Abstract
Bioresorbable vascular scaffolds (BVSs) represent the newest tool in the treatment of coronary artery disease (CAD). Conversely to the previous metal stents and thanks to the polylactate-based backbone, BVSs could be visualized by magnetic resonance imaging (MRI) without artifacts. These properties allow a potential non-invasive assessment of coronary artery patency after percutaneous coronary intervention (PCI), avoiding cardiac catheterization included iodine contrast and radiation exposure, and potentially more sophisticated imaging tool as the optical coherence tomography (OCT). We reviewed the available medical literature on the coronary MRI evaluation of BVS after PCI, also discussing its potential diagnostic role in the long-term follow-up of these patients.
Highlights
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Conversely to the previous metal stents and thanks to the polylactate-based backbone, bioresorbable vascular scaffolds (BVSs) could be visualized by magnetic resonance imaging (MRI) without artifacts
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Cardiac magnetic resonance could assess the coronary artery patency after BVSs implantation, avoiding cardiac catheterization, iodine contrast and radiation exposure, and potentially more sophisticated imaging tool as the optical coherence tomography (OCT).
1
Introduction
Percutaneous coronary intervention (PCI) is a well-established therapy for patients with coronary artery disease (CAD). During the last years, several clinical trials have demonstrated that drug-eluting stents (DES) can significantly reduce the restenosis ratio . However, DESs still have some limitations as the risk of neo-atherosclerosis and the hypersensitivity reaction due the stent’s polymer which can lead to stent failure in the long-term period . These limitations have generated a growing interest in stents development, leading to the creation of bioresorbable vascular scaffolds (BVSs). Nowadays, different types of scaffolds are under development for the treatment of CAD, however, nowadays only three BVSs are approved in the European Union: the Absorb BVS™ (Abbott Laboratories, Abbott Park, IL, USA), the DESolve™ (Elixir Medical Corporation, Sunnyvale, CA, USA) and the Magmaris (Biotronik, Bulack, Switzerland) . Theoretically, BVSs can eliminate the occurrence of late and very late in-stent thrombosis (IST), restoring normal coronary vessel physiology and potentially allow the use of aorto-coronary by-pass grafting, if required, once the bioresorption process has been completed. . The current standard technique for the long-term evaluation of the patency of coronary artery stents after percutaneous coronary intervention (PCI) is represented by coronary angiography (CA). Indeed, non-invasive imaging assessment of the coronary lumen by computed tomography (CT) or magnetic resonance imaging (MRI) is not yet recognized and/or recommended as follow-up diagnostic procedure due to stent artifacts . Conversely, BVSs allow in-scaffold assessment of the coronary lumen because, after it bioresorption, due the Kreb’s cycle, only the two radio-opaque markers at each edge of the stent remained visible, not interfering CT or MRI. As matter of a fact, medical treatment after stent implantation has a fundamental role in maintaining coronary artery patency. Nowadays, the optimal time and duration of dual-antiplatelet treatment (DAPT) for patients revascularized by means of BVS has not yet been clarified. Current practice suggests that the duration of DAPT in these subjects should be 12 months after the BVS implantation . Conversely, in the ABSORB II study, patients received DAPT with ≥75 mg of aspirin daily and wither 75 mg of clopidogrel or 10 mg of prasugrel daily for at least 180 days . At the end of the study there were no significant differences regarding the incidence of scaffold thrombosis, but only patients with non-complex coronary lesions were enrolled. During the post-interventional follow-up, a complete artifact-free stent can be very useful because it can allow a contemporary non-invasive evaluation of cardiac function and vessel patency at cardiac MRI in most of the patients with post-interventional angina or ischemic symptoms . Only isolated case reports and short communications have assessed the role of coronary magnetic resonance (CMR) imaging in depicting of coronary patency after BVSs implantation. In this manuscript, we reviewed the available medical literature on the CMR evaluation of BVS after PCI, also discussing its potential diagnostic role in the long-term follow-up of these patients.
2
Material and methods
A mini-review of the literature was conducted using Pubmed database. The relevant case reports, short communications, in-vivo or in-vitro studies in English language were identified using a combined text word and MeSH (Medical Subject Headings) search strategy. The following combination of keywords was used: “Bioresorbllbe Vascular Scaffolds and Magnetic Resonance”, “Bioresorbabele coronary scaffolds and MRI” and “BVS and MRI”. Moreover, we searched the bibliographies of target studies for additional references. The final research was conducted in December 2016.
2
Material and methods
A mini-review of the literature was conducted using Pubmed database. The relevant case reports, short communications, in-vivo or in-vitro studies in English language were identified using a combined text word and MeSH (Medical Subject Headings) search strategy. The following combination of keywords was used: “Bioresorbllbe Vascular Scaffolds and Magnetic Resonance”, “Bioresorbabele coronary scaffolds and MRI” and “BVS and MRI”. Moreover, we searched the bibliographies of target studies for additional references. The final research was conducted in December 2016.
3
Literature results
The current medical literature revealed 3 case reports , one short communication and two in-vitro studies on the post-interventional role of coronary MRI in the assessment of coronary artery patency after BVSs implantation. In particular, one of the latter studies was presented as a hybrid research, assessing in a first step the in-vitro feasibility of CMR and then confirming the observations in-vivo . The results of case reports available in the English literature are summarized in Table 1 . The mean age was 51.2 ± 28.3 years (2 males and 2 females). Three cases considered adult patients while one examined the role of coronary MRI after BVS implantation in a young man with a previous history of Kawasaki disease (KD). Two patients have an involvement of the left coronary artery (LCA), while the others two have endovascular lesions in the right coronary artery (RCA). Generally, only one BVS was implanted; only a single report evidenced an overlapping stenting . In all patients, coronary MRI revealed absence of artifacts and complete visualization of scaffolded coronary arteries in 3D–dark blood navigator-gated TSE as well as in 3D bright-blood navigator-gated FLASH sequences. CMR follow-up was available only in two cases after six months and in one case after 18 months. In all cases, follow-up CMR confirmed absence of residual stenosis. The results of in-vivo and in-vitro studies are summarized in Table 2 . Reiss et al. made a hybrid evaluation, performing in a first step an in-vitro evaluation and subsequently confirming their results in vivo . However, they performed the analysis only in on one type of available BVS (Absorb, Abbott Laboratories, Abbot Park, IL, USA). Conversely, Hickethier et al. performed an original in-vitro study with the aim to investigate both CT and MRI visualization properties on the two CE-marked coronary BVSs: the Elixir DESolve (Elixir Medical Corporation, Sunnyvale, CA, USA) and Abbot Absorb (Abbott Laboratories, Abbot Park, IL, USA) . Their study was performed inserting BVSs in plastic pipes filled with contrast agent and subsequently scanned with a 3.0 T MR system (Ingenia 3.0 T; Philips Healthcare, Best, The Netherlands). MRI demonstrated for both types of BVSs a good coronary lumen visibility (DESolve 92%, Absorb 89%) and an unimpaired signal intensity (DESolve 103%, Absorb 100%). To quantify the inhomogeneity of the signal intensity, lumen homogeneity was evaluated as the standard deviation (SD) of the lumen signal (the average of 2 measurements) divided by the mean intensity within the ROI (average of 2 measurements). As results, DESolve and Absorb revealed a lumen homogeneity of SD 7.1% and 9.5%, respectively . In accordance with these findings was the in-vivo study proposed by Von Zur Muhlen et al. They analyzed, using a 3.0 T MRI system, a small cohort of 11 patients receiving one or more BVS in proximal segments of coronary arteries due to angina, NSTEMI or STEMI . As results, in all patients no susceptibility or RF-shielding artifact from the BVS were seen in both spin-echo and gradient-echo images. Moreover, the coronary arteries treated by BVSs were visualized without any limitations. In-vitro and in-vivo studies evaluated both bright- and dark-blood sequences without obtaining any artifacts, despite different type of magnets were used. Dark blood 3D turbo spin echo and bright-blood-T1-weigheted 3D FLASH sequences were the mainly used sequences in in-vivo studies. However, two reports did not specify the CMR/CMA approach limiting our analysis. Conversely, in two in-vitro studies 3 T magnets were used. In these studies, 3D bright-blood navigator-gated FLASH and turbo spin echo (TSE) sequences were mainly adopted. However, considering the few studies/case reports available in medical literature and also the absence of specific technical indications in some of these, it is quite difficult to compare and to establish which are the best MRI sequences that should be adopted in these patients.
| References | Gender | Age | Coronary artery lesions [type of stent] | MRI magnet | MRI sequences | Time F-W MRI | MRI results |
|---|---|---|---|---|---|---|---|
| Reiss et al. | F | 76 | Subtotal occlusion of LAD [Absorb™ (3.0/18 mm)] | 1.5 T (1.5 T (Siemens Symphony, Erlangen, Germany) |
| N/R |
|
| Reiss et al. | F | 73 | Diffusely disease of RCA [Proximal: Absorb™ (3.0/18 mm); Distal: Absorb™ (3.5/28 mm)] ⁎ | 1.5 T (1.5 T (Siemens Symphony, Erlangen, Germany) |
| N/R |
|
| Barone- Rochette et al. | M | 39 | Complete occlusion of the LAD [Absorb™ (3.5 × 18 mm] | NR | NR | 6 months |
|
| Luu et al. | M | 17 | Occlusion of RCA in KD [Absorb™ (3.5/18 mm)] | NR | NR | 6 and 18 months |
|
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