Impact of Pulmonary Venous Inflow on Cardiac Flow Simulations: Comparison with In Vivo 4D Flow MRI

Abstract

Blood flow simulations are making their way into the clinic, and much attention is given to estimation of fractional flow reserve in coronary arteries. Intracardiac blood flow simulations also show promising results, and here the flow field is expected to depend on the pulmonary venous (PV) flow rates. In the absence of in vivo measurements, the distribution of the flow from the individual PVs is often unknown and typically assumed. Here, we performed intracardiac blood flow simulations based on time-resolved computed tomography on three patients, and investigated the effect of the distribution of PV flow rate on the flow field in the left atrium and ventricle. A design-of-experiment approach was used, where PV flow rates were varied in a systematic manner. In total 20 different simulations were performed per patient, and compared to in vivo 4D flow MRI measurements. Results were quantified by kinetic energy, mitral valve velocity profiles and root-mean-square errors of velocity. While large differences in atrial flow were found for varying PV inflow distributions, the effect on ventricular flow was negligible, due to a regularizing effect by mitral valve. Equal flow rate through all PVs most closely resembled in vivo measurements and is recommended in the absence of a priori knowledge.Electronic supplementary materialThe online version of this article (10.1007/s10439-018-02153-5) contains supplementary material, which is available to authorized users.

Demonstration of Patient-Specific Simulations to Assess Left Atrial Appendage Thrombogenesis Risk

“…Our work improves over most previous computational studies of the LA flow (Bosi et al, 2018;Garcia-Isla et al, 2018;Masci et al, 2020) by considering patient-specific inflow/outflow boundary conditions, similar to Otani et al (2016). One limitation of our simulations is that PV flow rates were evenly distributed (Lantz et al, 2019). More patient-specific modeling of inflow boundary conditions would involve measuring the flow rate through each pulmonary vein (e.g., by transesophageal echocardiography) or modeling the flow impedance of each pulmonary vein based on imaging data such as vein diameter (Shi et al, 2011).…”

“…Since we did not have patientspecific measurements of the flow rate through each PV, Q PV was split evenly among all the PVs, i.e., Q i = Q PV (t)/4. CFD analysis with evenly split pulmonary flow rates has been previously shown to produce reasonable LA hemodynamics when compared to phase contrast MRI data (Lantz et al, 2019). To further evaluate this choice of inflow boundary conditions, we performed preliminary simulations for one of the cases comparing this approach to splitting Q PV proportionally to the area of the pulmonary veins, so that the bulk mean velocity was the same in all PVs.…”

Demonstration of Patient-Specific Simulations To Assess Left Atrial Appendage Thrombogenesis Risk

“…Our work improves over most previous computational studies of the LA flow [3,8,18] by considering patient-specific inflow/outflow boundary conditions, similar to Otani et al [22]. One limitation of our simulations is that PV flow rates were evenly distributed [16]. More patient-specific modeling of inflow boundary conditions would involve measuring the flow rate through each pulmonary vein (e.g., by transesophageal echocardiography) or modeling the flow impedance of each pulmonary vein based on imaging data such as vein diameter [26].…”

Numerical Simulation of Hemodynamics in Two Models for Total Anomalous Pulmonary Venous Connection Surgery

“…The mass flow of the pulmonary vein was defined as the boundary condition at the inlet (Figure 4). The average flow rate in a cardiac cycle was distributed to four pulmonary veins in proportion to the area of the pulmonary veins (Lantz et al, 2019). In addition, mitral orifice was defined as the outlet boundary condition of computational fluid model with average left atrial pressure (Migliavacca et al, 2003), as shown in Table 1.…”