Revascularization Treatment Recommendations Based on Atherosclerotic Disease Distribution: Coronary Artery Bypass Grafting versus Stenting Kim I. de la Cruz, MD, Peter I. Tsai, MD, William E. Cohn, MD, and Denton A. Cooley, MD
Corresponding author Denton A. Cooley, MD Texas Heart Institute, MC 3-258, PO Box 20345, Houston, TX 77225, USA. E-mail:
[email protected] Current Atherosclerosis Reports 2008, 10:434 – 437 Current Medicine Group LLC ISSN 1523-3804 Copyright © 2008 by Current Medicine Group LLC
In patients with coronary artery disease, the need for more accurately defined treatment recommendations based on the distribution of atherosclerotic disease has given rise to multiple trials designed to evaluate the efficacy of medical therapy versus percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). To clarify these treatment recommendations, we reviewed relevant trials. Patients with chronic stable angina who have one-vessel or two-vessel coronary artery disease without involvement of the left main or left anterior descending coronary arteries fare similarly regardless of treatment modality. In contrast, patients with multivessel disease and inducible ischemia are better served by revascularization by either CABG or PCI. In patients who have left main involvement, diffuse disease with severe atherosclerosis, diabetes mellitus, advanced age, or left ventricular dysfunction, the outcome with regard to survival, anginal relief, and freedom from additional intervention is better with CABG than with PCI.
Introduction Studies have shown that medical management is as effective as coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI), defi ned as
coronary angioplasty with stenting, for treating patients with chronic stable angina and mild coronary artery disease (CAD). Patients with mild CAD are defi ned as those with one-vessel or two-vessel disease that does not involve the left main or left anterior descending (LAD) coronary artery [1, 2]. For the treatment of moderate to severe CAD, defi ned as disease involving three or more vessels with or without LAD involvement, revascularization, either by CABG or PCI, confers a survival advantage over medical therapy and relieves angina more effectively. Furthermore, patients with left main involvement or diffuse multivessel disease are better served by CABG than by PCI. This review evaluates recently published studies regarding the optimal treatment of CAD on the basis of disease distribution and describes the current standard of practice at the Texas Heart Institute (THI) in Houston.
Evolution of Therapy for CAD Treatment of CAD continues to evolve as available drugs and coronary revascularization technologies improve. In patients with chronic stable CAD, the treatment goal is to prevent myocardial infarction (MI) and sudden cardiac death and to relieve angina. Several treatment options are available, depending on disease severity and symptoms. Medical therapy and CABG have long been mainstays of disease management. In the 1980s, stents were developed as an important adjunct to balloon angioplasty. Since their fi rst clinical use in 1986, stents have been increasingly used as fi rst-line therapy for patients with CAD. Although bare metal stents (BMS) were approved by the US Food and Drug Administration in 1994 [3], these devices have been associated with a considerable incidence of in-stent restenosis and the need for reintervention. In 2003, drugeluting stents (DES) were introduced to address restenosis.
Coronary Artery Bypass Grafting versus Stenting
Trials comparing these two types of stents have shown that DES are superior to BMS with respect to early restenosis, the need for target vessel revascularization, and the incidence of other major cardiac events. Recent studies, however, suggest that DES may be associated with late stent thrombosis, raising concerns regarding their safety [4,5]. Nevertheless, DES are used extensively with excellent results and are considered first-line therapy at THI for patients with discrete branch lesions and appropriate anatomy.
Summary of Comparative Trials The most current guidelines for surgical revascularization, which were established jointly by the American College of Cardiology and American Heart Association, are the result of numerous studies done during the past 30 years to compare medical therapy with surgical revascularization and PCI. Although retrospective studies from established databases are limited by their potential selection bias, they represent a population that better reflects the “real-world” setting [6••]. Most randomized prospective studies are limited because they have small sample sizes and involve short follow-up periods. Moreover, because many patients who undergo PCI or CABG also receive medical therapy, including antiplatelet agents, statins, and β -blockers, attributing a clear benefit to any single therapy is challenging. In reviewing such studies, these limitations should be considered [7•]. Landmark studies such as the Coronary Artery Surgery Study (CASS) [8], the Veterans Administration Cooperative Study [9], and the European Coronary Surgery Study (ECSS) [10] showed that surgical revascularization had the greatest benefits in the highest-risk patients with chronic stable angina. Risk was determined by number of diseased vessels, severity of symptoms, and presence of left ventricular dysfunction. In patients with single-vessel disease, coronary revascularization did not offer a survival advantage over medical therapy. The Medicine, Angioplasty or Surgery Study-II (MASS-II) [11], which compared medical therapy, PCI, and CABG, also confi rmed that CABG offers better survival, relief of angina, and freedom from additional intervention in high-risk patients with multivessel disease than does PCI. It is important to note that not every patient in MASS-II underwent stent placement, and that the study was performed before the introduction of DES. Nevertheless, PCI was associated with a 14% need for subsequent revascularization and a 25% incidence of recurrent angina as compared with CABG, in which the incidence of need for repeat revascularization (0%) and postprocedural angina (6%) were considerably lower. In addition, MASS-II suggested that CABG improved the quality of life in low-risk patients, for whom no survival benefit was described. These fi ndings were confi rmed by retrospective studies that focused on the Duke Cardiovascular Disease Databank and the New York State Database [7•].
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Several studies of CABG versus PCI with stent placement in patients with isolated LAD disease have demonstrated similar results [12•,13]. The two treatment strategies were similar in the combined primary outcomes of MI, stroke, or death. Patients who underwent PCI had a significantly higher reintervention rate than those who underwent CABG. Although the Arterial Revascularization Therapies Study (ARTS) [14] showed no difference in mortality at 5 years in patients who received stents and in those who underwent CABG, the study population comprised mostly low-risk patients who represented only 5% of the patients screened. Patients were excluded if they had lesions unfavorable for PCI: chronic total occlusions, diffuse disease, high atherosclerotic burden, and complex lesions involving bifurcations. These exclusion criteria strongly biased results in favor of PCI. Nevertheless, the CABG group had lower postprocedural mortality, MI, stroke, and repeat revascularization rates at 5 years. The multicenter Argentine Randomized Trial of Coronary Angioplasty with Stenting versus Coronary Bypass Surgery in patients with Multiple Vessel Disease (ERACIII) [15,16] showed that the 30-day mortality was 5.6% for CABG patients versus 0.9% for stent recipients, but 5-year survival and freedom from nonfatal MI were similar in the two treatment groups. Subgroup analysis in ERACI-II (as well as in ARTS), however, showed a marked survival advantage for diabetic patients who underwent CABG as compared with those who underwent PCI. Moreover, freedom from repeat revascularization was noted in 71% of PCI patients and 92% of CABG patients, and freedom from major adverse cardiac events was 65% and 76% in the respective groups. Interestingly, the seven institutions involved in the study had an average annual CABG volume of only 57 cases, and internal mammary artery usage was only 89%; both of these statistics are modest by current standards and may have contributed to the somewhat high 30-day mortality reported. In the ARTS II trial, results with DES (Cypher; Johnson & Johnson, New Brunswick, NJ) were compared with the results in the CABG arm of ARTS I. ARTS II demonstrated a decreased incidence of death (1.0% vs 2.7%), stroke (0.8% vs 1.8%), and MI (1.0% vs 3.5%) for DES when compared with CABG, but showed a slightly higher need for subsequent CABG (2.0% vs 0.7%) or reintervention (5.4% vs 3.0%) in DES patients. This study clearly demonstrates the value of DES when used in appropriate patients. The advantage of several other types of DES over BMS has been shown in numerous studies, including TAXUS V [17 ] and SPIRIT III [18].
Current Practice at the Texas Heart Institute At THI, the current practice varies among practitioners, but some themes emerge (Table 1). Most patients who have insulin-dependent diabetes and left main, multivessel, or diffuse disease are referred for CABG. In addition,
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Clinical Trials and Their Interpretations
Table 1. Guidelines for the use of CABG versus PCI with stent placement Patient characteristics
Preferred treatment
CAD with diabetes mellitus
CABG
Multivessel disease
CABG
Left main CAD
CABG
Acute coronary syndrome Unfavorable lesions*
PCI CABG
Focal lesions
PCI
Severe comorbidities
PCI
No IMA available Diffuse disease Stable CAD without LAD artery lesion
PCI CABG PCI
Other lesion requiring surgery
CABG
Ejection fraction < 40%
CABG
No bifurcation lesions
PCI
*Long lesions, bifurcation lesions, or heavy calcification. CABG—coronary artery bypass grafting; CAD—coronary artery disease; IMA—internal mammary artery; LAD—left anterior descending; PCI—percutaneous coronary intervention.
patients who have undergone PCI and experienced significant in-stent restenosis are generally referred for surgery. CABG is also preferred for patients without diabetes in whom significant left main stenosis is present. However, stents are being used more often in patients with left main disease, especially in high-risk patients with discrete proximal lesions. Although long-term data are lacking, the use of stents for left main stenosis is an attractive option in patients with comorbidities that would increase the risk of surgical revascularization. In patients with chronic total occlusions, diffuse calcified vessels, and bifurcation stenosis involving significant branches, the technical challenges associated with achieving a successful PCI make CABG a better option. New tools and techniques are being developed to facilitate PCI in challenging patients, but intermediate-term and long-term data are not available. Moreover, refinements in surgical technique and the increased use of arterial conduits are improving surgical results, with many large centers like THI reporting a 30-day mortality of only 1% to 2%. The evolution of new approaches, including the ability to perform many CABG procedures without cardiopulmonary bypass, has improved results in some patients in whom cannulation or extracorporeal circulation would previously have had an adverse impact on outcome. Both surgeons and interventional cardiologists have a growing appreciation for PCI in very high-risk patients, even when the coronary anatomy is only marginally suitable. Patients with significant comorbidities that in the past would have prohibited surgical revascularization are now often treated with PCI at THI, even if only
partial revascularization can be achieved. This approach of incomplete revascularization is especially attractive in patients with acute or ongoing ischemia that would require a challenging reoperation or in whom coagulopathy is present, either due to cirrhosis or treatment with warfarin or clopidogrel. Occasionally, a “culprit vessel” PCI procedure, often done in conjunction with placement of an intra-aortic balloon pump, is used to stabilize the patient until the coagulopathy can be resolved. Then, CABG or reoperative CABG can be performed on a less urgent basis. Similarly, patients with left main stenosis who are considered poor operative candidates are frequently treated with PCI, even if the left main lesion is not ideally suited. New forms of temporary hemodynamic support, including percutaneous left ventricular assist devices [19], have had a favorable impact on the ability to perform PCI in challenging patients. Increased awareness of the importance of long-term antiplatelet therapy with clopidogrel and aspirin has increased the use of point-of-care assays to assess drug efficacy. Patients in whom side effects prohibit the use of these drugs or in whom effective platelet suppression cannot be demonstrated by assay are probably better served by CABG as primary therapy, even if their disease is amenable to catheter-based intervention. Extensive data demonstrate the outstanding long-term patency of grafts constructed from the in situ left internal mammary artery (LIMA) when used to bypass the LAD [20]. Because the evidence indicates that a patent LIMAto-LAD graft confers a significant survival advantage, many physicians believe that depriving a patient with extensive CAD from receiving such a graft is beneath the optimal standard of care. This enthusiasm for the LIMAto-LAD graft must be counterbalanced by the perceived morbidity of an open surgical procedure, which many patients wish to avoid. Significant technical advances have been made to reduce this perceived morbidity, such as the development of limited access procedures, the introduction of surgical telemanipulation “robots,” the use of off-pump CABG, and the creation of grafts using automated anastomotic devices. However, these new tools require additional development before they can be widely applied. Nevertheless, in the near future, a combination of closed-chest CABG and PCI used in a hybrid strategy may be a valuable tool in the treatment of CAD.
Conclusions Over the past two decades, continued refi nements in tools and techniques have improved results after CABG and PCI. Given the age and comorbidities of patients and the increasing complexity of cases that physicians are called upon to evaluate in the current era, an intimate familiarity with the benefits and limitations of the different approaches is essential in choosing the best option for each patient.
Coronary Artery Bypass Grafting versus Stenting
Disclosures No potential confl icts of interest relevant to this article were reported.
References and Recommended Reading Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
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