Fehmi Keçe

Chapter 2 38 2.3 Multi-electrode catheters 2.3.1 Historical overview Multi-electrode RF catheters have the potential to reduce ablation and procedural time. The pulmonary vein ablation catheter (PVAC, Medtronic, Minneapolis, MN, USA) can deliver RF energy in different duty-cycled unipolar/bipolar modes. One-year AF free survival off AAD with the first-generation device was 61% in patients with paroxysmal AF (42). To reduce the embolic risk potentially associated with non-irrigated RF catheters, submerging the catheter in saline before introduction and maintaining an activated- clotting time (ACT) above 350s have been recommended. As interaction of electrodes 1 and 10 was associated with occurrence of asymptomatic cerebral embolism (43), the current generation catheter (PVAC-Gold, Figure 2) has only 9 electrodes with a larger inter- electrode spacing and different electrode composition (from platinum to gold) for better heat conductivity. Reported one-year AF free survival with PVAC-Gold ranges from 60- 71% (44-46). Studies comparing the efficacy of PVAC and PVAC-Gold found no significant difference at 1-year follow up (64-65% and 68-70%, respectively (45, 47)). Other (irrigated) multi-electrode catheters in the past were withdrawn because of safety concerns (e.g. new multipolar irrigated radiofrequency ablation catheter, Biosense Webster Inc., Multi- array septal catheter/Multi-array ablation catheter, Medtronic Inc. and High Density Mesh ablator, Bard Electrophysiology, Lowell, MA)(48). 2.3.2 Procedure time Ablation with a smaller number of simultaneously activated electrodes to reduce thrombo- embolic risk has significantly prolonged procedure times (159±39 vs. 121±15 min) with the first generation PVAC (49). For the PVAC-Gold catheter shorter procedure times (94-117 min) have been reported (45, 47). 2.3.3 Complications Asymptomatic cerebral embolisms were significantly higher with PVAC (incidence 38-39%) than with irrigated RFCA and cryoballoon ablation (50-53). The potentially high embolic risk is supported by studies on micro-embolic signals recorded with transcranial Doppler ultrasonography (54-56). However, after technical modifications to eliminate electrode 1-10 interaction, the duration of micro-embolic signals was reduced with only 33% (57, 58). The clinical relevance of asymptomatic cerebral embolism detected on MRI and trans- cranial Doppler remains, however, unclear (59, 60). Despite technical improvements, the second-generation PVAC-Gold catheter still showed a high incidence of asymptomatic