SYNTAX defines borders between CABG and PCI with TAXUS drug-eluting stents

Coronary artery bypass grafting (CABG) should remain the "standard of care" for patients with complex coronary artery disease, concludes the SYNTAX study, published in the New England Journal of Medicine (online February 18, 2009, Print edition March 5).

The SYNTAX study, led jointly by Patrick Serruys from Erasmus University Medical Center (Rotterdam, the Netherlands) and Fred Mohr from the University of Leipzig (Germany), set out to compare CABG and PCI using DES to investigate whether the situation has changed. The findings of the SYNTAX study were first presented at the European Society of Cardiology meeting in Munich, August 30 to September 3, 2008.

Improved technology is making it possible to treat increasingly complex coronary artery lesions with percutaneous coronary intervention (PCI), a technique first introduced in 1977. But studies comparing PCI using bare metal stents (BMS) with CABG - such as the ARTS I, SoS and MASS II studies - showed that higher rates of repeat revascularization procedures were needed following PCI. Set against this background, other studies have been showing that newer drug eluting stents (DES) require less repeat revascularization than the older BMS.

Commenting on the study, Dr William Wijns, spokesperson for the European Society of Cardiology and president of the European Association for Percutaneous Cardiovascular Interventions (EAPCI) said: "The SYNTAX study shows the importance of including both interventional cardiologists and cardiac surgeons in the decision making process. The fact SYNTAX concludes CABG should be considered the standard of care means all centres should be standing back and considering it."

But before drawing any firm conclusions from the SYNTAX data, he cautioned, it is important to wait for the two year update, expected to be presented at the European Society of Cardiology annual meeting in September 2009. "The big caveat with SYNTAX is that with CABG the highest risk of problems occurs in the first month following surgery, but with PCI problems gradually increase with time. It's therefore possible that the two year data will show the curves diverging."

Commenting on the SYNTAX score data for PCI, Dr Wijns said that wider use of the scoring system would provide clarity on which patients were most appropriate for different procedure. "Until now the borders between PCI and CABG have been quite blurred, but these results show that PCI can give excellent results in a predefined lower to intermediate risk sub group, but that it's not appropriate for high risk groups," he said, adding that he looked forward to the score becoming widely available so that clinicians could use it in the decision making process.

The European Society of Cardiology has recently set up a new joint task force with the European Association for Cardio Thoracic Surgery to produce guidelines on revascularization procedures. "Previously we had guidelines looking at PCI, but this time we plan to have guidelines reviewing the clinical issue of choosing the best revascularisation procedure for different patients," said Dr Wijns. The American College of Cardiology Foundation , Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgery have recently published guidelines (online JACC, Jan 5 2009) reviewing appropriate revascularization procedures in 180 different clinical scenarios. These guidelines, however, were prepared prior to the availability of SYNTAX results.

Between March 2005 and April 2007, 1800 patients with three-vessel or left main coronary artery disease (considered the most complex cases), from 62 sites in Europe and 23 sites in North America, were randomly assigned to undergo CABG or PCI in a 1:1 ratio. Patients were only entered into the randomisation if an interventional cardiologist and cardiac surgeon both judged that they could achieve equivalent results with either procedure. Patients for whom only one treatment option was considered suitable were entered into either a PCI registry (n=198) or a CABG registry (n=1,077), with data reported separately.

Results at 12 months show that the rates of major adverse cardiac or cerebrovascular events (defined as the primary end point for the study) were significantly higher in the PCI group than the CABG group (17.8 % versus 12.4%, P=0.002). The differences could be largely accounted for by patients in the PCI group requiring increased repeat revascularization. Altogether 13.5 % of patients in the PCI group underwent repeat revascularization compared to 5.9 % in the CABG group (P<0.001).

At 12 months the rates of overall death (defined as the secondary end point) were similar for the two groups – 3.5 % in the CABG group versus 4.4% in the PCI group ( P=0.37). Stroke, however, was significantly more likely to occur in the CABG population - 2.2 % of CABG patients experienced stroke compared with 0.6 % of PCI patients (P=0.003).

For the first time investigators used a measure known as the SYNTAX score, which had been designed to evaluate the complexity of the coronary disease. By splitting the population in tertiles, a low score was defined as less than 22, an intermediate score as between 23 and 32 and a high score as greater than 33. For patients receiving CABG, the major adverse cardiac or cerebrovascular events were similar in all three SYNTAX score groups. In contrast, for patients receiving PCI, the rate of major adverse cardiac or cerebrovascular events was 23.4 % for those with high SYNTAX scores, 16.7 % for those with intermediate scores and 13.6 % for those with low scores. For high versus low scores P=0.002.

In an accompanying editorial Richard Lange and David Hillis, from the University of Texas Health Science Center in San Antonio, considered the increased risk of stroke in CABG patients. "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*," they write.