The SYNTAX trial cracked open the door for the use of PCI as a treatment option for select patients with complex coronary artery disease (CAD). Since the trial's enrollment closed, refinements in technologies and techniques continue to nudge the door wider for PCI at the same time that longer-term data from SYNTAX shine favorably on CABG for higher-risk patients. But the verdict is still out on how best to treat patients with multivessel or left main coronary disease if they are not clear-cut candidates for either procedure.PCI ventures into left main
"The results of the SYNTAX trial were more positive for left main disease and somewhat less positive for complex triple-vessel disease than were anticipated [for PCI]," says Gregg W. Stone, MD, director of the medical research and education division at the Cardiovascular Research Foundation and director of cardiovascular research and education at the Center for Interventional Vascular Therapy at New York-Presbyterian Hospital/Columbia University Medical Center in New York City. "From SYNTAX, left main PCI in particular got out of Class III 'stent jail' and went to Class IIA/IIB in the guidelines."
SYNTAX compared PCI using paclitaxel-eluting stents (Taxus, Boston Scientific) with CABG surgery in 1,800 patients with untreated left main CAD, three-vessel disease or a combination of both diseases in a randomized trial (N Engl J Med 2009;360:961-972). First-year results showed less invasive PCI with a higher rate of major adverse cardiac or cerebrovascular events (MACCE) of 17.8 percent vs. 12.4 percent for CABG, prompting investigators to conclude that CABG should remain the standard of care. But each method or approach had its drawbacks: in the case of PCI, a revascularization rate of 13.5 percent compared with 5.9 percent for CABG; and in CABG, a higher rate of stroke, at 2.2 percent vs. 0.6 percent for PCI.
The picture has changed over time though, particularly when the SYNTAX score entered the equation. The SYNTAX score assesses CAD in a calculation that includes the location, extent and severity of coronary stenosis, with scores ranked as low (22 or below), intermediate (between 23 and 32) and high (33 and above). Three-year SYNTAX results presented at the 2010 European Association of Cardiothoracic Surgery meeting in Geneva gave a nod to PCI, showing that while overall MACCE rates remained higher in the PCI group, cumulative MACCE rates for patients with a low score were nearly identical in both the PCI and CABG groups.
Four-year results, unveiled at TCT.11 in San Francisco, showed a cumulative MACCE rate for the low SYNTAX score left main subset of 26 percent for PCI and 28.4 percent for CABG. When broken down by complexity of the disease, though, PCI appeared to benefit patients with left main only and left main plus single-vessel diseases but not patients with more complex disease states.
"In isolated left main disease and low SYNTAX score left main disease, the outcomes appear equivalent with CABG and PCI at four years," says Michael J. Mack, MD, medical director of cardiovascular surgery at Baylor Health Care System in Dallas, and a member of the writing panel for the American College of Cardiology (ACC) and American Heart Association (AHA) 2011 CABG guidelines. In a collaboration with the 2011 PCI guideline writers, the authors of each publication offered identical recommendations in sections dealing with PCI and CABG to ensure interventional cardiologists and cardiac surgeons receive the same guidance.
"That is what drove the guidelines to change in terms of upgrading PCI in left main disease," says Mack, who also is president of the Society of Thoracic Surgeons (STS). CABG to improve survival in significant left main CAD received a Class I level recommendation in the 2011 guidelines. PCI was elevated from a Class III "no benefit/harm" designation to a Class II "may be considered" ranking and was deemed an acceptable alternative to CABG for left main disease patients with a low SYNTAX score (J Am Coll Cardiol 2011;58;e44-e122).
"In left main with multivessel disease or SYNTAX scores higher than 33, there is a mortality benefit to surgery," Mack adds. "It is not appropriate to use PCI in those patients." CABG also was associated with better outcomes for patients with diabetes mellitus.
The multivessel milieu
The use of PCI has outpaced CABG in recent years. An analysis of coronary revascularizations in the U.S. concluded that the annual CABG surgery rate