Developing a Protocol for Fluoroless AF Ablation

Introduction

Ablation for atrial fibrillation (AF) is now a widely accepted treatment and is commonplace in many electrophysiology laboratories around the world. Since the original surgical Cox Maze procedure, catheter ablation has advanced and, for the most part, become the primary modality for the treatment of symptomatic AF worldwide. Techniques and approaches for treating paroxysmal and persistent AF continue to be developed using catheter-based technologies, with the goal of maintaining normal sinus rhythm over the long term without medical therapy. While arguments regarding the best approach to ablation are still debatable (pulmonary vein isolation [PVI], linear ablation, complex fractionated atrial electrograms [CFAE], and rotor ablation), what cannot be argued is the cumulative radiation exposure to patient and personnel. During these initial lengthy and sometimes repeat procedures, radiation can be minimized and perhaps avoided altogether. 

When potential sources of radiation are taken into account, the exposure is not miniscule. Many electrophysiologists will incorporate a pre-procedural cardiac CT to gain information about left atrial anatomy (in particular, the pulmonary veins) as well as use it to merge as part of a 3D map. The ALARA (As Low As Reasonably Achievable) principle is supported by the ACC/HRS, and is a goal worthy of our attention. 

According to the U.S. Nuclear Regulatory Commission, an individual’s average annual radiation exposure from natural sources is 310 mrem per year. The average CT scan of the chest delivers an effective dose of 800 mrem. Fluoroscopy times during ablation procedures continue to be quite variable, but based on one study in 2006, 40 minutes of fluoroscopy equated to about 12,900 mrem of exposure, or about 40 times the annual background dose.  The lifetime risk of excess fatal malignancies normalized to 60 minutes of fluoroscopy was 0.07% for women and 0.1% for men.  While the risk may be acceptably low, it is not without hazard. Additionally, the cumulative risk for physicians and lab staff raises the occupational hazard to those directly involved in facilitating these procedures. The risk includes, but is not limited to, malignancy as well as orthopedic sequelae from wearing leaded aprons.

The emergence of three-dimensional electroanatomic mapping and intracardiac echocardiography are fundamental to limiting fluoroscopic exposure. While the reporting of fluoroscopy during AF ablation procedures is not standardized, it remains clear that the reduction in cumulative radiation dose has not been prioritized by practitioners performing these complex lengthy procedures. 

In our laboratory, I have developed a protocol for performing AF ablation based on published reports. It has been well documented in the literature that ablation without fluoroscopy is both feasible and can be performed without jeopardizing overall success.^3,4 What it takes is a commitment to not stepping on the fluoroscopy pedal as well as trusting in the three-dimensional map and ultrasound images being generated.

Challenges in Achieving Zero Fluoroscopy

The process by which one comes to achieve a completely fluoroless AF ablation does not happen by chance. Coming out of my electrophysiology fellowship, I relied heavily on fluoroscopy for monitoring the position of my catheters and performing transseptal puncture. I found myself stepping on X-ray more often than not to confirm what I already knew about the position of my catheters. After my initial experience with AF ablation as an attending, I could not accept that additional exposure without making some effort to limit radiation. Initial fluoroscopy times ranged from 15-20 minutes; with little change to my approach, I was able to reduce my exposure time to closer to 10 minutes by simply not stepping on the pedal. It became readily clear to me that without further alterations in my technique and process, I would not be able to achieve my goals. Using refinement, careful manipulation, and caution continued to help lower the doses over time, but then there was a plateau. I could not achieve times much fewer than two minutes. For six years, I had seen this as a fundamental hurdle that I could not improve upon. Interestingly, throughout this process I did not see an increase in procedure time as one would have expected. However, what was even more difficult to overcome was EP lab staff and colleagues suggesting that two minutes was excellent by comparison and that further attempts to reduce X-ray exposure were trivial. For a period of time I accepted that notion, until I started counting the years ahead of me performing AF ablation and the avoidable risk that was possible by eliminating this unnecessary exposure. 

While my goal was fluoroless AF ablation, logic would suggest I needed to walk before I could run. I chose a case of cavotricuspid isthmus-dependent atrial flutter to be my launching pad. The mental hurdles were tremendous, and the fear of perforating was palpable. As I inserted my catheters and reviewed the ICE images, I quickly realized that nothing had changed. I wasn’t really seeing anything less than I was used to seeing, but rather relying more heavily on different imaging modalities. It’s not as if fluoroscopy provides anatomical information helpful to catheter positioning. My standard approach in the past was to place diagnostic catheters in the right atrium (RA) and coronary sinus (CS) under fluoroscopy using complementary LAO and RAO views, then insert the ablation catheter with a RAMP sheath (St. Jude Medical) and ablate the isthmus while documenting my lesions utilizing 3D mapping. All this took place while dragging my catheter under fluoroscopy and watching the intracardiac EGMs on the recording system. During this particular case, I inserted a SoundStar catheter (Biosense Webster, Inc., a Johnson & Johnson company), maneuvered it into the RA, and positioned it such that the isthmus could be delineated and mapped. However, doubt was still present. I then doublechecked my positioning by inserting the ablation catheter into the right atrium and generating a 3D map of the SVC, IVC, RA, and CS with FAM (fast activation mapping). Next, I placed my diagnostic catheters with similar ease as I would normally place them under fluoroscopy. I inserted my ablation catheter up across the isthmus, and with both imaging modalities (ICE and 3D mapping), I confirmed my position to be safe and appropriate.

Once I overcame that obstacle, I quickly began burning the isthmus. Within minutes, the flutter terminated. I went on to complete the case without complication, and it was then that I realized this approach was truly possible. However, burning the isthmus is distinctly simpler than burning the left atrium and performing transseptal puncture. The principles were not any different, but the fear was more intense. 

While attempting my first several AF cases, my nervous energy got the best of me. I found myself doubting my transseptal sheath position, and could not overcome my own mental obstacles. How could I be sure that the transseptal sheath was in the right location? Frustration set in as my first three case attempts were met with failure. This failure was magnified by my fears of doing harm to my patient. Finally, after careful changes to my own workflow, I felt confident in my approach. Achieving careful transseptal sheath position, transseptal puncture, and left atrial ablation were all possible. Additionally, by utilizing Biosense Webster’s ThermoCool SmartTouch catheter, I could also feel secure that I was not applying exorbitant force to the endocardial surface and causing perforation. 

I chose a similar approach of creating a right atrial map prior to proceeding with transseptal puncture. I found it easy to insert the ThermoCool SmartTouch catheter up to the RA, which I determined once I noted the atrial electrograms on my catheter. I then zero the force in order to gauge the amount of contact that I am creating with the endocardial surface. The next step is to generate a 3D map with enough detail to place my catheters and identify the septum. Once that is complete, I place my CS catheter and SoundStar catheter in their usual positions. The SoundStar catheter, like my diagnostic catheters, can be easily visualized on the 3D map, so maneuvering it up to the RA is not often difficult. I then position my transseptal sheath by inserting the ThermoCool SmartTouch catheter via the long sheath and guiding it up to the SVC while using my map as a guide. Once in the SVC, I advance the sheath slowly to cover the proximal ablation pole, which can be determined when the pole turns black on the Biosense Webster Carto system. I then remove my ablation catheter and insert a dilator over a wire, simultaneously withdrawing the sheath over the dilator at the end of insertion. The wire is then withdrawn and a BRK-1 Transseptal Needle (St. Jude Medical) is inserted 2 cm from the tip. At this point, I withdraw the transseptal apparatus while watching ICE images. This allows me to see the sheath fall along the fossa ovalis posteriorly directed toward the left-sided pulmonary veins. I then subsequently perform my puncture solely by using ICE as a guide. The needle is then removed, and an exchange length guide wire is reinserted via the sheath with placement in the left superior pulmonary vein. While watching under ICE, I push my dilator and sheath across the septum. Once across the septum, the wire and dilator are removed, and a second puncture is performed in the manner as just described. Once in the left atrium, the challenging aspect from a fluoroscopy standpoint is essentially complete. Creation of an LA map could be done by creation of a SoundStar map or simple FAM. I typically perform FAM with either a 20-pole Lasso or PentaRay catheter (Biosense Webster, Inc., a Johnson & Johnson company). Within minutes, an entire left atrium can be reconstructed. From that point forward, the need for fluoroscopy is eliminated and the procedure proceeds as planned. With the presence of ICE, confirmation of catheter position (particularly in the pulmonary veins and left atrial appendage) can be verified if uncertainty exists with the 3D map.

Final Thoughts

Interestingly enough, I am embarrassed to say that while I continue to perform AF ablation procedures without fluoroscopy, I continue to wear my lead apron and goggles. However, my EP staff and Carto representatives have abandoned their aprons for a more upright posture, and have displayed their confidence in my skills as an operator. Perhaps one day I will also feel that my gear can stay on the sidelines. The usefulness of being able to safely and reliably perform these procedures extends to more sensitive patient populations, including young children, pregnant women, younger women in their childbearing years, and patients who have had prior malignancies. By striving to limit radiation exposure, I can envision an electrophysiology lab of the future in which fluoroscopy doesn’t exist except in the annals of medical history. 

Disclosure: The author has no conflicts of interest to report regarding the content herein. Outside the submitted work, he reports receiving speaker fees from Biosense Webster.

References

1. Theocharopoulos N, Damilakis J, Perisinakis K, Manios E, Vardas P, Gourtsoyiannis N. Occupational exposure in the electrophysiology laboratory: quantifying and minimizing radiation burden. Br J Radiol. 2006;79:644-651.
2. Lickfett L, Mahesh M, Vasamreddy C, et al. Radiation exposure during catheter ablation of atrial fibrillation. Circulation. 2004;110:3003-3010.
3. Ferguson JD, Helms A, Mangrum JM, et al. Catheter ablation of atrial fibrillation without fluoroscopy using intracardiac echocardiography and electroanatomic mapping. Circ Arrhythm Electrophysiol. 2009 Dec;2(6):611-619. 
4. Reddy VY, Morales G, Ahmed H, et al. Catheter ablation of atrial fibrillation without the use of fluoroscopy. Heart Rhythm. 2010 Nov;7(11):1644-53.