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Abstract. Background: A variety of basic factors such as electrode tip pressure, -ow around the electrode and electrode orientation in-uence lesion size during radiofrequency ablation, but importantly is dependent on the chosen mode of ablation. However, only little information is available for the frequently used temperature-controlled mode. The purpose of the present experimental study was to evaluate the impact during temperature-controlled radiofrequency ablation of three basic factors regarding electrode-tissue contact and convective cooling on lesion size.
Methods and Results: In vitro strips of porcine left ventricular myocardium were ablated in a tissue bath. Temperature-controlled ablation at 80 8C for 60 s was performed using a 7F 4 mm tip electrode in either perpendicular or parallel contact with the endocardium at a pressure of 10 or 20 g. Increased -ow around the electrode was induced by circulating the saline in the tissue bath at a -ow-velocity of 0.1 m/s. Lesion volume was determined by cutting lesions in 1 mm thick slices, staining with nitroblue tetrazolium and planimetering. A total of 107 lesions was created. Lesion size was signi~cantly larger for perpendicular electrode orientation compared to parallel for both pressure-settings and both levels of -ow around the electrode (p , 0.05). Increased -ow around the electrode enlarged lesion size (p , 0.005). Electrode-tissue contact pressure had no signi~cant impact on lesion size.
Conclusions: During temperature-controlled radiofrequency ablation increased external cooling of the electrode tip due to either -ow of the surrounding liquid or poor electrode tissue contact, as exempli~ed by perpendicular versus parallel electrode orientation, increases lesion size signi~cantly. This is in contrast to the impact of these factors during power-controlled ablation due to the lack of increased power-delivery in the latter situation.
Key Words. radiofrequency ablation, electrode contact, lesion size
During radiofrequency ablation of cardiac arrhythmias the size of the induced lesion, as well as the accuracy of the mapping of the targeted arrhythmia, is of major importance for the success-rate. The impact on lesion size of several factors, i.e., electrode tip pressure, -ow around the electrode, orientation of the electrode tip and electrode tip size are dependent on the chosen mode of ablation: power-controlled, temperature-controlled [1] or irrigated tip ablation [2], but these factors affecting lesion size have mainly been investigated for the power-controlled...