Predicting Hemodynamic Performance of Fontan Operation for Glenn Physiology using Computational Fluid Dynamics: Ten Patient-specific Cases

Abstract

Single ventricle hearts have only one ventricle that can pump blood effectively and the treatment requires three stages of operations to reconfigure the heart and circulatory system. At the second stage, Glenn procedure is performed to connect superior vena cava (SVC) to the pulmonary arteries (PA). For the third and most complex operation, called Fontan, an extracardiac conduit is used to connect inferior vena cava (IVC) to the PL and thereafter no deoxygenated blood goes to the heart. Predicting Hemodynamic Performance of Fontan Operation using computational fluid dynamics (CFD) is hypothesized to improve outcomes and optimize this treatment planning in children with single-ventricle heart disease. An important reason for this surgical planning is to reduce the development of pulmonary arteriovenous malformations (PAVM) and the need to perform Fontan revisions. The purpose of this study was to develop amodel for Fontan surgical planning and use this model to compare blood circulation in two designed graft types of Fontan operation known as T-shape and Y-graft. The functionality of grafts was compared in terms of power loss (PL) and hepatic flow distribution (HFD), a known factor in PAVM development. To perform this study, ten single-ventricle children with Glenn physiology were included and a CFD model was developed to estimate the blood flow circulation to the left and right pulmonary arteries. The estimated blood flow by CFD was compared with that measured by cardiovascular magnetic resonance. Results showed that there was an excellent agreement between the net blood flow in the right and left pulmonary arteries computed by CFD and CMR (ICC= 0.98, P-value ≥0.21). After validating the accuracy of each CFD model, Fontan operations using T-shape and Y-graft conduits were performed in silico for each patient and the developed CFD model was used to predict the post-surgical PL and HFD. We found that the PL in the Y-graft was significantly lower than in the T-shape (P-value ≤0.001) and HFD was significantly better balanced in Y-graft compared to the T-shape (P-value=0.004).

Keywords: Blood flow; Cardiac MRI; Catheterization; Computational fluid dynamics; Fontan operation; Simulation of cardiac surgeries; Single-ventricle.

Figure 1.

CFD Model for the estimation of hemodynamic parameters in Glenn pathway. (a) CFD simulation workflow and (b) generated 3D model and boundary conditions for one patient. Inputs (i.e., inlets) to the CFD analysis model are right and left superior vena cava (RSVC and LSVC) flow by CMR and mean pressure values in the right and left pulmonary artery (RPA and LPA) by catheterization. Outputs (i.e., outlets) from the CFD analysis model are the time-resolved blood flow in the RPA and LPA. CFD, computational fluid dynamics; CMR, cardiovascular magnetic resonance.

Figure 2.

Schematic overview of Glenn physiology (a), Fontan with T-shape conduit (b), and Fontan with Y-graft conduit (c). Q_LPA, flow at left pulmonary artery; Q_RPA, flow at right pulmonary artery; Q_IVC, flow at inferior vena cava; Q_SVC, flow at superior vena cava; P_LPA, pressure at left pulmonary artery; P_RPA, pressure at right pulmonary artery; P_LA, pressure at left atrium; P_RA, pressure at right atrium; R_LPA, pulmonary vascular resistance at left pulmonary artery; and R_RPA, pulmonary vascular resistance at right pulmonary artery.

Figure 3.

Generated Glenn pathway mesh models for the 10 patients with blood flow streamlines showing the blood flow distributions from the right and left superior vena cava (RSVC and LSVC) to the right and left pulmonary artery (RPA and LPA). The colors indicate estimated blood flow distributions from SVC to RPA and LPA. In patients with bilateral SVCs, red and blue colors display blood flow circulations from LSVC and RSVC, respectively, while in patients with single SVC, only blue color is used. SVC, superior vena cava.

Figure 4.

CFD-simulated times-series flow curves and CMR-measured time resolved flow curve at RPA and LPA from 10 single-ventricle patients with Glenn physiology. CFD, computational fluid dynamics; CMR, cardiovascular magnetic resonance, and LPA and RPA, left and right pulmonary arteries.

Figure 5.

Bland-Altman plot showing the agreement between the CFD-simulated net blood flow and measured CMR net blood flow at the RPA and LPA for all patients. CFD, computational fluid dynamics; CMR, cardiovascular magnetic resonance; LPA, left pulmonary artery; RPA, right pulmonary artery.

Figure 6.

Streamlines of simulated blood flow in constructed T-shape and Y-graft connections for five patients (1–5). FC, Fontan conduit; HFD_RPA, hepatic flow distribution to the right pulmonary artery; LPA, left pulmonary artery; LSVC, left superior vena cava; PL, power loss; RPA, right pulmonary artery; RSVC, right superior vena cava; SVC, superior vena cava.

Figure 7.

Streamlines of simulated blood flow in constructed T-shape and Y-graft connections for five patients (6–10). FC, Fontan conduit; HFD_RPA, hepatic flow distribution to the right pulmonary artery; LPA, left pulmonary artery; LSVC, left superior vena cava; PL, power loss; RPA, right pulmonary artery; RSVC, right superior vena cava; SVC, superior vena cava.

Figure 8.

Effect of connection type (T-shape or Y-graft) in Fontan operation on power loss (PL) and hepatic flow distribution (HFD) to the left and right pulmonary arteries. Lower PL was observed in Y-graft connection type (a). The HFD to the right (HFD_RPA) and left pulmonary artery (HFD_LPA) is more balanced in Y-graft compared to T-shape (b).