The rate of TVF, which was set as the primary endpoint of the registry for 5-years, was 11.6%. What do you make of this result?
We think this result is valid. It should be noted that the TVF was mainly driven from revascularization and the rate of myocardial infarction from the target vessel was extremely low even at 5-years. which may indicate the long-term safety of foregoing FFR-guided revascularization in chronic coronary artery disease patients in Japan.
In a previously published journal, the rate of TVF at 2-years was 5.5%. What does that say about the results of this study?
Overall, we believe that the fact that the event rate did not increase after 2-years and remained constant demonstrates the validity of deferring FFR-guided revascularization. Interestingly, when TVF rates were examined in detail using FFR values, 5-year TVF was similar across the two groups with FFR 0.75-0.80 (the so-called gray-zone FFR) and FFR 0.81-0.85. For that reason, we are proposing the new concept of ‘borderline FFR’ for FFR 0.75-0.85.
This result suggests that the long-term prognosis of patients whose cardiologists defer revascularization for any reason, even with gray-zone FFR, is similar to that of FFR 0.81-0.85. On the other hand, the study did not include patients who underwent revascularization based on the results of FFR, so these results do not negate the use of gray-zone FFR for revascularization. The optimal treatment strategy for gray-zone FFR is still the subject of limited research reports and requires further investigation.
There were 28 facilities across the country that participated in this study. What are the criteria for selecting these facilities?
There are no specific criteria; we asked for the cooperation of cardiologists who were interested in taking part, regardless of the number of FFRs performed. As a result, this study includes a mix of both high and low FFR centers.
The patients included those with relatively high risk, such as about 60% with a history of PCI, 40% with diabetes, 30% with a history of MI, and 30% were smokers. What were the risk factors considered in these areas when you deferred?
Although the reasons for deferral could not be ascertained in this study, we believe that the patient background does reflect actual clinical practice in Japan. A history of PCI was associated with 5-year TVF, but those other patient characteristics were not, which may have been due to the appropriate optimal medical therapy and lifestyle intervention after the deferral of revascularization.
Have you had any insights into the characteristics of the patients who had the event?
As mentioned above, this study demonstrated the long-term safety of foregoing FFR-guided revascularization in patients with chronic coronary artery disease, but we believe that caution should be exercised in certain patient or lesion characteristics. In particular, left main trunk (LMT) lesions and dialysis cases are strongly associated with 5-year TVF, and appropriate treatment strategies in these cases need to be explored further.
What were some of the difficulties you encountered in conducting this study?
The most difficult part was collecting data for the long-term follow-up. A certain level of follow-up rate (e.g., 90% or more) is required to ensure the quality of the study, but since this was a real-world registry, and not an RCT, it was difficult to gather the 5-year data. Because of this, we had to make numerous phone calls and send numerous e-mails to each investigator to request data collection. In the end, the 5-year follow-up rate was 92.2%, which is one of the strengths of this study and for that, we would like to take this opportunity to thank each of the cardiologists who participated in the study for their contribution.
In your opinion, what is the clinical significance of the results of this study?
This study was based on the question, “Is it safe to defer with FFR?” This was a clinical question. Now you might assume this was obvious from the foreign data; however, at the time, there was no large-scale real-world registry, and as a result, we believe that this study was important in bridging the gap between RCTs and actual clinical practice.
In addition, this data is from actual clinical practice in Japan, and when deferring in actual clinical practice, you may be able to provide specific explanations to patients based on the data from this study. For example, an FFR of 0.81-0.85 may result in an event of about 2.5% per year, in which case you would need to explain to the patient that the result is based upon maintaining a good lifestyle and treatment regimen. We expect that many sub-analyses will emerge from this registry in the future, and that each of them will contain an important clinical message.
