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Ann Thorac Surg 2005;79:625-631
© 2005 The Society of Thoracic Surgeons
a Clinic for Cardiovascular Surgery, Berne, Switzerland
b Division of Pediatric Cardiology, University Hospital, Berne, Switzerland
Accepted for publication July 29, 2004.
* Address reprint requests to Dr Carrel, Clinic for Cardiovascular Surgery, University Hospital, CH-3010 Berne, Switzerland (E-mail: thierry.carrel{at}insel.ch).
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Abstract |
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METHODS: A total of 38 Contegra valved conduits (12 to 22 mm) were implanted from October 1999 to June 2004, in 36 children less than 5 years old and in 2 patients 8 and 21 years old. Diagnosis included the following: tetralogy of Fallot (n = 21); pulmonary atresia (n = 4); double outlet right ventricle + pulmonary stenosis (n = 3); d-transposition of the great arteries, ventricular septal defect, and pulmonary stenosis (n = 3); truncus arteriosus (n = 3); and other complex malformations (n = 4).
RESULTS: There was no mortality following initial surgery and no valved-conduit–related early morbidity. Early postoperative echocardiographic assessment after 3 months demonstrated favorable hemodynamics in all patients. However, during further follow-up, 5 conduits had to be replaced because of severe stenosis at the level of the distal anastomosis (2 of them had moderate to severe dilatation of the conduit proximally to the valve). Excessive intimal peel formation and severe perigraft scarring reaction were observed in all cases. One child died before surgery.
CONCLUSIONS: The Contegra valved conduit is an interesting concept for reconstruction of the RVOT. However, because of unpredictable incidence of supravalvar stenosis during mid-term results, we cannot recommend routine use of this material.
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Introduction |
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The use of homograft and xenograft conduits to re-establish continuity between the pulmonary ventricle (eg, the right ventricle) and the pulmonary artery bifurcation has been an important advance in repair of complex congenital malformations [4–7]. The principal late problem related to extracardiac conduit operations is the inevitable need for one or more conduit replacements because of patient somatic growth or progressive conduit degeneration and calcification leading to stenosis [8–11].
Some years ago, a totally integrated valved conduit (Contegra; Medtronic Inc., Minneapolis, MN) derived from a bovine jugular vein with a trileaflet venous valve has been developed and introduced on the market. Some of the main advantages are the structural continuity between the lumen of the conduit and the valve it incorporates as well as the availability for pediatric and adult patient sizes and the proximal and distal cuffs allowing for extended reconstruction.
Several reports have shown promising early hemodynamic and clinical results with this conduit [12–17]. In this study we focus on a small number of patients who developed severe stenosis at the distal anastomosis leading to explantation of the conduit.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentConclusionReferences |
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Only patients who received a Contegra valved conduit are considered here. There were 36 children less than 5 years old (mean age 2.1 ± 0.6 years) and 2 patients 8 and 21 years old. All available sizes of the Contegra conduit (12 to 22 mm) were implanted. Initial diagnosis included tetralogy of Fallot (TOF; n = 21), pulmonary atresia (n = 4), double outlet right ventricle (DORV) + pulmonary stenosis (DORV + PS; n = 3), d-transposition of the great arteries (d-TGA), ventricular septal defect (VSD) and PS (n = 3), truncus arteriosus (n = 3), and 4 patients with complex malformations. In 29 patients the conduit was inserted to re-establish the continuity between the pulmonary ventricle and the pulmonary artery bifurcation because absent pulmonary valve, hypoplasia of the pulmonary anulus pulmonary atresia or to connect the right ventricle to the pulmonary artery during the Rastelli procedure or during repair of truncus arteriosus. In 9 patients, the conduit was inserted because of severe pulmonary regurgitation following previous RVOT repair with transanular polytetrafluoroethylene (PTFE) patch (n = 2), monocusp patch (n = 5), homograft (n = 1), or to replace a small Hancock conduit in a patient with truncus arteriosus (n = 1). All patients were operated by two surgeons only (P.B. and T.C.); the choice of the conduit was mainly defined by the surgeon's preference.
Characteristics of the Conduit and Operative Technique
Initially developed by VenPro (Irvine, CA) and currently owned and marketed by Medtronic, Inc. (Minneapolis, MN), the Contegra conduit is a 0.25% glutaraldehyde-fixed segment of bovine jugular vein, containing a venous valve; the whole xenograft is fixed under minimal pressure, less than 3 mm Hg. Therefore, the main characteristic of the conduit that served to generate its name Contegra (conduit with integral valve) is the absence of discontinuity between the inlet and the outlet part of the conduit and the trileaflet venous valve of the jugular vein. The conduit is provided in 10-cm length and the valve is centered in the conduit (except in the 12-mm conduit in which the length is 7 cm). The conduit is available in size range between 12 and 22 mm with a consistent quality. The material has to be rinsed during 15 minutes in physiologic electrolyte solution before implantation but there is no thawing nor preclotting procedure necessary. In vitro data have demonstrated that valve leaflet strength and flexibility are well preserved in the Contegra conduit and experimental and clinical datas have been encouraging.
The conduit is available as native jugular vein or as supported model. The supported model has two polyester-cloth–covered polypropylene rings, one located at the valve inflow and the other at the level of the commissures of the valve. The objectives of the ring support are to provide support at the valve annulus and the commissural level, to prevent compression of the conduit through the sternum that may result in pulmonary valve regurgitation. Caution should be exercised that the ring does not compress the coronary arteries.
Patients are operated using standard cardiopulmonary bypass and moderate hypothermia (32 to 34°C). Myocardial protection using cardioplegic solution is optional since we prefer to operate on the beating heart when isolated RV-PA conduit insertion is required.
During insertion of the Contegra valved conduit, care was taken to locate the valve as cranial as possible immediately below the bifurcation of the pulmonary artery. This avoids geometrical distortion of the valve at the site of proximal implantation in the right ventricle. In 7 patients the conduit was inserted in a strictly orthotopic in situ position through a longitudinal opening of the main pulmonary artery. In all other 32 patients, the xenograft was inserted as an extracardiac conduit with a ventriculotomy. The distal anastomosis was performed with running 6.0 polypropylene suture in 33 patients or with interrupted U-clips (Coalescent, Sunnywale, CA) technique (n = 6). In 11 of 40 patients, a patch enlargement of the pulmonary bifurcation (n = 8) or of a side branch (n = 3) was necessary before RV-PA reconstruction. The proximal anastomosis was always performed with 5.0 or 6.0 polypropylene running suture.
Usually there is no need for proximal augmentation with an additional patch material because length of the conduit allowed for direct closure of the right ventriculotomy. Postoperative anticoagulation treatment included low dose aspirin treatment (eg, 25- to 50-mg daily) during the first 3 months.
Two-dimensional and Doppler echocardiography was performed in all patients before discharge and after 3, 6, and 12 months. All data related to peak and mean transvalvular pressure gradients were recorded, as well as the presence of pulmonary regurgitation and any residual intracardiac lesion.
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Results |
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There was no hospital mortality following initial surgery and no perioperative morbidity related to the conduit. Early postoperative echocardiographic assessment before discharge and at 3 months follow-up demonstrated satisfactory hemodynamic characteristics (mean peak 
P across the valve was 14.5 mm Hg, ranging from 8 to 26 mm Hg. Trivial pulmonary regurgitation was seen in 11 patients.
After a mean follow-up of 18 ± 5 months, 6 patients had to be scheduled for conduit replacement because of excessive gradient (peak P ranging from 50 to 120 mm Hg) through the conduit. On echocardiography, the gradient originated mainly at the site of distal anastomosis whereas the function of the valve was normal in all patients. The main findings of these 6 patients are summarized on Table 1. Explantation-free survival was calculated according to the Kaplan-Meier actuarial analysis and is illustrated in Figure 1. In 2 patients, prestenotic dilation of the RVOT was observed with impressive aneurysm formation of the patch used to close the ventriculotomy. In the adult patient, an attempt to dilate the distal anastomosis was performed but was not successful (Fig 2). One patient had severe cyanotic crisis during induction of the anesthesia. This boy unfortunately died before operation could be started. Main intraoperative macroscopic finding was an excessive intimal peel formation in all patients accompanied by a severe perigraft scarring reaction around the distal anastomosis. In 1 patient a calcification was observed on one leaflet and another proximally to the valve. One patient developed a recurrent ostial stenosis of the left pulmonary branch despite patch enlargement during initial surgery. The sizes of the explanted conduits were 12 mm (2x), 14 mm (2x), and 18 and 22 mm (one each). The explanted Contegra conduits were replaced by a pulmonary homograft in 1 patient and a Shelhigh pulmonic conduit in 4 patients.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentConclusionReferences |
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Forbess and colleagues [7, 9] reported that durability and the type of the implanted conduit may be a less critical issue in younger children who receive smaller conduits, because this group of patients will outgrow their conduit before degeneration occurs.
In the past a large number of valved xenografts have been developed and implanted in the pulmonary position [5, 12, 13, 15, 17, 20–22]. None have demonstrated superiority over homografts so far. However, one of the major advantage of these conduits is their unlimited availability for all pediatric and adult sizes.
Preliminary results following repair of the RVOT using a Contegra conduit have been favorable in several reports [14–16]. However the observational interval has been short in the majority of cases. Recently, several investigators have described the appearance of severe stenosis or thrombosis of the conduit in the mid-term follow-up [23–27]. Our experience confirms this observation. Six of 38 patients required explantation of the conduit. One patient did not survive mechanical reanimation that occurred during induction of the anesthesia. He had severe stenosis of the conduit. In the remaining 32 patients, 6 have unexpected high gradients and may require intervention. During the same time interval, only 1 patient with a pulmonary homograft had to undergo redo surgery. There was not one reintervention following implantation of a Shelhigh or Hancock conduit.
The results of some of the largest clinical series are summarized. Breymann and coworkers [16] presented a series of 71 patients operated on between 1999 and 2001. The mean age was 1.2 years old (range 2 days old to 17.5 years old). The main pathology was similar to that of our series, and the size of the conduit ranged from 12 to 22 mm. The longest follow-up was 27 months. No conduit or valve degeneration was observed during this interval. Early postoperatively, maximal transvalvular pressure gradient was between 25 and 42 mm Hg, but it did not increase over time. However 6 patients developed pressure gradients larger than 70 mm Hg. The authors did not localize the site of gradient properly. No Contegra conduit had to be explanted, which differs significantly from the experience with homografts and porcine xenograft in this group.
Bové and coworkers [17] summarized their experience with 41 children (mean age 1.9 years old, ranging from 7 days old to 13 years old and with a mean weight of 8.4 ± 4.4 kg), who received the Contegra conduit, and compared the results with those of pulmonary homografts. Immediate outcome was comparable without any significant conduit-related complication. No patient had a significant gradient at the level of the conduit valve. These authors considered that the valved bovine jugular vein offers a promising substitute for RVOT reconstruction.
During the Ross operation, aortic or pulmonary homografts have been used to replace the native pulmonary valve. Corno and coauthors [28] reported their preliminary experience with 10 patients (mean age 19.9 years old, ranging from 9 to 42 years old and with a mean body weight of 56.9 ± 22.3 kg). A majority of them received the largest-sized Contegra conduits (22 mm). Hemodynamic results were very promising at a mean follow-up of 8 months. The average peak pressure gradient was 19.8 ± 9.9 mm Hg (range 6 to 38 mm Hg). So far the results were encouraging with no early nor late mortality, no reoperation and satisfactory hemodynaimcs even in larger patients with a very active lifestyle.
Van Garsse and associates [25] reported at the 2004 Annual Meeting of the American Association of Thoracic Surgeons a series of 58 patients (mean age 9 years old) who received a Contegra conduit. Freedom of severe stenosis was 91% at 3 months, 68% at 12 months, and 49% at 24 months. Young age significantly related to the occurence of severe stenosis. All stenosis were located at the distal anastomosis. Seventeen conduits required balloon dilatation and seven were explanted. The authors discouraged the use of this conduit.
Recently, Boudjemline and colleagues [27] reported a case of aneurysm of the RVOT following insertion of a Contegra conduit. In this case the distal anastomosis between the 14-mm conduit and the pulmonary artery, which had been performed with a running suture of absorbable material, was severly stenotic and found to be responsible for the proximal dilatation. The conduit had to be exchanged 14 months following insertion. Histologic examination revealed an important fibrointimal proliferation in the area of pulmonary anastomosis and a mild foreign body reaction was observed at the outside layer of the conduit.
The mechanism that leads to severe stenosis at the distal anastomosis is totally unclear. Although some believe that surgical technique may be responsible, we cannot agree with this explanation. First, the distal anastomosis had been performed according different suturing techniques (either with running 6.0 polypropylene or polydiaxone suture 6.0 or using interrupted technique with nitinol U-clips (Coalescent, Sunnywale, CA) [29, 30]. Second, a technical reason is difficult to admit since postoperative echocardiography depicted very satisfactory hemodynamic findings and the stenotic process appears usually during the second half of the first postoperative year.
Excessive intimal peel formation and severe perigraft scarring reaction was observed in all patients of our series. Histologic examination revealed an important fibrointimal proliferation in the area of pulmonary anastomosis and a mild foreign body reaction was observed at the outside layer of the conduit.
Boudjemline and colleagues [27] postulated that an abrupt reduction of the vascular bed at the end of the conduit – in case of hypoplastic pulmonary branches – may create a pressure gradient and acceleration of blood flow. The increased shear forces may stimulate a local intimal proliferation. The authors recommended particular care to avoid suboptimal reconstruction in patients with small pulmonary branches.
The intensive narrowing process observed in some patients following implantation of a bovine jugular vein conduit may be the result of a strong cellular immunologic reaction against the xenograft. Wojtalik and coworkers [31] have observed a significant rise (as high as 150% of the norm value) of B cells between 3 and 6 months postoperatively. The T-lymphocyte activation study revealed higher number of CD69+ and CD71+ cells 1 year after implantation of the xenograft. Several reasons were thought to be responsible for potential antigenicity of this particular xenograft: large surface contact between the xenograft and the host – in contrast to the majority of bioprosthetic valves; presence of cellular remnants within the implant; and nonhomogenous fixation through glutaraldehyde. The presence of plasma cells in the histology of explanted valves may support the hypothesis of a humoral immune response. Experimental studies indicate the maximum of immunologic response about 3 months after implantation. Interestingly, this type of reaction has also been observed following insertion of Shelhigh first generation pulmonic conduit [26].
Another problem that has been observed following implantation of Contegra conduit is early valve failure secondary to local thrombotic process. However, in a long-term canine experiment, no thrombus adhesion was found on the leaflets and endothelialization of the graft surface occurred without intimal hyperplasia. In Munich, Tiete and associates [23] reported on thrombus formation on the valve occurring as early as 2 weeks postoperatively. Under anticoagulation with low molecular-weight heparin, the thrombus disappeared in both cases. This group recommends prophylactic anticoagulation. Schoof and coworkers [24] reported the combined experience from Leiden and Groningen using this bovine conduit for extracardiac Fontan completion. All 3 patients who received this conduit developed thrombosis, 2 patients died and 1 survived with a neurologic deficit. The authors discouraged the use of the Contegra conduit in the Fontan circulation. Considering this potentially dangerous complication, it seems that anticoagulation during the first postoperative weeks is preferable.
Some alternative xenograft valved conduits exist: the Medtronic Freestyle prosthesis is a glutaraldehyde-fixed porcine aortic valve and root originally concepted for aortic valve replacement. Several surgeons have used this device to reconstruct the RVOT as well. One of the disadvantages is that the aortic root is rather short and for reconstruction of the whole RVOT, additional pericardial or prosthetic patches are needed. Nevertheless, early results are very promising but follow-up is still less than 3 years.
Other stentless xenografts have been developed during the last years, including the following: the LabCor from Sulzer Carbomedics (Austin, TX); the Biocor from St Jude Medical (Belo Horizonte, Brasil), which is a bovine pericardial conduit with an aortic porcine valve; and the Shelhigh pulmonic conduit (Union, NJ), which consists of a pericardial bovine tube with a stentless porcine pulmonary valve.
French surgeons reported on the LabCor conduit: 55 implants were described with a mean observational follow-up of 27 months. In small patients (eg, neonates and children under the age of 1 year), replacement of the conduit was necessary after 24 months [22].
The porcine material of the Shelhigh conduit is prepared with the no-react process, which is intended to reduce calcification. The conduit is available from 12 mm to 23 mm. Unfortunately, some negative reports were published with a high rate of replacement after a short follow-up period [32]. Conduit stenosis was due to intimal peel formation at the distal anastomosis. The mechanisms involved in this type of conduit failure are unknown. The similarity of outcome of Shelhigh and Contegra conduits is troublesome and emphasizes the potential role of immune response [26]. Host inflammatory reaction was not found at the time of conduit retrievement but initiated probably the inappropriate intimal proliferation. Additional factors such as endothelial lesions made during conduit suture, residual glutaraldehyde release from the implant, and shear stresses related to hemodynamic conditions at the level of the anastomosis might amplify this proliferative reaction. The second generation includes a pericardial cuff, and so far no similar reports exist.
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Conclusion |
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TopAbstractIntroductionPatients and MethodsResultsCommentConclusionReferences |
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The bovine jugular vein Contegra valved conduit is an interesting substitute for reconstruction of the RVOT when a pulmonary valve has to be inserted. The main advantages of this conduit are: use of natural tissue as raw material; unlimited avaibility; sufficient length at both inflow and outflow; and favorable in vitro hemodynamic performance due to an effective orifice area.
Although preliminary animal and human reports have shown excellent durability, several groups have experienced less enthusiastic results because of extensive intimal proliferation at the level of distal anastomosis, more diffuse stenosis by tissue ingrowth, conduit kinking, and compression. No similar findings were observed in patients with other types of conduit. Because adverse outcomes following insertion of Contegra conduits are not predictable, we do not recommend routine use of this material, especially in the small sizes until more details are known about incidence and mechanisms of stenosis at the distal anastomosis.
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