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Ann Thorac Surg 1996;62:258-261
© 1996 The Society of Thoracic Surgeons

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Case Report

Late Conduit Occlusion After Modified Fontan Procedure With Classic Glenn Shunt

Departments of Cardiology, Pediatric Cardiology, and Surgery, Duke University Medical Center, Durham, North Carolina

Accepted for publication January 22, 1996.

	Abstract

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A number of patients with complex congenital heart disease who were initially palliated with a classic Glenn shunt subsequently underwent modified Fontan procedures. This report discusses the operative management of complete occlusion of right atrial-to-right ventricular conduits in patients with patent classic Glenn shunts. The literature is reviewed regarding similar patients, and alternative treatment strategies are discussed.

	Introduction

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See also page 261.

Surgical techniques for palliation of children with complex congenital heart disease and single-ventricle physiology have evolved significantly since the introduction of the superior vena cava to right pulmonary artery (PA) anastomosis by Glenn. Fontan demonstrated that the entire systemic venous return could be directed to the PAs, providing a method of definitive palliation for these patients. Some patients initially palliated with a Glenn anastomosis subsequently underwent modified Fontan procedures. The Glenn shunt was frequently left intact, and the inferior vena caval drainage was directed to the left lung using either a direct atriopulmonary connection or a conduit. The conduits were placed from the right atrium (RA) to either the right ventricle (RV) or the main PA. Potential long-term complications include pulmonary arteriovenous malformations (AVMs) in the right lung, atrial thrombus, atrial arrhythmias, and conduit obstruction or occlusion. This report discusses the management of 2 patients presenting with complete occlusion of RA-RV conduits more than 10 years after classic Glenn shunt and subsequent modified Fontan procedure.

	Case Reports

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Patient 1
The first patient is a 24-year-old woman with pulmonary atresia and intact ventricular septum who had undergone multiple procedures including a Waterston shunt, placement of an RV outflow patch, and a classic Glenn shunt. In 1981, at 11 years of age, a modified Fontan repair was performed with an RA-RV Dacron conduit with a porcine valve. She was well until January 1994, when increasing cyanosis (room air O₂ saturation, 81%), worsening exercise tolerance, and atrial fibrillation developed. Cardiac catheterization revealed a dilated RA with a mean pressure of 21 mm Hg, and moderate conduit stenosis (5 mm Hg gradient). The Glenn shunt was patent, although multiple small AVMs were noted in the right lung. In August 1994 she was hospitalized for worsening cyanosis (room air O₂ saturation, 46%) and dyspnea. Catheterization revealed a mean RA pressure of 26 mm Hg with complete occlusion of the RA-RV conduit. A magnetic resonance imaging scan revealed a patent left PA. The patient was referred for revision of her modified Fontan repair.

Normothermic femorofemoral cardiopulmonary bypass was commenced before sternotomy. The superior vena cava was not cannulated, the Glenn anastomosis was left intact, and the left ventricle was allowed to eject. The RA-RV conduit and degenerated porcine valve were removed and replaced with a 20-mm externally ribbed polytetrafluoroethylene (PTFE) graft. Blood loss from the RA was controlled using a 30-mL balloon catheter passed through the conduit and inflated in the atrial cavity during the RA anastomosis. The catheter was removed and the graft clamped during the distal anastomosis. Postoperative transesophageal echocardiography demonstrated unobstructed flow in the conduit. She was begun on anticoagulation with warfarin sodium. At discharge, she was in normal sinus rhythm, her room air O₂ saturation was 89%, and her exercise tolerance had significantly improved. She remains well 1 year postoperatively.

Patient 2
The second patient is a 34-year-old woman with tricuspid atresia, normally related great vessels, and a ventricular septal defect. She underwent a classic Glenn shunt in 1965, at 5 years of age, and a left modified Blalock-Taussig shunt in 1974. In 1976, a modified Fontan procedure was performed with an RA-RV valved homograft conduit, atrial septal defect closure, and ligation of the Blalock-Taussig shunt. She was well until April 1994, when atrial fibrillation developed. She was admitted in August 1994 for worsening cyanosis, with a room air O₂ saturation of 79%. Transesophageal echocardiography revealed a large RA thrombus; however, the conduit was not well visualized. Catheterization revealed a dilated RA (mean pressure, 19 mm Hg) with a large thrombus, a small residual atrial septal defect with right-to-left shunting, and complete occlusion of the RA-RV conduit. The Glenn shunt was patent and multiple small AVMs were present in the right lung. The left PA filled by multiple systemic collaterals. Evaluation for a hypercoagulable state demonstrated an antithrombin III deficiency. She was referred for revision of her modified Fontan repair and received antithrombin III supplementation preoperatively.

Normothermic femorofemoral cardiopulmonary bypass was instituted before median sternotomy. The superior vena cava was not cannulated and the Glenn anastomosis was left intact. The heart was electrically fibrillated, a right atriotomy performed, the atrial thrombus removed, and the residual atrial septal defect closed. The heart was defibrillated and the left ventricle allowed to eject. The calcified RA-RV homograft conduit was excised and replaced with a 20-mm externally ribbed PTFE graft in the same manner as in patient 1. The postoperative course was complicated by mediastinal hemorrhage secondary to large chest wall collaterals, requiring reexploration. A heparin infusion and antithrombin III supplementation were continued until adequate anticoagulation with warfarin sodium was established. Postoperative transesophageal echocardiography revealed unobstructed conduit flow. At discharge the patient was in normal sinus rhythm with a room-air O₂ saturation of 90% and improved exercise tolerance. Cardiac catheterization 2 months postoperatively demonstrated a patent conduit with no obstruction. Symptoms of fatigue and cyanosis subsequently developed. Repeat catheterization 8 months postoperatively demonstrated a patent conduit; however, new mitral regurgitation and left ventricular dysfunction with a pulmonary capillary wedge pressure of 20 mm Hg had developed. She improved symptomatically after treatment with an angiotensin-converting enzyme inhibitor.

	Comment

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Conduit obstruction is a common problem when extracardiac conduits are used to construct a Fontan circuit; however, complete conduit occlusion is rare. Freedom from reoperation for pathway obstruction after Fontan repair has been reported to be only 59% at 15 years after operation; the hospital mortality for those patients undergoing reoperation for conduit obstruction was 24% [1]. There also appears to be a higher incidence of reoperation for conduit obstruction in patients with RA-RV conduits compared with other modified Fontan connections [1]. Factors contributing to conduit obstruction include valve calcification, neointimal proliferation in the conduit, sternal compression of the conduit, and thrombosis. In patients who have undergone Fontan procedures, a hypercoagulable state may develop postoperatively, increasing the risk of thrombosis. A recent review described 14 patients with thrombosis of the right side of the heart after Fontan procedure with 6 deaths [2].

Many patients initially palliated with a classic Glenn shunt subsequently underwent a modified Fontan procedure using a conduit to provide RA-PA or RA-RV continuity and leaving the Glenn shunt intact. The patients in this report demonstrate many of the potential long-term complications of this type of correction, including conduit occlusion, AVMs in the right lung, atrial thrombus, and atrial arrhythmias. If complete occlusion of the RA-RV conduit occurs in patients with a classic Glenn shunt, perfusion of the right lung is usually maintained and the onset of symptoms may be gradual. The most common presentation is cyanosis and decreased exercise tolerance. Five cases of occluded RA-RV conduits have been previously reported in patients with a classic Glenn shunt, all within 2 years of the repair (Table 1) [3, 4]. Two patients died after takedown of the Fontan circuit and creation of a systemic-pulmonary shunt. In 3 patients, conduit replacement was performed, and all survived. In the current report, conduit occlusion occurred many years after the repair and likely represents the natural history of valved conduits, although 1 patient had an antithrombin III deficiency, which may have been a contributing factor.

Both of our patients also had extensive AVMs in the right lung. Some recent reports have suggested that diversion of hepatic venous blood from the pulmonary circulation (such as after Glenn shunt or Kawashima operation) may be responsible for the development of pulmonary AVMs [7]. Although Knight and Mee [8] have reported regression of pulmonary AVMs after redirecting hepatic venous blood to the lungs in a patient with extensive AVMs after a Kawashima operation, the fate of these AVMs after reincorporation of the right lung into a Fontan circulation is not known. One potential result is significant right-to-left shunting causing hypoxemia, especially if the AVMs are long-standing. The presence of pulmonary AVMs is a likely explanation for our patients' continued mild hypoxemia despite an adequate repair.

In 3 previously reported cases of RA-RV conduit occlusion with a patent Glenn shunt, as well as in the cases in this report, conduit replacement has been successful (see Table 1) [3]. Our operative method was designed to provide a safe approach to conduit replacement in these complex patients with multiple previous thoracic operations. Femorofemoral cardiopulmonary bypass was used to support the circulation before median sternotomy in both patients, and was easily instituted in these young adult patients. Because the majority or all of their cardiac output relied solely on a classic Glenn shunt, the circulation is certainly vulnerable to the institution of positive-pressure ventilation, and circulatory collapse may occur after induction of anesthesia. Right atrial-RV conduits are often adherent to the posterior table of the sternum, and therefore are vulnerable to injury on redo sternotomy. Femorofemoral bypass allows decompression of the heart, which helps protect against cardiac injury on sternal reentry. If injury to the heart or conduit should occur, the circulation is supported as the operation continues, and shed blood is returned directly to the patient. Conduit replacement can be performed without extensive mediastinal dissection or PA reconstruction. If an intracardiac repair is not necessary and there are no intracardiac shunts, the use of normothermic femorofemoral bypass reduces the need for extensive mediastinal dissection and the operation can be performed with the heart beating. The use of a nonvalved, externally ribbed PTFE graft may potentially result in a lower incidence of reobstruction, although the long-term care of this type of conduit is not well known. A valve is usually not required in the Fontan circuit, and the PFTE graft may have a lower incidence of neointimal peel formation. The support provided by the external ribbing also makes the conduit less vulnerable to sternal compression. Although conduit replacement reduces atrial pressure, it does not reduce the portion of the RA exposed to elevated pressure, so some RA dilatation may persist, increasing the risk of atrial arrhythmias. However, both our patients in the current report remain in sinus rhythm. Even if conduit replacement alone is successful, the long-term prognosis of these patients is not known, and continued close follow-up is necessary.

	Footnotes

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Address reprint requests to Dr Gaynor, Pediatric Cardiothoracic Surgery, The Children's Hospital of Philadelphia, Philadelphia, PA 19104.

	References

Top Footnotes Abstract Introduction Case Reports Comment References

 

1. Fernandez G, Costa F, Fontan F, et al. Prevalence of reoperation for pathway obstruction after Fontan operation. Ann Thorac Surg 1989;48:654–9.[Abstract/Free Full Text]
2. Hedrick M, Elkins RC, Knott-Craig CJ, et al. Successful thrombectomy for thrombosis of the right side of the heart after the Fontan operation: report of two cases and review of the literature. J Thorac Cardiovasc Surg 1993;105:297–301.[Abstract]
3. DeLeon SY, Koopot R, Mair DD, et al. Surgical management of occluded conduits after Fontan operation in patients with Glenn shunts. J Thorac Cardiovasc Surg 1984;88:601–5.[Abstract]
4. Laks H, Williams WG, Hellenbrand WE, et al. Results of right atrial to right ventricle and right atrial to pulmonary artery conduits for complex congenital heart disease. Ann Surg 1980;192:382–9.[Medline]
5. Kao JM, Alejos JC, Grant PW, et al. Conversion of atriopulmonary to cavopulmonary anastomosis in management of late arrythmias and atrial thrombosis. Ann Thorac Surg 1994;58:1510–4.[Abstract/Free Full Text]
6. Giannico S, Corno A, Marino B, et al. Total extracardiac right heart bypass. Circulation 1992;86(Suppl 2):110–7.
7. Srivastavo D, Preminger T, Lock JE, et al. Hepatic venous blood and the development of pulmonary arteriovenous malformations in congenital heart disease. Circulation 1995;92:1217–22.[Abstract/Free Full Text]
8. Knight WB, Mee RBB. A cure for pulmonary arteriovenous fistulas? Ann Thorac Surg 1995;59:999–1001.[Abstract/Free Full Text]

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Theodore C. Koutlas Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Koutlas, T. C. Articles by Gaynor, J. W. Search for Related Content PubMed PubMed Citation Articles by Koutlas, T. C. Articles by Gaynor, J. W. Related Collections Related Article