Japan is participating in the PARTNER 3 trial, and Keio University is also enrolled. First of all, please tell us your honest opinion about the results.
As someone who has personally been receiving this treatment since 2009, I can breathe a sigh of relief that this day has finally come. Considering the serious complications and high perioperative mortality rate, I am deeply moved by the results of this study, which showed that TAVR was superior to open thoracotomy in the composite endpoint of death, stroke, and rehospitalization in low-risk patients.
Six patients from three institutions in Japan, including three patients from our hospital, were enrolled in this very important international trial. However, it is an important step for Japan to become an equal partner with the international community in the field of SHD, and I am very honored to be a part of it. I would like to take this opportunity to express my sincere gratitude to the regulators, colleagues, and companies who have allowed this framework to be established.
The results of the TAVR study were positive. Was that expected?
The three patients who were enrollees from our hospital were also young and healthy, which is completely different from the usual TAVR patients, and their postoperative course was very good regardless of which treatment they received. Therefore, I thought that non-inferiority would be well demonstrated, but it was surprising that TAVR proved to be superior in the composite endpoint.
As the indication is expanded, I am concerned about the durability of the valve. To what extent is there evidence for durability?
According to the European and American guidelines, it is only a matter of time before the indication for TAVR is expanded to low-risk patients. As for the future of Japanese guidelines, I think it is necessary to maintain a certain level of consistency in order for Japan to not be left behind by the international community.
However, what we need to realize is that low risk is different from young age. For example, if we calculate the STS score of a patient in his mid-80s with no comorbidities, it will be less than 4, which is classified as low risk for a perioperative surgical risk score. In fact, many facilities take into account the individual patient's frailty and social factors, and ultimately offer TAVR after consultation with the heart team. Furthermore, did you know that the STS score was revised last year and is now calculated much lower than before? As a result, patients who were previously considered moderate risk are now considered low risk, and the results of previous large-scale clinical trials are no longer applicable.
In light of this situation and the results of low-risk trials, the perioperative surgical risk score is no longer applicable in determining the indication for TAVR. One of the current issues that TAVR must overcome is the durability of the bioprosthesis. Currently, there is some data available for up to eight years, and the recent results of the NOTION 2 trial even showed that the durability of TAVR valves was better. However, because the average age of patients eligible for TAVR has been around 85 years, there is still a lack of data for more than 10 years. Therefore, we believe that the time has come when indications for TAVR will be determined not by the perioperative risk score, but by taking into account the age, frailty, procedural risk of TAVR/SAVR in individual patients, anatomical characteristics, and patient values.
What do you do when a prosthetic valve implanted by TAVR fails to function in actual clinical practice?
First of all, if the cause of the malfunction is a thrombus, the situation may be improved by additional anticoagulation. If the valve has completely deteriorated, there is a technique to insert another TAVR valve where the last one was, but this treatment is not available in all cases due to the differences in device and anatomy. In other countries, there is a proposal that TAVR should be performed first in young patients, and if the valve deteriorates, the first thoracotomy should be performed, and if the surgical valve deteriorates again, the valve-in-a-valve technique should be performed. This would ensure that only one thoracotomy is needed in a lifetime.
In Japan, there are approximately 150 facilities that can perform TAVR. Will the number of these facilities increase as the indication expands?
In the future, when it comes to the treatment of valvular disease, catheterization will be essential as well as surgery. Therefore, patients with valvular disease will be concentrated in TAVR facilities, and a system that can perform TAVR will be necessary to continue surgical treatment. In the near future, the number of cases is expected to more than double what it is now, and it is a field that is developing rapidly.
Interviewed in March 2019
