High efficacy and safety of focal endocardial pulsed electrical field ablation via contact force-controlled catheters for mitral isthmus ablation

Background: A new technology of a pulsed field generator enables established contact force-controlled radiofrequency (RF) catheters to apply point by point monopolar pulsed electrical field (PEF) energy for linear lesions in atrial fibrillation (AF) ablation. We evaluated this novel focal PEF ablation technique for creating lateral mitral isthmus ablation lines in case of perimitral flutter or complex AF patients non responder to pulmonary vein isolation (PVI).

Methods: Patients (n=49, age 65±10 years) referred for ablation/re-ablation of AF with spontaneous or inducible perimitral atrial flutter (n=38, 78%) or persistent AF and severe enlarged atrium (n=8) or de novo longstanding persistent AF (n=3) without signs of atrial fibrosis were included in our patient cohort for lateral mitral isthmus ablation with PEF applications. After 3D high density voltage mapping of the left atrium with multipolar microelectrode catheters, and confirmation/completion of PVI, an endocardial lateral mitral isthmus line was performed. Using contact force sensing catheter (IntellaNav StablePoint, Boston Scientific, or SmartTouch ST or SF, Biosense Webster), 25A PEF energy pulses (Centauri, CardioFocus) were applied targeting a minimum of 10g contact force and an interlesion distance ≤5mm. Before PEF application 0.2 mg nitroglycerin was intravenously injected. If the inferolateral mitral isthmus line to the left inferior pulmonary vein could not be blocked, more superior strictly lateral lines to the left superior pulmonary vein were performed. If the mitral isthmus could not be blocked by endocardial PEF application or conduction recurred after adenosine injection an additional epicardial ablation via RF application in the coronary sinus was performed.

Results: Exclusively endocardial PEF application blocked the lateral mitral line in 44 out of 49 cases (90%) with 23±14 PEF applications. After an unsuccessful inferior lateral mitral line, or recurrence of conduction after adenosine injection, in 34% of cases a second superior lateral mitral line have to be performed. Only in five cases additional epicardial RF applications via coronary sinus and endocardial additional RF application were necessary to complete the mitral isthmus block. Block time between superior-lateral mitral anulus and inferolateral coronary sinus was 176±42 ms. An additional left atrial roof line was successfully performed with PEF applications in 62% of cases. Besides one pericardial tamponade which could be successfully drained, no other serious complication occurred throughout all procedures (no ST segment elevation, no tamponade requiring surgery, no cerebrovascular event). After a median follow-up of 9 months, 10 of 49 pts (20%) had recurrence of tachyarrhythmias, in 5 pts atypical atrial flutter and in 5 pts AF recurred. In 6 cases of reablation, three pts had recurrence of lateral mitral isthmus conduction, which could be blocked by RF ablation. However, one patient after surgical mitral ring reconstruction had a second recurrence of mitral isthmus conduction.

Conclusion: Blockade of left atrial mitral isthmus line with PEF application via contact force-sensing catheters for ablation of complex atrial fibrillation patients is very efficient and safe. Especially the high efficacy of exclusively endocardial PEF application for creation of a lateral mitral isthmus block in most patients is very promising. However, the long term permanence of the linear lines have to be awaited.