You are in: eMedicine Specialties > Cardiology > Cardiac Catheterization Procedures Percutaneous Transluminal Coronary AngioplastyArticle Last Updated: Aug 23, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 8
  Author: Robert Vincent Kelly, MD, Consulting Staff, Division of Interventional Cardiology, University of North Carolina Hospital Coauthor(s): George A Stouffer III, MD, Henry A Foscue Distinguished Professor of Medicine and Cardiology, Director of Interventional Cardiology, Cardiac Catheterization Laboratory, Chief of Clinical Cardiology, Division of Cardiology, University of North Carolina Medical Center; Jeb Burchenal, MD, Assistant Professor of Medicine, University of Colorado School of Medicine; Consulting Staff, South Denver Cardiology Associates; James Maddux, MD, Consulting Staff, Department of Cardiology, International Heart Institute Editors: Gregory Joseph Dehmer, MD, Director, Division of Cardiology, Professor, Department of Medicine, Scott & White Clinic, Texas A&M University School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Marschall S Runge, MD, PhD, Marion Covington Distinguished Professor of Medicine, Vice Dean for Clinical Affairs, Chairman, Department of Medicine, University of North Carolina at Chapel Hill School of Medicine; Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital; Michael E Zevitz, MD, Assistant Professor of Medicine, Finch University of the Health Sciences, The Chicago Medical School; Consulting Staff, Private Practice Author and Editor Disclosure Synonyms and related keywords: percutaneous transluminal coronary angioplasty, PTCA, coronary artery disease, CAD, bare metal stent, BMS, coronary artery bypass surgery, CABG, unstable angina, drug-eluting stents, DES, myocardial infarction, MI, percutaneous coronary interventions, PCI, target vessel revascularization, TVR, rotational atherectomy, directional coronary atherectomy, laser atherectomy, balloon angioplasty, intracoronary stents, stable angina, surgical revascularization, coronary angioplasty, fibrinolytic therapy, primary angioplasty, primary PCI OVERVIEW AND HISTORICAL PERSPECTIVESection 2 of 8
  Since the first human percutaneous transluminal coronary angioplasty (PTCA) procedure was performed in 1977, the use of this procedure has increased dramatically, becoming one of the most common medical interventions performed. The technique, originally developed in Switzerland by Andreas Gruentzig, has transformed the practice of revascularization for coronary artery disease (CAD). Initially used in the treatment of patients with stable angina and discrete lesions in a single coronary artery, coronary angioplasty has multiple indications today, including unstable angina, acute myocardial infarction (MI), and multivessel CAD. With the combination of sophisticated equipment, experienced operators, and modern drug therapy, coronary angioplasty has evolved into an effective nonsurgical modality for treating patients with CAD. In 2000, more than 500,000 percutaneous coronary interventions (PCIs) were performed in the United States. By 2004, the number exceeded 650,000 in the United States with rapid growth in other developed countries. Worldwide, the number of PCIs continues to increase annually. Clinical indications and contraindications to PTCA
Angiographic indications and contraindications to PTCA
Recent advances in guidewires, stents, and devices to cross chronically occluded arteries are evolving so that more patients with CTOs are now being successfully treated percutaneously. Improvements in catheter technique and the development of new devices, wires, stents, drug-eluting stents, and medications have occurred parallel to advances in the understanding of cardiovascular physiology, the pathogenesis of atherosclerosis, and the body's response to vascular injury. Intracoronary stents and atherectomy devices were developed to increase the success rate of, and decrease the complications associated with, conventional balloon dilation and to expand the indications for revascularization. These devices have enabled the interventionalist to safely treat more complex coronary lesions and restenosis. Now, stents have evolved to a level where the problems of restenosis seen with bare metal stents are a less frequent occurrence after drug-eluting stents are implanted. At the same time, advances in imaging techniques, including intravascular ultrasonography (IVUS), fractional flow reserve evaluation, and Doppler flow analysis, have improved the understanding of coronary plaquemorphology, plaque vulnerability, and coronary physiology. Furthermore, many of these technologies are able to help identify those patients who will benefit most from PCI or from medical therapy. Adjunctive pharmacologic therapies aimed at preventing acute reocclusion have also improved the safety and efficacy of coronary angioplasty. The growth of PCIs has been remarkable and will likely continue as new technologies have resulted in improved outcomes. Since 1994, the use of intracoronary stents has risen dramatically, and now with drug-eluting stents, stents are used in more than 80% of PCI cases in the United States. Innovations in PCIs over the last 2 decades have been paralleled by a dramatic reduction in 30-day death, MI, and target vessel revascularization rates. MECHANISMS AND DEVICES OF ANGIOPLASTYSection 3 of 8
Mechanism of angioplastyThe original description of angioplasty by Dotter and Judkins described enlargement of the vessel lumen through a mechanism of atheromatous plaque compression. Plaque compression is now understood to account for very little of the observed improvement following balloon angioplasty. Most of improvement in luminal diameter following balloon angioplasty results from stretching of the vessel wall by the balloon. Balloon inflation actually results in overstretching of the vessel wall and partial disruption of not only the intimal plaque but also the media and adventitia, resulting in enlargement of the lumen and the outer diameter of the vessel. Axial redistribution of plaque material also contributes to improvements in lumen diameter. Atherectomy devices and, subsequently, intracoronary stents were developed, in part, to decrease the early and late loss in luminal diameter observed with conventional balloon angioplasty. Devices for coronary interventionsBalloon angioplasty The primary device for balloon angioplasty is the balloon-tipped catheter. Several different balloon catheter designs exist (over-the-wire, monorail, fixed wire) with balloon materials that have different compliance characteristics allowing various degrees of expansion with increasing pressure. Irrespective of the balloon design, a steerable guidewire precedes the balloon into the artery and allows navigation through a considerable portion of the coronary tree. The development of balloon catheters that bend, allowing easy advancement through tortuous vascular segments (trackability), and that have increased shaft stiffness (pushability), allowing the catheter to be forced through stenotic lesions, has increased their versatility significantly. Another evolving feature of catheter design has been a reduction in the diameter of the deflated balloon, allowing easier passage through very stenotic lesions. Over the last decade, improvements in catheter design have been partially responsible for the improved success rates of PCIs. The balloon catheter also serves as an adjunctive device for many other interventional therapies, including atherectomy and coronary stents. Atherectomy devices and coronary stents As a result of technical challenges, as described above, suboptimal clinical outcomes, and the significant rates of restenosis following percutaneous coronary artery balloon angioplasty, 2 innovative types of devices were developed and studied in large-scale clinical trials. The idea behind atherectomy devices was to physically remove atheroma, calcium, and excess cellular material from the site of a coronary occlusion or stenosis. Mechanical and laser-based approaches are described below. An alternative approach developed at about the same time was intracoronary stent placement, based on the notion that permanent implantation of a scaffold to hold open the coronary artery at the site of an intervention would improve outcomes. As is discussed below, long-term outcomes from atherectomy alone have been disappointing and little better than balloon angioplasty in most cases. Stents, particularly stents coated with materials to reduce inflammatory and cell growth responses, have resulted in greatly improved outcomes. Atherectomy is still used for specific, niche indications, but the most common intracoronary device used today is a stent. Rotational atherectomy The rotational atherectomy catheter (Rotablator) is a device designed for the removal of plaque from coronary arteries. This device, which has a diamond-studded burr at its tip, rotates at about 160,000 rpm and is particularly well suited for ablation of calcific or fibrotic plaque material (see Image 1). Unlike other atherectomy devices that rely on tissue cutting, the rotational atherectomy device relies on plaque abrasion and pulverization. Rotational atherectomy is successful in 92-97% of these cases, with a low incidence of major complications. It causes dislodgement of particles into the microcirculation, which occasionally may lead to infarction and no reflow. Currently, the use of rotational atherectomy is largely confined to fibrotic or heavily calcified lesions that can be wired but not crossed by a balloon catheter. The Excimer Laser, Rotational Atherectomy, and Balloon Angioplasty Comparison (ERBAC) Study showed rotational atherectomy was associated with a higher short-term success rate than balloon angioplasty (90% vs 80%), but major ischemic complications and repeat revascularization were higher 6 months after treatment (46% vs 37%). In a recent meta-analysis that compared rotational atherectomy, cutting balloon angioplasty, and laser atherectomy failed to show any significant difference in mortality, major adverse cardiovascular events (MACE), or revascularization rates in patients treated with either rotational atherectomy, laser, or cutting balloon angioplasty when compared with balloon angioplasty alone. In some cases, rotational atherectomy was actually associated with an increase in periprocedural MI. However, none of these trials compared stent-related outcomes. In fact, many of these devices may be used to facilitate stent delivery in complex lesions, especially when balloon angioplasty alone has failed. Directional coronary atherectomy/laser atherectomy Since 1987, directional coronary atherectomy (DCA) has been used to debulk coronary plaques. A steel fenestrated cage housing a cup-shaped blade is positioned against the coronary lesion by a low-pressure positioning balloon, allowing any protruding plaque to be removed. Atherectomy is typically followed by balloon dilation and stenting. The acute gain, therefore, is a combination of the removal of atheromatous plaque and radial displacement of plaque from dilation. Major complication rates associated with directional atherectomy are low and similar to conventional balloon angioplasty. Other complications (eg, distal embolization of plaque, transient side-branch occlusion, coronary vasospasm, the no reflow phenomenon, non–Q-wave MI) are greater with DCA than with balloon angioplasty. Because of the increased complication rates and the greater technical demands of DCA compared with balloon angioplasty or stenting, the use of DCAs has greatly decreased in recent years. Although initial excitement about the development of laser atherectomy was considerable, it is not used widely because of the technical demands of this device and no clear improvements in outcome over therapy with other devices. Intracoronary stents Intracoronary stents have been used widely since the early 1990s. Many different stents are available and differ in composition (eg, stainless steel, tantalum, chromium cobalt), architectural design (slotted tube vs coiled wire), and mode of implantation (balloon expandable vs self-expanding). In the last 3 years, the development of drug-eluting stents (DESs) has revolutionized coronary intervention to the extent that balloon angioplasty and bare metal stents did in the 1980s and 1990s. Today, multiple types of DESs are available, with the 2 most commonly used in the United States being the sirolimus (Cypher) stent (SES) and the paclitaxel (Taxus) stent (PES). These stents comprise a metal stent with a polymer that elutes a drug that reduces neointimal hyperplasia. Newer stent platforms are evolving with more uniform drug delivery systems and with the ability for some stents to store different drugs for local intracoronary delivery (eg, to improve coronary artery blood flow and myocardial perfusion during primary angioplasty). SES and PES have both been extensively tested in a wide spectrum of coronary lesions, all of which have demonstrated significant reductions in restenosis and target lesion revascularization (TLR) rates when compared with bare metal stents. Any differences between the SES and PES appear to be small, with some registries and meta-analyses suggesting fewer Q wave MIs and subacute thromboses with SES than PES. Intracoronary imaging techniques Coronary angiography provides a display of luminal narrowing in multiple planes and is useful in guiding coronary interventions. However, angiography cannot provide information about the vessel wall, which is where the atherosclerotic process resides. IVUS was developed to provide information about the plaque and the vessel wall in addition to the degree of luminal narrowing. IVUS provides a tomographic cross-section of the vessel, allowing operators to gather significant qualitative and quantitative information that is potentially valuable in assessing stenosis severity and the true extent of atherosclerotic involvement (see Image 5). Intracoronary Doppler flow wires are able to characterize coronary physiology and to estimate the impact of lesion severity on coronary blood flow. This technology measures the ratio of maximal myocardial flow in a stenotic area to the maximum myocardial flow in the same territory if the stenosis were absent. (This is performed during a period of maximal hyperemia induced by an injection of intravenous or intracoronary adenosine). Comparison of pressure distal to a lesion with aortic pressure enables determination of fractional flow reserve (FFR). FFR measurement below 0.75 during maximal hyperemia is consistent with a hemodynamically significant lesion and this may help determine whether to perform PCI in an angiographic intermediate lesion. Clinical data, namely the DEFER study, support using this approach, with a low event rate seen in medically managed patients with angina and an FFR measurement greater than 0.75. This form of physiologic lesion assessment is also useful for defining optimal stenting, assessing the angiographic severity of jailed side branch lesions, helping guide the decision for mutivessel PCI or CABG in multiple intermediate lesions, and assessing the severity of instant restenosis (see Image 6). FFR measurements have excellent correlation with IVUS analysis, especially when determining lesion severity, such as in ambiguous left mainartery anatomy. COMPLICATIONSSection 4 of 8
Early registries of balloon angioplasty results showed complication rates that were much higher than those typically observed today. With advancements in technique, devices, and adjuvant medical therapy, percutaneous transluminal coronary intervention is now associated with mortality and emergency bypass rates of less than 1%. The rate of nonfatal MI following coronary angioplasty ranges from 5-15%, whereas the rate following stent placement is 2-5%. Restenosis after balloon angioplasty requiring a second revascularization procedure is a major limitation occurring in about 30-50% of patients, depending on the definition of restenosis applied. However, with drug-eluting stents (DESs), restenosis rates are now less than 10%. Reduction in the complications of balloon angioplasty has been complemented by improvements in the acute success rate. Registries, such as the National Heart, Lung, and Blood Institute (NHLBI) Coronary Angioplasty Registry from the early 1980s, reported primary success rates of 61%. Today, success rates are as high as 95% following conventional balloon angioplasty and are even higher with the use of DESs and adjunctive pharmacotherapy. Acute complications The mechanism by which balloon angioplasty or stenting improves luminal diameter is associated with significant local trauma to the vessel wall, which can in turn lead to occlusive complications in a minority of patients. Coronary artery dissection typically results from the vessel injury secondary to balloon expansion. Animal and postmortem studies have shown that localized dissection at the site of balloon expansion is a common occurrence detected angiographically in as many as 50% of patients immediately following the procedure. Such small dissections probably are necessary to obtain adequate lumen expansion, rarely interfere with antegrade blood flow, and rarely are important. Angiographic follow-up typically shows no residual evidence of a dissection as early as 6 weeks after angioplasty in most of the cases studied. However, larger dissections can lead to complications. Abrupt vessel closure may occur in as many as 5% of balloon angioplasty cases and typically develops when compression of the true lumen by a large dissection flap occurs, thrombus formation, superimposed coronary vasospasm, or a combination of these processes. The presence of large coronary dissections immediately after balloon angioplasty is associated with a 5-fold increase in the risk of abrupt closure. This underscores the importance of a good postprocedure angiographic result on clinical outcomes. Today, the use of intracoronary stents and new antiplatelet drugs has decreased the incidence of abrupt closure significantly (to <1%). Microembolization of plaque debris or adherent thrombus may also cause acute complications during angioplasty and may contribute to postprocedure cardiac enzyme elevation and chest pain in some patients. In less than 1% of patients undergoing angioplasty, microembolization of the platelet-rich thrombus may cause diffuse distal arteriolar vasospasm secondary to the release of vasoactive agents, resulting in the phenomenon of no-reflow. This complication is difficult to treat but may respond to intracoronary calcium channel antagonists, adenosine, or nitroprusside. Patients undergoing balloon angioplasty of saphenous vein graft lesions and primary angioplasty in the setting of acute MI with a large amount of adherent thrombus are at greatest risk of distal embolization. Coronary perforation or rupture following balloon angioplasty is very rare (<1%) and typically is associated with the use of ablative devices or oversized balloons. Restenosis Following balloon angioplasty or stent implantation, the vessel wall undergoes a number of changes. Platelets and fibrin adhere to the site within minutes of vessel injury. Within hours to days, inflammatory cells infiltrate the site and vascular smooth muscle cells begin to migrate toward the lumen. The vascular smooth muscle cells then hypertrophy and excrete an extensive extracellular matrix. During this period of vascular smooth muscle cell proliferation, endothelial cells colonize the surface of the lumen and regain their normal function. Over the course of several weeks to months, multiple forces interact to cause remodeling of the vessel wall with either a decrease in lumen diameter (negative remodeling) or an increase in lumen diameter (positive remodeling). The amount of late loss in lumen diameter is dependent on the amount of neointimal proliferation and the degree of remodeling following intervention. After 6 months, the repair process stabilizes and the risk of restenosis decreases significantly (see Image 7). Several studies have shown that the lumen diameter or area after treatment is one of the major predictors of restenosis. The use of coronary artery stents has decreased the rate of restenosis by improving the acute gain achieved and by minimizing negative remodeling. Depending on the definition used, angiographic restenosis has been reported in as many as 50% of patients within 6 months after balloon angioplasty, necessitating repeat target vessel revascularization (TVR) in approximately 20-30% of patients. Today, DESs have reduced restenosis rates to less than 10%. Poststent lumen diameter and lesion complexity are still the major predictors of restenosis with these newer stents. While DESs have significantly reduced restenosis events, concerns of stent thrombosis with these newer stents still exist. In fact, the rate of thrombosis with DES is virtually identical to that for bare metal stent (BMS) (0.4-1.5%). The biggest factor contributing to stent thrombosis is interruption of antiplatelet therapy. Another important factor is final stent diameter and area. Underdeployment or incomplete apposition of the DES may also increase the risk for stent thrombosis. This is extremely important because acute and subacute stent thrombosis often have a fatal outcome. Late stent thrombosis is another consideration. DES may take up to 4 years to endothelialize on the coronary vessel wall and discontinuing antiplatelet therapy may expose these patients to an increased risk for sent thrombosis over time. In some clinical situations (such as before urgent noncardiac surgery where antiplatelet therapy may have to be discontinued and in patients with known or potential medicine compliance issues), implanting a BMS may be preferred during PCI rather than using a DES. COMPARISON OF ANGIOPLASTY WITH OTHER TREATMENTSSection 5 of 8
Stable angina (PCI vs medical therapy) Early trials (VA, ACME, RITA II, ACIP) demonstrated the benefit of percutaneous transluminal coronary angioplasty (PTCA) over medical therapy for symptomatic angina in single and multivessel coronary artery disease (CAD), with improvements in symptoms, reduction in need to take antianginal medications, improvement in exercise duration, and similar survival rates to medical therapy. In the Randomized Intervention in the Treatment of Angina (RITA-II) study, 1018 patients with stable angina were randomized to balloon angioplasty or medical therapy, and their cases were followed for a mean of 2.7 years. Death or definite myocardial infarction (MI) occurred in 6.3% of the balloon angioplasty patients compared with 3.3% of the medical patients (P=0.02), but only 44% of the deaths were actually due to heart disease. Angina improved in both groups, but a 16.5% absolute excess of grade 2 or worse angina occurred in the medical group 3 months following randomization. Angioplasty patients had a greater improvement in exercise duration compared with the medically treated group, and 23% of the medical group required revascularization during follow-up. During follow-up, 7.9% of the angioplasty patients required bypass surgery, compared with 5.8% of the medically treated patients. Although the patients in RITA-II were asymptomatic or mildly symptomatic, emphasizing that most had severe anatomic CAD is important; 62% had multivessel CAD, and 34% had important disease of the proximal left anterior descending artery. Thus, RITA-II demonstrated that balloon angioplasty results in better control of ischemic symptoms and improves exercise capacity compared with medical therapy, but balloon angioplasty is associated with an increased incidence of the combined end point of death and MI. The Asymptomatic Cardiac Ischemia Pilot (ACIP) study suggested that revascularization either by surgery or by angioplasty compares favorably with medical therapy in patients with myocardial ischemia with or without angina. In the Atorvastatin Versus Revascularization Treatment (AVERT) trial, 341 patients with stable CAD symptoms, normal left ventricle (LV) function, and class I or II angina were assigned randomly to balloon angioplasty or medical therapy with atorvastatin. After 18 months of follow-up, 13% of the medically treated group had ischemic events compared with 21% of the angioplasty group (P=0.048), suggesting that, in low-risk patients with stable CAD, aggressive lipid-lowering therapy may be as effective as balloon angioplasty in reducing ischemic events. Based on the limited data available from randomized trials comparing medical therapy with balloon angioplasty, considering medical therapy seems prudent for the initial management of most patients with Canadian Cardiovascular Society Classification Class I and II symptoms and reserving percutaneous or surgical revascularization is appropriate for patients with more severe symptoms and ischemia. Overall, medical therapy is recommended as first-line therapy in stable angina patients unless the following occur: a change in symptom severity, early positive stress test result, failed medical therapy, coronary anatomy, and/or LV dysfunction or patient age concerns that provide an indication for cardiac catheterization and percutaneous coronary intervention (PCI) of coronary artery bypass graft (CABG). Stable angina (PCI vs surgical revascularization) Two prospective clinical trials have evaluated balloon angioplasty versus surgery for revascularization of isolated left anterior descending coronary artery disease. Using a combined endpoint (cardiac death, MI, or refractory angina requiring revascularization by surgery), the Medicine, Angioplasty, or Surgery Study (MASS) showed, after 3 years of follow-up, that endpoint events occurred in 24% of angioplasty patients, 17% of medical patients, and 3% of surgical patients. However, overall survival was similar among the 3 groups. The other trial compared balloon angioplasty versus bypass surgery with an internal mammary artery graft to the left anterior descending artery and also showed no difference in survival during follow-up. Although 94% of the angioplasty patients and 95% of the bypass patients were free of limiting symptoms, those treated by angioplasty required more antianginal drugs. At median follow-up of 2.5 years, 86% of the surgery patients versus 43% of angioplasty patients were free from late events (P <0.01), and this difference primarily was due to restenosis requiring a second revascularization procedure. Emphasizing that balloon angioplasty was used in these trials rather than stent placement is important; thus, current rates of restenosis with stenting should be lower. Five large (>300 patients) randomized trials comparing balloon angioplasty with bypass surgery in patients with multivessel CAD have been conducted (see Table 1). The major findings from these trials have a consistent theme. In appropriately selected patients with multivessel CAD, the incidence of death or MI is similar whether balloon angioplasty or bypass surgery is used, but more patients treated with angioplasty require a second revascularization procedure. In the Bypass Angioplasty Revascularization Investigation (BARI), 5-year survival was 86.3% for those assigned to angioplasty versus 89.3% for those assigned to surgery (P=0.19), and 5-year freedom from Q-wave MI was 78.7% and 80.4%, respectively. However, after 5-years of follow-up, 54% of those assigned to angioplasty required an additional revascularization procedure compared with only 8% of those assigned to surgery. Table 1. Comparison of Surgical Therapy and Coronary Angioplasty
*Meta-analysis of the results of 3 trials at 1 year: Patients with single-vessel disease were studied (Pocock, 1995). † Meta-analysis of the results of 3 trials at 1 year: Patients with multivessel disease were studied (Pocock, 1995). ‡Reported results are for the 5-year follow-up. Patients with multivessel disease were studied. § Coronary artery bypass graft II P <0.05 In a similar manner, the 3-year follow-up of the Argentine Randomized Trial of Percutaneous Transluminal Coronary Angioplasty Versus Coronary Artery Bypass Surgery in Multivessel Disease (ERACI) showed that freedom from combined cardiac events was significantly better for bypass surgery (77% vs 47%, P <0.001) compared with angioplasty. However, no differences occurred in overall and cardiac mortality rates or in the frequency of MI between the 2 groups. Patients who had bypass surgery were free of angina more frequently (79% vs 57%) and had fewer additional revascularization procedures (6% vs 37%) than patients treated with angioplasty. An exception to equivalent mortality rate results of balloon angioplasty and bypass surgery in multivessel disease exists for patients with diabetes mellitus. Among diabetic patients in the BARI trial, 5-year survival was 65.5% in those treated by balloon angioplasty compared with 80.6% for those having bypass surgery (P=0.003). The improved survival with surgery was due to a reduced cardiac mortality rate (5.8% vs 20.6%, P=0.0003) and was confined to those receiving at least 1 internal mammary artery graft. Better survival among diabetic patients with multivessel disease treated with bypass surgery rather than angioplasty also was observed in a large retrospective study. The major limitations of balloon angioplasty have been acute vessel closure and restenosis. Early studies with intracoronary stents showed that these devices were highly effective for treating or preventing acute or threatened vessel closure and, thus, avoiding emergency bypass surgery. In 1994, 2 randomized trials, STRESS and BENESTENT, demonstrated that coronary stenting of de novo lesions in native vessels reduced angiographic restenosis by approximately 30% compared with conventional balloon angioplasty. Stenting produces a larger lumen diameter than conventional balloon angioplasty immediately following the procedure (acute gain) and at follow-up (net gain), resulting in less restenosis. The use of stenting, instead of balloon angioplasty, was compared with bypass surgery for the treatment of multivessel CAD in the Arterial Revascularization Therapies Study (ARTS). After 1 year of follow-up, no difference was noted between the groups in the rate of death, stroke, or MI. Event-free survival was better in the surgery group compared with the stent group (87.8% vs 73.8%), and only 3.5% in the surgery group required a second revascularization procedure. The stent or surgery (SoS) trial compared BMS and CABG in similar patients and reported a 21% 2-year target vessel revascularization (TVR) rate in stent patients versus 6% in CABG patients, with a similar death and MI rate in both groups. However, the SoS trial had a higher noncardiac death rate in the PCI arm, thought to be attributed to a type II error that may have affected the study results. Few stent patients in the SoS trial received glycoprotein (GP) IIb/IIIa receptor inhibitors. Still, this and the ARTS study do point to the safety of PCI treatment in multivessel disease. Mortality risk is low (discounting the noncardiac deaths) and the rates of need for repeat TVR have been halved. Drug-eluting stents and coronary artery bypass graft The use of DES was compared with CABG in stable angina populations in the ARTS II trial, which was a registry comparing sirolimus (Cypher) stent (SES) with the PTCA and CABG arms of the ARTS I trial. SESs were associated with an 8% MACE rate (13% for CABG in ARTS I) and an 8.5% TVR rate (4% for CABG and 21% for PTCA in ARTS I). The 1-year MACE rate was 10.5% for SES patients. Overall, DESs are equivalent to CABGs except in patients with diabetes where conflicting data exist. DES data show similar outcomes in the ARTS and AWESOME trials for patients with diabetes mellitus. The ongoing FREEDOM trial will compare DES and CABG in patients with diabetes and multivessel CAD. The SYNTAX trial is currently comparing paclitaxel (Taxus) stent (PES) and CABG in multivessel CAD that includes left main disease. COMBAT is a similar trial design using SES. Acute coronary syndromes The management of patients with non–Q-wave MI and unstable angina has changed considerably over the past 5 years. Before the widespread use of stents and GP IIb/IIIa receptor inhibitors, conventional balloon angioplasty in this subgroup of patients was associated with substantial risks, including MI (as much as 9%), restenosis (as much as 50%), need for emergency coronary bypass surgery (as much as 12%), and death (as much as 5%). The optimal strategy in patients presenting with acute coronary syndromes remains a controversial issue in contemporary cardiology. Several studies have investigated the use of a conservative strategy versus an early invasive strategy of revascularization for patients with unstable coronary syndromes. The Veterans Affairs Non–Q-Wave Infarction Strategies in Hospital (VANQWISH) trial compared an invasive strategy with conservative medical treatment in patients with non–Q-wave MI. The rates of death or nonfatal MI were higher in the invasive strategy group than in the conservative strategy group before hospital discharge, at 1 month, and at 1 year. Criticisms of this study include the following: (1) the exclusion of patients at very high risk, (2) the lack of current aggressive medical therapies, (3) a high rate of crossover to angiography in the conservative arm, (4) a higher surgical mortality rate than expected compared with contemporary standards, and (5) the observation that most of the complications at 30 days occurred in patients who underwent coronary artery bypass surgery and very few occurred in patients who underwent balloon angioplasty. In contrast to the VANQWISH trial, 3 randomized studies found that an early invasive approach in patients with acute coronary syndromes was associated with improved outcomes. Data from the Treat angina with Aggrastat and determine Cost of Therapy with an Invasive or Conservative Strategy-Thrombolysis in Myocardial Infarction (TACTICS-TIMI) 18 trial showed that the primary endpoint of death, MI, or rehospitalization at 6 months occurred in 19.4% of the conservative group versus 15.9% of the invasive group (P=0.0025) with the incidence of death and/or MI occurring in 9.5% versus 7.3%, respectively (P <0.05). Patients who had a positive troponin, who had ST segment changes, who were older than age 65 years, and especially women with elevated brain natriuretic peptide (BNP) and C-reactive protein (CRP) levels did particularly better from an early invasive strategy. Acute myocardial infarction The recognition that intracoronary thrombosis is the primary mechanism of vessel occlusion in acute MI and that prompt restoration of vessel patency provides significant clinical benefit has lead to the development of aggressive new treatments for this disorder. Thrombolytic therapies, such as front-loaded tissue plasminogen activator (t-PA), reteplase (r-PA), and tenecteplase (TNK), open approximately 80% of infarct-related vessels within 90 minutes, but only 50% will have normal (TIMI grade 3) flow. In addition, 10% of vessels opened by thrombolysis either reocclude or are the source for recurrent symptoms of angina. Because of these limitations to thrombolytic therapy, several randomized trials have evaluated mechanical revascularization, so-called primary angioplasty, in the setting of acute MI. A recent analysis of 23 trials confirms the superiority of primary angioplasty over fibrinolytic therapy in terms of adverse event and mortality reduction both in the short and long term. Overall, primary PCI was associated with significant reductions in death (P=0.0002), recurrent MI (P <0.0001), reinfarction (P <0.0001), and the combined end point of death, MI, and stroke. In the situation where patients are transferred from outside hospitals, primary angioplasty is often preferred to on-site fibrinolytic therapy for patients with the following: expected door-to-balloon time less than 90 minutes and symptom duration less than 3 hours, symptom duration more than 3 hours, cardiogenic shock, contraindications to fibrinolytic therapy, and age older than 75 years. The use of thrombolytic therapy and then referral for intentional PCI (facilitated PCI) has not been shown to be superior to primary PCI and may actually worsen outcomes with increased risk of stroke and bleeding (ASSENT 4). Recent data suggest that early use of GP IIb/IIIa inhibitors may help to achieve earlier infarct vessel patency and better outcomes during PCI. Whether this is so for all of these agents is being assessed in several studies. A recent meta-analysis has shown that abciximab is associated with a 46% reduction in death and reinfarction in primary PCI patients and the AHA/ACC STEMI guidelines currently recommend early use of abciximab in these patients. When fibrinolytic therapy is given but fails to produce ST resolution, then immediate PCI (rescue PCI) is recommended. Some of the most important considerations in providing effective primary PCI relate to the logistic issues and barriers that are known to exist: the PCI system or network, ambiguity of leadership and organization, protocols/care, pathways/interfacility transfer, and reimbursement issues are the main areas of contention. Studies of the US primary PCI sites that are considered the best (those sites who deliver door-to-balloon times consistently within 90 minutes, which is currently in about 5% of the US MI population) have identified the key determinants of shorter door-to-balloon times as the following: ECG being performed within 10 minutes, the ED independently making the decision to engage the catheterization laboratory team, and interdisciplinary teamwork. The key factor for effective primary PCI is timely reperfusion therapy. Recent studies from the National Registry of Myocardial Infarction (NRMI) data have shown that shortening door-to-balloon time to less than 90 minutes is associated with a reduction in mortality. In certain situations, timely reperfusion may be best achieved with fibrinolytic therapy if delays are likely in accessing primary PCI. From a procedural perspective, because primary PCI involves a thrombotic plaque, the potential risk of more complications exists, especially no reflow and distal embolization. These patients should achieve final TIMI 3 flow. Stenting plus GP IIb/IIIa inhibition has been shown to improve outcomes, reducing TVR and MI rates in comparison with balloon angioplasty. The use of adjunctive antithrombotic approaches, including early GP IIb/IIIa inhibition use and mechanical thrombectomy or embolic protection devices, is the subject of ongoing debate. Important issues remain as to which type of stent to use (DES or BMS), timing of antiplatelet therapy (both IV and oral), and whether a facilitated approach (using fibrinolytic therapy or GP IIb/IIIa inhibition) in a shorter time frame might provide better outcomes for certain patients. ADJUNCTIVE THERAPIES IN THE CATHETERIZATION LABORATORYSection 6 of 8
Aspirin and heparin have been the traditional adjunctive medical therapies for patients undergoing coronary angioplasty and have been shown to decrease complications following the procedure. Since 1994, several new antithrombotic drugs have been developed that have advantages over standard heparin therapy. Although an effective anticoagulant, heparin has several limitations, including variable pharmacokinetics requiring careful monitoring, inhibition by substances released from activated platelets, and an inability to inhibit fibrin-bound thrombin. To address these limitations, several direct thrombin inhibitors have been developed. Hirudin and bivalirudin (Angiomax) were evaluated in 2 multicenter trials. Both were found to be slightly better than heparin in preventing ischemic complications during balloon angioplasty, but they had no effect on restenosis rates. Low molecular weight heparins are also being substituted for standard heparin in some centers in patients with acute coronary syndromes and during coronary interventions. Newer factor IX and factor Xa inhibitors are being evaluated as potential alternative anticoagulants. However, recent trials have failed to show a significant difference in efficacy of factor Xa inhibition compared with unfractionated heparin (UFH). In the early days of stenting, multiple antiplatelet agents and warfarin were used in an attempt to prevent stent thrombosis, but thrombosis continued to occur in approximately 6% of patients. In elective situations, clopidogrel is most effective when given prior to PCI. In acute situations, this may not be practical and clopidogrel is often given after PCI. Concerns still exist in relation to risk of bleeding and platelet transfusion requirements in patients taking clopidogrel who require urgent CABG. However, as emergent CABG is rare, there may be time to risk-stratify patients and to give clopidogrel before cardiac catheterization. If CABG is required, the effect of clopidogrel usually diminishes within 5 days. Another important consideration is the dose of clopidogrel. If given 2 hours prior to PCI, 600 mg is recommended; if given more than 2 hours prior to PCI, then 300 mg is recommended. Some centers have even given 900 mg instead of 600 mg. At present, the ACC/AHA guidelines recommend giving 300 mg up to 6 hours prior to PCI. Development of newer intravenous antiplatelet therapies with shorter half lives may help to overcome these issues. Aspirin 325 mg should be given prior to all PCI and then maintained at 81 mg daily. All types of percutaneous coronary interventions result in disruption of the coronary endothelium, which leads to platelet activation. Activated platelets bind to the vessel wall (adhesion) and to each other (aggregation) and release numerous vasoactive compounds. Aspirin blocks the cyclooxygenase pathway and reduces thrombotic complications after balloon angioplasty. However, despite heparin and aspirin therapy, thrombotic complications are not eliminated. Further studies identified the importance of the GP IIb/IIIa receptor, which binds fibrinogen and mediates the cross-linking of platelets and platelet aggregation. The introduction of GP IIb/IIIa receptor inhibitors has had a major influence on current treatment strategies in the catheterization laboratory. Abciximab, tirofiban, and eptifibatide have all been shown to reduce ischemic complications in patients undergoing balloon angioplasty and coronary stenting. In primary PCI, GP IIb/IIIa receptor inhibitors have also been shown to improve flow and perfusion and to reduce adverse events. Abciximab may improve outcomes in patients when given prior to their arrival in the catheterization lab for primary PCI. A recent meta-analysis of GP IIb/IIIa inhibitor trials showed a significant reduction in early mortality rates when these agents are used during coronary intervention. The combined end point of death or MI was also reduced significantly at 30 days. Thus, these agents are effective at reducing ischemic complications of PCIs. However, they have not been shown to improve outcome in saphenous vein graft (SVG) PCI. MULTIMEDIASection 7 of 8
REFERENCESSection 8 of 8
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