LESION SIZE IN RELATION TO ABLATION SITE DURING RADIOFREQUENCY ABLATION

This study was designed to investigate the effect of the convective co oling of the tip of the ablation electrode during temperature controll ed radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ab lation was performed during two different flow-velocities in a tissue bath, while electrode contact pressure and position were unchanged. Ta rget temperature was 80 degrees C. Obtained tip temperature, power con sumption and lesion dimensions were measured. In vivo lesion volume, d epth and width were found significantly larger for septal applications than apical applications (p<0.01) and more paver was used (p<0.001). Obtained tip temperature was significantly lower in the septal applica tions (p<0.001). In vitro increased convective cooling by induction of flow yielded larger lesion volume, depth and width (p<0.01), and had higher power consumptions (p<0.01). Obtained tip temperature did not d iffer significantly. For the given chosen target temperature power con sumption was positively related to lesion volume (r = 0.66 in vivo and 0.65 in vitro), whereas obtained tip temperature was not (r = -0.49 i n vivo and -0.61 in vitro). We conclude that during temperature contro lled radiofrequency ablation lesion size differs for septal and apical left ventricular applications. Differences in convective cooling migh t play an important role in this respect. This is supported by our in vitro experiments, where increased convective cooling by induction of a flow around the electrode tip increases lesion dimensions and power consumptions. Furthermore we conclude that for the given target temper ature the power consumption is positively correlated with lesion volum e (p<0.001), whereas the obtained tip temperature is not.