Why might aortic valve leaflet modification be useful?

Toby Rogers, MD: Certain patients are at risk for coronary obstruction during transcatheter aortic valve replacement (TAVR) and it is usually a function of two things: the patient’s own anatomy and the type of aortic valve in place. Is it their native valve or is it a bioprosthetic valve? The percentage of patients who are at risk for coronary obstruction varies depending on that specific combination. In the setting of TAVR for native aortic stenosis, the rate of coronary obstruction, based on data from several registries, is less than 1%. In the setting of TAVR for a failed surgical bioprosthetic valve, the rate is 3-4%. But that also is an oversimplification because if you drill down into specific types of surgical valves, there are some that are higher risk than others, specifically the surgical valves that have externally mounted leaflets. The most common are the Trifecta (Abbott) and the Mitroflow (Sorin Group) bioprosthetic aortic valves. As operators, we often have to treat these valves, and because of the way they were designed, these two surgical valves are more likely to obstruct the coronaries. The problem is that coronary obstruction, if it happens, is catastrophic, with procedural mortality rates of over 50%. Coronary obstruction is rare, but when it happens, it is a catastrophic, devastating complication.

Over the years, we have improved our ability to identify patients who are high risk. We now have a greater understanding of which valves are at risk and which anatomy is at risk. We are also better at analyzing pre procedure CT scans to identify patients who are high risk. For a patient who is high risk, there are a few options. You can tell them we can't do TAVR because there is a high risk of obstructing the coronaries and the patient will have to stay with their degenerated bioprosthetic valve or aortic stenosis. Or you can send them for surgery because the surgeons will cut out the old valve and then implant the new one. But many of the patients we are talking about are not good surgical candidates because either they are elderly and frail, or because they have already had one aortic valve replacement surgery with a bioprosthesis that has now failed. In most of these cases, surgery is not a good option.

We are then left with the question of how to do a TAVR procedure safely without obstructing the coronaries. There are two options available. One option is to place stents to protect the coronaries and prevent the leaflets as they are pushed out from blocking coronary ostia. This is referred to as chimney or snorkel stenting. I personally do not favor snorkel stenting because it involves putting a lot of metalwork in the coronary ostium and extending it out in the aorta, and there are risks in doing so. Stenting may not prevent coronary obstruction because the TAVR can still push the leaflet and crush the stent. It increases the risk of thrombosis, because of all the unopposed metalwork of the stent. Finally, it almost certainly means that it will difficult if not impossible to get back into that coronary if, in the future, the patient has a heart attack, because now stents are sticking out of the coronary behind the valve.

The alternative to snorkel stenting is leaflet modification, which is the BASILICA procedure. BASILICA involves cutting the leaflet down the middle to create a slice, so that when you implant the valve, the leaflet splays to either side and there is room through the middle for blood flow, but also for a catheter if you need to engage the coronary for percutaneous coronary intervention in the future.

How is the BASILICA procedure performed?

Toby Rogers, MD: Here it gets interesting because there are some dedicated devices currently under investigation, but I will first start with the way we do BASILICA today. We currently use guidewires and catheters that were not intended or designed to do this procedure. First, one catheter is placed above the valve and one catheter below in the left ventricular outflow tract (LVOT). In the outflow tract catheter, we deploy a snare and sit it immediately below the valve. From the catheter on top, we direct a guidewire onto the base of the leaflet and electrify it to burn through into the LVOT, then we capture it in the snare that is sitting under the valve. We make a kink in the wire at the midpoint, scrape a little bit of the coating off, and pull that in to the body so that the kink or ‘flying-V’ comes to sit on the leaflet. We re-electrify the guidewire, and the flying-V slices through the leaflet from base to tip. This is how we first developed BASILICA 6 years ago and the way we have been doing it hasn't changed at all until recently. This same technique has been done in probably thousands of patients. We have collected data on several hundred patients from tens of sites in a registry that we published recently.¹ But what is exciting is that we now have some new devices.

Can you tell us about these new devices?

Toby Rogers, MD: Two technologies are currently being evaluated and both are under investigation in clinical trials in the U.S. today. One of them, the Telltale electrosurgical guidewire system (Transmural Systems), in many ways, replicates how we do BASILICA today, using an electrified wire. The key difference is that the catheters, guidewire, and accessories are all designed, tested, and optimized for transcatheter electrosurgery for the conduction of electricity, ensuring that the electric current goes to the right spot and doesn't leak anywhere else. The Telltale catheters also have the shapes that we need for BASILICA. It is basically a set of equipment, the core of which is a guidewire that is optimized for electrosurgery, to make the whole procedure easier, safer, and smoother.

The second system is a device called the ShortCut (Pi-Cardia), which uses a different mechanism of action. Instead of using radiofrequency energy to cut the tissue, it has a scalpel on the tip to cut the leaflet using mechanical laceration.

Assuming the results of both trials are favorable, then hopefully a year from now, we will be able to say there are now two dedicated devices on the market for leaflet modification. Whereas today, there are none and if a doctor has a case tomorrow, unless they are participating in a trial, they are going to be doing BASILICA the old-fashioned way with off-label devices.

What is the current perspective on leaflet modification in the structural heart field?

Toby Rogers, MD: I think we have gotten to a point where the community accepts that leaflet modification is a necessary tool in the TAVR operator’s armamentarium. The challenge is, how do we get it in everyone’s hands? How do we teach people to do it? That has been hard since the technique currently involves using guidewires and catheters that are not intended or designed for that purpose. The best way that we can make leaflet modification a simple, easy add-on, and also make it teachable and reproducible, is by having on-label dedicated devices that are easier to use and can be taught. Then procedures can be supported by proctors, and we can make it a much more safe and reproducible procedure.

Any final thoughts?

Toby Rogers, MD: There was a live Telltale case performed at TVT this year, broadcast from Emory University by Adam Greenbaum and Vasilis Babaliaros (Friday, June 9, 2023; Live Case 13: BASILICA; TAVR Valve-in-Valve [Telltale Dedicated Guidewire]). There was also a taped case, from Columbia University by Susheel Kodali using the ShortCut device (Thursday, June 8, 2023; Live Case 9: SHORTCUT Leaflet Modification TAVR Valve-in-Valve). TVT this year demonstrated both of these new technologies.

Reference

1. Khan JM, Babaliaros VC, Greenbaum AB, Spies C, Daniels D, Depta JP, Oldemeyer JB, Whisenant B, McCabe JM, Muhammad KI, George I, Mahoney P, Lanz J, Laham RJ, Shah PB, Chhatriwalla A, Yazdani S, Hanzel G, Pershad A, Leonardi RA, Khalil R, Tang GHL, Herrmann HC, Agarwal S, Fail PS, Zhang M, Pop A, Lisko J, Perdoncin E, Koch RL, Ben-Dor I, Satler LF, Zhang C, Cohen JE, Lederman RJ, Waksman R, Rogers T. Preventing coronary obstruction during transcatheter aortic valve replacement: results from the multicenter international BASILICA registry. JACC Cardiovasc Interv. 2021 May 10; 14(9): 941-948. doi: 10.1016/j.jcin.2021.02.035

Find more: 
TVT Newsroom (With a Special Focus on TAVR)

Find Dr. Rogers’ slides here.