radiofrequency energy delivery in an in vitro canine epicardial preparation and compare the effects of those of high energy electrical ablation in a similar preparation. Ten joules of direct current energy or 40 volts of radiofrequency energy were delivered by a 6 French 2-mm tip catheter to the epicardial surface of 2 x 3 cm epicardial strips superfused with Tyrode's solution. Direct current energy delivery produced a crater and central zone of necrosis surrounded by a border zone of viable but damaged tissue that extended up to 10-12 mm from the site of energy delivery. Cellular electrophysiological abnormalities that included a less negative resting membrane potential, decreased peak dV/dT, decreased action potential amplitude, and decreased action potential duration (APD) were approximately linearly related to the distance from the crater edge. In addition, viable and inexcitable cells were frequently interspersed. Between 2 and 5 mm from the crater edge, 36.4% of the cells were inexcitable whereas others displayed normal action potential characteristics. In contrast, radiofrequency current produced a central zone of necrosis surrounded by a smaller border zone. Cellular damage that was qualitatively similar to that produced by direct current energy extended only up to 6-8 mm from the edge of the crater. In addition, severe abnormalities were noted in intracellular potentials recorded within 2 mm of the ablation site, and only minor abnormalities further away. Lesions were relatively homogeneous. Between 2 and 5 mm from the ablation site only 2.6% of the cells were inexcitable (P < 0.05 vs direct current). In conclusion, radiofrequency current produces lesions that are smaller and more homogeneous than those produced by direct current ablation. Although the border zone is small, a region of partially depolarized but viable myocardium is present after radiofrequency current energy delivery. These findings provide a cellular basis for several clinical observations that have been made following radiofrequency current energy delivery.
Ge et al. (Wed,) conducted a other in in vitro canine epicardial preparation. Radiofrequency energy vs. Direct current energy was evaluated on Percentage of inexcitable cells between 2 and 5 mm from the crater edge (p=< 0.05). Radiofrequency current produced smaller, more homogeneous lesions with fewer inexcitable cells between 2 and 5 mm from the ablation site compared to direct current (2.6% vs 36.4%, P<0.05).
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