NONUNIFORM HEATING DURING RADIOFREQUENCY CATHETER ABLATION WITH LONG ELECTRODES - MONITORING THE EDGE EFFECT

Background Long, narrow electrodes are being considered for radiofrequ ency ablation of atrial fibrillation; however, preliminary work reveal ed coagulum formation on the electrodes and lack of lesion continuity. This may be due to the ''edge effect,'' which concentrates radiated e nergy at sharp geometric gradients. It is proposed that temperature se nsors at electrode edges are preferable to a single centered sensor fo r temperature feedback and monitoring of long electrode geometries. Me thods and Results A finite element model was used to predict the heati ng properties of new long electrode geometries. Sixteen dogs with atri al fibrillation underwent left and right atrial ablation using cathete rs with multiple 12.5-mm coil electrodes. Electrodes with a single the rmistor were compared with electrodes with dual thermocouples placed a t opposite ends and on opposing sides of the electrode. Power, tempera ture, and impedance were recorded for all lesions, and coagulum adhesi on and magnitude were noted in a subset of lesions. Finite element ana lysis shows uneven heating, with the main heating concentrated at the electrode edges and a propensity toward temperatures >100 degrees C wi th single-thermistor feedback control. Ablations with dual thermocoupl e electrodes achieved higher measured temperatures at lower power leve ls than those that used single-thermistor electrodes. Impedance rises and coagulum adherence occurred less frequently with dual thermocouple electrodes than with single, centered thermistor electrodes (176 of 3 95 versus 9 of 425 lesions; P<.0001; 46 of 98 Versus 7 of 150 lesions; P<.0001, respectively). Conclusions Maximum healing from radiofrequen cy energy occurs at the electrode edges, particularly with long electr odes. The safety of temperature-feedback atrial ablation with these el ectrodes is significantly improved by monitoring temperatures at the e dges.