Extracardiac Cavopulmonary Research Articles

Total cavopulmonary connection with a new bioabsorbable vascular graft: First clinical experience

ObjectivesTo assess safety and clinical performance of a novel bioabsorbable vascular graft in pediatric patients with univentricular cardiac malformation who received surgical correction via an extracardiac cavopulmonary conduit. MethodsThe implanted graft material is designed to attract patient's own cells and proteins, which trigger a cascade of physiological events leading to endogenous tissue restoration. As the graft resorbs progressively after implantation, components of native tissue including collagen, endothelial lining, and capillary blood vessels develop and organize into a natural tissue. Five patients (aged 4-12 years) received this new vascular graft as interposition between the inferior vena cava and the pulmonary artery. They were followed up to 12 months after surgery. The conduit was assessed by echocardiography, computed tomography and magnetic resonance imaging, including 4-dimensional flow. ResultsAll patients recovered from the procedure without complications. No device-related adverse events were reported. Two patients required interventional occlusion of aortopulmonary collaterals. At 12 months, there was a significant improvement in the patients' general condition. Imaging studies demonstrated anatomical (conduit diameter, length and wall thickness) and functional (blood flow pattern) stability of the bioabsorbable grafts in all patients with no significant changes at 12 months compared with early postoperative data. ConclusionsInitial clinical experience with a novel absorbable graft underlines the potential of this new material to improve cardiac and vascular surgical procedures. In addition, better biocompatibility may reduce permanent implant-related complications. A longer follow-up is needed to assess the long-term effectiveness of biodegradable vascular grafts, including their ability to grow.

Invited Commentary

Invited Commentary

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.

Results of 100 Consecutive Extracardiac Conduit Fontan Operations

Throughout the years, the experience with Fontan's operation has increased and has opened the way to a much wider application of this principle. A number of major risk factors have been identified and managed by several modifications of the original Fontan procedure. In the past 15 years, operative and postoperative risks have been controlled to a major extent by the application of intermediate surgical procedures. Modifications to the original technique have been designed to simplify surgery and better protect the myocardium by avoiding, as much as possible, prolonged ischemic time. In 1988, we developed a new form of total extracardiac right heart bypass by means of associating an extracardiac conduit placed between the inferior vena cava (IVC) and the pulmonary artery with a bidirectional cavopulmonary anastomosis (BCPA)--the so-called total extracardiac cavopulmonary connection (TECC). Between November 1997 and October 2003, 100 patients with complex cardiac anomalies underwent a modified Fontan operation by TECC. In 88 patients, the repair was staged by preliminary BCPA that was bilateral in 15 patients and associated with a modified Damus-Kaye-Stansel procedure to bypass a subaortic obstruction in 24 patients. Early (in hospital) deaths occurred in 6% of patients and the extracardiac conduit was taken down in 2 additional patients for a total early failure rate of 8%. The cause of death was myocardial failure in 5 patients. Pulmonary artery distortion or hypoplasia appeared to be the cause of death in 1 patient and the cause of failure in 1 patient. Atrioventricular valve regurgitation was the cause of failure in 1 patient. Follow-up to December 2003 was available in all surviving patients. There were no late deaths. At follow-up, 87 patients (89%) were in New York Heart Association (NYHA) functional class I, 4 in class II, and 3 in class III due to moderate to severe atrioventricular valve regurgitation. Use of the following guidelines can result in the achievement of orthoterminal repair with complete separation of pulmonary and systemic circulation, with negligible early mortality and a long-term NYHA class I: (1) Not all patients with univentricular heart (UVH) should undergo the extracardiac Fontan procedure; (2) in UVH with favorable streaming, a Q (p)/Q (s) ratio of approximately 1 to 1, and mild cyanosis, natural history might be preferable to surgical history; (3) any form of fenestration is contradictory to orthodox application of Fontan's principle. Children in whom a planned fenestration seems necessary because of suboptimal conditions should instead undergo a combination of BCPA and associated forward pulmonary blood flow; and (4) negligible mortality should be considered mandatory in UVH, normal pulmonary arteries, and absent cardiomegaly after appropriated and correct staging.

The patterns of flow in the total extracardiac cavopulmonary connection

more than 30 years ago, fontan and baudet proposed bypass of a dysfunctional right ventricle by connecting the pulmonary arteries directly to the right atrium, the so-called atriopulmonary anastomosis. since then, much experience has been accrued in the field of the functionally univentricular circulation. the proposed connections have been subjected to several modifications, aiming towards minimizing the losses of energy in the cavopulmonary system, and thereby improving the clinical outcomes. a remarkable improvement was achieved with the introduction of the concept of the total cavopulmonary connection, specifically the combination of a bi-directional glenn anastomosis with a tubular intracardiac extension from the inferior caval venous to the pulmonary arteries. this design was shown to avoid the dissipation of energy associated with the swirling patterns seen in the traditional atrio-pulmonary anastomosis.

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).

The beneficial vortex and best spatial arrangement in total extracardiac cavopulmonary connection

Objective: Total extracardiac cavopulmonary connection is an established procedure, but the best spatial arrangement remains controversial. On the basis of our clinical experience with total extracardiac cavopulmonary connection, we performed quantitative and qualitative flow analysis on total extracardiac cavopulmonary connection models simulating the two most frequent arrangements applied to our patients to determine the most favorable hydrodynamic pattern. Methods: We selected two main groups among 110 patients who underwent total extracardiac cavopulmonary connection, those with left-sided inferior vena cava anastomosis (type 1) and those with facing superior and inferior vena cava anastomoses (type 2). Blown-glass total extracardiac cavopulmonary connection phantom models were constructed on the basis of nuclear magnetic resonance and angiographic images. Flow measurements were performed with a Nd:YAG Q-switched laser and a particle imaging velocimetry system. A power dissipation study and a finite-element numeric simulation were also carried out. Results: When applying superior and inferior vena caval flow proportions of total systemic venous return of 40% and 60%, respectively, a vortex was visualized in the type 1 phantom that rotated counterclockwise at the junction of the caval streams. This apparent vortex was not a true vortex; rather, it represented a weakly dissipative recirculating zone modulating the flow distribution into the pulmonary arteries. The power dissipation and finite-element numeric stimulation confirmed the beneficial nature of the apparent vortex and a more energy-saving pattern in the type 1 phantom than in the type 2 phantom. Conclusion: Total extracardiac cavopulmonary connection with left-sided diversion of the inferior vena caval conduit anastomosis is characterized by a central vortex that regulates the caval flow partitioning and provides a more favorable energy-saving pattern than is seen with the total extracardiac cavopulmonary connection with directly opposed cavopulmonary anastomoses.J Thorac Cardiovasc Surg 2002;124:471-8

Late Results of Extracardiac Fontan Repair

The Fontan procedure by means of an extracardiac conduit was initially proposed for patients presenting with anomalies of intra-atrial anatomy. We extended this technique to all patients with functional anatomic single ventricle. Between 1988 and 1998, 206 patients with complex cardiacanomalies underwent a total extracardiac cavopuolmonary connection. In 202 patients we used a conduit, in 4 patients we performed an IVC to pulmonary artery direct anastomosis. Ten patients underwent Conversion of a filing atriopulmonary Fontan procedure to a total extracardiac cavopulmonary connection. Early deaths occurred in 10% of patients and the extracardiac conduit was taken down in 3 additional patients. The cause of death was myocardial failure in 13 patients. Pulmonary distortion or hypoplasia in 6. No deaths have occurred in our last 45 patients. We observed no cases of conduit obstruction and thrombosis. Arrthymias were present in 16 patients. Ten patients underwent conversion of a formed modified Fontan. There were no immediate postoperative deaths. These results demonstrate that the total extracardiac cavopulmonary connection provide good early and mildterm results and is the technique of choice for a Fontan type repair. Copyright 1999 by W.B. Saunders Company

Extracardiac Fontan operation for complex cardiac anomalies: Seven years' experience

Methods: Between 1988 and 1995, 60 patients with complex cardiac anomalies underwent a total extracardiac cavopulmonary connection, a combination of a bidirectional cavopulmonary anastomosis with an extracardiac conduit interposition between the inferior vena cava and pulmonary arteries, except in one patient in whom direct anastomosis was possible. In 40 patients the total extracardiac cavopulmonary connection followed preliminary bidirectional cavopulmonary anastomosis, associated with a modified Damus-Kaye-Stansel anastomosis in 16. The conduits were constructed of Dacron fabric ( n = 34), homografts ( n = 3), and polytetrafluoroethylene ( n = 22). Results: Total early failure rate was 15% ( n = 9). Six patients died, and three more had conduit takedown owing to pulmonary artery stenosis and hypoplasia ( n = 2) and severe atrioventricular valve regurgitation ( n = 1). Two other patients required anastomosis revision owing to stricture. In a mean follow-up of 48 months (6 to 86 monthe) there were no late deaths (actuarial 5-year survival 88% ± 4%); 52 of 54 patients are in New York Heart Association class I or II. Two patients required pulmonary artery balloon dilation or stent implantation, or both, after total extracardiac cavopulmonary connection. Late tachyarrhythmias were detected in four of 54 patients: two had sick sinus syndrome with flutter necessitating a pacemaker implantation and two had recurrent flutter (actuarial 5-year arrhythmia-free rate 92% ± 4%). Conduit patency was evaluated by serial magnetic resonance imaging studies. Preliminary data showed a 17.8% ± 7.6% mean reduction in conduit internal diameter during the first 6 months after total extracardiac cavopulmonary connection, with no progression over the next 5 years. Conclusion: These results demonstrate that the total extracardiac cavopulmonary connection provides good early and midterm results and may reduce the prevalence of late arrhythmias in patients undergoing the Fontan operation. (J Thorac Cardiovasc Surg 1997;114:1020-31)

Conversion of the Hemi-Fontan Procedure to Fenestrated Total Extracardiac Cavopulmonary Bypass

Conversion of the Hemi-Fontan Procedure to Fenestrated Total Extracardiac Cavopulmonary Bypass