Impact of vascular morphology and plaque characteristics on computed tomography derived fractional flow reserve in early stage coronary artery disease

BACKGROUND: Computed-tomography (CT) derived fractional-flow-reserve (FFRCT) gradually may decrease from proximal to distal vessels even without apparent coronary artery disease (CAD). It may be unclear whether the decrease in FFRCT at the distal coronal artery is physiological or due to stenosis. We decided to study predictive factors of an FFRCT decline below the pathological value of 0.80 in no-apparent CAD.

METHODS: A total of 150 consecutive patients who had both CT angiography coupled to FFRCT analysis and invasive angiogram showing < 20% coronary stenosis were included. Vessels were divided into two groups according to FFRCT at the distal vessel: FFRCT > 0.80 (n = 317) and FFRCT ≤ 0.80 (n = 114). ΔFFRCT was defined as the change in FFRCT from proximal to distal vessel. Vessel morphology (vessel length and lumen volume) and plaque characteristics [low-attenuation plaque volume, intermediate-attenuation (IAP) plaque volume, and calcified plaque volume] were evaluated.

RESULTS: FFRCT decreased from proximal to distal for the three major vessels in both FFRCT > 0.80 and FFRCT ≤ 0.80. Compared to FFRCT > 0.80, IAP volume was significantly higher in all three major vessels in FFRCT ≤ 0.80. ΔFFRCT was correlated with vessel length and lumen volume in FFRCT > 0.80, whereas ΔFFRCT was correlated with IAP volume in FFRCT ≤ 0.80. IAP volume above 44.8 mm3 was the strongest predictor of distal FFRCT of ≤ 0.80.

CONCLUSIONS: The presence of IAP is a major predictor of gradual decrease of FFRCT below 0.80 in no-apparent CAD vessels. Vessel morphology and plaque characteristics should be considered when interpreting FFRCT.