Angioplasty

Angioplasty with or without stenting is a nonsurgical procedure used to open clogged or narrow coronary arteries due to underlying atherosclerosis. The procedure involves introducing an inflatable balloon-tipped catheter through the skin in extremities and inflating the balloon once it traverses the stenosed arterial site. It presses the intraluminal plaque of atherosclerosis against the arterial wall and widens the luminal diameter. Thereby it normalizes the blood flow to the myocardium and achieves the goal of angioplasty or percutaneous coronary intervention (PCI) by alleviating the chest pain. The PCI concept was introduced 40 years ago with the introduction of "plain old balloon angioplasty" (POBA) without stenting. In the mid-1980s, POBA use was limited because of an early complication of vascular recoil property and restenosis after balloon deflation which led to the invention of bare metal stents (BMS). During the procedure, professionals use a tube-like metallic meshwork, and its scaffolding properties counteract vascular recoil property, thereby avoiding the early restenosis of POBA due to vascular recoil. However, long-term, in situ BMS, can induce wall stress, endothelial discontinuity, and permanent presence of the metallic foreign body in arteries leading to inflammation with fibrin deposition and promoting myofibroblast migration which gives rise to in-stent restenosis (IRS) due to a mechanism of neointimal hyperplasia.

This issue led to the development of drug-eluting stents (DES). DES technology uses a coating of an antiproliferative drug on top of the metallic structure of stents with the benefit of causing less neointimal hyperplasia and stent restenosis as compared with BMS. Late stent thrombosis is also associated with DES due to impaired arterial healing with a lack if re-endothelialization and fibrin deposition due to underlying chronic inflammation more commonly in first-generation DES. Second-generation DES has an extra coating of biocompatible polymer with better endothelial healing. Cobalt-chromium everolimus-eluting stents (second-generation DES) is safer than paclitaxel-eluting stent (first-generation DES) and BMS due to better vascular healing and re-endothelialization of stent struts as evidenced in an animal model. Recent studies show that second-generation DES with biodegradable polymer coating proved to have more efficacy in reducing target-vessel revascularization (TVR), target-lesion revascularization (TLR), in-stent late loss (ISLL), and late-stent thrombosis as compared to BMS. Studies also showed the higher efficacy of DES in complex lesion as compared to BMS.

The latest novel agent bioresorbable scaffolds system (BRS) maintains cyclic pulsatility with fewer chances of vascular remodeling and IRS due to the removal of metallic meshwork in stents platform which serves as triggering agent for late-onset complications such as IRS and stent thrombosis. However, BRS requires best implantation techniques and struts size. The limitation to BRS is struts thickness because in early post-procedural period restenosis is due to vascular recoil property which is counteracted by a metallic scaffold of BMS and DES. If struts size of BRS is reduced, vascular recoil cannot be antagonized adequately. Second-generation BRS has achieved this property somehow. After a time, BRS disappears entirely due to resorption which can be followed up with intravascular ultrasound (IVUS). IVUS and optical coherence tomography (OCT) can be used to install BRS appropriately. There is not much data available on the safety of BRS, but the idea of the metal-free stent that helped develop BRS is criticized because scaffold thrombosis has been reported. Recently, Brown et al. suggested that during BRS implantation, both pre-dilatation and post-dilatation with pressure over 20 ATM is mandatory for preventing acute vascular recoil, and better scaffold expansion, and lower rates of scaffold thrombosis which is best predicted by minimal luminal area on IVUS.

While treating small-sized coronaries arteries, DES has low efficacy with an increased incidence of IRS due to thicker stent’s struts size and luminal loss. To overcome this issue and treating IRS secondary to BMS and DES, drug-eluting balloons (DEB) served the purpose with higher efficacy. In a meta-analysis, a combination treatment of de novo coronary artery disease patients with DEB+BMS was superior to BMS alone with a significant reduction in major adverse cardiac events (MACE) and late lumen loss (LLL). However, DEB plus BMS combination was inferior to DES alone with higher rates of MACE, LLL or TLR.