Impact of Revascularization on the Distal to Proximal Pressure Ratio in Case of Multiple Coronary Stenoses

Abstract

Objective: In order to take a decision about the revascularization approach to be adopted, it is of fundamental importance to determine whether coronary artery stenoses induce ischemia or not. An index, named (Fractional Flow Reserve), based on pressure measurements has been proposed to this aim and is usually interpreted in terms of flows. The objective of this work is to compute simultaneously pressures and flow rates in the coronary network of patients with three-vessel disease, in order to study more precisely the relationship between these two quantities. Approach: 22 patients have been included in the study. Some pressure and flow rate measurements were collected during by-pass surgery. These clinical data allow determining parameters for a patient's specific model, based on the electric/hydraulic analogy. Collateral pathways are included in the model, as well as the severity of the disease and the impact of revascularization. Main Results: For patients with stenoses on LAD, LCx, LMCA and occlusion of the RCA, the flow rate delivered to the right territory is of course a function of the aortic pressure, the left stenoses severity, and the pressure distal to the thrombosis. But it mainly depends on the capillary and collateral resistances, and on the proportion between them. Abnormal microvascular hemodynamics, may be present in patients with non-hemodynamic significant lesions as assessed by the pressure ratio. Complete revascularization with the 3 grafts is demonstrated to be fully justified. The direction of collateral flows may be reversed, depending on the pressure gradient. In any case, they remain low and become negligible when the 3 grafts are operating. Significance: Surgical decision based only on pressure measurements may miss some real hemodynamic problems due to the considered stenosis. This risk is even greater in case of serial stenoses.

Evaluation of intracoronary hemodynamics identifies perturbations in vorticity

“…To model maximal hyperemia, coronary flow velocity and microresistance were changed based on the methods described in (Wilson et al, 1990;Taylor et al, 2013). Distal resistance has a strong influence on the modeling of patient-specific arterial hemodynamics (Anselmi et al, 2021). Therefore, for each arterial tree we carefully compute the distal resistance of every outlet based on the vessel diameter, mean flow and mean aortic pressure derived from the clinical measurements of that patient (Table 1).…”

Modeling cardiac microcirculation for the simulation of coronary flow and 3D myocardial perfusion

“…Still, an accurate mathematical description of coronary hemodynamics remains a challenge because of two main reasons: firstly, the coronary circulation spans over a broad range of length scales (from few millimeters to few microns of vessel diameter), making it impossible to run even 1D fluid-dynamics simulations in the fully resolved tree; secondly, cardiac contraction deeply affects coronary flow, mainly through the well known systolic impediment effect [4], which is challenging to model in an effective way. To address the first issue, previous works have proposed either a focus on large coronaries with outflow conditions, surrogating microvasculature, based on lumped parameter models [5,6] or on extendend Murray's law [7]; or multiscale models, often treating blood dynamics in the microcirculation through Modeling cardiac microcirculation for the simulation of coronary flow and 3D myocard a homogenized porous medium approach (Darcy equations, [8]), coupled with a 1D [9] or 3D [10] description of fluid-dynamics in the large coronaries. This has been further extended with the proposal of multicompartment Darcy formulations to account for the different length scales in the microcirculation [11][12][13][14].…”