How Abbott designed TriClip to repair the ‘forgotten’ tricuspid heart valve

Abbott’s TriClip development offers lessons for other device developers, structural heart product development leader Santosh Prabhu said.

As Abbott worked toward FDA approval of its MitraClip more than a decade ago, it was already looking for ways to improve the heart valve technology and find other applications for it.

They found their answer in tricuspid valve regurgitation, winning FDA approval for the first-of-its-kind TriClip transcatheter edge-to-edge repair (TEER) system in April 2024.

“We identified the treatment of tricuspid regurgitation as an unmet clinical need,” said Santosh Prabhu, division VP of product development for Abbott’s structural heart business. “We had the MitraClip technology for treating mitral regurgitation, and thought it would be a good idea to evaluate if we can leverage the mitral technology on the tricuspid side.”

In an interview with Medical Design & Outsourcing, Prabhu discussed the development and design of the resulting TriClip TEER system.

“As we were thinking about using MitraClip-based technology in the tricuspid side, one of the things we realized what a lot of our users were also trying to use the MitraClip product to treat tricuspid regurgitation, even though it was not designed for that,” he said. “That gave us an indication that maybe now it is time [to] accelerate developing the TriClip product.”

Characterizing and clipping the “forgotten” tricuspid valve

“The tricuspid valve for a long time was known as the forgotten valve because of a lack of options and lack of success in treating patients with tricuspid regurgitation,” Prabhu said. There was a shortage of information on the tricuspid valve, so we spent quite a bit of time trying to characterize the tricuspid valve.”

The tricuspid valve is on the opposite side of the heart than the mitral valve and tends to be larger. The tricuspid valve has more leaflets (three versus two), and mitral leaflets are less pliable due to calcification. The leaflets on both valves are less than 1 mm thick, but tricuspid leaflets are 40% to 50% thinner than mitral leaflets.

All that could affect clipping strategy, placement and effectiveness, so the Abbott team evaluated whether the existing clip technology would work with or without modifications. They also had to figure out which leaflets to clip for the best results.

Bench testing, excised porcine heart models, cadaver models and animal studies showed the existing MitraClips would get the job done. Though they come in a range of sizes, the fourth-generation TriClip and MitraClip clip implants are identical in formulation, geometry, sterilization and manufacturing processes.

Abbott makes its MitraClip and TriClip clip implants out of cobalt-chromium, nitinol and polyester. They’re so small and precisely engineered that Prabhu calls them “the Swiss watch of medical devices.”

“It’s all assembled under a microscope very carefully,” he said. “There are 16 different components in that little clip, and all of that has to work in perfect unison: you open the clip, you drop the grippers, you close the clip, lock the clip, deploy the clip. … It’s a small device that makes a big difference in the lives of these patients.”

Designing TriClip’s delivery system

The biggest challenge would be engineering the TriClip TEER system to deliver and place the leaflet clips on the tricuspid side of the heart.

With MitraClip delivered with a catheter through the femoral vein to the mitral valve, the team considered jugular access for the tricuspid valve on the opposite side of the heart, but their research convinced them to stick with femoral access.

Then, using anatomical models made from CT scans of tricuspid regurgitation patients, they got to work on modifications to the MitraClip’s steerable guide catheter and clip delivery system.

“Just to give one example, when you take the MitraClip system and try to use it on the tricuspid side, you don’t get enough height over the valve. When the clip delivery system goes into the right atrium, in many cases it would go directly into the valve so there’s no room for the doctor to steer and grab the leaflets,” Prabhu said. “We had to make changes to the curves of the delivery system so when the doctor goes into the right atrium, he has adequate height over the valve.”

They added and relocated control knobs to make it easier to get to the tricuspid valve’s leaflet pairs, but kept the gripper mechanism the same on the handle because there’s no difference when opening or closing the clips whether its on the mitral or tricuspid valve.

The braided MitraClip delivery catheter has pre-set curves for placement of the clips once inside the heart, so Abbott moved the curves for the TriClip system to give the clip more clearance on the tricuspid side.

“Ultimately, we were able to get it to get to the point where it became very easy for the clinicians to get the clip to any part of the tricuspid valve. … Some of the IP is around how we how we shape the curves of the catheter and what those curves are that differentiate this system from some of the other ones, which could be more generic.”

Imaging is the other challenge of minimally invasive transcatheter procedures for the tricuspid valve. Open chest surgery allows for direct visualization of the valve, but transcatheter procedures used transesophageal echocardiography (TEE) before the advent of intracardiac echocardiography (ICE).

“The tricuspid valve is anterior — located more toward the front of the heart — and when you do TEE, a probe is inserted through your mouth to the esophagus,” Prabhu said. “Since the valve is located more toward the front, it becomes a little bit more difficult to visualize. That was one of the bigger challenges. Now with technologies like ICE, it becomes a little bit easier to visualize the leaflets.”

Abbott TriClip engineering takeaways

Abbott’s experience holds an important lesson for other device designers and engineers.

“What I tell all the engineers in my team — and this is what I did myself — is you always have to understand the clinical need,” Prabhu said. “A lot of times you have a hammer looking for a nail, but if you want to design a product, go and observe cases, go and see how clinicians are performing the procedure. [Often] you go in and give a questionnaire to the clinician and they answer those questions, but that’s their perception. The solution that you have might be something different and more elegant. So you have to observe cases, identify the unmet clinical need and try to address those issues, the pain points that they have. And in developing those solutions, one of the things you want to figure out is: What are the technology elements that are already available, and what are the technology elements that we need to develop?”

“Going from MitraClip to TriClip, we knew the technology elements were there,” he continued. “We knew the clip technology worked. That was one of the first things we proved. We had to develop the clinical understanding of the valve, those models, and then make changes to the delivery system. We were able to accelerate and get into the clinic very quickly because we identified the need, we identified the technology elements that we already had, and then figured out the other things we needed to do to develop a safe and effective product.”

Read more from our interview with Abbott’s Santosh Prabhu: Nitinol grips prevent slips in Abbott’s heart valve clips