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

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.

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

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80751 ◽

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.

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

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206492 ◽

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].

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Effect of Flow Pulsatility on 2nd Stage Fontan Hemodynamics: An In Vitro Investigation

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-204573 ◽

2009 ◽

Author(s):

Christopher M. Haggerty ◽

Lakshmi P. Dasi ◽

Jessica Kanter ◽

Ajit P. Yoganathan

Keyword(s):

Congenital Heart ◽

Single Ventricle ◽

Heart Defects ◽

Superior Vena ◽

Fontan Procedure ◽

Pulmonary Arteries ◽

Vena Cava ◽

Second Stage ◽

In Vitro Investigation

The Fontan procedure [1] is the staged, palliative surgical approach used to treat patients suffering from single ventricle congenital heart defects. The second stage of this procedure involves the connection of the superior vena cava (SVC) to the pulmonary arteries (PAs) in either an end-to-side (known as the Bi-Directional Glenn (BDG)) or side-to-side (or Hemi-Fontan (HF)) fashion. Because of obvious disparities at the connection site, there are understandable differences in the fluid dynamics between the two geometries.

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

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19683 ◽

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.

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Investigation of Vessel Growth and its Impact on Hemodynamics in Patients With Lateral Tunnel Total Cavopulmonary Connection

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80329 ◽

2012 ◽

Author(s):

Maria Restrepo ◽

Lucia Mirabella ◽

Elaine Tang ◽

Chris Haggerty ◽

Mark A. Fogel ◽

...

Keyword(s):

Heart Defects ◽

Fontan Procedure ◽

Pulmonary Arteries ◽

Vena Cava ◽

Total Cavopulmonary Connection ◽

Lateral Tunnel ◽

Vessel Growth ◽

Original Size ◽

The Right ◽

Cavopulmonary Connection

Single ventricle heart defects affect 2 per 1000 live births in the US and are lethal if left untreated. The Fontan procedure used to treat these defects consists of a series of palliative surgeries to create the total cavopulmonary connection (TCPC), which bypasses the right heart. In the last stage of this procedure, the inferior vena cava (IVC) is connected to the pulmonary arteries (PA) using one of the two approaches: the extra-cardiac (EC), where a synthetic graft is used as the conduit; and the lateral tunnel (LT) where part of the atrial wall is used along with a synthetic patch to create the conduit. The LT conduit is thought to grow in size in the long term because it is formed partially with biological tissue, as opposed to the EC conduit that retains its original size because it contains only synthetic material. The growth of the LT has not been yet quantified, especially in respect to the growth of other vessels forming the TCPC. Furthermore, the effect of this growth on the hemodynamics has not been elucidated. The objective of this study is to quantify the TCPC vessels growth in LT patients from serial magnetic resonance (MR) images, and to understand its effect on the connection hemodynamics using computational fluid dynamics (CFD).

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

Journal of Fluids Engineering ◽

10.1115/1.4040214 ◽

2018 ◽

Vol 140 (12) ◽

Cited By ~ 1

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.

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A Study of TCPC-Stent Conjunction for Cavopulmonary Assist in Fontan Patients With Right Ventricular Dysfunction

Volume 7: Fluids Engineering ◽

10.1115/imece2016-68760 ◽

2016 ◽

Cited By ~ 2

Author(s):

Jakin Jagani ◽

Alexandrina Untaroiu

Keyword(s):

Energy Loss ◽

Power Loss ◽

Therapeutic Option ◽

Superior Vena ◽

Fontan Operation ◽

Pulmonary Arteries ◽

Vena Cava ◽

Paediatric Population ◽

Circulatory Support ◽

Blood Distribution

Mechanical circulatory support devices have gained significant importance in recent years as a viable therapeutic option to support paediatric population and children with single functional ventricle. The Fontan operation helps to reroute the deoxygenated blood to the lungs by bypassing the dysfunctional right ventricle. Total Cavopulmonary Connection (TCPC) is usually a method opted by the clinicians to connect the superior vena cava (SVC) and inferior vena cava (IVC) to the left and right pulmonary artery (LPA and RPA). However, the non-physiologic flow patterns created by the Fontan procedure leads to an increase in chances of platelet deposition and pressure loss which calls for heart transplantation to prevent early and late stage pathophysiology. This had led to modification of TCPC geometry to reduce the pressure and energy loss and thereby unload the single functional ventricle to ensure longer survival period. A study on mechanical circulatory device in conjunction with the modified TCPC geometry has seen little exposure and has opened new gates to develop a variety of state-of-art cavopulmonary assist devices. This study is focused on the selection of optimal TCPC to reduce energy loss and the effect of stent inside the modified TCPC on hemodynamics and flow structures. Four TCPC connections, developed for a particular age group of children, were studied for the velocity field, overall pressure and energy loss. In addition, the four TCPC connection geometries were also studied for distribution of hepatic blood from the IVC to both pulmonary arteries, and hence the lungs, to prevent development of any arteriovenous malformations. The entire stent assembly mounted inside the two best performing TCPC connections was examined for the hemodynamic effects using a series of 3D-CFD simulations. The curved-type connection for the TCPC proved to provide minimum pressure and energy loss along with reduced traces of vortex and recirculation. However, it was not efficient in terms of hepatic blood distribution. The flared geometry performed second best in terms of both minimum power loss and even hepatic blood distribution. There was a slight difference in power loss between the flared and the curved TCPC configuration with stent but the flared geometry had better hepatic blood distribution. This study demonstrated that a stent in conjunction with a TCPC leads to development of a helical flow pattern which provides better mixing of blood and even distribution to both the pulmonary arteries. The design of a stent with the best performing flared TCPC configuration can be optimized to reduce the amount of power loss and vortex generation and can be used to design similar scaled models for paediatric population of various age groups.

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Comparison of Clinical and Simulation Results for the Stanford Y-Graft Fontan Pilot Trial

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80928 ◽

2012 ◽

Author(s):

Weiguang Yang ◽

Jeffrey A. Feinstein ◽

V. Mohan Reddy ◽

Frandics P. Chan ◽

Alison L. Marsden

Keyword(s):

Inferior Vena ◽

Single Ventricle ◽

Heart Defects ◽

Fontan Procedure ◽

Pilot Trial ◽

Pulmonary Arteries ◽

Vena Cava ◽

Extracardiac Conduit ◽

Lateral Tunnel ◽

Third Stage

Without surgical palliation, single ventricle heart defects are uniformly fatal. A three-staged surgical repair is typically performed on these patients, who are otherwise severely cyanotic. In the third stage, the Fontan procedure, the inferior vena cava (IVC) is connected to the pulmonary arteries (PAs) via a lateral tunnel or extracardiac conduit. Following Fontan completion, deoxygenated blood from the upper and lower body is redirected to the PAs, bypassing the heart.

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Kawashima by Fenestrated Hemi-Fontan for Palliation Following Prior Stage I Norwood Operation

World Journal for Pediatric and Congenital Heart Surgery ◽

10.1177/2150135118769326 ◽

2018 ◽

Vol 9 (4) ◽

pp. 451-453 ◽

Cited By ~ 1

Author(s):

Jenny E. Zablah ◽

Michael Ross ◽

Neil Wilson ◽

Brian Fonseca ◽

Max B. Mitchell

Keyword(s):

Single Ventricle ◽

Superior Vena ◽

Fontan Procedure ◽

Venous Blood ◽

Young Infant ◽

Pulmonary Arteries ◽

Vena Cava ◽

Stage I ◽

Azygos Continuation ◽

Cavopulmonary Shunt

Single ventricle patients with interrupted inferior vena cava (IVC) and azygos continuation to the superior vena cava (SVC) are typically palliated with a bidirectional cavopulmonary shunt (BCPS), known as the Kawashima operation in this setting. Because the volume of venous blood directed to the pulmonary arteries is substantially greater in the presence of interrupted IVC, Kawashima procedures are commonly delayed to older age compared to other single ventricle patients undergoing BCPS. We report two young infant single ventricle patients with interrupted IVC and azygos continuation to the SVC who underwent stage I Norwood procedures for initial palliation. In both cases, a fenestrated hemi-Fontan procedure achieved successful Kawashima circulations.

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