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FFR-CT in Patients With Multivessel CAD
Study Questions:
How does a noninvasive functional SYNTAX score (FSS) using coronary computed tomography angiography (CCTA) compare to an invasive functional SYNTAX score?
Methods:
This study examined 73 patients with three-vessel coronary artery disease (CAD) undergoing CCTA prior to physiology-guided percutaneous coronary intervention as part of the SYNTAX II study (A Trial to Evaluate a New Strategy in the Functional Assessment of 3-Vessel Disease Using SYNTAX II Score in Patients Treated With PCI). Patients with left main disease were excluded. Agreement between noninvasive FSS and invasive FSS was evaluated. Noninvasive FFS used anatomy from CT and fractional flow reserve derived from CT (FFR-CT); invasive FFS used invasive coronary angiography with instantaneous-wave free ratio (iFR).
Results:
Noninvasive FFS was feasible in 53/77 individuals (69%). Noninvasive and invasive FSS was not significantly different (21.6 ± 7.8 vs. 21.2 ± 8.8, p = 0.59). Noninvasive FSS reclassified 30% of patients from intermediate/high-risk tertiles to a low-risk tertile, while invasive FSS reclassified 23% of patients from intermediate/high-risk tertiles to a low-risk tertile. The agreement on tertiles based on Kappa statistics was fair for FSS (Kappa = 0.32). The diagnostic accuracy of FFR-CT to detect functional significant stenosis in comparison to iFR revealed an area under the curve of 0.85 with a sensitivity of 95%, specificity of 61%, positive predictive value of 81%, and negative predictive value of 87%.
Conclusions:
Noninvasive FFS was feasible in over two thirds of individuals with three-vessel CAD and resulted in a similar mean score in comparison to invasive FFS. FFR-CT has excellent sensitivity, but only moderate specificity for identification of functionally significant lesions in these individuals.
Perspective:
The addition of invasive functional information to the SYNTAX score has been associated with fewer patients identified as high risk, and improved clinical outcomes in comparison to the anatomic SYNTAX score. This predefined substudy from the SYNTAX II trial compares a CT-derived FFS to invasive FFS in a subset of patients with available CCTA. Noninvasive FFS was only feasible in 69% of these individuals with three-vessel CAD. In this small cohort, there was no difference in mean values of FFS between noninvasive and invasive methods, although the agreement was only fair. Further, while FFR-CT had high sensitivity to identify functionally significant lesions, it had limited specificity. If confirmed in larger studies, these findings could suggest a possible future role of noninvasive FFS, particularly given its currently observed high sensitivity and negative predictive value.
Keywords: Angiography, Cardiac Surgical Procedures, Coronary Angiography, Coronary Artery Disease, Constriction, Pathologic, Diagnostic Imaging, Fractional Flow Reserve, Myocardial, Myocardial Ischemia, Percutaneous Coronary Intervention, Tomography, X-Ray Computed
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