Evolution of drug-eluting coronary stents: a back-and-forth journey from the bench-to-bedside

Coronary stents have revolutionized the treatment of coronary artery disease. Compared with balloon angioplasty, bare-metal stents effectively prevented abrupt vessel closure but were limited by in-stent restenosis due to smooth muscle cell proliferation and neointimal hyperplasia. The first-generation drug-eluting stent (DES), with its antiproliferative drug coating, offered substantial advantages over bare-metal stents as it mitigated the risk of in-stent restenosis. Nonetheless, they had several design limitations that increased the risk of late stent thrombosis. Significant advances in stent design, including thinner struts, enhanced polymers' formulation, and more potent antiproliferative agents, have led to the introduction of new-generation DES with a superior safety profile. Cardiologists have over 20 different DES types to choose from, each with its unique features and characteristics. This review highlights the evolution of stent design and summarizes the clinical data on the different stent types. We conclude by discussing the clinical implications of stent design in high-risk subsets of patients.

Planned use of GP IIb/IIIa inhibitors is safe and effective during implantation of the Absorb Bioresorbable Vascular Scaffold

Bioresorbable Vascular Scaffolds (BVS) have the potential for adaptive vessel remodeling, restoration of vasomotion, and late luminal enlargement, thus allowing them to circumvent target lesion failures associated with bare metal stents (BMS) and drug-eluting stents (DES). However, recent data has shown a concerning increase in BVS-associated scaffold thrombosis (ScT) compared to DES. Upfront administration of GP IIb/IIIa inhibitors (GPIs) has shown to reduce early stent thrombosis (ST) compared to standard of care in BMS and DES. Since the use of GPIs was limited in BVS studies, the effect of GPIs on the rate of BVS-associated ScT is largely unknown. This is the first study investigating whether a planned use of GPIs during implantation of the Absorb BVS represents a safe and effective strategy in reducing ScT. In a retrospective chart review of 22 patients undergoing PCI with BVS implantation and planned GPI administration, no acute ScT, in-hospital MACE, or in-hospital major/minor bleeding events were observed. Bleeding reduction strategies such as shorter GPI infusion and radial access were implemented. This study provides valuable preliminary evidence on the benefit and safety in using planned GPI administration to reduce the incidence of ScT after implantation of BVS.

Biomaterials and heart recovery: cardiac repair, regeneration and healing in the MCS era: a state of the "heart"

Regenerative medicine is an emerging interdisciplinary field of scientific research that, supported by tissue engineering is, nowadays, a valuable and reliable solution dealing with the actual organs shortage and the unresolved limits of biological or prosthetic materials used in repair and replacement of diseased or damaged human tissues and organs. Due to the improvements in design and materials, and to the changing of clinical features of patients treated for valvular heart disease the distance between the ideal valve and the available prostheses has been shortened. We will then deal with the developing of new tools aiming at replacing or repair cardiac tissues that still represent an unmet clinical need for the surgeons and indeed for their patients. In the effort of improving treatment for the cardiovascular disease (CVD), scientists struggle with the lack of self-regenerative capacities of finally differentiated cardiovascular tissues. In this context, using several converging technological approaches, regenerative medicine moves beyond traditional transplantation and replacement therapies and can restore tissue impaired function. It may also play an essential role in surgery daily routine, leading to produce devices such as injectable hydrogels, cardiac patches, bioresorbable stents and vascular grafts made by increasingly sophisticated biomaterial scaffolds; tailored devices promptly fabricated according to surgeon necessity and patient anatomy and pathology will hopefully represent a daily activity in the next future. The employment of these devices, still far from the in vitro reproduction of functional organs, has the main aim to achieve a self-renewal process in damaged tissues simulating endogenous resident cell populations. In this field, the collaboration and cooperation between cardiothoracic surgeons and bioengineers appear necessary to modify these innovative devices employed in preclinical studies according to the surgeon's needs.

Possible mechanical causes of scaffold thrombosis: insights from case reports with intracoronary imaging

The advent of intracoronary stents has greatly increased the safety and applicability of percutaneous coronary interventions. One of the drawbacks of drug-eluting stents (DES) is the increased risk of late and very late stent thrombosis (ST). It was anticipated that the risks of ST after DES implantation would be solved with the advent of fully biodegradable scaffolds, which offer the possibility of transient scaffolding of the vessel to prevent acute vessel closure and recoil while also transiently eluting an antiproliferative drug to counteract constrictive remodelling and excessive neointimal hyperplasia. In spite of the enthusiasm for the concept of bioresorbable scaffolds, current clinical data on the Absorb bioresorbable vascular scaffold (BVS) have generated concerns about scaffold thrombosis (ScT) in both the early and late phases. However, the causes of ScT in both the early and late phases have yet to be fully elucidated. This article seeks to provide insights into the possible mechanical causes of ScT in the early and late phases with data stemming from intracoronary imaging (intravascular ultrasound and optical coherence tomography) of the currently published ScT cases following the implantation of BVS and reviews the practical recommendations for implantation of the BVS made by a group of experts.

Biodegradable Cable-Tie Rapamycin-eluting Stents

"Cable-tie" type biodegradable stents with drug-eluting nanofiber were developed to treat rabbit denuded arteries in this study. Biodegradable stents were fabricated using poly-L-lactide film following being cut and rolled into a cable-tie type stent. Additionally, drug-eluting biodegradable nanofiber tubes were electrospun from a solution containing poly (lactic-co-glycolic acid), rapamycin, and hexafluoroisopropanol, and then mounted onto the stents. The fabricated rapamycin-eluting cable-tie stents exhibited excellent mechanical properties on evaluation of compression test and collapse pressure, and less than 8% weight loss following being immersed in phosphate-buffered saline for 16 weeks. Furthermore, the biodegradable stents delivered high rapamycin concentrations for over 4 weeks and achieved substantial reductions in intimal hyperplasia associated with elevated heme oxygenase-1 and calponin level on the denuded rabbit arteries during 6 months of follow-up. The drug-eluting cable-tie type stents developed in this study might have high potential impacts for the local drug delivery to treat various vascular diseases.

Optical Coherence Tomography Findings in Bioresorbable Vascular Scaffolds Thrombosis

BACKGROUND

Everolimus-eluting bioresorbable vascular scaffolds have been developed to improve late outcomes after coronary interventions. However, recent registries raised concerns regarding an increased incidence of scaffold thrombosis (ScT). The mechanism of ScT remains unknown.

METHODS AND RESULTS

The present study investigated angiographic and optical coherence tomography findings in patients experiencing ScT. Fifteen ScT (14 patients, 79% male, age 59±10 years) occurred at a median of 16 days (25%-75% interquartile range: 1-263 days) after implantation. Early ScT (<30 days) occurred in 8 cases (53%). Possible causal factors in these patients included insufficient platelet inhibition in 2 cases and procedural factors (scaffold underexpansion, undersizing, or geographical miss) in 4 cases. No obvious cause could be found in 2 early ScT. In late (>1 month) and very late (>1 year) ScT (respectively, 5 and 2 cases), 5 scaffolds showed intimal neovessels or marked peristrut low-intensity areas. Scaffold fractures were additionally found in 2 patients, and scaffold collapse was found in 1 patient with very late ScT. Extensive strut malapposition was the presumed cause for ScT in 1 case. One scaffold did not show any morphological abnormality. Thrombectomy specimens were analyzed in 3 patients and did not demonstrate increased numbers of inflammatory cells.

CONCLUSIONS

The mechanisms of early ScT seem to be similar to metallic stents (mechanical and inadequate antiplatelet therapy). The predominant finding in late and very late ScT is peristrut low-intensity area.

Absorb bioresorbable stents for the treatment of coronary artery disease

Bioresorbable stents are considered to be the 'fourth revolution' in percutaneous coronary intervention. The first clinically available Absorb(®) bioresorbable device is made of poly-l-lactic acid polymer and elutes everolimus. The process of bioresorption is completed in 3 years. The introduction of this device into clinical practice went through several logical phases: first-in-man studies, randomized Absorb II study with moderately complex patients and lesions, registries of real life patient population and reports of challenging cases. The procedural results are excellent; many insights have been gained by intracoronary imaging. Intermediate-term outcomes are very encouraging both from imaging and from clinical perspectives. The issue of increased stent thrombosis rate was raised in one study, but other studies have been reassuring. Excellent lesion preparation, sizing and complete expansion of the Absorb device are crucial for optimal procedural and clinical results. Results of ongoing large randomized studies will determine the future role of this technology.

Bioresorbable vascular scaffold implantation in acute coronary syndromes: clinical evidence, tips and tricks

Percutaneous coronary intervention (PCI) with a drug-eluting stent (DES) is routine treatment for patients with acute coronary syndromes (ACS). However, permanent metallic caging of the vessel has several shortcomings, such as side branch jailing and impossibility of late lumen enlargement. Moreover, DES PCI is affected by vasomotion impairment. In ACS a high thrombus burden and vasospasm lead to a higher risk of acute and late acquired stent malapposition than in stable patients. This increases the risk of acute, late and very late stent thrombosis. In this challenging clinical setting, the implantation of bioresorbable vascular scaffolds (BVS) could represent an appealing therapeutic option. Temporary vessel scaffolding has proved to have several advantages over metallic stent delivery, such as framework reabsorption, late lumen enlargement, side branch patency, and recovery of physiological reactivity to vasoactive stimuli. In the thrombotic environment of ACS, BVS implantation has the benefit of capping the thrombus and the vulnerable plaque. Bioresorbable vascular scaffolds also seems to reduce the incidence of angina during follow-up. Acute coronary syndromes patients may therefore benefit more from temporary polymeric caging than from permanent stent platform implantation. The aim of this review is to update the available knowledge concerning the use of BVS in ACS patients, by analyzing the potential pitfalls in this challenging clinical setting and presenting tricks to overcome these limitations.

ST-segment elevation myocardial infarction – ideal scenario for bioresorbable vascular scaffold implantation?

Bioresorbable vascular scaffolds (BVS) represent a breakthrough technology for percutaneous coronary intervention (PCI). In this context, because of the unique properties of bioresorbable devices, ST-segment elevation myocardial infarction (STEMI) may represent the ideal scenario for BVS implantation. Consistently, 57% of physicians declare they currently use BVS in this group of patients. However, continuous and growing evidence on the good performance of these devices has been actually shown only in small studies with short- and mid-term follow-up. For these reasons, we need data from sufficiently large observational studies, with long-term follow-up, to confirm that BVS can deliver the same results as 2nd-generation drug-eluting stents when using an appropriate implantation technique. In this review, we discuss the potential advantages of BVS implantation in STEMI patients, together with the most recent evidence from clinical studies, highlighting safety and procedural concerns.