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PCI vs. CABG for Severe CAD: The SYNTAX Study
Abstract & commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Serruys PW, et al. Percutaneous coronary intervention versus coronary artery bypass grafting for severe coronary artery disease. N Engl J Med. 2009;360:961-972.
Revascularization, in conjunction with optimal medical therapy, remains a critical component in therapy for patients with obstructive coronary artery disease (CAD). Coronary artery bypass graft surgery (CABG) initially showed benefit over medical therapy and, subsequently, over percutaneous transluminal coronary angioplasty (PTCA) as well. Studies comparing percutaneous coronary intervention (PCI) in the era of bare-metal coronary stents (BMS) with CABG suggested CABG remained superior to PCI. However, PCI techniques have advanced rapidly over recent years, including the introduction of drug-eluting stents (DES), allowing more complex patient and lesion subsets to be treated percutaneously than in the past. Recent studies suggest that patients with multi-vessel CAD can be treated relatively safely with DES, albeit at higher risk for needing repeat revascularization than patients treated with CABG. Accordingly, the SYNTAX trial randomized patients with severe CAD to CABG or PCI with DES to determine the optimal approach to these patients.
This was a multi-center, randomized trial conducted at 85 sites, recruiting consecutive patients with severe, previously untreated CAD (triple-vessel or left-main disease) who could be treated with either PCI or CABG. Eligible patients were assessed by an interventional cardiologist and a cardiac surgeon at their local site. Those suitable for inclusion were then randomized to undergo CABG or PCI with DES, with the aim of complete revascularization of all vessels at least 1.5 mm in diameter and with at least 50% stenosis severity. Symptomatic angina, or ischemia, was an inclusion criterion. Exclusion criteria were history of prior PCI or CABG, acute myocardial infarction, and the need for concomitant cardiac surgery. For the CABG patients, internal mammary artery grafting of the left anterior descending artery was recommended and, in patients younger than 70 years of age, arterial revascularization was recommended; all other surgical techniques were at the surgeon's discretion. In the PCI arm, standard PCI techniques were recommended and clopidogrel was preloaded and continued for at least six months.
After screening 4,337 patients, 1,800 patients were randomized to receive PCI (n = 903) or CABG (n = 897). The baseline characteristics were well matched between groups, with mean age 65 years, 77% male, 25% diabetics, and BMI 28 in each group. The only differences were slightly more patients with hypertension in the PCI arm and more patients with elevated triglycerides and low HDL in the CABG arm. Time-from-randomization, procedure duration, and length of hospital stay after the procedure were significantly longer in the CABG arm, with complete revascularization achieved more often (63% vs 57%; p = 0.005). Both the PCI and CABG arms enrolled high-risk patients, with no differences seen in terms of euroSCORE, Parsonnet score, or SYNTAX score between the groups. A mean of 4.4 lesions per patient were treated in both groups. In the CABG group, 97.3% of patients had arterial grafts, with an average of 2.8 conduits and 3.2 distal anastomoses per patient. In the PCI group, more than four stents were placed per patient on average; 14% had staged procedures and 63% had at least one bifurcation or trifurcation lesion.
The primary outcome was 12-month major adverse cardiac or cerebrovascular event (MACCE) rate, which included death, myocardial infarction (MI), stroke, and revascularization. CABG had a lower rate of the primary endpoint than PCI (12.4% vs. 17.8%, p = 0.002); thus, the non-inferiority endpoint for PCI was not met and CABG was considered superior. Similar MACCE rates were observed when analysis was performed on an as-treated and intention-to-treat basis. There was no difference between the rates of death (4.4% vs. 3.5%; p = NS) or MI (4.8 vs. 3.3; p = NS) between PCI and CABG, respectively. CABG resulted in a significantly higher stroke rate than PCI (2.2% vs. 0.6%; p = 0.003), and PCI resulted in a higher rate of revascularization (13.5% vs. 5.9%; p < 0.001), which was the primary driver of the higher overall MACCE rate with PCI. The rates of symptomatic graft occlusion and stent thrombosis were similar. When outcomes were analyzed based on the complexity of the coronary artery disease, as assessed by the SYNTAX score, CABG performed well regardless of the complexity of the disease. PCI, on the other hand, had higher MACCE rates in patients with a high SYNTAX score, compared to those with a low or intermediate score. Similarly, PCI resulted in similar rates of MACCE compared to CABG in patients with low or intermediate SYNTAX scores, although CABG performed better in those with high SYNTAX scores. Serruys et al concluded that CABG, as compared to PCI, is associated with a lower rate of MACCE at one year among patients with three-vessel or left-main CAD (or both) and should, therefore, remain the standard of care for such patients.
The SYNTAX study provides important new insights into the most appropriate methods for revascularization for patients with severe CAD. CABG continues to be an excellent choice for revascularization, providing low adverse event rates and freedom from the need for repeat revascularization. PCI with DES performed well in this all-comer design trial in severe CAD. This study gives us more detail to discuss with patients when deciding on the options of CABG or PCI for severe CAD. Both therapeutic options are likely to results in similar rates of death or MI; CABG is likely to reduce the need for repeat revascularization, and PCI is likely to result in a lower rate of stroke. Importantly, the decision of which option to pursue was not made on the cath lab table. The procedure was stopped after the diagnostic angiogram, and discussion occurred between the cardiologist and the cardiac surgeon. Now we are able to allow patients to make a more informed decision, but only after a comprehensive discussion has occurred.
It should be noted that the trial was sponsored by the manufacturer of paclitaxel-eluting stents, and yet, the study was, if anything, biased against PCI by inclusion of revascularization as an endpoint. Why this combined endpoint was chosen is not immediately clear. Furthermore, all stents used in this study were paclitaxel-eluting stents, and the results may not exactly extrapolate to other stent types. In fact, other stent types may have lower rates of revascularization based on previous clinical trials.
The inclusion of the SYNTAX score is invaluable. This score gives a numerical value to the complexity of the coronary artery anatomy, something that is often overlooked in the debate between PCI and CABG. In a subgroup analysis, Serruys et al demonstrate that patients with less complex anatomy perform just as well with either PCI or CABG, but that CABG outperforms PCI in patients with more complex anatomy. Although that may seem self-evident, Serruys et al should be congratulated on formally studying this type of variable. The decision to pursue PCI or CABG on an individual patient can now be better informed, rather than considering one option superior to the other in all cases. The SYNTAX trail provides us with valuable new information in treating patients with severe CAD.