Impact of vessel morphology on computed tomography derived fractional flow reserve (FFRCT) in normal coronary artery disease: a novel marker for the predictor of FFRCT changes

Computed tomography (CT) derived fractional flow reserve (FFRCT) decreases continuously from the proximal to the distal segments of the vessel even in normal coronary arteries. It has been empirically proved that the degree of FFRCT decline varies based on vessel morphology even in the same vessel length.

To investigate the vessel morphological factors that influence FFRCT in normal coronary arteries.

A total of 1402 outpatients with suspected CAD who underwent CT angiography (CTA) with FFRCT analysis between January 2017 and October 2021 were evaluated. Among them, 234 consecutive patients who underwent both CT angiography including FFRCT and invasive coronary angiography, resulting in <20% stenosis in right coronary artery (RCA) were evaluated. RCA vessels from ostium to just proximal site of the posterior descending branch were analysed and divided into two groups according to distal FFRCT: FFRCT >0.80 (n=219) and FFRCT ≤0.80 (n=15). FFRCT was measured at proximal and distal segments of the RCA. Vessel morphology (vessel length, lumen diameter and volume, and plaque volume) and left ventricular mass were assessed. The ratio of lumen volume and vessel length was defined as the V/L ratio.

Whereas vessel length was almost the same between FFRCT >0.80 and ≤0.80 (>0.80 vs. ≤0.80, 115.9±17.3 vs. 119.6±28.7 mm), lumen volume (1135.2±369.3 vs. 906.2±362.6 mm³, p<0.05) and V/L ratio (9.8±2.6 vs. 7.5±2.3, p<0.01) were significantly higher in FFRCT >0.80. Distal FFRCT correlated with plaque-related parameters [low-attenuation plaque, intermediate-attenuation plaque, and calcified plaque (CP)] and vessel-related parameters (proximal and distal vessel diameter, vessel length, lumen volume, and V/L ratio). Among all vessel-related parameters, V/L ratio showed the highest correlation with distal FFRCT (r=0.44, p<0.0001) (Figure 1). Multivariable analysis showed that CP volume was the strongest predictor of distal FFRCT (β-coefficient = −0.38, p<0.0001), followed by V/L ratio (β-coefficient = 0.95, p=0.007). V/L ratio was the strongest predictor of a distal FFRCT ≤0.80 (cut-off 8.2, AUC 0.73, sensitivity 66.7%, specificity 69.3%, 95% CI 0.60–0.86) (Figure 2).

Our study findings suggest that the V/L ratio can be a measure to predict subclinical coronary perfusion disturbance.

Type of funding sources: None.