Numerical simulation of the fractional flow reserve (FFR)

Abstract

The fractional flow reserve (FFR) provides an efficient quantitative assessment of the severity of a coronary lesion. Our aim is to address the problem of computing non-invasive virtual fractional flow reserve (VFFR). In this paper, we present a preliminary study of the main features of flow over a stenosed coronary arterial portion, in order to enumerate the different factors affecting the VFFR. We adopt a non-Newtonian flow model and we assume that the two-dimensional (2D) domain is rigid in a first place. In a second place, we consider a simplified weakly coupled FSI model in order to take into account the infinitesimal displacements of the upper wall. A 2D finite element solver was implemented using Freefem++. We computed the VFFR profiles with respect to different lesion parameters and compared the results given by the rigid wall model to those obtained for the elastic wall one.

Virtual FFR Quantified with a Generalized Flow Model Using Windkessel Boundary Conditions

“…Like presented in our previous paper [1], to measure the fractional flow reserve (FFR) during the invasive test, the operator crosses the coronary lesion with an FFR-specific guide wire. is guide wire is designed to record the coronary arterial pressure beyond the lesion ( Figure 5(a)).…”

“…e aortic pressure P aortic is the central blood pressure at the root of the aorta, while the distal pressure P distal corresponds to the pressure at the surface of the sensor (pressure wire in Figure 5(a)). Both pressures given by the FFR instrument are calculated as a temporal mean, over the cardiac cycle, of pressures p s (t) captured at each frequency drop (see [1]).…”

“…In fact, a clinically usable FFR value (to be compared to real FFR measurements) is not our ultimate goal in this paper. We implement an algorithm to compute a virtual FFR following the same calculation strategy as used by the clinical FFR device, like in [1]. At each time step, the aortic pressure P a is calculated by the mean pressure of the points at 1 cm from the inlet of the coronary tree, in order to avoid all the transient effects at the entrance.…”

“…us, a detailed hemodynamic evaluation of the flow and its spatial and temporal distribution may give important insight to understand the pathology. In this view, the fractional flow reserve (FFR) plays a central role (see [1]). e fractional flow reserve (FFR) is an invasive measure that consists in introducing a pressure wire to a diseased artery to measure in vivo two values of blood pressure: the aortic pressure, P aortic , and the pressure distal to a lesion, P distal .…”

“…On the other hand, the choice of suitable boundary conditions is crucial. In our previous paper [1], we presented a first virtual FFR estimation using the generalized fluid model in [5] and conducted different simulations to study the impact of the lesions parameters on the FFR value. However, we considered a simplified 2D geometry and reduced boundary conditions.…”