Normalized wall shear stress maps derived from angiography-based scaling laws were equivalent to invasive Doppler measurements, with a median inflow difference of 0.08 ml/s [-0.01; 0.20].
Observational (n=8)
Can reliable patient-specific wall shear stress (WSS) be computed using diameter-based scaling laws for boundary conditions compared to intravascular Doppler measurements in patients with coronary bifurcations?
Normalized wall shear stress can be reliably obtained from angiography data alone using diameter-based scaling laws, but caution is needed for absolute wall shear stress computations.
The aim of this study was to determine if reliable patient-specific wall shear stress (WSS) can be computed when diameter-based scaling laws are used to impose the boundary conditions for computational fluid dynamics. This study focused on mildly diseased human coronary bifurcations since they are predilection sites for atherosclerosis. Eight patients scheduled for percutaneous coronary intervention were imaged with angiography. The velocity proximal and distal of a bifurcation was acquired with intravascular Doppler measurements. These measurements were used for inflow and outflow boundary conditions for the first set of WSS computations. For the second set of computations, absolute inflow and outflow ratios were derived from geometry-based scaling laws based on angiography data. Normalized WSS maps per segment were obtained by dividing the absolute WSS by the mean WSS value. Absolute and normalized WSS maps from the measured-approach and the scaled-approach were compared. A reasonable agreement was found between the measured and scaled inflows, with a median difference of 0.08 ml/s -0.01; 0.20. The measured and the scaled outflow ratios showed a good agreement: 1.5 percentage points -19.0; 4.5. Absolute WSS maps were sensitive to the inflow and outflow variations, and relatively large differences between the two approaches were observed. For normalized WSS maps, the results for the two approaches were equivalent. This study showed that normalized WSS can be obtained from angiography data alone by applying diameter-based scaling laws to define the boundary conditions. Caution should be taken when absolute WSS is assessed from computations using scaled boundary conditions.
Schrauwen et al. (2016) conducted an observational in Atherosclerotic human coronary bifurcations (n=8). Geometry-based scaling laws (scaled-approach) vs. Intravascular Doppler measurements (measured-approach) was evaluated on Agreement between measured and scaled inflows and outflow ratios. Normalized wall shear stress maps derived from angiography-based scaling laws were equivalent to invasive Doppler measurements, with a median inflow difference of 0.08 ml/s [-0.01; 0.20].