Simplified coronary flow reserve calculations based on three-dimensional coronary reconstruction and intracoronary pressure data

Figures

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  Figure 1. A. Detection of the segments by QAngio XA 3D. The stenotic segment lies between the two green lines, marked by shaded green color; B. Sample pressure trace after intracoronary adenosine injection. Red line: proximal (aortic) instantaneous pressure trace, red dashed line: moving average of the proximal pressure, blue line: instantaneous pressure trace distally to the coronary stenosis, blue dashed line: moving average of the distal pressure, green line: the ratio of the average distal and the proximal pressure (FFR); min — minimum; max — maximum; 3D — three-dimensional; D — diameter; mm — millimeter; MLA — minimal lumen area; Hgmm — millimeter of mercury; pa mean — mean pressure value in the proximal lumen area; pd mean — mean pressure value in the distal lumen area; FFR — fractional flow reserve; s — second.

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  Figure 2. The simplified model of the target vessel is based on the three-dimensional quantitative coronary angiography geometry; CFR — coronary flow reserve; MLA — minimal lumen area; A’d — post-stenotic vessel area-averaged on the segment 5 mm away from the stenotic segment; Ap — proximal cross-sectional area; Lp — length of the proximal segment; As — cross-sectional area of the stenosed segment; Ls — length of the stenosis; Ad — cross-sectional area of the distal segment; Ld — length of the distal segment; Pa — aortic pressure; Pd — pressure distal to the stenosis; Qhyper — flow rate under hyperemia; Qrest — flow rate at rest; Δpv,prox — friction-related pressure loss in the proximal segment; Δpv,sten — friction-related pressure loss in the stenosis; Δpv,dist — friction-related pressure loss distal to the stenosis; Δpv,sep — separation-related pressure loss; ksep — correction for the entrance effects detailed in equation (6) [19].

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  Figure 3. Sample display of the velocity field near the stenosis in the hyperemic and resting condition at the time instant of the highest velocity (case no. 5). The inset figure shows a sample cross-section of the mesh in the stenotic segment.

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  Figure 4. Correlations between the models and their corresponding Bland-Altman plots. Correlation coefficients can be found on the bottom of Table 2; CFRS — coronary flow reserve with steady calculation by ANSYS; CFRU — coronary flow reserve with unsteady calculation by ANSYS; CFRM — coronary flow reserve calculated with the simple model.

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  Figure 5. Flow rate as a function of the pressure difference Q(Δp). Three distinct cases that represent the lowest (blue), middle (green) and largest (red) resistances in the studied population. The solid and dashed line depicts the curve defined by the simple model and steady CFD simulations by ANSYS, respectively. The marked points on each curve are the solutions of the flow equations by substituting the pressure drop of the given case from the resting and hyperemic condition; CFD — computational fluid dynamics calculation by ANSYS; Q — flow rate; mL/s — milliliter/second; CFR — coronary flow reserve; Δp — pressure loss; mmHg — millimeter of mercury.