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CT-derived FFR yields higher diagnostic performance than coronary CTA alone
Compared with coronary CTA interpretation alone, CT-derived fractional flow reserve yields higher diagnostic performance and differentiation of ischemia among patients and vessels with high Agatston scores, according to recent findings.
In a substudy of the prospective, multicenter NXT trial, researchers measured coronary calcification with the Agatston score in 214 patients with suspected CAD who underwent coronary CTA, CT-derived fractional flow reserve (FFR-CT) and FFR in 333 vessels.
The researchers evaluated FFR-CT of 0.8 or lower for the detection of vessel-specific ischemia across Agatston score quartiles. They assessed the performance of FFR-CT in patients and vessels with low-mid (quartiles 1 through 3) vs. high (quartile 4) Agatston scores. Coronary CTA stenosis was defined as lumen reduction greater than 50% in a major epicardial segment of at least 2 mm in diameter.
The mean per-patient Agatston score was 302 ± 468 and the mean per-vessel Agatston score was 95 ± 172. No statistically significant disparities were observed in the diagnostic accuracy, sensitivity or specificity of FFR-CT across the quartiles of Agatston scores. FFR-CT showed high discrimination of ischemia among patients with high Agatston scores (416-3,599) and low-mid Agatston scores (0-415), with no disparity in area under the curve (AUC; 0.86; 95% CI, 0.76-0.96 vs. 0.92; 95% CI, 0.88-0.96). Likewise, FFR-CT demonstrated high discrimination in vessels with high Agatston scores (121-1,703) and low-mid Agatston scores (0-120; AUC, 0.91; 95% CI, 0.85-0.97 vs. 0.95; 95% CI, 0.91-0.98). FFR-CT showed higher diagnostic accuracy and specificity than CTA stenosis interpretation in each Agatston score quartile at the per-patient (P < .001) and per-vessel level (P < .05) with comparable sensitivity, the researchers wrote. In vessels with high Agatston score, FFR-CT demonstrated improved differentiation of ischemia vs. coronary CTA alone (AUC, 0.81 vs. 0.71; P = .004), although this difference was not statistically significant at the per-patient level (AUC, 0.86 vs. 0.72; P = .09).
“The findings in this study support the potential of FFR-CT as a reliable gatekeeper to [invasive coronary angiography] and coronary revascularization across a representative cohort of patients,” the researchers wrote. “Moreover, the high diagnostic performance of FFRCT in patients with coronary calcification, together with future improvements in [CT] spatial resolution and/or FFR-CT technology, may potentially expand the eligibility of coronary CTA testing to patients with higher pre-test probability of disease.” – by Jennifer Byrne
Disclosure: Nørgaard reports receiving research grants from Edwards Lifesciences. Please see the full study for a list of all other authors’ relevant financial disclosures.