Editor：Jiamo Ren Data：28-08-2020
Mitral Regurgitation (MR) is the most common heart valve disease of the mitral valve. Transcatheter valve therapy is currently a hot topic of discussion and research. Related clinical research is developing rapidly, and the results are endless. At the CIT 2020 Cloud Conference, the opinions of domestic and foreign experts collided, and opinions were exchanged on the cloud to explore the difficulties of valve treatment. The journal specially invites Professor David Scott Lim of the University of Virginia Medical Center to conduct an in-depth interview on the latest developments in mitral and tricuspid valve intervention
International Circulation:As an expert in mitral and tricuspid valve treatment, would you please share us the current international research status of mitral and tricuspid valve intervention?
Professor David Scott Lim: It is my honor to participate in this interview, particularly for many of my colleagues and friends in China. I’ll start with the mitral valve and then the tricuspid. For a long time, the mitral valve has been the mainstay of our surgical colleagues’ armamentarium, in terms of, when patients have significant mitral regurgitation, open mitral valve surgery to repair or, even in some cases, to replace has been the primary procedure to be done. However, of late, we have been doing a lot of research and clinical trials regarding repairing or replacing the mitral valve via a less invasive transcatheter approach. The first such therapy was called the MitraClip, for which we didn’t even make an incision in the patient’s chest, but it was delivered via a transvenous transeptal approach through a femoral venous insertion point. We are able to place this MitraClip device on the regurgitant leaflets of the mitral valve, affecting a repair. We initially studied that in the EVEREST II trial, which showed that in very high-risk patients, we saw a benefit because it was a very safe procedure. It may not reduce the mitral regurgitation to the same extent as open surgery does, but in the hands of a competent operator and in a patient who is high-risk for open heart surgery, this is where it really shines. We next studied it in the COAPT trial, which took patients with mitral valve regurgitation secondary to a cardiomyopathy. In these patients, we had known that open heart surgery had never been known to improve survival or keep them out of hospital. In the COAPT trial, we showed that those patients who were already on guideline-directed medical therapy for heart failure, the addition of a MitraClip procedure significantly improved survival, symptoms, and the ability to live a healthy and productive life out of the hospital. From that, we have a lot of excitement for doing transcatheter mitral valve repair. Unfortunately, there are some types of mitral valve disease where doing a repair procedure, such as the MitraClip or similar device, is not going to work due to the complexity of the leakage, or that there may be a benefit from a more complete elimination of the mitral valve regurgitation that comes from replacing the valve. We have a number of clinical trials currently in progress on how to replace the regurgitant mitral valve all via a catheter. Initially, this was done with a transapical approach, and now we have started using a transfemoral venous approach as well. Many of the same concepts we have been applying and studying with the mitral valve have started to be transferred to the regurgitant tricuspid valve. One of the challenges of the regurgitant tricuspid valve is that it is intimately connected with the right ventricle of the heart, and therefore may be associated with a lot of right ventricular dysfunction. We are having to learn who are the right patients to do this procedure in, and who not to. Either way, these repair and replace technologies are all delivered from a femoral venous approach, a percutaneous and very much less invasive approach. I think, right now in the current era, it is very exciting to be using these new technologies in a less invasive way to repair or replace a regurgitant mitral or tricuspid valve.
International Circulation: There have been many trials on transcatheter interventional therapy of the mitral valve. What is your opinion about the different results of these trials? What are the challenges in its clinical treatment?
Professor David Scott Lim: I think the most important challenge is understanding appropriate patient selection. Who are the right patients for a given transcatheter therapy? Using the COAPT trial and the MITRA-FR trial as examples, in both cases, we studied patients with secondary or functional mitral regurgitation. Those patients have a significant degree of leakage from their mitral valve that is due to an underlying weak left ventricle - a cardiomyopathy of the left ventricle. But there is a spectrum. Some patients have more mitral regurgitation but a less weak left ventricle, whereas other patients can have a greater degree of cardiomyopathy and therefore weakness of the left ventricle with lesser degrees of mitral regurgitation. Which of those patients we should or should not be treating had not been entirely clear in the past, until we did two relatively large randomized clinical trials. One was the MITRA-FR trial out of France. There they tended to study patients that had worse left ventricles and not quite as bad mitral regurgitation. It also wasn’t quite clear if they were on optimal guideline-directed medical therapy. But in that group of patients, treatment with a percutaneous approach like the MitraClip did not meet the primary endpoint of the study. On the other hand, around the same time, we did another large randomized clinical trial, the COAPT trial. In those patients, they were clearly failing guideline-directed medical therapy, they had more severe degrees of mitral regurgitation, and their left ventricles were less severely affected. In that grouping of patients, intervention with the MitraClip significantly improved survival, symptoms and hospitalization rates. These types of clinical trials with different results illustrate the very powerful effect of appropriate patient selection, and for learning which patient is best for which therapy.
International Circulation: Could you share us your view about the future of transcatheter valve technology？
Professor David Scott Lim: Thanks for this really important question. For me, that is so much about what I do as a cardiologist in trying to advance the field. I do believe that with less invasive approaches we can truly help our patients with less morbidity and fewer complications. So often, we have seen that in other clinical trials, that a transcatheter approach, due to its less invasive nature is inherently safer, but perhaps not as efficacious as seen in some studies. That efficacy is improving as physicians, cardiologists and cardiac surgeons get better at applying the technology, as well as getting better at learning about appropriate patient selection, on top of all the technological advances. I can give a great example of that with one of the early transcatheter mitral valve repair technologies, the MitraClip. The MitraClip evolved over time. The most recent iteration of the MitraClip, MitraClip G4, is very exciting with the new possibilities it presents. There is another repair device as well called the PASCAL by Edwards Lifesciences, similarly introduced via a transvenous transeptal approach, and the early results from the non-randomized early feasibility study were quite encouraging, with very high success rates in terms of reducing mitral regurgitation (MR) to even 1+ or less. There is also very high safety with that device. That has been so encouraging that there is now a randomized clinical trial comparing head-to-head the latest MitraClip versus the PASCAL device. This all speaks to the idea that one day we will have a virtual armamentarium of different repair and replace technologies. Using a tailored approach, we will be able to choose the right therapy for the patient in front of us with a less invasive approach than we have had in the past.
At the same time, I would like to talk about what I see in store for the Chinese community. With all the transcatheter repair and replacement technologies that are being developed, one of the other exciting things for me is seeing so many of my colleagues, both in industry, and academic cardiologists and cardiac surgeons in China developing similar fascinating repair and replacement technologies for the mitral and tricuspid valves. I think the opportunity for me to work with my Chinese colleagues in developing the next generation of transcatheter therapies has been, and will continue to be, a very rewarding one. I think there is a bright future for future Chinese patients who are struggling with mitral or tricuspid regurgitation. We are going to have therapies in China for that.
I participated in this year’s CIT conference and have given some talks and sat on some panels. I really value the contribution I have been able to give with my colleagues to this CIT conference. I know it is a virtual conference, but I think they have done a great job this year adjusting to the needs of being a virtual conference.
International Circulation: What are your thoughts on China’s current standing in international interventional technology?
Professor David Scott Lim: Unfortunately, China has lagged behind the US and European Union in the development of some of these interventional technologies for mitral and tricuspid valve disease. However, China is rapidly catching up, and I have seen a lot of exciting designs that are truly innovative from my Chinese colleagues that will help, not just China, but the rest of the world better treat and better care for our patients with valve disease.
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