The noninvasive assessment of stenosis severity by calculating the functional SYNTAX score (FSS) using computed tomography angiography-derived fractional flow reserve (FFRCT) was shown to have a high degree of accuracy in detecting functionally significant lesions in patients with three-vessel coronary artery disease (CAD). The results of this analysis of a cohort of patients from the SYNTAX trial was presented May 22 during EuroPCR in Paris and simultaneously published in the Journal of the American College of Cardiology.

Using data from the SYNTAX II study, Carlos A. Collet, MD, et al., calculated the CTA-SS in 77 patients with three-vessel CAD to assess the feasibility of and validate the noninvasive functional SYNTAX score in ischemia-producing lesions. The risk reclassification was compared between the noninvasive FSS and the invasive physiological assessment. The diagnostic accuracy of FFRCT was assessed by the area under the receiver-operating characteristic curve.

Results showed that of the 77 patients, obtaining the CTA-SS was feasible in 86 percent and the noninvasive FSS was feasible in 80 percent. While the anatomic SYNTAX score was shown to be overestimated by CTA compared with conventional angiography, the calculation of the FSS yielded similar results between the noninvasive and invasive imaging modalities.

The authors also found that the noninvasive FSS reclassified 30 percent of patients from the high and intermediate SYNTAX score tertiles to the low-risk tertile, whereas the invasive functional SYNTAX score reclassified 23 percent of patients from the high and intermediate SYNTAX score tertiles to the low-risk tertile.

Furthermore, the diagnostic accuracy of FFRCT to detect functionally significant stenosis – based on an instantaneous-wave free ratio of 0.89 or less – revealed an area under the receiver-operating characteristics curve of 0.85 with a sensitivity of 95 percent, specificity of 61 percent, positive predictive value of 81 percent and negative predictive value of 87 percent.

In an accompanying editorial comment, Bjarne L. Nørgaard, MD, PhD, et al., note that this study may present a new era in the management of CAD and "the days of having patients going to the catheterization laboratory with nothing more than symptoms and a positive stress test result may be coming to an end." They add, "This study may be signaling a shifting paradigm with CAD diagnosed and thoroughly characterized non-invasively, revascularization planning made in a collaborative fashion integrating the heart team, and a wealth of non-invasive data that will hopefully lead to more effective and cost-efficient revascularization strategies."

Keywords: ROC Curve, Coronary Artery Disease, Constriction, Pathologic, Exercise Test, Tomography, X-Ray Computed, Sensitivity and Specificity, Radiographic Image Enhancement, Angiography, Catheterization, Cohort Studies

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