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SYNTAX at 10 Years: Bypass vs PCI Still a Toss-Up Overall

— But CABG beats stenting for important subgroups

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PARIS -- With outcomes data spanning over a decade, an extension study of confirmed that certain patients with complex coronary lesions get different benefits from coronary artery bypass grafting (CABG) and stenting.

Overall, mortality curves did not diverge over time for SYNTAX participants now included in the trial's extension study SYNTAXES: by 1o years, all-cause death reached 27.0% among those randomized to percutaneous coronary intervention (PCI) and 23.5% of the CABG arm (HR 1.17, 95% CI 0.97-1.41), according to Daniel Thuijs, MD, of Erasmus University Medical Centre in Rotterdam, the Netherlands.

However, people with three-vessel disease had particularly high mortality when assigned to PCI in lieu of CABG (27.7% vs 20.6%, HR 1.41, 95% CI 1.10-1.80), whereas peers with left main disease were no worse off after either procedure (26.1% vs 26.7%, HR 0.90, 95% CI 0.68-1.52), Thuijs told the audience during a late-breaking trial session at the European Society of Cardiology's . The study was also published online in .

Type of coronary disease thus mattered in CABG's survival benefit (P=0.019 for interaction).

There was no formal treatment-by-subgroup interaction according to ordered SYNTAX score tertiles, but a numerical trend did suggest greater benefit to CABG with higher SYNTAX score in three-vessel disease.

"According to our prespecified subgroup analyses, patients with more complex coronary disease (e.g., three-vessel disease and those with ) continued to derive a benefit of CABG over PCI beyond the 5-year follow-up," the authors suggested.

It was "reassuring" that people in the lower SYNTAX score groups did not experience a "catch-up phenomenon" in mortality following PCI as they continued to do as well as the CABG patients, commented Andreas Baumbach, MD, of Queen Mary University of London and Barts Heart Centre.

However, PCI was associated with more all-cause death (34% vs 29%, HR 1.18, 95% CI 1.00-1.39) at maximum follow-up (median 11.2 years). The SYNTAXES investigators cautioned that this is a hypothesis-generating result given the limited power.

Then there is the question of whether one should be thinking about SYNTAX score as a gradient.

It's really about high versus "not-high" SYNTAX scores, commented session discussant Gregg Stone, MD, of Columbia University Medical Center/NewYork-Presbyterian and the Cardiovascular Research Foundation in New York City. He also suspected that the SYNTAX score is overestimated in left main disease.

Ultimately, the decision of how to revascularize patients with three-vessel disease or left main coronary artery disease should be made by a multidisciplinary heart team that considers the presence or absence of mortality differences in patient subgroups, overall , and other cardiovascular risk factors of the individual, Thuijs' team urged.

"With longer-term outcome data now available, there is, in the absence of medical contraindications or patient preference, a clear mandate to expand the role of CABG and to adopt a more cautious indication for PCI," argued David Taggart, MD, of John Radcliffe Hospital in Oxford, England, and Domenico Pagano, MD, of University Hospital Birmingham, England.

From NOBLE, EXCEL, and other studies, there are no statistically powered data to support the equivalence of PCI in left main coronary artery disease even in lower-severity anatomical disease, while other data strongly suggest the superiority of CABG, the pair wrote in an .

SYNTAX was a non-inferiority trial involving 1,800 patients with de novo three-vessel and/or left main coronary artery disease randomized to CABG or PCI with the Taxus drug-eluting stent. Upon enrollment, the cohort averaged age 65 years and under a quarter were women. Mean SYNTAX score was 29.

Information on vital status at 10 years was complete for 94% of patients.

Like patients with left main disease, those with diabetes experienced similar mortality in the decade following stenting or surgery (HR 1.10, 95% CI 0.80-1.52).

"This finding is in contrast to that of the -- the most definitive trial of CABG versus PCI in patients with diabetes -- which reported an accelerating survival benefit with CABG with extended follow-up," Taggart and Pagano noted.

Cause of death could not be determined in the study, SYNTAXES investigators said, nor could they analyze other outcomes such as MI, stroke, and stent thrombosis. There was also no data available on crossovers over the whole 10-year period.

Baumbach cited use of the Taxus stent -- now discontinued -- as a limitation to SYNTAX, and cited NOBLE and EXCEL -- testing left main stenting with newer products against CABG -- as perhaps more relevant. The two trials have years to go before reaching 10-year follow-up, however.

But Stone argued that SYNTAX still applies today because, although PCI outcomes are improving, so are those of surgery.

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    Nicole Lou is a reporter for Ƶ, where she covers cardiology news and other developments in medicine.

Disclosures

The extended SYNTAX trial was funded by the German Foundation of Heart Research.

SYNTAX was funded by Boston Scientific.

Thuijs, Stone, and Taggart disclosed no conflicts.

Baumbach reported receiving institutional research support from Abbott Vascular; and consultation and speaker fees from AstraZeneca, Sinomed, Microport, Abbott Vascular, Cardinal Health, KSH, Medtronic.

Pagano is the Secretary General of the European Association for Cardiothoracic Surgery.

Primary Source

European Society of Cardiology

Thuijs DJFM, et al "SYNTAX Extended Survival (SYNTAXES) trial: ten-year survival in patients randomized to percutaneous coronary intervention versus coronary artery bypass grafting in the randomized SYNTAX trial" ESC 2019.

Secondary Source

European Society of Cardiology

Stone GW "Ten-year survival in patients randomized to PCI versus CABG: the SYNTAX extended study (SYNTAXES) study" ESC 2019.

Additional Source

The Lancet

Taggart DP, Pagano D "Expansion or contraction of stenting in coronary artery disease?" Lancet 2019; DOI: 10.1016/S0140-6736(19)32040-9.