Incremental diagnostic value of perivascular fat attenuation index for identifying hemodynamically significant ischemia with severe calcification

Abstract

To explore the incremental value of perivascular fat attenuation index (FAI) to identify hemodynamically signi cant ischemia in severe calci ed vessels. MethodsPatients who underwent coronary computed tomographic angiography (CCTA) examination at Chinese PLA General Hospital from 2017 to 2020 and subsequently underwent fractional ow reserve (FFR) examination within 1 month were consecutively included. Several CCTA-derived indices were measured, including the coronary artery calci cation score (CACS), lesion length, ≥CAD-RADS 4 proportion, perivascular FAI and CT-FFR. The included vessels were divided into a nonsevere calci cation group and a severe calci cation group according to the quartile of CACS. FFR ≤ 0.80 represents the presence of hemodynamically signi cant ischemia. ResultsA total of 124 patients with 152 vessels were included (age: 61.1 ± 9.2 years; male 64.5%). Signi cant differences in lesion length (28.4 ± 14.2 vs. 23.1 ± 12.3 mm, P = 0.021), perivascular FAI (-73.0 ± 7.5 vs. -79.0 ± 7.4 HU, P < 0.001) and CT-FFR (0.78 ± 0.06 vs. 0.86 ± 0.04, P < 0.001) were noted between the FFR ≤ 0.80 group (47 vessels) and the FFR > 0.80 group (105 vessels). Furthermore, the perivascular FAI in the FFR ≤ 0.80 group was signi cantly greater than that in the FFR > 0.80 group (nonsevere calci cation: -73.2 ± 7.5 vs. -78.2 ± 7.4 HU, P = 0.002; severe calci cation: -72.8 ± 7.7 vs. -82.7 ± 6.3 HU, P < 0.001). In discriminating hemodynamically signi cant ischemia, the speci city and accuracy of CT-FFR were signi cantly affected by severe calci cation, which demonstrated a signi cantly declining trend (P = 0.033 and P = 0.010, respectively). The diagnostic performance of CT-FFR in the severe calci cation group was lower than that in the nonsevere calci ed group. However, perivascular FAI showed good discriminative performance in the severe calci cation group. In combination with perivascular FAI, the predictive value of CT-FFR in identifying hemodynamically signi cant ischemia with severe calci cation increased from an AUC of 0.740 to 0.919. ConclusionFor coronary artery with severe calci cation, the diagnostic performance of CT-FFR in discriminating ow-limiting lesions could be greatly impaired. Perivascular FAI represents a potential reliable imaging marker to provide incremental diagnostic value over CT-FFR for identifying hemodynamically signi cant ischemia with severe calci cation.