Initial Experience with a Minimally Invasive Laser Balloon Option for the Treatment of Atrial Fibrillation

The treatment of paroxysmal atrial fibrillation has largely been unchanged since the notion that the pulmonary veins were the primary target of ablation. The importance of durable effective pulmonary vein isolation (PVI) remains the cornerstone of any atrial fibrillation procedure. While the target is in agreement, the best method for achieving that goal has become a hot topic of debate amongst electrophysiologists. Catheter ablation remains the gold standard by which newer technologies are compared. Recently, balloon-based technologies have enabled alternative strategies for ensuring a successful ablation. Until recently, the only commercially available balloon technology in the United States utilized cryo energy. Then in April 2016, the HeartLight^® Endoscopic Ablation System (CardioFocus) was granted FDA approval for the treatment of atrial fibrillation based on data from the multicenter HeartLight U.S. Pivotal Clinical Study. The HeartLight System is a catheter-based technology that incorporates a visually-guided laser balloon (VGLB) to perform PVI. It is the first technology of its kind to utilize direct endoscopic visualization within a beating heart. 

Similar to other procedures, left atrial access is obtained by transseptal puncture using an SL1 sheath (Abbott). Guided by intracardiac echo imaging, I then place an Amplatz Super Stiff Guidewire (Boston Scientific) via the sheath and into the left superior pulmonary vein (LSPV). The SL1 sheath is removed, and a deflectable sheath (CardioFocus) is placed over the wire and across the septum. This is a unidirectional sheath with a 12 French (Fr) inner diameter (Figure 1). The dilator and wire are then removed. Next, the balloon catheter is prepped and advanced through the deflectable sheath into the left atrium. The catheter is 12 Fr, with a balloon at the end, that fills with deuterium oxide (Figure 2). There is an atraumatic tip just beyond the balloon to allow for maneuverability while minimizing the risk of perforation. The balloon is highly compliant and can be sized accordingly depending on the vein size and anatomy from a control panel on the HeartLight console (Figure 3). The catheter has a lumen to accommodate a 2 Fr endoscope that has a 110-degree field of view, which can be recycled for up to 10 procedures (Figure 4). Additionally, the laser can be delivered along the long axis of the balloon to the desired location, and deliver an ablation lesion with a 30-degree arc. 

When we acquired the HeartLight System in January 2018, I become the first physician to perform visually-guided laser balloon ablation in the state of Florida. As an early adapter of the technology, I found myself in unchartered waters. I was attempting to relearn what I was so experienced doing already with radiofrequency (RF) catheters. With only a few centers in the U.S. currently using this technology, there were few people I could turn to for advice and insight into the procedure. Nevertheless, I was intrigued by the technology and what it could offer my patients. I scheduled two cases of patients with symptomatic paroxysmal atrial fibrillation. 

The first case using any new device is always difficult. However, I quickly found that the workflow was not all that dissimilar from my usual approach. Once I was in the left atrium, I made the decision to utilize 3D mapping the way I would normally for RF cases. I used a PENTARAY (Biosense Webster, Inc., a Johnson & Johnson company) and intracardiac echo catheter to quickly build a 3D map as well as identify all the veins. I then placed the PENTARAY catheter in the LSPV, and used it as a guide to successfully place the balloon catheter in the vein. Undoubtedly, I quickly found that maneuvering the deflectable sheath took some adjusting to, compared to the Agilis sheaths (Abbott) that I routinely use in cases. Nonetheless, I was able to place the balloon in the LSPV without difficulty. At this point, the case really became intriguing. The balloon was inflated slowly, until I began to see first-hand what I had envisioned in my mind for so many years. A live PV before my eyes, and blood flowing back and forth between my balloon and the PV walls where I had poor contact. Looking under fluoroscopy, I could see the balloon was a bit deep, and by pulling back, I allowed it to take its natural pear shape. Additionally, reviewing the intracardiac echo, I could see I had good occlusion of the vein. Next, it was time for some finer adjustments. Looking at the live video, I could see areas of excellent contact (white blanching on the periphery) with areas of poor contact (black pools of blood that appeared stationary in some, and moving in others). I began rotating the balloon catheter, and subsequently advanced the deflectable sheath to better wedge the balloon into the vein. Finally, I could see excellent contact around the periphery of the balloon. There was no need to perform any contrast injections, as is common with the cryoballoon, as contact was verified endoscopically. The Z marker on the shaft of the balloon catheter helped me orient myself anterior, posterior, superior, and inferior. Next, I adjusted the position of my laser to a site ostial to the vein. Serial ablation was performed using a power-controlled setting of 5.5 to 12 watts, depending on the contact and the location of the site being ablated. 

Areas of moving blood, and especially stagnant blood, are not desirable sites for ablation. With fine manipulations of the laser, I was able to find a site where I had adequate contact, and ablate at a safe power setting. I moved from the left superior to the left inferior to the right superior vein. When I approached the right inferior pulmonary vein (RIPV), I encountered my first substantial challenge. Never did I appreciate the importance of the optimal transseptal puncture site more so than when I tried to wedge the balloon in the RIPV. My usual target area in the fossa ovalis is in the mid portion directed posteriorly toward the left-sided vein. For the HeartLight System, a low and anterior puncture is extremely important, because it allows for easier access to the RIPV. It took only one time struggling to position the balloon catheter in the RIPV to make sure that the next time around, I would ensure an optimal transseptal puncture site. (Figures 5-8)

The data for VGLB ablation is compelling. Direct PV visualization is intriguing and offers further insight into performing atrial fibrillation ablation that couldn’t have been appreciated by alternate ablation techniques. It becomes obvious after just a few cases due to the complexity of the PV anatomy. Veins are not simply tubes jutting from the atrial body — they are heterogeneous with complex anatomy. I found it satisfying that in my first two cases, I was able to isolate all four pulmonary veins on my first pass without having to do any touchups. This speaks to the potential of laser as an energy source as well as to the ease of using a balloon to achieve adequate contact. 

Herein lies the crux of why I am beginning to explore VGLB as an alternative for patients with paroxysmal atrial fibrillation. If durable PVI is the goal, then there is much promise in doing VGLB ablation. Acute PVI is high (98%) based on clinical data.¹ However, the durable PVI rate in experienced operators >10 procedures performed is 89% at 3 months.¹ At 12 months, the drug-free rate of freedom from atrial fibrillation or atrial tachycardia was 71%.¹ In my limited experience with VGLB ablation, I have been able to achieve acute PVI without much difficulty. Based on the HeartLight pivotal study, 15 cases represented the threshold by which operators achieved improved safety, efficacy, procedure time, and fluoroscopy time.² This represents a stark contrast from RF catheter ablation, where the threshold to achieve similar results is much higher. 

In critiquing my first cases, I found that getting into the RIPV was more difficult than anticipated. I owe some of the increased difficulty to the deflectable sheath, which is unidirectional. Additionally, I did not place enough importance on the site of transseptal puncture. In order to make the turn and be able to properly position the balloon in the RIPV, a low and anterior puncture makes for an easier transition from the right superior to the RIPV. Radiofrequency ablation with catheters is much more forgiving in this regard. 

In comparing other balloon technologies such as cryo, there is no prospective, randomized, controlled study to date. However, there is one single-center study comparing the two modalities; in this study, they randomized 140 patients in a 1:1 fashion.³ Acute procedural PVI was similar in both groups, along with fluoroscopy time. In 12 months of follow-up, there was a higher rate of phrenic nerve palsy (5.7%) for the cryoballoon vs the laser balloon group (4.2%). Also, there was a higher rate of atrial fibrillation recurrence at 12 months in the cryoballoon group (37% vs 27%); however, both of these were found not to be statically significant.³ In regard to PV stenosis, there have been no documented cases with the HeartLight System. Phrenic nerve palsies are estimated to be 3.5%; however, persistent diaphragmatic paralysis at 12 months has been reported to be 1.8%.² These are not dissimilar for the cryoballoon (2.7%), as reported in the FIRE AND ICE study, with one patient having persistent paralysis at 12 months.⁴

This has been an exciting time for electrophysiologists performing atrial fibrillation ablation, as new technologies and approaches to PVI continue to unfold. I believe the HeartLight System is more than novel and innovative. The ability to directly visualize the pulmonary veins is intriguing and enhances the operator’s ability to deliver higher energy at sites of excellent contact. Data suggests that using the highest power output that is safe and feasible at all sites decreases the risk of PV reconnection, and therefore, improves freedom from atrial fibrillation.

Disclosure: Dr. Weisman has no conflicts of interest to report regarding the content herein.  

References

1. Dukkipati SR, Neuzil P, Kautzner J, et al. The durability of pulmonary vein isolation using the visually guided laser balloon catheter: Multicenter results of pulmonary vein remapping studies. Heart Rhythm. 2012;9(6):919-925.
2. Dukkipati SR, Cuoco F, Kutinsky I, et al. Pulmonary vein isolation using the visually guided laser balloon: a prospective, multicenter, and randomized comparison to standard radiofrequency ablation. J Am Coll Cardiol. 2015;66(12):1350-1360.
3. Bordignon S, Chun KR, Gunawardene M, et al. Comparison of balloon catheter ablation technologies for pulmonary vein isolation: the laser versus cryo study. J Cardiovasc Electrophysiol. 2013;24(9):987-994. 
4. Kuck KH, Brugada J, Fürnkranz A, et al. Cryoballoon or Radiofrequency Ablation for Paroxysmal Atrial Fibrillation. N Engl J Med. 2016;374(23):2235-2245.