Neoatherosclerosis - Long-Term Assessment of Bioresorbable Vascular Scaffold

Abstract

Although metallic stents improved the safety and efficacy of percutaneous coronary intervention (PCI), even the latest generation of drug-eluting stents (DES) is still limited by several factors. The limitations of DES are mainly related to the permanent metallic caging in vessel, chronic inflammatory response to the polymer and adverse effects of antiproliferative drug on endothelial tissue, leading to impaired physiological vasomotor response and late stent-related adverse events such as stent thrombosis and neoatherosclerosis. Bioresorbable vascular scaffold (Absorb BVS; Abbott Vascular) was designed to overcome these drawbacks of DES by disappearing from the vessel wall. Absorb BVS, however, was withdrawn from the world market because of increased incidence of scaffold thrombosis compared with DES. Importantly, only very limited long-term post-BVS implantation data are available, especially with regard to neoatherosclerosis, which can lead to very late adverse events even after resorption of the scaffold. Therefore, the goal of this review was to highlight the mid to long term clinical outcomes published to date, and to describe the features of the intimal healing process and neoatherosclerosis in the 5 years following Absorb BVS implantation, mainly based on our previous study. This may provide important information on the pathophysiology of the scaffolded vessel for clinicians, and promote identification of future bioresorbable materials for PCI that will minimize the stimulus for neoatherosclerosis.

Keywords: Bioresorbable vascular scaffold; Neoatherosclerosis; Percutaneous coronary intervention.

Figure 1.

Typical optical coherence tomography findings of neoatherosclerosis at 5 years after Absorb bioresorbable vascular scaffold. (A) Lipid-laden intima is defined as a diffusely bordered, signal-poor region with overlying signal-rich bands in the intima. (B) Plaque rupture. (C) Thin-cap fibroatheroma-containing intima: fibrous cap thickness ≤65 μm at the thinnest segment and an angle of lipid tissue ≥180° with thrombus. (D,E) Calcification as a well-delineated, signal-poor region with sharp borders (white arrow). (F) Neovascularization as the presence of signal-poor holes or tubular structures with a diameter of 50–300 μm that are not connected to the vessel lumen (box). (G) Macrophage infiltration as a bright spot with a high signal variance from surrounding tissue (white arrowhead).

Figure 2.

In-scaffold calcium growth at 5 years, in a 73-year-old woman with angina pectoris. Two Absorb bioresorbable vascular scaffolds rev.1.1 3.0×18 mm were implanted at the distal right coronary artery with sufficient scaffold expansion. At 1-year follow-up, optical coherence tomography (OCT) showed good expansion of scaffold without any malapposition. At 5 years, scaffolds were not visible on OCT. Calcium growth (white arrowhead) was observed in neointimal tissue (≤200 μm from the end-luminal border). CAG, coronary angiography; F/U, follow-up; PCI, percutaneous coronary intervention.

Figure 3.

In-scaffold thin-cap fibroatheroma (TCFA) at 5 years, in a 65-year-old man with angina pectoris. Absorb bioresorbable vascular scaffold (BVS) rev.1.1 3.0×28 mm was implanted at the proximal left anterior descending coronary artery with sufficient expansion of scaffold. At 1-year follow-up, optical coherence tomography (OCT) showed sufficient expansion of BVS and intimalization over scaffold. At 5 years, although the scaffolds were completely absorbed, TCFA was identified with moderate luminal narrowing on OCT. CAG, coronary angiography; F/U, follow-up; PCI, percutaneous coronary intervention.

Figure 4.

In-scaffold vasospastic angina at 5 years, in a 78-year-old man who had undergone percutaneous coronary intervention with bioresorbable vascular scaffold (BVS) 3.0×18 mm in significant organic stenosis of the proximal left anterior descending coronary artery. (A–C) Coronary angiography (CAG) and optical coherence tomography (OCT) showed excellent results. At 5 years after the index procedure, he was referred from the other hospital because of frequent atypical chest pressure. CAG indicated significant stenosis in the in-scaffold segment (red arrowhead). After nitroglycerine (NTG) injection, the lesion was fully expanded with resolution of symptoms. (E) On detailed observation, OCT confirmed neoatherosclerosis including lipid-plaque with luminal narrowing. (D,F) Proximal and distal edge of BVS. This patient was diagnosed with vasospastic angina, and an oral calcium channel blocker improved the chest symptom.

Figure 5.

Summary of clinical and imaging data following Absorb bioresorbable vascular scaffold (BVS) implantation. CoCr-EES, Cobalt-chromium everolimus-eluting stent; PSP, pre-dilatation, sizing and post-dilatation; TLR, target lesion revascularization.