Pulmonary vein isolation by duty-cycled bipolar and unipolar radiofrequency energy with a multielectrode ablation catheter

Background

Pulmonary vein (PV) isolation for ablation of atrial fibrillation (AF) remains a complex and lengthy procedure.

Objective

The purpose of this study was to evaluate the feasibility and safety of a novel multielectrode catheter that delivers duty-cycled bipolar and unipolar radiofrequency (RF) energy.

Methods

Patients eligible for catheter ablation of paroxysmal AF after screening with magnetic resonance imaging and transesophageal echocardiography were included in the study. A decapolar (3-mm electrode, 3-mm spacing, 25-mm diameter), circular, over-the-wire mapping and ablation catheter was deployed in the antrum of each PV. Ablation was performed with 60-second, 60°C applications of duty-cycled bipolar/unipolar RF in a 4:1 ratio simultaneously at all selected electrode pairs until local activity was no longer observed. At 6 months, 7-day Holter monitoring was performed to determine freedom from AF without use of antiarrhythmic drugs.

Results

In 98 patients (mean age 59 ± 9 years), the PV ablation catheter was used for ablation of 369 veins (20 common left antra). All targeted veins (100%) were isolated as confirmed by the absence of potentials in the ostium either by PV ablation catheter or Lasso mapping. Mean number of RF applications was 27 ± 7, total procedural time 84 ± 29 minutes, and fluoroscopy time 18 ± 8 minutes. Follow-up after 6 months without antiarrhythmic drugs showed freedom from AF in 83% of patients. No procedure-related complications were observed.

Conclusion

PV isolation by duty-cycled bipolar/unipolar low-power RF energy through a circular, decapolar catheter can be achieved safely and efficiently, with good efficacy at 6 months.

Introduction

Radiofrequency (RF) catheter ablation has become first-line therapy for patients with drug-refractory atrial fibrillation (AF).1, 2 An early ablation strategy consisted of focal ablation of triggers inside the pulmonary veins (PVs).³ To prevent complications of PV stenosis, this method was modified to electrical isolation of the PV by segmental isolation at the ostium.4, 5 Strategies evolved to include wide area encircling of the PV antrum using sophisticated three-dimensional mapping systems that could reconstruct atrial anatomy for guiding ablation and limiting fluoroscopy time.6, 7 In complex cases of persistent or permanent AF, additional ablation lines can be added, or complex fractionated electrograms can be targeted for ablation.8, 9, 10 The evolution in ablation strategies led to increasingly complex and lengthy procedures and the need for high-technology equipment. Intracardiac echocardiography, computed tomography/magnetic resonance imaging (MRI) integration, and robotic steering have been proposed as new tools for facilitating the procedure. However, the availability of imaging, mapping, and steering options has not necessarily led to better outcomes for patients, and a wide range of success rates is reported in the literature.¹¹

Little progress has been made in the development of new ablation catheters. Traditional catheter ablation is performed in a single-tip, point-by-point ablation process. This technique requires a high degree of operator skill and procedures are lengthy, often more than 4 hours. In addition, creating reliable contiguous transmural lesions with a single-point catheter is difficult. Therefore, there is a need for specialized RF ablation catheters specifically designed for AF ablation. Alternative energy sources currently under investigation may offer advantages over conventional unipolar RF ablation. Here we describe a novel technique for isolation of the PVs by ablation using an over-the-wire multielectrode catheter delivering duty-cycled bipolar and unipolar RF energy at relatively low power.12, 13, 14, 15, 16