Most Popular Angioplasty Web Site
Stent Center Stent Center
with support from Medtronic Cardiovascular
Noriaki Moriyama, MD
Email Bookmark and Share

Dr. Noriaki Moriyama is a member of the Department of Cardiology, Shonan Kamakura General Hospital in Kamakura, Japan. He is the lead author on a paper, published in the May 1st issue of the Journal of the American College of Cardiology, entitled “Neoatherosclerosis Five Years After Bioresorbable Vascular Scaffold Implantation.”

This part of the ABSORB EXTEND study demonstrated the occurrence and progression of in-scaffold neoatherosclerosis with luminal narrowing at five years after BVS 1.1 implantation. Angioplasty.Org’s partner site, TCROSS NEWS, recently interviewed Dr. Moriyama, a principal author of the ABSORB EXTEND study in the Shonan Kamakura General Hospital cohort, regarding background and important findings of the study.

    Noriaki Moriyama, MD, FACC
Noriaki Moriyama, MD, FACC

Q: The present study utilized coronary angiography, CT angiography, OCT, and vasomotion to demonstrate long-term outcome of the Absorb BVS. Could you explain the background of this analysis?
Dr. Moriyama: The bioresorbable vascular scaffold, known as BVS, was developed to overcome the weaknesses of metallic stents. Firstly, impairment of physiological vasomotion is a weakness of metallic stents. Indeed, many previous studies focused more on physiological assessment of vasomotion by qualitative coronary angiography (QCA) after BVS implantation. Though some studies demonstrated improvement of vasomotion function at five years after implantation of BVS, the issue has remained controversial. Secondly, evaluation using less invasive CT angiography is often difficult following metallic stent implantation due to poor visibility. Fortunately, BVS is biologically resorbed within five years after implantation, which theoretically enables evaluation of the artery via CT angiography, as if it were a native vessel. For example, we had a patient with angina pectoris who underwent BVS implantation five years ago. CT angiography was performed and revealed the presence of severe calcification in the BVS implanted lesion. We clearly recognized its location by observing residual proximal and distal edge metallic makers of BVS. Therefore, we decided to use intravascular imaging modalities because CT angiography failed to identify the interior vessel characteristics because of calcification. OCT analysis demonstrated the presence of calcification and lipid-rich plaque in the BVS implanted areas. Because atherosclerotic findings were present in stented areas, as imaged by OCT, we defined them as the development of typical neoatherosclerosis. In other words, neoatherosclerosis that developed in metallic stents also occurred in BVS.

The present study is therefore generated by the hypothesis that neoatherosclerosis also develops inside of the vessel after implantation of BVS. To understand properties of BVS, we performed a vasomotor response test (CAG/QCA), a less invasive test (CT), and an intravascular imaging test (OCT/CT).

Q: Could you explain links or relationships between imaging and clinical outcomes (e.g. TLR, scaffold thrombosis)?
Dr. Moriyama: One patient in the ABSORB EXTEND cohort who received a BVS in our institution suffered scaffold thrombosis (ScT). We identified an OCT image of a collapsed scaffold which was similar to a previous report. Thus, I consider that OCT is a useful tool which enables the mechanism of ScT in real-world practice. The INVEST Registry covers more details about the usefulness of intravascular imaging. We had two patients who underwent TLR because of restenosis. One of them occurred at an area where BVSs were overlapped at the edge. Based upon the OCT finding, this negative outcome was assumed to be caused by scaffold thickness (>150μm). In fact, evaluation using this imaging modality gives us valuable information to presume an event mechanism after implantation of BVS. In this regard, however, more clinical studies are required to assess future clinical events based upon imaging findings.

Q: The present study demonstrated that reference diameter and minimum lumen diameter declined significantly at five years as compared to baseline. Could you explain these phenomena?
Dr. Moriyama: As was expected, the development of neoatherosclerosis is considered to be a mechanism of vessel narrowing. However, we did not identify severe vessel narrowing that required therapeutic intervention in the present study. BVS is reported to develop positive vessel remodeling by mid-term observation. But regardless of a high frequency of neoatherosclerosis, the development of vessel narrowing was only mild to moderate. Perhaps this is a specific phenomenon for BVS, but we did not evaluate vessel remodeling by IVUS, which was indicated as a limitation of the present study. Also, because BVS vanishes in five years, the measurement of intima thickness is not possible with the current methodology. Therefore, we cannot specify a principal factor affecting intimal narrowing with the current technology.

Q; At patient-level analysis, 8 of 20 patients (40%) had at least 1 atherosclerotic finding in neointima at one year, and 17 of 17 patients (100%) at five years. What is your opinion about that?
Dr. Moriyama: At cross-sectional-level analysis, atherosclerosis was only confirmed at 80/4,777 cross sections (1.7%) following 1-year after BVS implantation. In this regard, it is expected that the intima within the first year after implantation of BVS showed good outcome. However, atherosclerosis was presented in 1361/4236 (32.1%) cross sections at five years. At patient-level analysis, atherosclerosis was presented in all subjects. Given consideration of the small sample size, it remains a matter of speculation whether the atherogenic factor is related to the BVS itself. Hereafter, studies include lipid profile data as well as larger sample size are warranted to verify our findings.

Q: Could you explain mechanism(s) of calcification contained in neoatherosclerosis frequently observed at five years?
Dr. Moriyama: The presence of calcified images following resorption of BVS has been reported in a previous study. In general, the presence of calcification is interpreted as a feature of stable plaque. Indeed, stable plaque is partly composed of calcification. However, the present study also demonstrated increased lipid and neovascularization, as well as other unstable atherosclerotic findings in arteries implanted with BVSs. Thus, calcification is only partly explained as a feature of stable plaque at five years follow-up by OCT, and therefore may be considered to be a finding of progressive atherosclerosis. In addition, if neoatherosclerosis of BVS develops as quickly as that of a metallic stent, long-term clinical follow-up is essential for the patient who has received BVS implantation. Larger sample size studies and/or pathological analysis are expected to elucidate these mechanisms.

Q: The present study mentioned different performance and outcomes between BVS 1.0 and BVS 1.1. Could you clarify their differences?
Dr. Moriyama: As mentioned in the editorial comment, thickness of the scaffold and the amount of excessive polymer are common problems in both BVSs. BVS 1.1 improved its radial forces as compared to BVS 1.0. As a result, biological absorption time between the scaffolds shows a difference. BVS 1.0 demonstrated a favorable endothelialization at five years in a previous study, but the current study using BVS 1.1 showed a negative outcome. If a causal relationship exists between the device and atherosclerosis, absorption time-lag between BVS 1.0 and BVS 1.1 possibly was responsible for such disparity. In our previous BVS 1.1 study, the presence of residual scaffold debris at five years was reported. The phenomenon is not reported in BVS 1.0 assuming it as one of the collateral evidences related by absorption time-lag. Possibly pathological analysis can elucidate this phenomenon in a future study.

Q: What do you see the future of BVS based the outcome observed in this study?
Dr. Moriyama: BVS follows the same course as metallic stents in that initially development of stent thrombosis, and then neoatherosclerosis, was reported. In other words, the only thing we can do is that optimally metallic stents should be implanted in appropriate lesions in real-world practice. Of course, a bioresorbable scaffold is still an attractive concept for interventional cardiologists. Improvement of the scaffold will offer more benefits for the patient in the future. Improvement of implantation technique and skill, as well as development of better biocompatible materials and breakthrough technology, will all contribute to the practical use of bioresorbable scaffolds in the future. Until that time, I, as an interventional cardiologist, will work hard to refine my skills.

In fact, the present study was not able to be accomplished without assistance. I would like to express my gratitude for Dr. Shigeru Saito who let the study itself, Dr. Koki Shishido who supported every process, Dr. Yutaka Tanaka who gave appropriate advice throughout the study, and all co-workers in the Department of Cardiology at Shonan Kamakura General Hospital. We have a lot of ongoing clinical trials at Shonan Kamakura General Hospital and expect to report new data and findings in near future.

This interview was conducted in May 2018 by TCROSS NEWS, Tokyo, Japan