Pulmonary Vein Isolation Employing a Second-Generation Multipolar Loop Ablation Catheter

Case Report

Despite a previous pulmonary vein (PV) isolation, a 51-year-old man developed recurrent paroxysmal atrial fibrillation (AF) after six months. AF occurred two to three times per week, with each episode lasting 24 to 30 hours. The patient had also undergone percutaneous coronary intervention with stent placement in the LAD three years previously. The original PV isolation procedure had only successfully isolated the left superior and left inferior pulmonary veins. Isolation of the right superior PV had been attempted but not completed due to limitations in procedure time. The patient was taking sotalol; he had failed both amiodarone and flecainide. During the second procedure, a new, second-generation multielectrode loop ablation catheter (REVELATION ® Helix STX 2.5, Cardima, Inc., Fremont, California) was used. This catheter has sixteen, 3-mm electrodes in a loop configuration; each electrode both maps and ablates and is surrounded by two thermocouples allowing independent temperature feedback. The catheter is used with INTELLITEMP ® (Cardima, Inc.), a multichannel radiofrequency (RF) energy management device. The combined system allows simultaneous firing of any combination of up to eight electrodes, with individualized temperature feedback. During the second procedure, all four PVs were isolated by placing the REVELATION ® Helix STX catheter against each PV os and ablating circumferentially. The catheter was deployed using a single transseptal puncture and positioned with an 11 French (Fr) guide sheath (NAVIPORT ®, Cardima, Inc.) for all four veins. Figure 1 illustrates the loop ablation catheter positioned at each of the four PV ostia. After a two-minute RF application (set temperature of 55 ºC, mean power 8-12 W and mean impedance 240-280 ohms), there was a significant reduction in PV potentials compared to pre-ablation on these electrodes. Applications on the remaining electrodes (9-16) completely abolished PV potentials completely in this segment. After successful isolation of all four pulmonary veins, a right-atrial Maze procedure, guided by non-contact endocardial mapping, was performed with a linear ablation catheter. In this part of the procedure, two lines were created between the SVC and IVC along the lateral wall and the septum. The total ablation time required to completely isolate all four PVs was 65 minutes. The total fluoroscopy time for the entire case, including RA Maze, was 61 minutes. The total procedure time was 225 minutes. The patient was discharged in NSR.

Discussion

The catheter used in this procedure (REVELATION ® Helix STX 2.5, Cardima, Inc.) is specially designed to allow creation of PV isolating lesions near the os of the pulmonary veins. The multielectrode aspect of this catheter, along with its deployment using a multichannel RF energy management device (INTELLITEMP ®, Cardima, Inc.), allows such lesions to be created more quickly. Typically, PV isolation using single-tip catheters and a dot-to-dot technique takes 20 to 30 minutes per vein, with a total procedure time of 180 minutes. Using the REVELATION ® Helix STX and the INTELLITEMP ® system, PV isolation took only 65 minutes. Note that placement of the ablation catheter was aided by use of an 11 Fr deflectable guide sheath (NAVIPORT ®, Cardima, Inc.). Use of the guide sheath is a substantial improvement over non-steerable sheaths with regards to positioning and ensuring good ablation catheter placement. It also allows the procedure to be completed without a second transseptal puncture. Several features of this system represent improvements over previous versions. First, the ablation catheter has 3 mm electrodes rather than 6 mm electrodes. Second, each electrode is surrounded by two thermocouples, which results in better temperature control. Third, when combined with the multichannel RF energy management device, all electrodes can be energized simultaneously. Fourth, positioning of the ablation catheter through the guide sheath helped to ensure good tissue contact. These system enhancements allowed the PV isolation procedure to be completed much more quickly, with no occurrence of char formation on the electrodes. In summary, the Helix catheter has the potential to make PV isolation easier and safer with decrease in procedure time.