Optimization of a Y-Graft Design for Improved Hepatic Flow Distribution in the Fontan Circulation

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Weiguang Yang ◽  
Jeffrey A. Feinstein ◽  
Shawn C. Shadden ◽  
Irene E. Vignon-Clementel ◽  
Alison L. Marsden
Keyword(s):  
Heart Diseases ◽  
Heart Defects ◽  
Superior Vena ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Flow Distribution ◽  
Patient Specific ◽  
Pulmonary Flow ◽  
Hemodynamic Performance ◽  
Branch Size

Single ventricle heart defects are among the most serious congenital heart diseases, and are uniformly fatal if left untreated. Typically, a three-staged surgical course, consisting of the Norwood, Glenn, and Fontan surgeries is performed, after which the superior vena cava (SVC) and inferior vena cava (IVC) are directly connected to the pulmonary arteries (PA). In an attempt to improve hemodynamic performance and hepatic flow distribution (HFD) of Fontan patients, a novel Y-shaped graft has recently been proposed to replace the traditional tube-shaped extracardiac grafts. Previous studies have demonstrated that the Y-graft is a promising design with the potential to reduce energy loss and improve HFD. However these studies also found suboptimal Y-graft performance in some patient models. The goal of this work is to determine whether performance can be improved in these models through further design optimization. Geometric and hemodynamic factors that influence the HFD have not been sufficiently investigated in previous work, particularly for the Y-graft. In this work, we couple Lagrangian particle tracking to an optimal design framework to study the effects of boundary conditions and geometry on HFD. Specifically, we investigate the potential of using a Y-graft design with unequal branch diameters to improve hepatic distribution under a highly uneven RPA/LPA flow split. As expected, the resulting optimal Y-graft geometry largely depends on the pulmonary flow split for a particular patient. The unequal branch design is demonstrated to be unnecessary under most conditions, as it is possible to achieve the same or better performance with equal-sized branches. Two patient-specific examples show that optimization-derived Y-grafts effectively improve the HFD, compared to initial nonoptimized designs using equal branch diameters. An instance of constrained optimization shows that energy efficiency slightly increases with increasing branch size for the Y-graft, but that a smaller branch size is preferred when a proximal anastomosis is needed to achieve optimal HFD.

Virtual Design for the Fontan Procedure: From Idealized to Patient Specific Models Using CFD and Derivative-Free Optimization

2010 ◽  
Author(s):  
Weiguang Yang ◽  
Guillaume Troianowski ◽  
Alexandre Birolleau ◽  
Irene Vignon-Clementel ◽  
Jeffrey A. Feinstein ◽  
...  
Keyword(s):  
Single Ventricle ◽  
Heart Defects ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Patient Specific ◽  
Virtual Design ◽  
Modeling Tools ◽  
Patient Specific Modeling

Single ventricle congenital heart defects are among the most challenging for pediatric cardiologists to treat. Children born with these defects are cyanotic, and these conditions are nearly uniformly fatal without treatment. A series of surgeries is performed to palliate single ventricle defects. The first stage consists of aortic reconstruction in a Norwood procedure. In the second stage, the Bidirectional Glenn procedure, the superior vena cava (SVC) is disconnected from the heart and redirected into the pulmonary arteries (PA’s). In the third and final stage, the Fontan procedure, the inferior vena cava (IVC) is connected to the PA’s via a straight Gore-Tex tube, forming a T-shaped junction with or without offset. Patient specific modeling tools provide a means to evaluate new designs with the goal of lowering long-term morbidity and improving patients’ quality of life.

Customization of the Fontan Y-Graft: Are Unequal Branches Necessary for Optimal Hepatic Flow Distribution?

2011 ◽  
Author(s):  
Weiguang Yang ◽  
Jeffrey A. Feinstein ◽  
Irene E. Vignon-Clementel ◽  
Shawn C. Shadden ◽  
Alison L. Marsden
Keyword(s):  
Heart Diseases ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Flow Distribution ◽  
Shunt Insertion ◽  
Second Stage ◽  
Clinical Complications ◽  
Surgical Complexity

Due to surgical complexity and clinical complications, single ventricle defects are among the most severe and challenging congenital heart diseases to treat. Patients usually undergo a three-staged surgery. The first stage consists of shunt insertion and aortic reconstruction in a Norwood procedure. In the second stage, the Bidirectional Glenn procedure, the superior vena cava (SVC) is disconnected from the heart and redirected into the pulmonary arteries (PA’s). In the third and final stage, the Fontan procedure, the inferior vena cava (IVC) is connected to the PA’s via a straight Gore-Tex tube, forming a T-shaped junction with or without offset.

Hemodynamics Characteristics of a Four-Way Right-Atrium Bypass Connector

2017 ◽  
Author(s):  
Elizabeth Mack ◽  
Alexandrina Untaroiu
Keyword(s):  
Blood Flow ◽  
Superior Vena Cava ◽  
Right Atrium ◽  
Superior Vena ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Design Parameters ◽  
Patient Specific ◽  
Optimal Size ◽  
The Right

Currently, the surgical procedure followed by the majority of cardiac surgeons to address right ventricular dysfunction is the Fontan procedure, which connects the superior and inferior vena cava directly to the left and right pulmonary arteries bypassing the right atrium. However, this is not the most efficient configuration from a hemodynamics perspective. The goal of this study is to develop a patient-specific 4-way connector to bypass the dysfunctional right ventricle and augment the pulmonary circulation. The 4-way connector is intended to channel the blood flow from the inferior and superior vena cava directly to the right and left pulmonary arteries. By creating a connector with proper hemodynamic characteristics, one can control the jet flow interactions between the inferior and superior vena cava and streamline the flow towards the right and left pulmonary arteries. In this study the focus is on creating a system that can identify the optimal configuration for the 4-way connector for patients from 0–20 years of age. A platform is created in ANSYS that utilizes the DOE function to minimize power-loss and blood damage propensity in the connector based on junction geometries. A CFD model is created to simulate the blood flow through the connector. Then the geometry of the bypass connector is parameterized for DOE process. The selected design parameters include inlet and outlet diameters, radius at the intersection, and length of the connector pathways. The chosen range for each geometric parameter is based on the relative size of the patient’s arteries found in the literature. It was confirmed that as the patient’s age and artery size change, the optimal size and shape of the connector also changes. However, the corner radius did not decrease at the same rate as the opening diameters. This means that creating different sized connectors is not just a matter of scaling the original connector to match the desired opening diameter. However, it was found that power losses within the connector decrease and average and maximum blood traversal time through the connector increased for increasing opening radius. This information could be used to create a more specific relationship between the opening radius and the flow characteristics. So in order to create patient specific connectors, either a new more complicated trend needs to be found or an optimization program would need to be run on each patient’s specific geometry when they need a new connector.

Effect of Flow Pulsatility on Modeling the Total Cavopulmonary Hemodynamics: A Numerical Investigation

2012 ◽  
Author(s):  
Reza H. Khiabani ◽  
Maria Restrepo ◽  
Elaine Tang ◽  
Diane De Zélicourt ◽  
Mark Fogel ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Heart Defects ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Venous Flow ◽  
Surgical Interventions ◽  
The Right

Single Ventricle Heart Defects (SVHD) are present in 2 per 1000 live births in the US. SVHD are characterized by cyanotic mixing between the de-oxygenated blood from the systemic circulation return and the oxygenated blood from the pulmonary arteries. Palliative surgical repairs (Fontan procedure) are performed to bypass the right ventricle in these patients. In current practice, the surgical interventions commonly result in the total cavopulmonary connection (TCPC). In this configuration the systemic venous returns (inferior vena cava, IVC, and superior vena cava, SVC) are directly routed to the right and left pulmonary arteries (RPA and LPA), bypassing the right heart. The resulting anatomy has complex and unsteady hemodynamics characterized by flow mixing and flow separation. Pulsation of the inlet venous flow during a cardiac cycle results in complex and unsteady flow patterns in the TCPC. Although various degrees of pulsatility have been observed in vivo, non-pulsatile (time-averaged) flow boundary conditions have traditionally been assumed in modeling TCPC hemodynamics, and only recently have pulsatile conditions been incorporated without completely characterizing their effect or importance. In this study, 3D numerical simulations were performed to predict TCPC hemodynamics with both pulsatile and non-pulsatile boundary conditions and to investigate the accuracy of applying non-pulsatile boundary conditions. Flow structures, energy dissipation rate and pressure drop were compared under rest and estimated exercise conditions. The results show that TCPC hemodynamics can be strongly influenced by the presence of pulsatile flow. However, there exists a minimum pulsatility threshold, identified by defining a weighted pulsatility index (wPI), above which the influence is significant.

Hemodynamics Characteristics of a Four-Way Right-Atrium Bypass Connector

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Elizabeth Mack ◽  
Alexandrina Untaroiu
Keyword(s):  
Superior Vena Cava ◽  
Right Atrium ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Right Ventricular Dysfunction ◽  
Patient Specific ◽  
Optimal Size ◽  
Size Change

Currently, the surgical procedure followed by the majority of cardiac surgeons to address right ventricular dysfunction is the Fontan procedure, which connects the superior vena cava and inferior vena cava (IVC) directly to the left and right pulmonary arteries (LPA and RPA, respectively) bypassing the right atrium. The goal of this study is to develop a patient-specific four-way connector to bypass the dysfunctional right ventricle and augment the pulmonary circulation. The four-way connector was intended to channel the blood flow from the inferior and superior vena cava directly to the RPA and LPA. By creating a connector with proper hemodynamic characteristics, one can control the jet flow interactions between the inferior and superior vena cava and streamline the flow toward the RPA and LPA. The focus for this study was on creating a system that could identify the optimal configuration for the four-way connector for patients from 0 to 20 years of age. A platform was created in ANSYS that utilized the design of experiments (DOE) function to minimize power-loss and blood damage propensity in the connector based on junction geometries. It was confirmed that as the patient's age and artery size change, the optimal size and shape of the connector also changes. However, the corner radius did not decrease at the same rate as the opening diameters. However, it was found that power losses within the connector decrease, and average and maximum blood traversal time through the connector increased for increasing opening radius.

Investigation of Pulsatile Hemodynamics in Patient-Specific Fontan Templates With Fenestration

2011 ◽  
Author(s):  
Onur Dur ◽  
Greggory Housler ◽  
Ergin Kocyildirim ◽  
Haifa Hong ◽  
Jinfen Liu ◽  
...  
Keyword(s):  
Superior Vena ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Surgical Techniques ◽  
Surgical Reconstruction ◽  
Patient Specific ◽  
Fontan Patient ◽  
Third Stage ◽  
Patients Experience ◽  
Fontan Patients

The third stage for palliative surgical reconstruction for children with functional single-ventricle (SV) physiology is the completion of the total cavopulmonary connection (TCPC), where the superior vena cava (SVC) and inferior vena cava (IVC) are routed directly into the pulmonary arteries. Approximately 5000 newborns in the US each year join to the existing SV (or Fontan) patient population, along with increasing numbers of adult Fontan patients surviving longer due to the advances in surgical techniques and post-op management. Although most post-operative Fontan patients experience an acceptable quality of life, their lifespan is shorter than normal with a significant number of these patients developing late hemodynamic complications (failing Fontan) and requiring heart transplantation. Donor shortage and the high-risk nature of transplantation for these complex and often very ill patients demand alternative therapeutic options [1].

In Vitro Study of Pulmonary Vascular Resistance in Fontan Circulation With Respiration Effects

2012 ◽  
Author(s):  
Marija Vukicevic ◽  
Timothy A. Conover ◽  
Jian Zhou ◽  
Tain-Yen Hsia ◽  
Richard S. Figliola
Keyword(s):  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Heart Defects ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Fontan Operation ◽  
Venous Pressure ◽  
Pulmonary Arteries ◽  
Pulmonary Regurgitation ◽  
Vena Cava

The Fontan operation is the final stage of palliative surgery for children born with single ventricle heart defects. The most common configuration is called total cavopulmonary connection (TCPC), wherein the inferior vena cava and superior vena cava are anastomosed directly to the pulmonary arteries; therefore the pulmonary circulation is driven by venous pressure only. The Fontan procedure, although successful in the early postoperative period, with time can decrease in efficiency or even fail within several years after the operation. The reasons of different clinical outcomes for some of the Fontan patients are not clear enough, even though it is commonly accepted that certain factors such as low pulmonary vascular resistance and proper shape and size of the TCPC construction are crucial for the succesful long term outcomes. Accordingly, one of the major problems is the increase in pulmonary vascular resistance due to altered hemodynamics after the surgery, causing venous hypertension and respiratory-dependent pulmonary regurgitation [1]. The main pulmonary arteries may also see increased resistance due to congenital malformations, surgical scarring, or deliberate surgical banding. Thus, the consequence of the increased pulmonary vascular resistance at both proximal and distal locations with respect to the TCPC junction, and its effect on the systemic pressures and flow rates, is the main objective of this study.

Influence of Offset on Hemodynamics of Intra-atrial Conduit Fontan's Procedure and Its Clinical Implications

2019 ◽  
Vol 68 (01) ◽  
pp. 038-044
Author(s):  
Jie Hu ◽  
Qian Wang ◽  
Zhirong Tong ◽  
Juanya Shen ◽  
Jinlong Liu ◽  
...  
Keyword(s):  
Pulmonary Artery ◽  
Comprehensive Evaluation ◽  
Superior Vena ◽  
Vena Cava ◽  
Flow Distribution ◽  
Left Pulmonary Artery ◽  
Central Line ◽  
Virtual Surgery ◽  
Trade Offs ◽  
Hemodynamic Performance

Background The desirable distance, defined as offset, between the central line of the superior vena cava (SVC) and the intra-atrial conduit after an intra-atrial conduit (IAC) Fontan's procedure remained unclear. We compared the hemodynamic features using virtual surgery with different offset designs in our study. Methods Three-dimensional models of IAC Fontan's procedure were reconstructed according to the magnetic resonance imagings (MRIs) of three patients, then four models for each patient with different offsets equaling 100, 67, 33, and 0% of the diameter of the IVC were reconstructed. Computational fluid dynamics (CFD) were performed in each model to predict the best hemodynamic features, including streamlines of blood flow, wall shear stress (WSS), energy loss (EL), and the hepatic flow distribution (HFD) ratio. Results Comprehensive evaluation of WSS, EL, and HFD revealed than an offset of 33% presents the best hemodynamic performance among the three patients modeled. In patient A, an offset of 33% resulted in the best HFD (left pulmonary artery/right pulmonary artery [LPA/RPA] = 35/65%). In patient B, the best trade-off between HFD (35/65%), and WSS was achieved with an offset of 33%. In patient C, EL peaked at an offset of 0% and significantly dropped at an offset of 33% with a desirable HFD (60/40%). Conclusions We verified that the offset distance influences hemodynamic performance in IAC Fontan's procedure. Considering several hemodynamic parameters, the best trade-offs between hemorheology, pulmonary perfusion, and energy efficiency were achieved at an offset of 33%. This distance should be taken into consideration and optimized during the surgical planning for the IAC Fontan's procedure.

Optimization of an Idealized Y-Graft for the Fontan Procedure Using CFD and a Derivative-Free Optimization Algorithm

2009 ◽  
Author(s):  
Weiguang Yang ◽  
Jeffrey A. Feinstein ◽  
V. Mohan Reddy ◽  
Alison L. Marsden
Keyword(s):  
Heart Defects ◽  
Superior Vena ◽  
Fontan Procedure ◽  
Survival Rates ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Protein Losing Enteropathy ◽  
Second Stage ◽  
Derivative Free Optimization ◽  
Derivative Free

The Fontan procedure is a surgery performed to treat patients with single ventricle congenital heart defects. The Fontan is the final of three surgical stages. The first stage consists of aortic reconstruction, in a Norwood procedure or variant thereof. In the second stage, the Bidirectional Glenn procedure, the superior vena cava (SVC) is disconnected from the heart and redirected into the pulmonary arteries (PAs). In the third and final stage, the inferior vena cava (IVC) is connected to PAs via a straight Gore-Tex tube, forming a T-shaped junction. Although early survival rates following the Fontan procedure can exceed 90%, significant morbidity remains after surgery including venous hemodynamic abnormalities, diminished exercise capacity, thromboembolic complications, protein-losing enteropathy, heart transplant etc. [1].

Effect of Flow Pulsatility and Wall Compliance on the Energy Loss in the Total Cavopulmonary Connection

2013 ◽  
Author(s):  
Reza H. Khiabani ◽  
Sulisay Phonekeo ◽  
Harish Srinimukesh ◽  
Elaine Tang ◽  
Mark Fogel ◽  
...  
Keyword(s):  
Energy Loss ◽  
Wall Motion ◽  
Heart Defects ◽  
Superior Vena ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Total Cavopulmonary Connection ◽  
Venous Flow ◽  
The Right ◽  
Cavopulmonary Connection

Single Ventricle Heart Defects (SVHD) are present in 2 per 1000 live births in the US. SVHD are characterized by cyanotic mixing between the de-oxygenated blood from the systemic circulation return and the oxygenated blood from the pulmonary arteries. In the current practice, surgical interventions on SVHD patients commonly result in the total cavopulmonary connection (TCPC) [1]. In this configuration the systemic venous returns (inferior vena cava, IVC, and superior vena cava, SVC) are directly routed to the right and left pulmonary arteries (RPA and LPA), bypassing the right heart. The resulting anatomy has complex and unsteady hemodynamics characterized by flow mixing and flow separation. Pulsation of the inlet venous flow during a cardiac cycle and wall motion may result in complex and unsteady flow patterns in the TCPC. Although vessel wall motion and different degrees of pulsatility have been observed in vivo, non-pulsatile (time-averaged) flow boundary conditions and rigid walls have traditionally been assumed in estimating the TCPC hemodynamic parameters (such as energy loss). Recent studies have shown that these assumptions may result in significant inaccuracies in modeling TCPC hemodynamics [2, 3].

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