Experience with Arctic Front Advance Cryoablation System for Paroxysmal Atrial Fibrillation in an Established Fluoroless EP Lab

Introduction

As atrial fibrillation (AF) becomes more prevalent, the demand for treatment also increases. There have been significant advancements in ablation technology within the last decade, but radiofrequency ablation has remained the mainstay of therapy. However, cryotherapy for pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF) has advanced treatment one step further, with use of the Arctic Front Advance Cryoablation System (Medtronic plc). Since the first AF ablation at Turkey Creek Medical Center (TCMC) in November 2013, we have performed more than 200 cases. Within six months, we switched to a zero fluoroscopy approach for all ablations. In August 2015, we performed the first cryoballoon ablation for PAF in the Knoxville area while maintaining zero radiation exposure. In this article, we share our first-hand initial experience.

Case Description

A 68-year-old male with history of hypertension, diabetes on oral hypoglycemic therapy, sleep apnea on CPAP, and for the last few years, paroxysmal atrial fibrillation with dyspnea and fatigue, was referred for ablation after failure of dronedarone. 
As per our protocol, the patient underwent CT angiography to define the pulmonary venous anatomy prior to his scheduled ablation. Left atrial (LA) volume was 116 cc. The superior and inferior pulmonary veins were widely patent bilaterally. The ostium of the right superior pulmonary vein (RSPV) measured 20 mm and the inferior (RIPV) 18 mm. The left superior pulmonary vein (LSPV) had an ostial diameter of 19 mm and the inferior (LIPV) 17 mm. All of our AF ablations are performed under general anesthesia. We use Biosense Webster’s Carto 3D mapping system. Patients with persistent AF, and those who present in AF, undergo transesophageal echocardiogram (TEE). On the day of procedure, this patient was noted to be in AF; TEE ruled out left atrial appendage thrombus or significant valvular abnormality. 

The right femoral vein was accessed with an 8.5 French (Fr) SL1 sheath (St. Jude Medical). The left femoral vein was accessed with two 9 Fr (10 cm) and 8 Fr (10 cm) sheaths. An 8 Fr SoundStar intracardiac echocardiographic (ICE) catheter and NaviStar 4 mm tip ablation catheter (Biosense Webster, Inc., a Johnson & Johnson company), respectively, were introduced through the left femoral vein. The right internal jugular vein was accessed with a 7 Fr (10 cm) sheath for placement of a fixed curve decapolar coronary sinus catheter. An esophageal temperature probe was used with the fixed quadripolar catheter for visualization with the mapping system. 

A right atrial map including the coronary sinus was created using fast anatomical mapping (FAM) technology (Biosense Webster, Inc., a Johnson & Johnson company) with a NaviStar ablation catheter. Desired transseptal entry was located at the anterior and lower septum using ICE. The NaviStar catheter was exchanged for a dilator. Once the pre-determined length of the dilator was introduced, a sheath was pulled over the dilator while maintaining desired transseptal location under ICE. A BRK-1 (71 cm) transseptal needle (St. Jude Medical) was introduced into sheath-dilator assembly. While maintaining forward pressure at the desired septal location, a stylet was used to puncture the interatrial septum. The dilator was then pushed forward into the left atrium. After confirming left atrial access, a ProTrack™ Pigtail Wire (Baylis Medical) was introduced into the left atrium. Transseptal entry was gradually dilated using a SL1 sheath; this sheath was exchanged for a FlexCath Steerable Sheath (Medtronic plc). Heparin was administered to maintain an ACT greater than 300 seconds. Left atrial FAM was performed by the NaviStar ablation catheter. Cryoballoon connector tubing was marked to identify the desired Achieve catheter position prior to insertion. A 28 mm Arctic Front cryoballoon catheter was prepped and introduced into the left atrium, led by a circular Achieve Mapping Catheter (Medtronic plc). The Achieve catheter was connected to the Carto patient interface unit (PIU) in order to be able to be visualized. 

The cryoballoon was introduced into each respective vein, led by the Achieve catheter under ICE guidance, starting from: LSPV→ LIPV →RSPV→ RIPV. Venous occlusion and ostial location were determined with ICE and LA pressure tracing. A circular mapping catheter was placed as ostial as possible to visualize pulmonary venous potentials during lesion delivery. It remains very difficult to obtain full circular venous signals in each vein. Esophageal temperature probe adjustment was guided by Carto. Esophageal temperature was monitored throughout ablation, and a cutoff of -25°C was used to terminate therapy. The phrenic nerve was monitored for injury by continuous pacing via a NaviStar ablation catheter in the high right atrium superior to the location of the RSPV. It was monitored via compound motor action potential (CMAP) and diaphragmatic contraction, as assessed by palpation. The LSPV received three lesions, for a total of 445 seconds, and the lowest temperature observed was -60°C. The LIPV received four lesions, for a total of 650 seconds, and the lowest temperature observed was -60°C. The RSPV received two lesions, for a total of 197 seconds, and the lowest temperature observed was -60°C. The RIPV received two lesions, for a total of 360 seconds, and lowest temperature observed was -54°C. Assessment of PVI was performed with adenosine infusion. As we were unable to confirm isolation in the LSPV, radiofrequency application was given for 41 seconds. The patient tolerated the procedure well. The procedure lasted for five hours. Fluoroscopy time was zero. No immediate complication was noted. After overnight observation, the patient was discharged home. Further follow-up in clinic remains uneventful while maintaining sinus rhythm, based on self report and documented by EKGs. The patient has now been off antiarrhythmic drugs for at least six months. 

Discussion

The risk of radiation exposure to the operator and patient is well documented.¹ In addition, the occupational hazard of wearing lead during prolonged procedures is well known.¹ Advancements in current mapping systems and intracardiac echocardiography have allowed a reduction in fluoroscopy during ablation procedures. More operators have shown interest and are able to reduce their fluoro time. Completely eliminating fluoro during radiofrequency ablation is safe and does not compromise outcome.² 

The second generation cryoballoon provides promising data with the proper selection of patients.³ It does require modification in workflow in order to reduce use of radiation. Despite challenges, it can be performed safely without compromising immediate outcomes. There is a learning curve before achieving optimal results and acceptable procedure times. Suggested techniques also need to be evaluated for cost effectiveness due to concurrent use of the mapping system and to assess long-term outcomes. 

We have performed eight cryoballoon cases at our center within the last six months. This low number presents a limitation in our experience due to patient selection. All cases are performed without use of fluoroscopy, and with minor modification, compare to the above method. There have been no complications. Short-term follow-up of all patients has been uneventful. The quality of intracardiac ultrasound is also very important. We have struggled in cases when either image quality was suboptimal or the pulmonary veins were difficult to identify, especially the RSPV. Use of pressure tracing to document PV occlusion is reliable. Greater sensitivity in detecting phrenic nerve palsy via CMAP is comforting.⁴ Color Doppler could also provide additional information; however, we have not used this. Utilizing Medtronic’s EvenCool Cryo Technology, Achieve Mapping Catheter, and FlexCath Steerable Sheath helps make the Arctic Front Advance Cryoablation System easy to use and safe. Use of a three-dimensional mapping system has also allowed us to eliminate fluoro. A bipolar voltage map at the end of the procedure confirmed wide area circumferential ablation. 

Further modifications in current cryoballoon systems are needed. A third generation short-tip cryoballoon is under evaluation and could increase visualization of PV potentials. Reduction in spacing of the Achieve catheter may allow better discrimination of far-field potentials. Modification of the FlexCath Steerable Sheath to allow transseptal access could eliminate sheath exchanges. 

Conclusion

In our initial experience, use of the Arctic Front Advance Cryoablation System for ablation of paroxysmal atrial fibrillation was easy to adopt. We have found it to be safe and to provide good immediate outcomes in our limited experience, even without use of fluoroscopy.

Radiofrequency AF ablation cases are prototype zero fluoro cases. Since we only just recently introduced cryoballoon cases to the lab, we are providing enough time to allow systemic learning using zero fluoro technology with similar efficiency as radiofrequency ablation. Our intent is to use this same technique with all of our cryoballoon cases for paroxysmal atrial fibrillation in future.

Disclosure: The author has no conflicts of interest to report regarding the content herein.   

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board.

References

1. Klein LW, Miller DL, Balter S, et al; Members of the Joint Inter-Society Task Force on Occupational Hazards in the Interventional Laboratory. Occupational health hazards in the interventional laboratory: time for a safer environment. Heart Rhythm. 2009;6(3):439-444.
2. Razminia M, Manankil MF, Eryazici PL, et al. Nonfluoroscopic catheter ablation of cardiac arrhythmias in adults: feasibility, safety, and efficacy. J Cardiovasc Electrophysiol. 2012;23(10):1078-1086.
3. Packer DL, Kowal RC, Wheelan KR, et al; STOP AF Cryoablation Investigators. Cryoballoon ablation of pulmonary veins for paroxysmal atrial fibrillation: first results of the North American Arctic Front (STOP AF) pivotal trial. J Am Coll Cardiol. 2013;61:1713-1723.
4. Mondésert B, Andrade JG, Khairy P, et al. Clinical experience with a novel electromyographic approach to preventing phrenic nerve injury during cryoballoon ablation in atrial fibrillation. Circ Arrhythm Electrophysiol. 2014;7:605-611.