Radiofrequency Ablation of Atrial Fibrillation: Modern Tools and Techniques for a Safe, Effective, and Efficient Procedure

Introduction

The cornerstone of therapy for atrial fibrillation ablation is pulmonary vein isolation.^1,2 Point-by-point radiofrequency (RF) ablation allows for tailored, titratable, and targeted therapy over single-shot balloon approaches. RF ablation also allows the ability for additional ablation of atrial flutter, atrial tachycardia, or other SVT mechanisms such as AVNRT in a single procedure with a single ablation catheter.^3-5

Standard RF ablation protocols traditionally included fixed curve sheaths with poor torque control and stability, or deflectable sheaths with pull wires. In addition, traditional ablation protocols included fluoroscopy use as well as low electrode density circular mapping catheters, 3D mapping systems without robust automated electrogram and lesion annotation, double transseptal punctures with transseptal needles, 20- to 30-second RF ablation lesions at low power, intermittent positive pressure ventilation during general anesthesia, creation of low-density low-resolution voltage and activation maps, and non-contact force-sensing ablation catheters.^6-8

Advancements in technologies and techniques with RF ablation over time have improved the safety, effectiveness, and efficiency of atrial fibrillation ablation procedures. This has resulted in improved operator experience with less physical fatigue, reduced anxiety about complications, reduced time of intense concentration during ablation, and reduced radiation exposure. This culminates into improved success of ablations, less redo procedures, and improved EP lab throughput.^9-12

This case presentation is an example of the technologies currently being used by a single operator in a private, medium sized, general hospital to accomplish safe, effective, and efficient atrial fibrillation ablations.

Case Description

This is a case of a 67-year-old woman with highly symptomatic paroxysmal atrial fibrillation who presented for pulmonary vein isolation ablation. She was placed under general anesthesia and high frequency jet ventilation (HFJV) was used. A radial arterial line was placed under ultrasound guidance for serial arterial blood gases and pressure monitoring. Ultrasound-guided femoral venous punctures were used. Intracardiac echocardiography was utilized to guide transseptal access, visualize catheters within the heart, and monitor for pericardial effusion. Three-dimensional electroanatomic mapping was performed from the initial catheter entering the femoral vein, and a geometry of the right atrium, superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus were created in a rapid succession. The Nagare^™ Steerable Sheath (Terumo Medical Corporation) was used for the transseptal puncture and to control the contact force-sensing ablation catheter. The power setting was 45 Watts x 7 seconds per lesion. A point-by-point technique was used with small precise movements by the Nagare Steerable Sheath between lesions.

Discussion

Technologies and Techniques.

The effectiveness of radiofrequency lesions depends on the amount and duration of RF current delivered, degree of catheter-to-tissue contact, and degree of catheter stability.¹³ Delivering a higher power for a longer duration will improve the durability of RF lesions. However, there is also concern for increased complication related to this method of power delivery. In recent years, the concept of high-power short-duration (HPSD) RF ablation has emerged after promising results were shown in several animal as well as human studies.^14-18 In comparison to the standard RF ablation protocol, HPSD protocol utilizes the application of 45-50W of power for 5-15 seconds per lesion. This method of power delivery was associated with lower complication rates, more localized and durable RF ablation lesions, and reduced procedural and fluoroscopy time.¹⁹ Using this protocol, we were able to significantly reduce the overall case time and improve durable RF lesions for our patients. (Figures 4 and 5)

A key tool utilized to accomplish these goals was the Nagare Steerable Sheath. Since tissue contact and catheter stability are vital to delivering effective RF ablation lesions, we have chosen to use Nagare in more than 200 cases because of its superior performance compared to other mechanical sheaths. Due to its patented TruVector^™ technology, Nagare offers improved stable catheter position and titratable contact force. Nagare’s stability and maneuverability are consistently reproducible during the entire case, irrespective of the length of the procedure. Nagare offers excellent torque transmission and a precise deflection mechanism. This allows for quicker isolation of the pulmonary veins because of the decreased catheter manipulation time and better contact force (Figure 2). In addition, we use Nagare as our initial sheath to cross the interatrial septum. Due to its column strength and smooth transition between the sheath and dilator, Nagare’s stable platform allows for safe crossing without a high push force from the operator.

The SafeSept^® Needle Free Transseptal Guidewire (Pressure Products) is my transseptal “needle” of choice for transseptal puncture. In conjunction with the Nagare Steerable Sheath, the needle guidewire offers a site-selective puncture of the interatrial septum that is easily confirmed prior to dilatation and a stable rail to safely advance the transseptal sheath into the left atrium with a single pass. The wire can be safely left in the left superior pulmonary vein or even the base of the left atrial appendage, and the sheath can be pulled back to the right atrium. This can then facilitate a single puncture, double-wire technique to advance two transseptal sheaths into the left atrium.

High frequency jet ventilation has been safely used on most of the RF atrial fibrillation ablations at our hospital for the last three years. Along with other mentioned technologies and techniques, HFJV has decreased procedure time and increased first-pass pulmonary vein isolation rates. HFJV uses rapid, shallow tidal volumes to oxygenate and ventilate the patient under anesthesia, eliminating most of the respiratory motion of the left atrium during mapping and ablation.

Contact force-sensing ablation catheters allow for safe advancement of the catheter within a deflectable sheath to prevent excessive force from being applied. Contact force catheters help the operator determine contact force amplitude, vector, and stability during ablation lesion creation.

The Advisor^™ HD Grid Mapping Catheter, Sensor Enabled (Abbott) creates a more complete 3D geometry of the left atrium, pulmonary veins, and left atrial appendage with less false space. Using the Advisor HD Grid, the operator can simultaneously create the detailed geometry and a high-density initial voltage map using the HD Wave sensing algorithm. Contiguous transmural RF lesions can be accomplished using this detailed geometry combined with automated lesion tagging (lesion size index, ablation lesion location variability, and impedance drop during ablation).

Procedures that do not use fluoroscopy are accomplished using ultrasound-guided venous access, ICE-guided, and 3D electroanatomic map-guided advancement of catheters, sheaths, transseptal needles, and wires. This has led to decreased radiation exposure to patients and staff, as well as a reduced risk of orthopedic injuries from wearing heavy lead aprons.

Summary

A multitude of newer technologies can be readily implemented in the modern electrophysiology laboratory to accomplish safe, effective, and efficient radiofrequency ablation of atrial fibrillation. One of the more important advancements in RF pulmonary vein isolation ablation has been the use of high-power, short-duration lesions. The Nagare sheath enables facile, precise, and rapid deployment of this ablation strategy. 

Disclosures: Dr. Daniel Friedman reports he is a consultant to Terumo. He also reports personal fees from Abbott outside the submitted work.

PM-02373

This article is published with support from Terumo Medical Corporation.

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