SNOWMASS, COLO. – The residual SYNTAX score is a powerful indicator of 5-year all-cause mortality after percutaneous coronary intervention for triple-vessel or unprotected left main coronary artery disease, Dr. David R. Holmes Jr. said at the Annual Cardiovascular Conference at Snowmass.
Cardiologists will find the residual SYNTAX score enormously valuable in shared decision making as to whether an individual with complex coronary artery disease is a reasonable candidate for PCI or better off with coronary artery bypass graft (CABG), predicted Dr. Holmes, professor of medicine at the Mayo Clinic in Rochester, Minn.
“I think the residual SYNTAX score is incredibly important. We need to be cognizant of it in our patient selection. I think we’ll see more and more use of it going forward,” the cardiologist said.
The SYNTAX score, as well as the residual SYNTAX score, grew out of the SYNTAX trial (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery), a multicenter, prospective, randomized study of PCI versus CABG in 1,800 all-comers with triple-vessel or unprotected left main coronary artery disease (CAD) who were deemed eligible for both revascularization strategies. The trial was led by a who’s who of prominent American and European interventional cardiologists and heart surgeons, including Dr. Holmes (N. Engl. J. Med. 2009;360:961-72)
“SYNTAX is probably the most pivotally important trial in cardiovascular revascularization strategies in the past 10 years or so. An important thing to remember from this study is that the SYNTAX score should be used in all patients with multivessel disease,” he said.
The SYNTAX score (www.syntaxscore.com) is an objective, quantitative measure of CAD complexity that takes into account factors including total occlusions, lesion tortuosity and length, calcifications, and bifurcations. It was calculated preprocedurally in all study participants.
Five years of follow-up established the baseline SYNTAX score to be a useful guide as to whether surgery or PCI is the better strategy in a given individual. Patients in the top tertile for SYNTAX score, with a score of 33 or greater, had a significantly lower 5-year mortality if randomized to CABG: 11.4%, compared with 19.2% for PCI. Mortality didn’t differ between surgically and percutaneously revascularized patients with an intermediate-range SYNTAX score of 23-32, although the composite major adverse cardiac and cerebrovascular event (MACCE) rate was significantly lower in the CABG arm at 25.8%, compared with 36% for PCI. In contrast, among patients with a SYNTAX score of 22 or less, MACCE rates were similar regardless of treatment strategy.
Based on the 5-year MACCE rates, SYNTAX investigators estimated that 71% of all patients with triple-vessel or unprotected left main coronary artery disease are best treated with CABG, adding that, for the remaining 29%, PCI is “a very reasonable alternative” (Lancet 2013;381:629-38).
The mean baseline SYNTAX score in the trial was 28.4. The mean residual score was 4.5. The residual SYNTAX score measures the extent of remaining obstructive coronary disease after revascularization. SYNTAX investigators validated the residual SYNTAX score as a potent predictor of 5-year mortality and other adverse outcomes in a separate analysis of 5-year outcomes in the 903 subjects randomized to PCI.
This analysis was done to validate the concept of “reasonable incomplete revascularization,” which the SYNTAX investigators concluded was a residual SYNTAX score of 8 or less. That’s because 5-year all-cause mortality in patients with a residual SYNTAX score of greater than 0-8 wasn’t significantly different than the 8.5% rate in the 43% of PCI recipients with a residual SYNTAX score of 0, which is indicative of complete revascularization. In contrast, the 17% of patients with a residual score above 8 had a 35% mortality rate (Circulation 2013;128:141-51).
Dr. Holmes recommended that cardiologists who are considering whether to recommend PCI or CABG for patients with multivessel CAD make a baseline estimate of the likely residual SYNTAX Score based upon what they can reasonably expect to achieve with PCI. For example, if a patient has multiple total occlusions and the cardiologist isn’t comfortable tackling such lesions, the estimated residual SYNTAX score is likely to be sufficiently high to point to CABG as the better option.
“If you don’t think you can provide pretty complete revascularization to viable myocardium, then much more consideration should be given to surgery,” he said.
Dr. Holmes reported serving as a consultant to Boston Scientific, which funded the SYNTAX trial.