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Ann Thorac Surg 1996;62:1347-1350
© 1996 The Society of Thoracic Surgeons
Cardiac Unit, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium
Accepted for publication May 24, 1996.
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Abstract |
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Methods. One atriopulmonary conduit replacement, four extraatrial cavopulmonary connections, and one intraatrial cavopulmonary repair were achieved by means of a homograft of the descending aorta with a diameter of 15 to 17 mm. Three pulmonary unifocalization procedures were carried out in 2 more patients using a curved homograft of the aortic arch with a diameter of 18 mm. Except for 1 patient, whose incompetent common atrioventricular valve was replaced with a mechanical prosthesis, all other patients were managed without anticoagulation.
Results. No conduit-related complications were seen during a follow-up of 18 to 42 months. One patient died perioperatively during an emergency central repair of the right ventricular outflow tract after bilateral unifocalization with arch homografts. Another patient died suddenly 4 months after cavopulmonary connection. The remaining 6 patients are currently doing well.
Conclusions. Regardless of the complexity of the underlying malformations, we are encouraged to use nonvalved thoracic aortic homografts in the repair of congenital cardiac diseases because of the reduction in thrombotic, hemorrhagic, and infectious complications associated with their use; convenience in handling; and their versatility in size and shape.
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Introduction |
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Given the excellent results seen in patients who have received valved homografts and the preferred use of human tissue to prosthetic materials, we have implanted nonvalved cryopreserved homografts from the descending aorta or aortic arch for right ventricular reconstruction. We describe here the suitability of aortic homografts as nonvalved conduits in congenital cardiac operations, because of the reduction in the risk of thromboembolic complications and late conduit stenosis caused by intimal peeling associated with their use, despite a potential for late calcification.
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Case Reports |
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Patient 2
A 13-month-old girl presented with a double-inlet, double-outlet univentricular heart with malpositioned great arteries, pulmonary and subpulmonary stenosis, and a small but competent left-sided atrioventricular (AV) valve. An atrial septostomy (Rashkind) was performed as palliation during the neonatal period. Because of severe cyanosis, surgical cure was achieved by total cavopulmonary connection, using an extraatrial descending aorta homograft (diameter, 16 mm) and extending from the inferior vena cava to the distal transposed pulmonary trunk (Fig 1
). Her early postoperative course was complicated by the occurrence of pleural effusion, necessitating drainage for 18 days.
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Patient 4
A 26-month-old girl presented with a complete AV canal defect with multiple ventricular septal defects, right ventricular dominance, and a regurgitant common AV valve. During the neonatal period a pulmonary artery banding procedure was performed as a palliative measure. Because of severe cyanosis, surgical repair was carried out 2 years later and involved the construction of a total cavopulmonary connection with a descending aorta homograft (diameter, 15 mm) in the extraatrial position. A 27-mm St. Jude valve was implanted in the atrioventricular position. Her early postoperative course was complicated by prolonged pleural effusion and pulmonary infection, necessitating temporary respiratory support. Clinically she tolerated the iatrogenic AV block well and recovered completely but died suddenly 4 months after repair. Retrospectively, a definitive pacemaker should have been implanted, despite her clinical tolerance of the conduction disorder.
Patient 5
A 1-year-old boy presented with a D-malposition of the great arteries, a single atrium, a single ventricle, pulmonary valve stenosis, and total pulmonary venous drainage into the superior vena cava. He underwent a total cavopulmonary connection using an extraatrial homograft of the descending aorta (diameter, 17 mm), leaving the pulmonary veins to drain into the cardiac end of the superior vena cava. No postoperative problems occurred.
Patient 6
A 2
-year old girl presented with congenital AV block, situs solitus, dextrocardia, L-transposition of the great vessels, an unrestrictive bulboventricular foramen, a double-inlet left ventricle, and pulmonary atresia. The mitral valve was incompetent. She underwent a palliative procedure at birth, consisting of a modified right Blalock-Taussig shunt procedure. Subsequent complete repair consisted of a total cavopulmonary connection using an extraatrial descending aorta homograft (diameter, 16 mm), along with atrial septectomy, patch occlusion of the mitral valve orifice, and AV sequential pacemaker implantation. Her postoperative course was uneventful.
Patient 7
A 15-year-old girl with tetralogy of Fallot underwent her first palliative procedure at birth, and this consisted of the construction of a Waterston shunt, which was undone at the age of 18 months, together with patch enlargement of the right pulmonary artery and pulmonary trunk. No intrapericardiac left pulmonary artery was noted, and the ventricular septal defect was left open. At 12 years of age, she underwent construction of a left modified Blalock-Taussig shunt on a very diminutive, disconnected left pulmonary artery, which permitted rapid and excellent growth of the pulmonary artery to a diameter of 16 mm. At the patient's current presentation, a left "hilus" was reconstructed using a 7-cm-long segment of distal arch and proximal descending aorta homograft, fed by the existing shunt, which was reconnected to one of the homograft arch vessels. Two weeks later, the homograft was joined to the pulmonary trunk, the shunt was ligated, and the ventricular septal defect was closed.
Patient 8
An 11-year-old boy with severe pulmonary atresia with total absence of intrapericardiac pulmonary vessels and a ventricular septal defect underwent his first palliative procedure at the age of 7 years, and this involved the creation of a left modified Blalock-Taussig shunt for a diminutive native left pulmonary artery. A good-sized native right pulmonary artery was fed by two major aortopulmonary collateral arteries. Because of progressive stenosis of the shunt, a left pulmonary arterial hilus was first constructed using a homograft of the aortic arch (diameter, 19 mm). The existing shunt was reimplanted on one of the homograft arch vessels after resection of its stenosed segment. One week later a similar procedure was carried out in the right chest, using an aortic arch homograft (diameter, 17 mm) and temporarily connecting one of the major aortopulmonary collateral arteries to one of the arch vessels. The central repair was done as an emergency, under cardiac massage, for the management of acute severe desaturation. The sutures fixing the right homograft to the pleuropericardial wall had loosened, and the junction between the major aortopulmonary collateral artery and the homograft had twisted. Despite complete repair of the right ventricular outflow tract with a central pulmonary valved homograft, construction of a transverse Dacron interpulmonary trunk, and closure of the ventricular septal defect, the child died 1 week later of uncontrolled hemoptysis. Autopsy was not granted.
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Comment |
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Motivated by our own experience with valved homografts, we have used homografts of the descending aorta and aortic arch in the repair of some complex cardiac malformations requiring a nonvalved conduit. This has been made possible further by the availability of cryopreserved nonvalved homografts of thoracic aorta from both beating and nonbeating heart donors from the European Homograft Bank. After ligature of the intercostal branch stumps, the grafts are sterilized in antibiotic solution and stored in liquid nitrogen (Fig 2).
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Since its description by de Leval and associates [2] in 1988, total cavopulmonary connection has proved to be an effective modification of the Fontan principle, with better hemodynamic performance and fewer supraventricular arrhythmias [6, 7]. Although the original procedure consisted of the construction of an intraatrial tunnel between the inferior vena cava and the right pulmonary artery using a prosthetic baffle, numerous technical modifications have been implemented since then [3, 8–10].
To reduce the risk for obstruction of pulmonary venous return (small right atrium, double-inlet ventricles, or abnormal pulmonary or systemic venous connections) and the potential for atrial arrhythmias, Marceletti and colleagues [3] used an extraatrial inferior vena cava–pulmonary artery bypass conduit made of Dacron. A potential weakness of this technique, however, is the excessive use of prosthetic tube material in a low-pressure circuit [3]. Although early follow-up showed no thromboembolic complications or conduit stenosis, oral anticoagulant treatment was advised [11]. However, if technically feasible, direct cavopulmonary connection by an autogenous atrial tunnel seems attractive, as growth of the channel can be expected, as occurs in patients who undergo a Senning-like procedure [8–10].
In our 6 patients who received a descending aorta homograft with a diameter of 15 to 17 mm, 4 children underwent construction of a cavopulmonary conduit in an extraatrial position because of anatomic reasons (small right atrium, anomaly of the AV valve, associated abnormal pulmonary venous return). In the first patient, a prosthetic atriopulmonary conduit was replaced with a descending aorta homograft with a diameter of 15 mm for the treatment of severe conduit stenosis caused by intimal peeling. In the third patient, an intraatrial homograft baffle was made together with reconstruction of the pulmonary confluence using the same material.
In keeping with our policy to treat all patients with implanted valved homografts with antiplatelet agents for at least 3 months, all patients received acetylsalicylic acid. Its use is especially indicated if these homografts are placed in an intracardiac position, thus exposing the adventitial surface of the conduit as a possible thrombogenic source. Only the patient who had a mechanical valve implanted in the atrioventricular position received anticoagulation treatment. Hence, early follow-up showed no conduit-related complications.
In this small series of patients who underwent modified Fontan procedures, we noted no supraventricular arrhythmias, which probably is attributable to the extraatrial conduit repair in 4 of the 6 patients. We are currently favoring the use of extraatrial reconstruction in total cavopulmonary connection.
The other major indication involved homografts of the aortic arch with a mean diameter of 18 mm, specifically for hilar reconstruction in 2 patients with complex tetralogy of Fallot and absent intrapericardiac pulmonary arteries. One of the 2 patients died from massive hemoptysis after complete central repair and previous bilateral hilar reconstruction.
The success of the last operation was jeopardized by the twisting of the right hilar homograft, caused by loosening of the fixing sutures to the pericardium and leading to impeded right lung circulation. The results of unifocalization operations are not yet clearly evident, because of differences in patient selection and the procedures used in reported series. The Great Ormond Street Group mentioned a series of 26 children undergoing unifocalization, most commonly with the interposition of prosthetic tubes. The patency rate of their unifocalizing anastomoses has varied between 5% and 100%, depending on the type of procedure [12]. No patency failure of the anastomoses occurred in our 2 patients who had three unifocalization procedures, despite the one catastrophic event that should be considered the result of a technical error.
Following the large experience with valved homografts, cryopreserved homografts of descending aorta and aortic arch appear to be suitable nonvalved conduits. They are technically easy to manage, result in little bleeding at the anastomoses, and tolerate some degree of flattening. During a follow-up of from 18 to 42 months, no thromboembolic events or anastomotic stenoses were noticed. From this point of view, the endothelial inner surface of these conduits may be a major advantage of homograft conduits over prosthetic conduits, and their use could avoid the need for oral anticoagulants.
The higher elastin and intrinsic calcium contents of aortic homografts make these conduits more susceptible to calcification, however [13]. With regard to the poor correlation between homograft calcification and conduit valve dysfunction, we believe that these nonvalved conduits will remain functional in the presence of calcification, even though our follow-up may not be long enough yet to bear this out.
Despite the fact that adult-sized homografts can be implanted, growth restriction is still a limiting factor, resulting in the possible need for reoperation in younger and smaller children. Availability should be a minor problem, however, because nonvalved homografts could also be obtained from the donors of valved conduits.
Nevertheless, long-term follow-up is needed to confirm our positive early experience with these nonvalved homograft conduits for the repair of complex cardiac malformations of the pulmonary circulation, which appear to be a valuable and attractive alternative conduit to prosthetic material.
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* A nonprofit organization. Address: c/o Military Hospital, Bruynstraat, Neder-Over-Heembeek, Belgium. 
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