Influence of antegrade pulmonary blood flow on the hemodynamic performance of bidirectional cavopulmonary anastomosis: A numerical study

Numerical Investigation of the Effect of Additional Pulmonary Blood Flow on Patient-Specific Bilateral Bidirectional Glenn Hemodynamics

The effect of additional pulmonary blood flow (APBF) on the hemodynamics of bilateral bidirectional Glenn (BBDG) connection was marginally discussed in previous studies. This study assessed this effect using patient-specific numerical simulation. A 15-year-old female patient who underwent BBDG was enrolled in this study. Patient-specific anatomy, flow waveforms, and pressure tracings were obtained using computed tomography, Doppler ultrasound technology, and catheterization, respectively. Computational fluid dynamic simulations were performed to assess flow field and derived hemodynamic metrics of the BBDG connection with various APBF. APBF showed noticeable effects on the hemodynamics of the BBDG connection. It suppressed flow mixing in the connection, which resulted in a more antegrade flow structure. Also, as the APBF rate increases, both power loss and reflux in superior venae cavae (SVCs) monotonically increases while the flow ratio of the right to the left pulmonary artery (RPA/LPA) monotonically decreases. However, a non-monotonic relationship was observed between the APBF rate and indexed power loss. A high APBF rate may result in a good flow ratio of RPA/LPA but with the side effect of bad power loss and remarkable reflux in SVCs, and vice versa. A moderate APBF rate could be favourable because it leads to an optimal indexed power loss and achieves the acceptable flow ratio of RPA/LPA without causing severe power loss and reflux in SVCs. These findings suggest that patient-specific numerical simulation should be used to assist clinicians in determining an appropriate APBF rate based on desired outcomes on a patient-specific basis.

Bidirectional cavopulmonary anastomosis with additional pulmonary blood flow: good or bad pre-Fontan strategy

Objectives

This study aimed to evaluate the influence of preserved additional pulmonary blood flow (APBF) on survival after bidirectional cavopulmonary shunt (BCPS) and completion of Fontan circulation.

Methods

From March 2003 and April 2015, 156 patients with a single ventricle underwent BCPS. After performing propensity score analysis (1:1) for the entire sample, 50 patients with APBF (APBF group) were matched with 50 patients without APBF (no-APBF group).

Results

Age ( P  = 0.90), sex ( P  = 0.57), weight ( P  = 0.75), single ventricle morphology ( P =  0.87), type of neonatal palliative procedure ( P =  0.52), saturation ( P =  0.35), ejection fraction ( P =  0.90), Nakata index ( P  = 0.70) and mean pulmonary artery pressure ( P  = 0.72) were not significantly different between the groups. No significant survival difference was demonstrated ( P  = 0.54). One and 4-year survival rates were both 89.1% ± 4.6% in the APBF group and 87.2% ± 4.9% and 83.4% ± 5.9%, respectively, in the no-APBF group. There was no significant difference in rates of Fontan completion ( P  = 0.24), which was achieved in 22 patients from the APBF group (55.0%) and 26 patients from the no-APBF group (65.0%). However, Fontan completion occurred significantly earlier in the no-APBF group ( P  < 0.01). In this group, Fontan procedure was performed before 36 months of inter-stage period in 45.9% ± 8.5% of cases (95% CI 31.0-63.7%) compared to only 13.3 ± 5.6% (95% CI 5.8-29.1%) in the APBF group.

Conclusions

Our study demonstrates that APBF does not affect survival after BCPS or Fontan completion rate. APBF allows postponing the Fontan procedure without a negative effect on clinical status.

Uncontrolled Antegrade Pulmonary Blood Flow and Delayed Fontan Completion After the Bidirectional Glenn Procedure: Real-World Outcomes in China

BACKGROUND

Given the low rate of Fontan completion, an aggressive policy for maintaining antegrade pulmonary blood flow (AnPBF) during the bidirectional Glenn procedure (BDG) was developed for the functional single ventricle.

METHODS

From 2008 to 2013, 294 patients who underwent the BDG were divided into two groups: group 1 (uncontrolled AnPBF, n = 270) and group 2 (controlled AnPBF, n = 24). Pulmonary artery banding was performed because of the high central venous pressure in group 2. In group 1, the patients who underwent BDG from 2008 to 2012 were further divided into group DF (delayed Fontan completion, n = 109) and group FC (Fontan completion, n = 42).

RESULTS

The Fontan completion rate was 16.3%, and the average interval time was 2.2 ± 1.1 years. The delay of Fontan completion did not reduce body weight gain or the survival rate. Furthermore, oxygen saturation was slightly reduced in group DF. Although no impairments of heart function were observed, the uncontrolled AnPBF in group DF resulted in an increase in ventricular end-diastolic diameter and aggravation of atrioventricular valve regurgitation over 24 months after BDG. Logistic regression analysis revealed that systemic right ventricular morphology was a risk factor for the aggravation of valve regurgitation.

CONCLUSIONS

The low Fontan achievement rate is a critical issue in China. Although the patients with delayed Fontan completion exhibited an acceptable survival rate and acceptable body weight gain, uncontrolled AnPBF was associated with ventricular enlargement and aggravation of valve regurgitation. Strategies for improving the Fontan completion rate in China should be explored and could benefit outcomes.

Influence of bypass angles on extracardiac Fontan connections: a numerical study

The extracardiac Fontan connection (EFC) is an effective treatment for congenital single ventricle heart defects. Numerous studies have sought to optimize the EFC design. However, the optimal design of EFC remains uncertain. This study aims to examine the influence of bypass angles between the inferior vena cava (IVC) and right pulmonary artery (RPA), and the angles between the IVC and superior vena cava (SVC), on hemodynamics. Furthermore, this study demonstrates a methodology for cardiovascular surgical planning. First, a three-dimensional anatomical geometry was reconstructed from the medical images of a patient with single ventricle heart defects. Second, based on haptic deformations, six computational models were virtually generated. Third, numerical simulations were conducted using computational fluid dynamics through the finite volume method. Finally, hemodynamic parameters were obtained and evaluated. The hemodynamic parameters, including the flow patterns, streamlines, and swirling flow, were obtained. Meanwhile, the energy loss and flow distributions of vena cava blood were calculated. First, the hepatic artery blood distribution to two lungs and the flow ratio of the left pulmonary artery to RPA are sensitive to the angle between the IVC and RPA and not to that between the IVC and SVC. Second, energy dissipation is mainly sensitive to the angle between the IVC and SVC and not to that between the IVC and RPA. Third, an appropriate increase in the angle between the IVC and RPA or that between the IVC and SVC may lead to optimal options. This study is useful for surgeons in evaluating optimal Fontan options.

Numerical study for blood flow in pulmonary arteries after repair of tetralogy of Fallot

Pulmonary regurgitation (PR) is a common phenomenon in pulmonary arteries in patients after repair of tetralogy of Fallot (TOF). The regurgitation fraction of left pulmonary artery (LPA) is usually greater than right pulmonary artery (RPA) according to clinic data. It may be related to blood flow in pulmonary arteries. Therefore, understanding hemodynamics in pulmonary arteries helps to comprehend the reason. The aim of this study is to use 3D reconstructed pulmonary artery models from magnetic resonance imaging (MRI) and to use numerical approaches for simulation of flow variations in pulmonary arteries after repair of TOF. From the numerical results, the blood flow is influenced by the bifurcation angles and geometry of pulmonary artery. The regurgitation happens first in LPA after repair of TOF due to the small angle between LPA and main pulmonary artery (MPA). The recirculation region which obstructs forward blood flow to the left lung is found in LPA during acceleration of systole. We also analyze the pressure distribution; the extreme pressure variations are in dilation area of MPA. Numerical data including regurgitation in MPA, LPA, and RPA are compared with phase contrast MR measured data. Good agreements are found between numerical results and measured data.