Advancing Retrograde Aortic Access in Ventricular Tachycardia Ablation: Clinical Insights and Impact on Procedural Workflows
© 2025 HMP Global. All Rights Reserved.
Any views and opinions expressed are those of the author(s) and/or participants and do not necessarily reflect the views, policy, or position of EP Lab Digest or HMP Global, their employees, and affiliates.
EP LAB DIGEST. 2025;25(5):12-14.
Interview With Albert Sun, MD, and Jason Koontz, MD, PhD
In this feature interview, EP Lab Digest speaks with cardiac electrophysiologists Albert Sun, MD, and Jason Koontz, MD, PhD, about their experience streamlining retrograde aortic access in ventricular tachycardia (VT) procedures, including the clinical significance of this approach and impact on procedural workflow.
What are the current challenges associated with retrograde aortic access?
Albert Sun, MD: Retrograde aortic access is sometimes a necessity because of anatomy. When we perform premature ventricular contraction (PVC) or ventricular tachycardia (VT) ablation, there are 2 main ways of getting to the left ventricle (LV), which include either a transseptal approach through the mitral valve (MV) or retrograde access through the aortic valve. Many of our patients have significant peripheral arterial disease or vascular disease, and many have some degree of aortic valvular pathology. There are currently no standardized tools designed to allow us to safely cross the aortic valve into the ventricle, when the anatomy and location of the arrhythmia dictate what would be the most efficient and best way to get there. That includes things like trauma to the arterial and aortic system. It involves difficulty crossing the valve itself as well as having to potentially go retrograde repeatedly with multiple different catheters. So, every time we change a catheter, whether it is a diagnostic or therapeutic ablation catheter, we must recross the valve. That repetition leads to increased case time, complication risk, and danger in terms of damage to the arterial system and vasculature. Even so, it is still oftentimes the best and most necessary way of getting to those needed locations for ablation.
Jason Koontz, MD, PhD: Historically, we have had to use the catheter itself to cross the valve, which is the catheter that is intended to provide the therapeutic benefits of the ablation. Regarding the characteristics of an ablation catheter that would make it ideal for crossing a valve—and I use the word “ideal” loosely, as it is not ideal for crossing a valve in any way—the characteristics that might make it easier to cross the valve are often not the best characteristics for then moving around the ventricle. However, we do not have a tool that is designed to cross that valve to provide access. So, we must compromise and either use an ablation catheter that is better suited for crossing and perhaps less effective for what we need to do in the ventricle, or a catheter that is better suited for what we need to do in the ventricle but is potentially more difficult to cross the valve. Making that decision among other compromises was part of our motivation for finding a better way.
What is the clinical significance of retrograde aortic access for LV ablation procedures?
Albert Sun, MD: Ultimately, the success of an ablation procedure relies on accurate mapping and the ability to deliver our therapeutic tools like ablation catheters to the right location, good stability, and safety, which comes first and foremost. Some locations in the LV are significantly easier to reach through a retrograde aortic approach because of anatomical limitations with going transseptal and through the MV. However, a transseptal approach can sometimes increase time, be more challenging regarding stability, and require extra movements in the ventricle to reach certain areas. Each time that happens, the potential increases for risk and complications. In some cases, retrograde is a more direct approach, and in turn is safer and more efficient.
Jason Koontz, MD, PhD: Regarding the approach of using the ablation catheter for retrograde access and the potential for trauma, particularly in many of these patients with atherosclerosis, there is a lot of force delivered with prolapsing the ablation catheter in the traditional retrograde method. Mapping and ablating VTs is already challenging, with only 2 avenues for access. Historically, retrograde was avoided because of the difficulties associated with it, however, relying solely on one access route can limit success in complex cases. There are certain areas where we have had to do retrograde access because we could not get there from a transseptal approach, so we accepted those risks. There are other areas where we have avoided retrograde access because although transseptal was not ideal in terms of maneuverability or stability, we chose to use it because of the potential for complication or the difficulty associated with retrograde access. So, simplifying access for the procedure makes it more straightforward.
Albert Sun, MD: It is helpful to have multiple approaches, because there will be scenarios that come up where one approach will not be feasible. For instance, if a patient has a mechanical MV, a transseptal approach would be too dangerous and thus not available, so we would choose retrograde. However, approaching various anatomical structures in the LV and approaching them from different angles increases the likelihood for a complete map, which in turn, makes for a more successful ablation.
What are the benefits of the Ventrax Delivery System?
Albert Sun, MD: The Ventrax® Delivery System (Merit Medical®), which Jason and I were involved in helping to create, was born out of historical experience with what the interventional cardiology field has been doing for decades, which is using a pigtail-shaped catheter to cross the aortic valve. It is a standard procedure in the cardiac catheterization laboratory. Pigtail catheters are widely used to measure pressure in the LV as well as for contrast delivery. There is a lot of experience with these tools, and they have a great safety track record. Using a pigtail-dilator and integrating that into a long braided sheath, the Ventrax Delivery System allows us to essentially get access to the femoral artery, and in a minimally traumatic motion, put in a guidewire and use a pigtail-dilator that is atraumatic and specifically designed to go retrograde to deliver a long braided directable sheath through the aortic valve without ever having to use alternative methods like using ablation catheters or other tools that were never designed for retrograde access.
Jason Koontz, MD, PhD: Interventional cardiologists in the cardiac catheterization lab have used a pigtail catheter across that valve for decades. The distinction is that you can put a pigtail catheter through a sheath and cross the valve, but then you do not have a sheath that can follow it and remain in the LV when the pigtail catheter is removed. This integrates that solution, allowing you to cross the valve in the manner cardiologists are taught to conduct a cardiac catheterization, but then following that over the pigtail catheter, delivering the sheath, and leaving the sheath across the valve, which then allows for access to put in any catheter.
Albert Sun, MD: Once that pigtail-dilator is across, the sheath itself has a soft tip that is minimally traumatic and slightly angled. The sheath has braids to it, which allow some maneuverability. The sheath also becomes a mechanism to
provide support for other tools in the LV. So, the LV can be accessed in a relatively minimal, atraumatic way. Once there, the sheath allows for maintained support, more directionality with the catheter, and increased maneuverability, because instead of the catheter itself having to traverse torturous aorta, arterial vasculature and retrograde, now you have the sheath essentially taking that friction from the course of the aortic system and the catheter can freely move within the sheath, which then allows for increased torqueability and transmission of torque, and what we found to be a lot more stable manipulation of the catheter in the ventricle once it is there. Overall, there are 2 key properties of the Ventrax Delivery System: access to the LV, and the maneuverability, stability, and support once you are in the LV.
Can you walk us through your experience using the Ventrax Delivery System in the first few cases?
Albert Sun, MD: It is a familiar tool and seems similar to what has been used for years in the cath lab. In our first cases, the dilator and sheath easily went up into the arterial system. The sheath with the dilator inserted has a smooth transition and delivers over an included extra stiff wire, which allows for straightening of the pigtail-dilator and smooth delivery of the sheath into the arterial system. Once you get the pigtail-dilator into the ascending aorta right above the valve, it is easy to cross. There are 2 different ways to cross. You can use the shape of the pigtail-dilator to prolapse it across the aortic valve, or you can use the wire to increase the diameter of the pigtail shape to make sure it is not getting stuck in the aortic cusp, and then have that prolapse with the wire into the LV. On my first couple of cases, I did one of each. The first time, I used the pigtail and it went through easily; the second time, I used the wire to give me a little larger diameter to then get that into the ventricle. The ablation catheter going from the sheath directly to the ventricle without touching any of the aorta or arterial system was a game changer for me. One of my most nervous parts of a procedure is getting the ablation catheter into the LV. With this sheath having direct access to the ventricle, it was a relief having direct access and letting that tool not go directly to the ventricle without touching the arterial system. Once it was in, we were surprised about the increased support as well as the torqueability and maneuverability. It allowed us to map what we needed to map. Both procedures were successful, and it was a great initial experience.
Jason Koontz, MD, PhD: With a new product and design, we were hoping to have access directly across the valve and not have to worry about the difficulty of crossing the valve, which is historically a problem. Similarly, we would not have to worry about the difficulty of accidentally losing access to the ventricle, having the catheter move back up to the ascending aorta, and then having to go through the whole process all over again. We were pleased that it delivered in those respects. Regarding some of the hoped for results—including greater maneuverability of the catheter, not having the binding points in the tortuosity of the arterial system but instead having a smooth inner liner, greater torqueability of the ablation catheter, and better stability both deep in the ventricle but also underneath the valve—those characteristics of manipulating the catheter in the ventricle were so much easier than we had ever seen before. It opened up our ability to bring back retrograde aortic access for many cases, when previously we had avoided it because of the difficulties associated with that approach, even though we knew that it would potentially be better.
How do you see this product affecting your procedural workflows?
Albert Sun, MD: We always think about safety first as we plan our cases and approach. For a long time, we avoided retrograde access because of the potential comorbidities associated with it. Having a sheath like this, which offers a safe and easy way of getting into the LV, will likely increase our use. It is also possible we may have improved efficacy because of the added stability and support. So, I am more likely to go retrograde when I think it is appropriate, because of that safety built in with the sheath. It also offers an opportunity to not second-guess yourself, meaning that you are free to determine if this is the right approach and go after it because we now have that ability.
Jason Koontz, MD, PhD: We have always done retrograde access when we knew it was necessary. You cannot do this procedure without retrograde access. In our institution, for the most part, we limit retrograde access to cases where we think it is absolutely necessary, because of the concern for potential morbidity and the challenges associated with the approach. Having the ability to add both approaches in many cases would improve mapping and the potential for stability for ablation, opening the possibility for more success. Other avenues for access gives us more possibilities.
Albert Sun, MD: The adage is “map more, ablate less.” In a lot of these cases, there is some hesitancy to add arterial access because of the associated morbidity, but I do not know if that is always right. In finding the right spot and being able to fully map both the left and right ventricle for some of these difficult PVCs, the LV summit, and left ventricular outflow tract (LVOT) PVCs, as a field of experts and as an individual operator, we are going to do it more. We are going to map more of the aortic cusps, do more LVOT mapping, and find the spot before we ablate. That is a good trend and I think that is probably more available now.
How did the idea of Ventrax come to fruition?
Albert Sun, MD: Jason and I were heavily involved in the development of the sheath. In everything we do, we are very precise. We map out arrhythmias to the millimeter, and we use tools that have been used for decades for safe access to go transseptal, map, and ablate. However, going retrograde always meant using tools that were never intended to cross the aortic valve. We figured out how to make those tools work for that situation, but it never felt right. Using ablation catheters to go retrograde was never how it was intended. When going retrograde and encountering a slightly potential increased risk for trauma and emboli, we sought to find a solution.
Jason Koontz, MD, PhD: We are a training institution, and both of us have been teaching trainees for years. When our trainees used to do retrograde aortic access for the first time, they were somewhat shocked because the tools were not purposely designed for that. This is an application for which there has not been a solution in the field and one had not been forthcoming. Something was missing. As EPs, when there are limitations in the field, vendors and engineers come together, often in collaboration with physicians, to find solutions.
Albert Sun, MD: We were lucky to have experience working with Merit Medical as a center that uses the Worley sheath for coronary sinus lead delivery and access. We needed an integrated system that makes it easy and straightforward. We wanted the tip of the sheath to be soft so it would be relatively atraumatic and we would not be worried about potentially causing injury or harm in the LV. A lot of the arterial system, especially the peripheral arterial system, is torturous, so we wanted the sheath to have a little stiffness so that it was not twisting. We asked to vary the stiffness throughout the sheath. The engineers at Merit Medical were wonderful in finding solutions for making these changes happen. We added braiding to allow transmission of torque so there was some maneuverability. In the end, there are a lot of engineering and technical aspects that people who use it will find to be intuitive and helpful. Jason and I perform a lot of PVC and VT ablations, so we wanted to know what we could ask for and what else could be done. Eventually, everything felt right and the end design was what we wanted.
Jason Koontz, MD, PhD: As physicians, we asked if it was possible to add in the ability to take away the tortuosity of the iliac system. We also asked about adding in not just braiding in the sheath but also braiding in the pigtail-dilator that we were using to cross the valve. A braided pigtail-dilator results in torqueability, which makes it less difficult to cross the valve. So, every step along the way, we asked a lot of questions, and the engineers were always responsive. It was a long process, but we could not have hoped for anything better with the final product.
Albert Sun, MD: At the end of the day, there are patients that this product was specifically designed for, where in my mind, we would delay a case until this sheath became available because it would ultimately be a safer and better procedure since that is what it is designed for. It is all about having the correct tools.
Jason Koontz, MD, PhD: That includes patients who we knew we could not wait for their first procedure. We had tried in the past, and our feeling was that if we had a better way to get there, we could have done better. There is a substantial number of patients who we had been waiting to bring back when we had the ability to finally use this product and have a better way to get retrograde aortic access.
The transcripts were edited for clarity and length.
Disclosures: Drs Sun and Koontz have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Sun and Koontz report consulting fees, speaking fee for education, and patents planned, issued, or pending from Merit Medical.
The information, views, and recommendations contained within this interview are those of Drs Albert Sun and Jason Koontz and do not necessarily reflect the views and opinions of Merit, its directors and officers. Before using any Merit product, refer to the Instructions for Use for indications, contraindications, warnings, precautions, and directions for use.
This content was published with support from Merit Medical.
