Coronary Bioresorbable Vascular Scaffold Use in the Treatment of Coronary Artery Disease

High Magnesium and Sirolimus on Rabbit Vascular Cells-An In Vitro Proof of Concept

Drug-eluting bioresorbable scaffolds represent the last frontier in the field of angioplasty and stenting to treat coronary artery disease, one of the leading causes of morbidity and mortality worldwide. In particular, sirolimus-eluting magnesium-based scaffolds were recently introduced in clinical practice. Magnesium alloys are biocompatible and dissolve in body fluids, thus determining high concentrations of magnesium in the local microenvironment. Since magnesium regulates cell growth, we asked whether high levels of magnesium might interfere with the antiproliferative action of sirolimus. We performed in vitro experiments on rabbit coronary artery endothelial and smooth muscle cells (rCAEC and rSMC, respectively). The cells were treated with sirolimus in the presence of different concentrations of extracellular magnesium. Sirolimus inhibits rCAEC proliferation only in physiological concentrations of magnesium, while high concentrations prevent this effect. On the contrary, high extracellular magnesium does not rescue rSMC growth arrest by sirolimus and accentuates the inhibitory effect of the drug on cell migration. Importantly, sirolimus and magnesium do not impair rSMC response to nitric oxide. If translated into a clinical setting, these results suggest that, in the presence of sirolimus, local increases of magnesium concentration maintain normal endothelial proliferative capacity and function without affecting rSMC growth inhibition and response to vasodilators.

SICI-GISE position document on the use of the Magmaris resorbable magnesium scaffold in clinical practice

Bioresorbable scaffolds have emerged as a potential breakthrough for the treatment of coronary artery lesions. The need for drug release and plaque scaffolding is temporary, and leaving a permanent stent once the process of plaque recoil and vessel healing has ended might be superfluous or even deleterious exposing the patient to the risk of very late thrombosis, eliminating vessel reactivity, impairing non-invasive imaging and precluding possible future surgical revascularization. This long-term potential limitation of permanent bare metal stents might be overcome by using a resorbable scaffold. The metallic and antithrombotic properties make the resorbable magnesium scaffold an appealing technology for the treatment of coronary artery lesions. Notwithstanding this, its mechanical properties substantially differ from those of conventional bare metal stents, and previous experience using polymer-based scaffolds has shown that a standardized implantation technique and optimal patient and lesion selection are key factors for a successful implantation. A panel of expert cardiologists gathered to find a consensus on the best practices for Magmaris implantation in a selected patient population and to discuss the rationale for new potential future indications.

Designing Better Cardiovascular Stent Materials - A Learning Curve

Cardiovascular stents are life-saving devices and one of the top 10 medical breakthroughs of the 21st century. Decades of research and clinical trials have taught us about the effects of material (metal or polymer), design (geometry, strut thickness, and the number of connectors), and drug-elution on vasculature mechanics, hemocompatibility, biocompatibility, and patient health. Recently developed novel bioresorbable stents are intended to overcome common issues of chronic inflammation, in-stent restenosis, and stent thrombosis associated with permanent stents, but there is still much to learn. Increased knowledge and advanced methods in material processing have led to new stent formulations aimed at improving the performance of their predecessors but often comes with potential tradeoffs. This review aims to discuss the advantages and disadvantages of stent material interactions with the host within five areas of contrasting characteristics, such as 1) metal or polymer, 2) bioresorbable or permanent, 3) drug elution or no drug elution, 4) bare or surface-modified, and 5) self-expanding or balloon-expanding perspectives, as they relate to pre-clinical and clinical outcomes and concludes with directions for future studies.

"The Unpredictable ABSORB" - Very Late Stent Thrombosis of Bioresorbable Vascular Scaffold

Bioresorbable vascular scaffolds represent the next revolution in stent technology. They serve the dual purpose of antiproliferative drug delivery to vascular lumen like a drug-eluting stents (DES) as well as phased strut resorption over time leading to virtual elimination of stent thrombosis. The ABSORB GT-1 stent was the prototype bioresrbable vascular scaffold with maximum clinical experience and initial promising results. However, reports of stent thrombosis emerged with ABSORB too. Although the use of intracoronary imaging and proper implantation technique has the potential to reduce stent thrombosis rates, the device has been withdrawn from the market for now. We report a case of late stent thrombosis with ABSORB which was managed with DES-supported intracoronary imaging.

Temporal Trends in Adverse Events After Everolimus-Eluting Bioresorbable Vascular Scaffold Versus Everolimus-Eluting Metallic Stent Implantation

Background:

Bioresorbable coronary stents have been introduced into clinical practice to improve the outcomes of patients treated with percutaneous coronary intervention. The everolimus-eluting bioresorbable vascular scaffold (BVS) is the most studied of these stent platforms; however, recent trials comparing BVS with everolimus-eluting metallic stents (EES) raised concerns about BVS safety. We aimed to assess the efficacy and safety of BVS versus EES in patients undergoing percutaneous coronary intervention.

Methods:

We searched Medline, Embase, the Cochrane Central Register of Controlled Trials, scientific sessions abstracts, and relevant Web sites for randomized trials with a follow-up of ≥2 years investigating percutaneous coronary interventions with BVS versus EES. The primary outcomes of our analysis were definite/probable stent thrombosis (ST) and target lesion failure (TLF; device-oriented composite end point of cardiac death, target vessel myocardial infarction, or ischemia-driven target lesion revascularization [TLR]). Secondary outcomes were target vessel myocardial infarction, TLR, and cardiac death. We calculated the risk estimates for main outcomes according to a fixed-effect model.

Results:

We included 7 trials comprising data for 5583 patients randomized to receive either a BVS (n=3261) or an EES (n=2322). Median follow-up was 24 months (range, 24–36 months). Patients treated with BVS had a higher risk of definite/probable ST compared with patients treated with EES (odds ratio, 3.33; 95% confidence interval, 1.97–5.62; P <0.00001). In particular, patients with BVS had a higher risk of subacute, late, and very late ST, whereas the risk of acute ST was similar. Patients treated with BVS compared with EES had a higher risk at 2 years of TLF (odds ratio, 1.47; 95% confidence interval, 1.14–1.90; P =0.003), driven mainly by an increased risk of target vessel myocardial infarction (odds ratio, 1.73; 95% confidence interval, 1.31–2.28; P =0.0001; I 2 =0%) and of TLR (odds ratio, 1.27; 95% confidence interval, 1.00–1.62; P =0.05). Of importance, the risk of TLF and TLR for patients with BVS was higher between 1 and 2 years, whereas there was no difference in the first year. Risk of cardiac death was similar between the 2 groups.

Conclusions:

Our meta-analysis of randomized trials with a follow-up of ≥2 years demonstrated a higher risk of ST and of TLF in patients treated with BVS compared with EES. Of note, BVS had a higher risk of subacute, late, and very late ST, whereas the risk of TLF and TLR was higher between 1 and 2 years.