Influence of Collaterals on True FFR Prediction for a Left Main Stenosis with Concomitant Lesions: An In Vitro Study.

With the aim of assisting interventional cardiologists during decision making for revascularization, reduced-order (0D) approaches have been developed to predict the true fractional flow reserve (FFRTrue) of individual stenoses in multiple-lesion arrangements. In this study, a general equation was derived to predict the FFRTrue of a left main (LM) coronary stenosis with downstream lesions, one in the left anterior descending (LAD) and the other in the left circumflex (LCx) artery, and distinct collateral circulations supplying each daughter artery. An in vitro model mimicking the fractal nature of LM bifurcation trees with collateral branches was developed to validate the FFR values obtained with the prediction model (FFR Pred Model ). Our results demonstrated that: (1) considering collaterals significantly improved the FFR Pred Model estimation for a moderate LM stenosis with two downstream lesions as compared to computations with no collateral consideration (p < 0.001): mean absolute error |FFR Pred Model - FFRTrue| ± SD was equal to 0.02 ± 0.01 vs. 0.04 ± 0.02 respectively, and (2) Deviations from FFRTrue for LM stenoses are correlated to both, downstream lesion severities and collateral developments. The present study supports the hypothesis that collateral circulations supplying the LAD and LCx must be considered when predicting the FFRTrue of an LM stenosis with downstream lesions.

Intraluminal Ultrasonic Palpation Imaging Technique Revisited for Anisotropic Characterization of Healthy and Atherosclerotic Coronary Arteries: A Feasibility Study.

Accurate mechanical characterization of coronary atherosclerotic lesions remains essential for the in vivo detection of vulnerable plaques. Using intravascular ultrasound strain measurements and based on the mechanical response of a circular and concentric vascular model, E. I. Céspedes, C. L. de Korte and A. F. van der Steen developed an elasticity-palpography technique in 2000 to estimate the apparent stress-strain modulus palpogram of the thick subendoluminal arterial wall layer. More recently, this approach was improved by our group to consider the real anatomic shape of the vulnerable plaque. Even though these two studies highlighted original and promising approaches for improving the detection of vulnerable plaques, they did not overcome a main limitation related to the anisotropic mechanical behavior of the vascular tissue. The present study was therefore designed to extend these previous approaches by considering the orthotropic mechanical properties of the arterial wall and lesion constituents. Based on the continuum mechanics theory prescribing the strain field, an elastic anisotropy index was defined. This new anisotropic elasticity-palpography technique was successfully applied to characterize ten coronary plaque and one healthy vessel geometries of patients imaged in vivo with intravascular ultrasound. The results revealed that the anisotropy index-palpograms were estimated with a good accuracy (with a mean relative error of 26.8 ± 48.8%) compared with ground true solutions.