Extracardiac Fontan Connections Research Articles

Virtual surgery to predict optimized conduit size for adult Fontan patients with 16-mm conduits.

Recent evidence suggests that conduits implanted in Fontan patients at the age of 2-4 years become undersized for adulthood. The objective of this study is to use computational fluid dynamic models to evaluate the effect of virtual expansion of the Fontan conduit on haemodynamics and energetics of the total cavopulmonary connection (TCPC) under resting conditions and increased flow conditions. Patient-specific, magnetic resonance imaging-based simulation models of the TCPC were performed during resting and increased flow conditions. The original 16-mm conduits were virtually enlarged to 3 new sizes. The proposed conduit sizes were defined based on magnetic resonance imaging-derived conduit flow in each patient. Flow efficiency was evaluated based on power loss, pressure drop and resistance and thrombosis risk was based on flow stagnation volume and relative residence time (RRT). Models of 5 adult patients with a 16-mm extracardiac Fontan connection were simulated and subsequently virtually expanded to 24-32 mm depending on patient-specific conduit flow. Virtual expansion led to a 40-65% decrease in pressure gradient across the TCPC depending on virtual conduit size. Despite improved energetics of the entire TCPC, the pulmonary arteries remained a significant contributor to energy loss (60-73% of total loss) even after virtual surgery. Flow stagnation volume inside the virtual conduit and surface area in case of elevated RRT (>20/Pa) increased after conduit enlargement but remained negligible (flow stagnation <2% of conduit volume in rest, <0.5% with exercise and elevated RRT <3% in rest, <1% with exercise). Virtual expansion of 16-mm conduits to 24-32 mm, depending on patient-specific conduit flow, in Fontan patients significantly improves TCPC efficiency while thrombosis risk presumably remains low.

Fontan-associated liver disease.

Fontan-associated liver disease.

Y-graft modification to the Fontan procedure: Increasingly balanced flow over time

ObjectiveThe use of Y-grafts for Fontan completion is hypothesized to offer more balanced hepatic flow distribution (HFD) and decreased energy losses. The purpose of this study was to evaluate the hemodynamic performance of Y-grafts over time using serial cardiac magnetic resonance data and to compare their performance with extracardiac Fontan connections. MethodsTen Fontan patients with commercially available Y-graft connections and serial postoperative cardiac magnetic resonance data were included in this study. Patient-specific computational fluid dynamics simulations were used to estimate HFD and energy losses. Y-graft performance was compared with 3 extracardiac conduit Fontan groups (n = 10 for each) whose follow-up times straddle the Y-graft time points. ResultsY-graft HFD became significantly more balanced over time (deviation from 50% decreased from 18% ± 14% to 8% ± 8%; P = .015). Total cavopulmonary connection resistance did not significantly change. Y-grafts at 3-year follow-up showed more balanced HFD than the extracardiac conduit groups at both the earlier and later follow-up times. Total cavopulmonary connection resistance was not significantly different between any Y-graft or extracardiac conduit group. ConclusionsY-grafts showed significantly more balanced HFD over a 3-year follow-up without an increase in total cavopulmonary connection resistance, and therefore may be a valuable option for Fontan completion. Additional follow-up data at longer follow-up times are still needed to thoroughly characterize the potential advantages of Y-graft use.

Interactive pre-surgical design of optimal extra-cardiac Fontan connections starting with cardiac MRI reconstructions of the Glenn anastomosis

Pre-surgical planning for Fontan procedures involves time-consuming patient-specific vascular segmentation and non-intuitive virtual surgical modeling which has encumbered utility in the clinic by surgeons. We present an interactive platform to design virtual surgical options and visualize pericardial enlargement strategy for Fontan connections, starting with patient-specific vascular templates.

Fontan Pathway Growth: A Quantitative Evaluation of Lateral Tunnel and Extracardiac Cavopulmonary Connections Using Serial Cardiac Magnetic Resonance

Typically, a Fontan connection is constructed as either a lateral tunnel (LT) pathway or an extracardiac (EC) conduit. The LT is formed partially by atrial wall and is assumed to have growth potential, but the extent and nature of LT pathway growth have not been well characterized. A quantitative analysis was performed to evaluate this issue. Retrospective serial cardiac magnetic resonance data were obtained for 16 LT and 9 EC patients at 2 time points (mean time between studies, 4.2 ± 1.6 years). Patient-specific anatomies and flows were reconstructed. Geometric parameters of Fontan pathway vessels and the descending aorta were quantified, normalized to body surface area (BSA), and compared between time points and Fontan pathway types. Absolute LT pathway mean diameters increased over time for all but 2 patients; EC pathway size did not change (2.4 ± 2.2 mm vs 0.02 ± 2.1 mm, p < 0.05). Normalized LT and EC diameters decreased, while the size of the descending aorta increased proportionally to BSA. Growth of other cavopulmonary vessels varied. The patterns and extent of LT pathway growth were heterogeneous. Absolute flows for all vessels analyzed, except for the superior vena cava, proportionally to BSA. Fontan pathway vessel diameter changes over time were not proportional to somatic growth but increases in pathway flows were; LT pathway diameter changes were highly variable. These factors may impact Fontan pathway resistance and hemodynamic efficiency. These findings provide further understanding of the different characteristics of LT and EC Fontan connections and set the stage for further investigation.

Three Indications for Bovine Jugular Vein Grafts in a Single Tertiary Centre in Jeddah: A Retrospective Study

Introduction and Aim of the Work: Bovine jugular vein grafts(Contegra) can be used not only in the reconstruction of an abnormal right ventricular outflow tract (RVOT) but also for VSD repairs and as an extra-cardiac conduit for the Fontan circulation.(1-2-3-4-5). We aimed to present and review the preliminary results of contegra in the 3 different indications. Patients and Methods: We reviewed the available charts of 22 patients who needed contegra as an RVOT reconstive graft, 23 cases for Fontan extracardiac conduits and 8 cases of VSD in a single tertiary centre in Jeddah in more than 8 years between 2002 and 2011. The available demographic data, operative, ECHO findings, results, complications and the follow up data are presented and analysed. Results: Fifty three cases were included in this retrospective study from June 2002 to January 2011. The Median age at the time of operation was 3.5 years (range 1-26 years). The thirty days mortality was 7.5 % (four patients); one Fontan patient died because of arrhythmia & sepsis, the other Fontan one due to lately detected thrombosed Fontan connection. The 3rd patient was a case of Fallot tetralogy who died because of ventricular dysfunction and the 4th one was a repaired VSD died because of sepsis and DIC. Follow-up was available for 40 (75.4%) patients at a mean of 19.8 months (range 8-78 months) postoperatively. Conclusion: The Contegra xenograft is a good conduit for RVOT reconstruction, a potential acceptable alternative conduit for the extracardiac Fontan connections and can be used to close the VSD if it is associated with one of the previous 2 indications Keywords: Bovine jugular vein grafts, Contegra. Read more →

Extracardiac conduit Fontan procedure versus intra-atrial lateral tunnel Fontan procedure

The Fontan procedure has provided excellent surgical palliation for patients with various types of univentricular hearts, and it has evolved over time. Among many modifications, the lateral tunnel Fontan connection (LTF) and the extracardiac Fontan connection (ECF) are currently the most popular techniques for completing the total cavopulmonary connection. The advantages and disadvantages of both techniques are reviewed here. The advantages of the ECF includes adaptability to all types of univentricular hearts, ease of construction without aortic cross clamping and fewer atrial suture lines. The advantages of the LTF include the ability to complete Fontan circulation in young, very small patients with potential for growth. This review also compares post-operative arrhythmias and fluid dynamics associated with both techniques.

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.

Practice variability and outcomes of coil embolization of aortopulmonary collaterals before fontan completion: A report from the Pediatric Heart Network Fontan Cross-Sectional Study

The practice of coiling aortopulmonary collaterals (APCs) before Fontan completion is controversial, and published data are limited. We sought to compare outcomes in subjects with and without pre-Fontan coil embolization of APCs using the Pediatric Heart Network Fontan Cross-Sectional Study database which enrolled survivors of prior Fontan palliation. We compared hospital length of stay after Fontan in 80 subjects who underwent APC coiling with 459 subjects who did not. Secondary outcomes included post-Fontan complications and assessment of health status and ventricular performance at cross-sectional evaluation (mean 8.6 ± 3.4 years after Fontan). Centers varied markedly in frequency of pre-Fontan APC coiling (range 0%-30% of subjects, P < .001). The coil group was older at Fontan (P = .004) and more likely to have single right ventricular morphology (P = .054) and pre-Fontan atrioventricular valve regurgitation (P = .03). The coil group underwent Fontan surgery more recently (P < .001), was more likely to have a prior superior cavopulmonary anastomosis (P < .001), and more likely to undergo extracardiac Fontan connection (P < .001) and surgical fenestration (P < .001). In multivariable analyses, APC coiling was not associated with length of stay (hazard ratio for remaining in-hospital 0.91, 95% CI 0.70-1.18, P = .48) or postoperative complications, except more post-Fontan catheter interventions (hazard ratio 1.74, 95% CI 1.04-2.91, P = .03), primarily additional APC coils. The groups had similar outcomes at cross-sectional evaluation. Management of APCs before Fontan shows marked practice variation. We did not find an association between pre-Fontan coiling of APCs and shorter postoperative hospital stay or with better late outcomes. Prospective studies of this practice are needed.

Bovine Valved Xenograft (Contegra) Conduit in the Extracardiac Fontan Procedure: The Preliminary Experience

Constructing a competent valve using the xenograft valved conduit (Contegra) in the extracardiac Fontan connection may maintain better forward flow into the pulmonary circulation. The preliminary results and potential advantages of using the Contegra are discussed in this review. A retrospective review of 18 patients who underwent the extracardiac Fontan connection using the Contegra conduit from June 2002 to September 2005. Median age at the time of operation was 4.5 year (range 2.5-34 years). In 15 patients (83%) a 4 mm fenestration was created. Overall operative mortality was 11 % (two patients); one patient died because of arrhythmia & sepsis, and the other one due to thrombosed Fontan connection. The ranges of intensive care unit stay, chest tube duration, and hospital stay were 1-18 days (median, 2 days), 4-38 days (median, 7 days), and 5-47 days (median, 12.5 days), respectively. Follow-up is available for 15 (94%) patients at a mean of 15.8 months (range 8-48 months) postoperatively. They were all asymptomatic and their room air oxygen saturation ranged between 88% and 100% (mean, 96.1%). There have been no further thromboembolic episodes during follow up. Echocardiograms demonstrated patent conduit in all patients with no hepatic vein reversal flow except to a minimal degree in five patients; however the valve competency was demonstrated radiologically. The Contegra xenograft is a potential alternative conduit for the extracardiac Fontan connections. These encouraging preliminary results may support better pulmonary forward flow.

Bovine valved xenograft conduits in the extracardiac Fontan procedure

Total cavopulmonary connection has been proposed as a rational alternative to atriopulmonary connection for complex Fontan operations. de Leval and colleagues proposed the concept of direct cavopulmonary connection as a way to minimize kinetic energy loss in the Fontan circuit. Total cavopulmonary anastomosis with the extracardiac conduit technique has gained favor because it streamlines the venous flow pattern and reduces the incidence of atrial arrhythmias. There are a number of potential advantages of the extracardiac conduit approach over other modifications of the Fontan procedure, including the improved hydrodynamics in the cavopulmonary connection. Conduits of different material have been used for the extracardiac Fontan procedure, examples of these conduits are the Dacron tube, the polytetrafluoroethylene tube (Gore-Tex; W. L. Gore & Associates, Inc, Flagstaff, Ariz), the homograft, and the pericardial tube, and each one has advantages and disadvantages. Bovine jugular vein xenograft (Medtronic’s Contegra, Medtronic, Inc, Minneapolis, Minn) has been used successfully to reconstruct the right ventricular outflow tract in patients with congenital heart disease, with promising early results. The Contegra conduit is a biologic valved conduit consisting of a glutaraldehyde-preserved heterologous bovine jugular vein with a trileaflet venous valve. The advantages of using the Contegra xenograft are easy availability, different size options, and the presence of a valve in the conduit. In this report we present potential advantages of using a xenograft valved conduit to construct the extracardiac Fontan connection between the inferior vena cava (IVC) and the pulmonary artery (PA).