Coronary Revascularization in Context

Coronary artery bypass grafting CABG, introduced in 1968, was the only method of coronary revascularization until 1977, when percutaneous balloon angioplasty was first performed. The complications of balloon angioplasty (acute vessel closure in 3 to 5% of patients and restenosis in almost half) prevented its use in patients with severe coronary artery disease. In the 1990s, the introduction of bare metal stents led to reduced rates of these complications. The improved short term and long term procedural success with percutaneous coronary intervention (PCI) allowed for its safe and effective performance in patients with severe coronary artery disease. By the year 2000, more PCI procedures than CABG procedures were being performed in the United States. In early 2000, drug eluting stents were approved for use in Europe and North America, after studies showed a markedly reduced incidence of restenosis with drug eluting stents as compared with bare metal stents. Subsequently, the use of drug eluting stents was rapidly adopted; in 2006, a total of 253,000 CABG procedures and 1,131,000 PCI procedures were performed in the United States,1 with drug eluting stents used in 90% of the PCIs.
Do CABG and PCI result in similar outcomes? A recent review3 of 23 randomized, controlled comparisons of CABG and PCI (by means of balloon angioplasty or bare-metal stenting) in approximately 10,000 patients showed that CABG was superior to PCI in relieving angina and averting repeat revascularization procedures. The rates of survival at 1, 5, and 10 years were similar for the two procedures, even though CABG carried a higher risk of stroke (1.2%, vs. 0.6% with PCI). However, most of the 23 studies did not involve patients with severe coronary artery disease (left main or three-vessel coronary artery disease) and did not use the latest revascularization techniques.
In this issue of the Journal, Serruys et al. describe the Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX), in which 1800 patients with left main or three vessel coronary artery disease were randomly assigned to undergo CABG or PCI (with drug-eluting stents) to determine which was the better revascularization strategy. Previously published studies comparing the two procedures in such patients were single-center, nonrandomized trials with relatively small numbers of patients, and the results were inconsistent some5 showed that CABG was associated with fewer major adverse events, whereas others6,7,8 showed that the outcomes with CABG and with PCI were similar.
In the SYNTAX trial, patients treated with PCI involving drug-eluting stents were more likely than those undergoing CABG to reach the primary end point of the study death from any cause, stroke, myocardial infarction, or repeat revascularization — within 12 months after randomization (17.8% of patients vs. 12.4%). In an analysis of secondary end points, the two treatment groups had similar rates of death from any cause, stroke, or myocardial infarction (7.6% for PCI and 7.7% for CABG). Patients undergoing PCI were more likely than those undergoing CABG to require repeat revascularization (13.5% vs. 5.9%) but were less likely to have a stroke (0.6% vs. 2.2%). The investigators do not discuss whether the strokes were related to the procedure or whether the risk of having a stroke was influenced by differences between the two groups in the occurrence of atrial fibrillation, use of aspirin or other antiplatelet agents, or presence of risk factors for atherosclerosis.
The study has several notable strengths. First, it was a prospective, multicenter trial in which a large number of patients were enrolled at 85 centers in Europe and the United States. Second, it attempted to include all comers with left main or three-vessel coronary artery disease. In contrast to previously published comparisons of PCI and CABG, in which only about 10% of screened patients were included, the enrollment rate in the SYNTAX trial was impressively high, with 71% of screened patients enrolled in the randomized or registry cohorts. Third, the study used state of the art CABG and PCI (with arterial grafts and drug eluting stents, respectively), both with excellent results. Fourth, a heart team consisting of an interventional cardiologist and cardiac surgeon reviewed each subject s data (including findings on coronary angiography), after which they reached agreement on which procedure or procedures should be offered to that subject.
The study also has limitations. First and most important, the follow up period was only 12 months the outcomes of PCI and CABG over a longer period of follow-up in patients with severe coronary artery disease are unknown. Second, since most of the patients (78%) were men, it is unknown whether these findings are applicable to women. Third, the patients who underwent CABG were less likely to receive optimal medical therapy (statins, aspirin or other antiplatelet agents, and angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists), which may have contributed to their increased risk of stroke.
How should revascularization be accomplished in a patient with left main or three vessel coronary artery disease? All pertinent data, including that from diagnostic angiography, should be reviewed by a cardiac surgeon and interventional cardiologist to determine the likelihood of safe and effective revascularization with PCI and with CABG. To ensure this kind of thorough review, coronary revascularization should not be performed at the time of diagnostic angiography, thereby allowing the heart team sufficient time to review all the data, reach a consensus, and discuss the findings with the patient. In the SYNTAX trial, the time from diagnostic angiography to revascularization averaged 6.9 days in the PCI group and 17.4 days in the CABG group.
An occasional patient is unable or unwilling to take dual antiplatelet agents (aspirin and clopidogrel), which are necessary after placement of a drug eluting stent. In others, complete revascularization can be accomplished much more effectively with CABG than with PCI. Approximately one third of the patients in the SYNTAX study had one of these two issues. Such patients should be encouraged to undergo CABG. Conversely, patients with serious coexisting conditions or vessels unsuitable for grafting (about 5% of patients in the SYNTAX study) are poor candidates for CABG they should be encouraged to undergo PCI.
If safe and complete revascularization is feasible with either PCI or CABG as was true in roughly 60% of the patients in the SYNTAX study an assessment of coronary anatomical characteristics should be performed, and a SYNTAX score assigned.9,10 The presence of complex coronary anatomical features (assigned a high SYNTAX score) identifies patients with an increased risk of a suboptimal outcome with PCI they should be encouraged to undergo CABG. Conversely, patients with less complex coronary anatomical features (a low SYNTAX score) should be presented with the advantages and disadvantages of each procedure and allowed to choose between them. Irrespective of which procedure is performed, the patient should receive optimal medical therapy involving an antiplatelet agent (or agents), a statin, and an ACE inhibitor, if appropriate.
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