Angioplasty

Article Author:
Muhammad Zain
Article Editor:
Waqas Siddiqui
Updated:
6/29/2018 10:09:58 AM
PubMed Link:
Angioplasty

Introduction

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 different mechanism of neointimal hyperplasia and stent thrombosis.

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 thrombosis 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 then, 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.

Indications

Angioplasty with stenting is currently the treatment of choice in patients with coronary artery disease like unstable angina, NSTEMI, STEMI, and spontaneous coronary artery perforation. Choice of stent depends on patient tolerance to dual antiplatelet therapy (DAPT) with minimal risk of bleeding. 

The main issue concerning the fact that whether DAPT can be tolerated for a duration sufficient enough to guarantee the stent luminal surface re-endothelialization with minimal risk of bleeding and stent thrombosis. It is recommended that DAPT should be continued for at least 1 month following BMS, for 6 to 12 months following first-generation DES implantation, and 3 months of DAPT following newest-generation DES implantation. Stable angina is managed with medical therapy and lifestyle modification to control risk factor for disease progression. Risk stratification can be evaluated by workup including diagnostic angiography with fractional flow reserve measurement. Patients who can tolerate dual-antiplatelet therapy (DAPT) for at least 3 months should be implanted with DES. In patients with high risk of bleeding, when DAPT is contraindicated, or in patients suspected for DAPT discontinuation within thirty days post-stenting, BMS should be the preferred type of stent. In patients requiring surgery within 30 days after the stenting procedure, BMS should be preferred. 

When the surgery is planned between the first and the third month following stenting, the choice between BMS and DES should be according to BA9-coated stent availability and the risk of restenosis as in patients at high bleeding risk. In patients who are poorly compliant with medical therapy, BMS should be preferred. In patients with atrial fibrillation and those on anticoagulant therapy, the use of the BA9-coated stent and 1 month of DAPT should be considered. In patients with high bleeding risk, single antiplatelet therapy after DES is a reasonable alternative if the BA9-coated stent is not available. BMS could be considered in coronary lesions at very low risk of restenosis (coronary vessel diameter greater than 3.5 mm), and in patients with a high bleeding risk profile. An additional pathway to be considered in the patient who has lesions at high risk for restenosis and may benefit from a DES is to perform transcatheter occlusion of the left atrial appendix and more safely continue DAPT.

Preparation

It is widely recognized that a stent’s metallic surface is thrombogenic; consequently, a significant feared sequel is acute vascular closure by acute stent thrombosis due to atheroma rupture, platelet activation, and tissue factor release during and after angioplasty. To prevent acute stent thrombosis, it is recommended to perform PCI under anticoagulation (AC) with the balanced risk of thrombosis and access site bleeding complication. AC can be achieved with multiple agents such as heparin (low molecular weight heparin (LMWH) or unfractionated), bivalirudin, P2Y12 blockers, direct thrombin inhibitors, and glycoprotein IIb/IIIa inhibitors. However, bivalirudin is associated with lower risk of access site bleeding complication, thrombocytopenia, and mortality, but studies show that bivalirudin is associated with slightly higher risk of acute stent thrombosis than with heparin. Notwithstanding, heparin can rarely cause hHeparin-induced thrombocytopenia (HIT). When a patient has previously had HIT, bivalirudin should be used for AC. Activated clotting time is used to manage periprocedural heparin use. After informed consent, the thigh or wrist area is shaved. Propofol is given intravenously to sedate the patient preoperatively. Midazolam is associated with respiratory depression, so propofol is preferred. The incision is made, and the artery is punctured via Saldinger technique, and the 5F sheath is introduced. With fluoroscopic guidance, coronaries are catheterized with use of dye.

In 5% to 10% of cases, a more complex lesion might be discovered. For example, these lesions may be very long, chronic with total occlusion and calcification, non-dilatable, and lesions with anatomical variations such as located at bifurcation or ostium. These require lesion preparation before stent implantation. The goal of lesion preparation is to facilitate optimum stent delivery and expansion and reduce the risk of distal plaque embolization. Several procedures are available to achieve this goal, such as directional or rotational coronary atherectomy, cutting balloon, FX miniRAIL catheter and arthroplasty for heavily calcified plaques. OCT guidance is necessary to implant stent in these cases accurately.

Technique

Angioplasty is the treatment of choice for acute myocardial infarction. Two main approaches used for catheterization are transfemoral: classical and transradial. The transbrachial approach is not routinely done; however, the choice of procedure depends on patient’s characteristics and expertise available.

Transradial Approach

The radial artery is very superficial so it can be easily punctured, and manual compression controls bleeding. Anatomically, there are no nearby major nerves or vessels present. Thus, there is a minimal risk of neurovascular injuries. However, the diameter of the radial artery is very small and small size catheters are required. Compared to transfemoral approach, transradial approach is cost-effective and associated with early discharge from the hospital. With advancement in interventional cardiology’s hardware, transradial approach emerged as a good alternative to classical transfemoral approach. Transradial approach is associated with low risk of access site bleeding or hematoma formation, pseudoaneurysm formation, morbidity and mortality, and lower risk of hand ischemia due to the good collateral blood supply of hand by ulnar artery via palmer arch. Assessment of palmar arches can be done with the help of Allen’s test or pulse oximetry examination. Transradial approach is associated with longer duration of the procedure, greater radiation exposure, anatomical variations leading to catheterization failure, and radial artery spasm which can be managed with local injection of vasodilatory medication such as nitrates and calcium channel blockers.

Transfemoral Approach

The transfemoral approach is the more classical procedure and associated with easy access, less radiation time, and less contrast use. However, access site complications are more common, especially in obese patients. The complexities include access site bleeding, hematoma, major retroperitoneal bleeding requiring a blood transfusion, arteriovenous fistula formation and pseudoaneurysm and neurovascular injuries. The femoral artery is the only source of blood to the leg, so there are more chances of ischemia compared with the transradial approach.

Complications

One rare but serious complication of angioplasty is iatrogenic coronary artery perforation (CAP) due to underlying complex lesion, occurring in 0.1% to 0.8 % of total cases undergoing angioplasty. CAP can be due to angioplasty guide wire perforation, balloon oversizing, and use of atherectomy devices. Management of CAP depends on the severity of the lesion, hemodynamic status, and Ellis class type of CAP. Class 1 is usually benign while class 3 is associated with higher chances of cardiac tamponade and need for emergent cardiac surgery. The mild CAP can be managed with an anticoagulation reversal (protamine sulfate in case of heparin use), prolonged balloon inflation, polytetrafluoroethylene-covered stents (CS), and trans-catheter embolization by autologous fat particles. CS use comes with the cost of stent thrombosis, and few cases of coronary arteriovenous fistula have also been reported due to CS failure. Complication of CAP is ST-segment elevation myocardial infarction, and early or delayed cardiac tamponade with or without hemodynamically instability which can require emergent pericardiocentesis.

In-stent restenosis (ISR) is defined as the reduction in vascular luminal diameter after percutaneous intervention (PCI). The underlying pathophysiology of ISR depends on the type of stent used during PCI. In case of POBA, it is acute in onset because of elastic recoil and vascular remodeling. BMS has the unique phenomenon of Neointimal Hyperplasia. DES has late stent thrombosis due to multiple underlying pathological causes such as decreased vascular re-endothelialization, polymer coating hypersensitivity, and increased fibrin deposition secondary to metal inducing chronic inflammation. In a meta-analysis, it was evident that patients with unstable angina or acute coronary syndrome who underwent PCI are more likely to develop ISR due to chronic inflammation which is predicted by higher C-reactive protein level (CRP) in these patients as compared to patients with stable angina who underwent PCI. Stent fracture (SF) is an infrequently reported adverse outcome of DES use during PCI which can either occur periprocedural or later on when drug elution has been completely done. SF has also been linked to the development of ISR and stent thrombosis. Irrespective of the type of intervention done during PCI, ISR can also be due to neoatherosclerosis. All of the causes mentioned above of ISR present with angina symptoms or acute coronary syndrome due to compromised blood flow to the myocardium and may require reintervention such as coronary artery bypass graft surgery or re-PCI. This reintervention is called target lesion revascularization. The incidence of ISR in the pre-stent era was 32% to 55% of all PCI done, 17% to 41% for BMS, and for second generation DES and DEB it dropped to less than 10% of total PCI done. Such a low rate is due to the evolution of stents under strong criticism and advanced technology.

Clinical Significance

Coronary heart disease (CHD) is prevalent in the worldwide elderly population. The 2016 Heart Disease and Stroke Statistics update of the American heart association reported that in the United States, 15.5 million people have CHD. It is a significant cause of mortality and morbidity in developed countries with nearly one-third of all deaths in people older than 35 years of age are due to underline CHD. The mortality due to CHD has gradually declined over the last few decades due to timely percutaneous coronary intervention with stenting. Therefore, angioplasty is a breakthrough advancement in reducing morbidity and mortality.