Researchers have confirmed that the extent of residual angiographic disease calculated using the residual SYNTAX score (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) or RSS has no association with ischemic events occurring subsequently in patients presenting with ACS. The study, published in JACC, reinforces the concept that functionally complete revascularization is applicable even in ACS patients.
Following angiography-guided percutaneous coronary intervention (PCI), the residual SYNTAX score was earlier shown to be a predictor of events. Although no utility was found in stable patients who underwent complete revascularization with fractional flow reserve (FFR) guidance, the ability of the RSS to predict outcomes in patients with acute coronary syndromes (ACS) was still unexplored. In order to assess this, a post hoc study was performed by Fearon et al. of the DANAMI-3-PRIMULTI, FAME, and FAMOUS-NSTEMI studies, where 547 patients presenting with ACS who received functionally complete revascularization (intervention in infarct- and non-infarct-related arteries with FFR 0.80 or below) were pooled. The primary endpoint was major adverse cardiac events (MACE) which was defined as a composite endpoint of all-cause death, nonfatal myocardial infarction, and any repeat revascularization. The RSS was based on the recalculation of the SYNTAX score after PCI. The differences in 2-year outcome were compared using the RSS subgroups: 0, 1 to <5, 5 to <10, ≥10 (where RSS = 0 represented angiographically complete revascularization).
Out of a total of 547 patients, there were 271 and 276 patients with unstable angina/non–ST-segment elevation myocardial infarction and ST-segment elevation myocardial infarction respectively. The mean RSS was found to be 6.7 ± 5.8. Overall, MACE at 2 years occurred in 12.6% of patients. A similar RSS was seen in patients with and without MACE in the 2 year period after achieving functionally-complete revascularization with PCI. (RSS: 7.2 ± 5.5 vs. 6.6 ± 5.9; p = 0.23). A similar incidence of MACE irrespective of the RSS subgroups was reflected by the Kaplan Meir curves which showed no difference in rates (p = 0.54). To sum it up, RSS was not a significant predictor of MACE or of each component of MACE, both with and without adjustment of clinical variables.
“Looking to the future, the ideal tool to guide revascularization strategy and predict cardiovascular outcomes in patients will require more than just visual anatomical assessment of coronary lesions. It will need to incorporate both angiographic and clinical variables, minimize intra- and interobserver variability, demonstrate “real-world” reproducibility, and perhaps above all, be user-friendly and minimize the number of input variables.” – Dr. C. Michael Gibson, M.D.
As similar findings have been demonstrated by Fearon’s group for stable patients receiving FFR-guided PCI, the investigators believe that these results are suggestive of the fact that functionally complete revascularization is applicable even in ACS patients with potentially vulnerable nonculprit stenoses. Additionally, the study does not support concerns regarding the safety and accuracy of FFR measurements in ACS patients in whom there is a potential for transient coronary microvascular dysfunction in the culprit vessel, and a known probability that nonculprit disease (which is not hemodynamically significant based on FFR) may trigger events following PCI for ACS.
Contemplating the implications of the study in an accompanying editorial, Dr. Marie-Claude Morice wrote, “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.” Nonetheless, while addressing the question of this score becoming obsolete, she noted, “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. Finally, although we have intuitively assumed that complete revascularization is a predictor of good outcomes in stable patients, it is reassuring to know that this also holds true for unstable patients with a less predictable prognosis.”
However, armed with the increasing use of quantitative coronary angiography (QCA), the availability of electronic medical records, and novel approaches for the evaluation of coronary stenosis, Dr. Michael Gibson, in his article in the Journal of Invasive Cardiology stated, “Looking to the future, the ideal tool to guide revascularization strategy and predict cardiovascular outcomes in patients will require more than just visual anatomical assessment of coronary lesions. It will need to incorporate both angiographic and clinical variables, minimize intra- and interobserver variability, demonstrate “real-world” reproducibility, and perhaps above all, be user-friendly and minimize the number of input variables.” Expressing his optimism in future research, he added, “A better tool is certainly within reach, and could lead to significant improvements in clinical outcomes and health care delivery.”
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