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Calculation of noninvasive functional SYNTAX score feasible, accurate
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The functional SYNTAX score can be calculated noninvasively and is comparable to calculations using invasive pressure-wire assessment, according to results of a SYNTAX II substudy.
The findings were presented at EuroPCR and simultaneously published in the Journal of the American College of Cardiology.
“The noninvasive [functional SYNTAX score] has the potential to individualize risk assessment, assist the heart team in the decision-making process prior to invasive angiography, and guide treatment planning in the noninvasive setting,” Carlos Collet, MD, from the department of cardiology at Academic Medical Center of Amsterdam, and colleagues wrote in the study background. “However, to date there is no data supporting the accuracy of this technology in patients with complex CAD.”
To assess the feasibility of and validate the noninvasive functional SYNTAX score in patients with three-vessel CAD compared with coronary angiography and instantaneous wave-free ratio, Collet and colleagues calculated the CT angiography SYNTAX score (CTA-SS) in patients included in the SYNTAX II study.
The researchers also aimed to compare the diagnostic accuracy of CT-derived fractional flow reserve (HeartFlow) to iFR.
The multicenter, all-comers, open-label, singe-arm study included 77 patients from 22 interventional cardiology centers from four European countries between February 2014 and November 2015.
According to the results, CTA-SS was feasible in 86% of patients and noninvasive functional SYNTAX score was feasible in 80% of patients.
Compared with conventional angiography, anatomic SYNTAX score was overestimated by CTA (27.6 ± 6.4 vs. 25.3 ± 6.9; P < .0001) and calculation of the functional SYNTAX score was similar between the noninvasive and invasive imaging modalities (21.6 ± 7.8 vs. 21.2 ± 8.8, respectively; P = .589).
The results of the study also showed that noninvasive functional SYNTAX score reclassified 30% of patients from the high- and intermediate-SYNTAX score tertiles to the low-risk tertile, whereas the invasive functional SYNTAX score reclassified 23% of patients from the high- and intermediate-SYNTAX score tertiles to the low-risk tertile.
The agreement on the classic SYNTAX score tertiles was low for the anatomic SYNTAX score (kappa statistic = 0.19) and fair for functional SYNTAX score (kappa statistic = 0.32), according to the researchers.
The diagnostic accuracy of FFR-CT to detect functional significant stenosis based on iFR of 0.89 or less was reflected in an area under the receiver operating characteristics curve of 0.85 (95% CI, 0.79-0.9), a sensitivity of 95% (95% CI, 89-98), a specificity of 61% (95% CI, 48-73), a positive predictive value of 81% (95% CI, 76-86) and a negative predictive value of 87% (95% CI, 74-94), Collet and colleagues found.
“Although invasive pressure-wire evaluation is steadily increasing, the National Institute for Health and Care Excellence guidelines have advocated the use of coronary CTA (with FFR-CT) as the first-line test for patients with suspected anginal pain,” the researchers wrote in JACC. “In the next decade, the use of coronary CTA is expected to increase 700%. The widespread adoption of these technologies brings the potential to change the clinical practice would be changed by refining the management of patients with CAD.”
According to an editorial in JACC by Bjarne Linde Nørgaard, MD, PhD, from the department of cardiology at Aarhus University Hospital, Denmark, and colleagues, the study presents a highly meaningful concept but has several limitations, including a small sample size and inadequate CT image quality for some patients.
“With all the limitations of this study acknowledged, these data suggest that we may be entering a new era in the management of CAD. The days of having patients entering the catheterization laboratory with nothing more than symptoms and a positive stress test result may be coming to an end,” they wrote. “This study may be signaling a shifting paradigm in which CAD is diagnosed and thoroughly characterized noninvasively, and revascularization planning made in a collaborative fashion integrating the heart team, and a wealth of noninvasive data that will hopefully lead to more effective and cost-efficient revascularization strategies.” – by Dave Quaile
References:
Collet C, et al. FFR-CT: A deep dive in Pacific, Syntax II substudy and Syntax III. Presented at: EuroPCR 2018; May 22-25, 2018; Paris.
Collet C, et al. J Am Coll Cardiol. 2018;doi:10.1016/j.jacc.2018.02.053.
Nørgaard BL, et al. J Am Coll Cardiol. 2018;doi:10.1016/j.jacc.2018.02.052.
Disclosures: Collet reports no relevant financial disclosures. Nørgaard reports he has received unrestricted institutional research grants from Edwards Lifesciences, HeartFlow and Siemens. Please see the full study and editorial for the other authors’ relevant financial disclosures.
Perspective
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Roxana Mehran, MD, MSCAI, FACC, FAHA, FESC
This is a small study, but it has very important implications. The investigators tried to see if we could classify patients using noninvasive FFR into SYNTAX scores using FFR-CT. In these patients, lesions were able to be reclassified similar to an invasive physiologic assessment. This is a very interesting way of us to be able to assess patient’s eligibility for PCI v. CABG and classifying their lesion severity non-invasively. This could allow the heart team to be more aware and fully engaged earlier than usual in patients with multivessel disease. We may be able to accurately downgrade or upgrade patients to bypass or PCI without an invasive measurement. Larger randomized studies are needed to validate these findings, but the feasibility of this approach has been shown and it could be an important game changer.
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