Experience and Workflow During Cryoablation Procedures Using the VersaCross Connect™ Access Solution for POLARSHEATH™

Discussion With Bradley Knight, MD 

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EP LAB DIGEST. 2024;24(3):15-16.

Can you tell us why you entertained the idea of using a different cryoablation system, the POLARx^™ Cryoablation System, after a long history with a known technology? 

Yes, I would be happy to. We have been using cryoballoon technology for over a decade since the first-generation cryoballoon became available. We have widely adopted it for first-time pulmonary vein isolation (PVI). The POLARx FIT cryoballoon (POLARx FIT Cryoablation Balloon Catheter, Boston Scientific; Figure 1) has several potential advantages and differences compared to the other commercially available system. For one, the balloon is a very low-pressure balloon when freezing. With the other system, when the balloon is inflated, it is low pressure. But when you freeze after you have created an occlusion, the balloon gets very high pressure, more rigid, and can occasionally back out and lose the occlusion during the freeze. The POLARx system (POLARx FIT Cryoablation Balloon Catheter) maintains a very low pressure when the freeze comes on, so this has some advantages of maintaining good contact and making sure that you do not lose your occlusion when the balloon is frozen.

A second difference is that the balloon that we previously used is 28 millimeters, whereas the POLARx system, when it is initially inflated, is also 28 millimeters. The difference is that (with POLARx FIT) you can increase that size to 31 millimeters. This provides several potential advantages. In our first case, the patient had a left common ostium and it was just about 30 millimeters in size. With inflation of the balloon to 31 millimeters, we had complete occlusion of a left common ostium and were able to isolate it with one freeze. That is an uncommon scenario. More typically, what we are taking advantage of is the ability to not allow the balloon to slide into a very large upper vein. So, the left upper, or even more commonly, the right upper PV is a little bit too big for the 28-millimeter balloon, and when you are applying force, it can slide up into the vein. One should be very careful not to do that to avoid phrenic nerve injury and PV stenosis. 

This system allows you to inflate the balloon to 31 millimeters for those larger veins. In the average size vein, I have not found it to help with an occlusion, but in that case, it can create a larger antral lesion set. So, there may also be some advantages in terms of outcomes when using that. I do not routinely go to 31 millimeters, some operators have, but it does give you the flexibility of doing that. In addition, the sheath with the POLARx system is highly deflectable and the catheter moves very freely and smoothly within that sheath. It is an easy sheath to cross transseptal with and to create a large deflection to get good contact when freezing the inferior PVs.

You were one of the early adopters of VersaCross Connect Access Solution for POLARSHEATH in the United States; however, prior to that, what was your transseptal workflow for cryoablation cases? 

Over the last several years, the way we do transseptal catheterization has evolved dramatically. Historically, we have always used mechanical transseptal needles. We were some of the first to adopt a dedicated radiofrequency (RF) needle, using the NRG^™ Transseptal Needle (Baylis Medical, now Boston Scientific), and it became our go-to system for all transseptals for the past 15 years. Recently, the VersaCross^™ system (VersaCross Access Solution; Figure 2) became commercially available, allowing us to use a standard 8 French (F) sheath with a malleable dilator to go across with a dedicated RF wire. There are off-label uses of electrocautery to cross with a standard, open-ended needle, but in studies we have done, these uses can unfortunately be associated with coring. Delivering electrocautery or a Bovie to the tip of a standard guidewire in order to use it to perforate into the left atrium (LA) has its own limitations of creating char and is not always effective when crossing. So, once there was a proprietary commercially available, specially-built RF wire with the VersaCross system, we moved almost exclusively to going transseptal with a RF VersaCross wire. The VersaCross system is the first transseptal approach we do for pretty much all left-sided procedures, including atrial fibrillation ablations, left atrial appendage closures (LAAC), or even accessory pathway ablations.

What are some current considerations when it comes to transseptal puncture today for the cryoablation procedure?

Currently, when we do a cryoballoon ablation procedure, we are placing a large-bore access sheath in the LA, typically a 14F deflectable sheath, with the commercially available balloon that has been available for years. We typically will place catheters in the femoral vein, one in the right femoral vein, and intracardiac echocardiography (ICE) and a coronary sinus catheter from the left femoral vein. We upsize from an 8F catheter to the transseptal 8F VersaCross system. We exchange the short 8F sheath with the 8F VersaCross transseptal system and cross into the LA with the VersaCross RF wire. Once we are in the LA, I still do a pulmonary venogram with that catheter, and we will use that to create a 3-dimensional map in preparation for the cryoballoon ablation. We then exchange the 8F transseptal sheath with a large 14F deflectable sheath. This exchange is done by first upsizing in the groin with a short 14F sheath. The cryoballoon is then delivered by the 14F deflectable sheath. You can see that this has resulted in a few different exchanges, particularly one exchange with the sheath in the LA.

What is your take on the tools available today for transseptal puncture in cryoablation procedures? 

The tools that are available for transseptal catheterization for cryoballoon ablation are really the same tools that we use for any left-sided procedure. They range from the standard mechanical needles that have been used for decades to a dedicated RF transseptal needle to a dedicated RF wire. The VersaCross RF wire has a lot of advantages. One, it allows you to more easily navigate up the iliac veins with a more flexible wire rather than with a needle, to position the powered tool to the tip of the dilator at the fossa ovalis. Having a wire also allows you to minimize the number of exchanges. Currently with a needle, whether it is a powered needle or a mechanical needle, a wire must be placed in the superior vena cava (SVC) and taken out, before the needle is advanced. With the VersaCross transseptal wire, the access wire is your transseptal wire, so that exchange is eliminated. Then, when we cross the septum, we take the needle out once the dilator is a little bit across and place a wire through. The VersaCross system avoids this exchange as well. The VersaCross wire can be used to access, cross the septum, and advance the dilator up into the LA, therefore eliminating exchanges and adding some efficiency. Theoretically, it also reduces some of the risks such as air embolism that can occur when you are exchanging in the LA.

Can you speak to your transseptal puncture experience using VersaCross Connect Access Solution for POLARSHEATH?

We currently have a lot of experience using VersaCross to perform transseptal catheterization with the sheath and dilator that comes with the system. What makes that system different than most transseptal products is that the dilator is not just plastic, it also has metal impregnated within so it allows you to shape the dilator much like you shape a needle, and it retains that shape. So if you need to add curve in a patient with a large right atrium, you can add curve directly to the standard dilator. This allows you to perform transseptal catheterization and then exchange for a large sheath. The advantage of the VersaCross Connect (VersaCross Connect Access Solution for POLARSHEATH; Figure 3) when used with the POLARx cryoballoon sheath (POLARSHEATH Steerable Sheath) is the elimination of that exchange. Now when we are performing transseptal catheterization with the POLARx system, we go right across with the deflectable sheath for the cryoballoon from the beginning. It is just one puncture and no exchanges. To do this, we usually have already gotten access to the right femoral vein. We place the VersaCross RF wire up into the SVC, predilate the groin with the 14F short sheath, and then advance the POLARx dilator (VersaCross Connect dilator) and sheath delivery system up into the right atrium. You do not need to go all the way up into the SVC like you do with a needle, because you are not advancing and retracting. You just have to start at a place approximately a couple centimeters above your target, pull down the dilator, then pull back the wire all the way, and use the VersaCross wire to cross into the LA through the POLARx dilator (VersaCross Connect dilator) and sheath. Typically, the POLARx sheath comes with its own dilator. This is substituted for the VersaCross dilator, which again, can be shaped just like the 8F dilator for the VersaCross system. The key is to be extra certain that you are in the right position before you take the next step. The first time you cross with a large 14F sheath, you must be extra vigilant about ensuring that you are in the right position. When I come down and we are confidently in the fossa, we use ICE as well as biplane fluoroscopy. When the wire crosses, I make certain that the wire is beyond the heart border. It is typically in the left upper superior PV before I have crossed with the 14F sheath. Doing the transseptal catheterization directly with the POLARx sheath and dilator with the VersaCross system does add some efficiency to the procedure. It eliminates the need to perform an exchange and theoretically reduces the risk of air embolism or other complications that could occur during an exchange, such as losing access to the LA and having to go back across. So, it certainly adds to the efficiency of the procedure.

Will using VersaCross Connect Access Solution for POLARSHEATH change how you teach your fellows about this procedure?

It may change how we do the procedure and we do almost all our cases with our trainees, so they will learn this more efficient approach, which can also be used for other procedures. The VersaCross Connect system is compatible with the POLARx cryoballoon sheath. It is also compatible with the transseptal sheath used with WATCHMAN^™ LAAC Devices (VersaCross Connect LAAC Access Solution, Boston Scientific). So, the fellows have already seen that in use, and they are now seeing us use it for cryoballoon procedures.

What are a few areas of opportunity for transseptal puncture that companies like Boston Scientific should focus on?

I think the technology has improved dramatically, so there is less room for improvement than there certainly was just a couple of years ago with these newer RF wire-based systems. Transseptal catheterization using RF wires is much more logical, simpler, and efficient compared to using needles. What seems to be happening is that these wire-based systems are being incorporated into other transseptal sheaths and dilators. The VersaCross system comes with a proprietary guidewire, a generator, and a malleable dilator. If the purpose-built VersaCross system can be incorporated into other LA access delivery sheaths outside of electrophysiology, such as in interventional and structural procedures or any left-sided procedures, it would increase some time savings, efficiency, and potentially cost savings. We have not talked much about cost. Every new system seems to be associated with a little more added expense, but you are eliminating the need to use 2 catheters and do an exchange. Doing the initial transseptal catheterization with the sheath that will ultimately be intended for delivery of the system on the left heart does provide some cost advantages. n

This content was published with support from Boston Scientific.

Disclosure: Dr Knight has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Knight discloses he received support for this content through Boston Scientific. He reports consulting fees, payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events, and participation on a data safety monitoring board for Boston Scientific.

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