Visual estimations of the completeness of revascularization failed to predict subsequent cardiovascular events for patients with acute coronary syndromes (ACS) who underwent stenting guided by fractional flow reserve (FFR), researchers reported in the Journal of the American College of Cardiology.
Residual SYNTAX scores (RSS) were developed to quantitatively assess the angiographic completeness of revascularization following percutaneous coronary intervention (PCI). While higher RSS was initially associated with worse outcomes in patients following angiography-guided PCI, recent measures of the functional significance of stenosis such as FFR have been found to be more predictive.
In this study, which pooled results from FFR-guided arms of three clinical trials, the mean RSS was similar in patients who did and did not experience a major adverse cardiovascular event (MACE) within two years of receiving functionally complete PCI. Patients with MACE and without MACE had average RSS of 7.2 and 6.6, respectively, with higher scores demonstrating a greater degree of residual stenosis—or more coronary artery disease left untreated.
“With and without adjustment of clinical variables, RSS was not a significant predictor of MACE or of each component of MACE,” which included all-cause death, myocardial infarction or repeat revascularization within two years, reported Stanford University Medical Center cardiologist Yuhei Kobayashi, MD, and colleagues.
“These results suggest that an FFR-guided PCI strategy offers an appropriate level of revascularization even in ACS patients with potentially vulnerable nonculprit stenoses,” they wrote.
Previously, there had been concern over the applicability of FFR for ACS patients, the authors said.
“This stems in part from the potential for transient coronary microvascular dysfunction in the culprit vessel territory, which theoretically could involve nonculprit territories as well, leading to a blunted maximal coronary flow down the nonculprit vessels and a falsely elevated FFR," wrote Kobayashi et al. "Deferral of PCI on unrecognized significant disease could lead to increased event rates.”
But consistent with previous studies of patients with stable coronary disease, this report suggests ACS patients also may have decent outcomes with residual stenosis as long as it isn’t functionally significant. Vessel narrowing may be evident upon angiography but not particularly dangerous.
Limitations of the analysis include the pooling of FFR-guided PCI patients from three studies—which featured different designs, revascularization strategies and antiplatelet treatments—as well as the likelihood that some functionally significant stenoses were left untreated due to case complexity, operator discretion or procedural failure.
“Because this study is a post hoc analysis of the FFR-guided PCI arm of the three clinical trials, which were not designed to assess the impact of residual lesions after FFR-guided PCI, the results of the present study should be interpreted as hypothesis-generating,” Kobayashi et al. wrote.
In a related editorial, Marie-Claude Morice, MD, pointed out the SYNTAX score was originally developed to predict outcomes of patients with multivessel disease and more complex lesions than were included in this study (average RSS: 6.7). Nevertheless, she said Kobayashi and colleagues “should be praised for providing new and consistent data collected in patients with acute coronary syndromes in favor of revascularization prompted by functional criteria.”
“Their findings may help tip the balance in favor of systematic FFR-guided complete functional revascularization as the most appropriate strategy for predicting optimal outcomes despite the presence of potentially ‘active’ residual lesions, even in patients with unstable coronary disease,” she wrote. “Even though its value is currently being questioned, the SYNTAX score can be credited with having paved the way for the stratification of the huge undifferentiated mass of patients with multiple vessel disease.”
Daniel joined TriMed’s Chicago editorial team in 2017 as a Cardiovascular Business writer. He previously worked as a writer for daily newspapers in North Dakota and Indiana.