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Ann Thorac Surg 2007;84:599-605
© 2007 The Society of Thoracic Surgeons
a Pediatric Cardiology Unit, Department of Cardiac Surgery, Centre Hospitalier Universitaire Vaudoise, Lausanne, Switzerland
b Department of Cardiac Surgery and Pediatric Cardiology, Leiden University Medical Center, Leiden
c Department of Pediatric Cardiology, VU Medical Center, Amsterdam, the Netherlands
Accepted for publication April 5, 2007.
* Address correspondence to Dr Hazekamp, Kinderhartcentrum D6-26, Leiden University Medical Center, PO Box 9600, Leiden, 2300 RC, the Netherlands (Email: m.g.hazekamp{at}lumc.nl).
Presented at the Poster Session of the Forty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 29–31, 2007.
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Abstract |
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Methods: From April 1999 to July 2005, 133 children with a median age of 30.9 months (range, 4 days to 19 years) underwent graft implantation. Echocardiography was performed during follow-up and retrospectively reviewed.
Results: Nongraft-related early mortality occurred in 8 patients. Late mortality occurred in 11 patients, 2 late deaths were graft related (endocarditis). Median follow-up was 31.6 months (range, 1 to 73). Twelve patients received a new graft, because of endocarditis (3), distal pulmonary artery branch stenosis (4), graft obstruction caused by fibrosis (4), or thrombosis (1). Echocardiography Doppler studies showed good conduit function, with 92% of the patients having absent, trivial, or only mild valve regurgitation at last follow-up. A moderate degree of conduit stenosis due to external compression was observed in 2 patients. Twenty-five patients with otherwise intact conduits had hemodynamically significant distal stenosis. In most cases, the pulmonary branch stenosis was related to preoperative small pulmonary arteries and young age at operation. At 31.6 months, significant graft dilatation was observed in 4 grafts and was related to pulmonary artery branch obstruction or pulmonary hypertension. Calcification did not occur in 5 years time. Survival was 85.7%, freedom from conduit explantation was 91%, and freedom from intervention for pulmonary artery branch stenosis was 80% after 5 years.
Conclusions: The bovine jugular vein graft is a valuable right ventricular outflow tract conduit, but younger age and small pulmonary arteries increase the risk of distal conduit stenosis.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Several authors reported encouraging initial clinical results with this conduit for RVOT reconstruction [7–10]. However, other groups expressed their concern about fibrous supravalvular stenosis at midterm follow-up [11, 12].
In this study, we report the 5-year experience in two centers with this conduit in a predominantly young pediatric population.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Between April 1999 and July 2005, 133 Contegra conduits have been implanted in a pediatric population, to reconstruct the RVOT. Age at operation ranged from 4 days to 19 years, with a median age of 30.9 months. Forty-three patients (32.3%) were younger than 12 months of age. Indications for right ventricle to pulmonary artery (PA) reconstruction are listed in Table 1. Table 2 shows the differences between the patient groups of the two centers. The median age of the patients was 0.9 years (range, 4 days to 19 years) in Leiden University Medical Center and 5.8 years (range, 2.8 months to 16.5 years) in Centre Hospitalier Universitaire Vaudoise. Overall, pulmonary atresia and tetralogy of Fallot formed the two most common groups (20.3% and 21.8%, respectively). Pulmonary atresia with ventricular septal defect (VSD) and major aortopulmonary collateral arteries (MAPCAs) was present in 15 cases. In tetralogy of Fallot, hypoplasia of the PAs formed an indication for the use of a RVOT conduit.
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Follow-Up
Follow-up was complete in all patients. Recent (within 3 months before closure of the study) echocardiography Doppler studies were available for all patients. All echocardiography studies were reviewed and reexamined by two observers.
Conduit valve insufficiency was graded with the use of color Doppler echocardiograpy. The following values were used to classify the pulmonary regurgitation: none, trivial, mild, moderate, and severe insufficiency. The mechanism of insufficiency was noted, as were structural and functional abnormalities of the cusps. Stenosis at valvular level and at the distal pulmonary artery or anastomosis were assessed by measuring the transvalvular and pulmonary artery peak velocity with continuous–wave Doppler technique and, in case of unilateral branch stenosis, with perfusion scintigraphy studies. Cardiac catheterization and echography was always performed when obstructions were considered as significant. Distal stenosis was considered significant in presence of gradients higher than 50 mm Hg. Internal graft diameters were measured and compared to the original diameter at the time of implantation. A measured diameter exceeding the diameter indicated at implantation with more than 50% was considered as conduit dilatation. Furthermore, attention was paid to the variability in anatomy of the PAs providing pulmonary blood flow. For analysis, a cut-off point of 3 mm was defined for PA branch diameter at the level of the origin of the first lobar branch to distinguish very small or diminutive PAs. The decision for reintervention (surgical or in the catheterization laboratory) was based on maximal pressure gradients exceeding 50 to 75 mm Hg or when distal PAs showed an important decrease in flow.
The median duration of follow-up was 31.6 months (range, 1 to 73).
Analysis of Data
The preoperative and postoperative data were collected retrospectively from patient records. All data in this study are presented as mean ± SD, range, and median where appropriate. Kaplan-Meier survival curves, with 95% confidence limits, were used to present survival and event-free survival. We used the log-rank test to compare the Kaplan-Meier curves and confirm the relationship between different variables and pulmonary stenosis.
All statistical analyses were performed with the statistical package SPSS 12.0.1 for Windows (SPSS, Chicago, Illinois).
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Results |
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Reoperations
At a maximal follow-up of 73 months, 91% of the 133 patients were free from conduit replacement. Twelve patients needed replacement of the bovine jugular vein graft 0.5 to 22.9 months (mean, 8.6 ± 6.9) after first implantation. Conduit endocarditis was reason for reoperation and graft replacements in 3 of 11 patients. Two of them died 11 and 46 days, respectively, after reoperation as a result of recurring endocarditis. One of these patients had bacterial endocarditis in the second graft, and subsequently a homograft was used to replace the conduit (Fig 1).
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Finally, 5 patients underwent conduit replacement because of obstruction due to fibrous pannus formation (4) at the distal anastomotic site or due to thrombus formation in the conduit (1). Two of the 4 patients with fibrous distal graft obstruction had primary surgery at 4 and 14 days of age, respectively, and the explanted grafts were both 12 mm in diameter.
Of the 20 patients who received a Ross operation with a Contegra graft orthotopically placed in the RVOT, 1 patient was reoperated on for distal conduit stenosis. No patient was reoperated on for isolated valve regurgitation.
Midterm Survival
Figure 1 shows the distibution of the Contegra patient population. Patients who died late during follow-up had enough data information and were included in the follow-up analysis. In all, 125 patients (with 114 survivors) were available for follow-up. The Kaplan-Meier analysis (Fig 2,
Fig 3A and B) showed a survival and an explantation-free survival of 85.7% and 91%, respectively, at more than 5 years after surgery.
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Regarding the presence of a transvalvular or pulmonary artery gradient, right ventricular outflow tract obstruction was observed in 25 patients. In only 2 cases (1.6%) was a moderate degree of conduit stenosis noted, both due to external chestwall compression. One of the 2 patients underwent successful stent placement below the pulmonary valve to relieve the stenosis. In all other patients, no pressure gradient or only a mild pressure gradient of 10 to 20 mm Hg was detectable across the conduit.
Considering the site of the other measured RVOT obstructions, all other gradients observed during follow-up were located at the anastomotic site between the Contegra conduit and the PAs. The majority of our patients (80%) showed no outflow obstruction or only minor Doppler gradients. A hemodynamically significant obstruction at the distal anastomotic site was present in 25 patients. Eight of these 25 patients have been reoperated on and given a new Contegra conduit, 12 patients underwent interventional catheterization for balloon dilatation or stent placement, and 2 patients underwent operative stent placement. Three patients are awaiting surgery. In all but 5 patients, surgical or interventional treatment was successful in reducing distal gradients. In the patients with preexisting diminutive PAs (pulmonary atresia/VSD/MAPCAs and truncus arteriosus), distal obstruction could not be relieved completely.
The log-rank test showed that the pulmonary artery branch obstructions were significantly (p < 0.001) related to preexisting small PAs. Besides, there was a significant relation between younger age (<1 year) at operation or small graft size (<14 mm) and the occurrence of pulmonary stenosis at last follow-up (p = 0.036 and p = 0.013, respectively). The Kaplan-Meier curves (Figs 4 and 5),
stratified by preexisting hypoplastic PAs and age, confirmed these findings. Furthermore, the curves show that in most cases the PAs were preoperatively diminutive or gradients developed quickly after operation.
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No patients showed evidence of Contegra calcification on echocardiography, catheterization studies, or chest roentgenograms.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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With regard to the limited durability and availability of homografts, especially in young patients, the Contegra bovine jugular vein conduit was introduced as an alternative in 1999. The venous wall is ideal for suturing, and no further interposition of foreign materials is necessary to make the anastomosis between the right ventricle and the PA. The leaflets of the valve are very thin and mobile. Moreover, the availability of the bovine jugular vein conduit in various diameters (12 to 22 mm) and length to augment PAs makes its use possible in the age range from neonate to adult.
Herijgers and colleagues [19] reported the resistance of the Contegra conduits to calcification when implanted in the pulmonary position in juvenile sheep. The Contegra grafts functioned well and showed only minimal calcifications after 5 months. Ichikawa and colleagues [20] described a 1-year animal study. One year after implantation of bovine jugular vein grafts in 8 adult dogs, the grafts worked perfectly as a right ventricular–PA valved conduit without anticoagulant therapy for a long time. Since the clinical introduction of the Contegra conduit, several reports have shown promising and encouraging initial clinical results for RVOT reconstruction with this conduit [6–8].
In this report, we describe our experience with 133 patients with bovine jugular vein conduits implanted. In contrast to other studies, our group of patients is quite young, with a median age of 30.9 months; and 32.3% of our patients were less than 1 year of age at time of implantation. Patients with younger age at implantation or small graft size, or both, could significantly be identified as "at risk" for early Contegra explantation. These determinants of durability are frequently reported in homografts as well [3–5, 15, 16].
We found the Contegra conduit function to be good, with more than 90% of the patients with absent, trivial, or only mild valve regurgitation. No conduit had to be explanted because of valve incompetence or stenosis. Recently, several studies have mentioned occasional problems with severe stenosis or thrombosis in the Contegra conduit in the midterm follow-up [1, 12, 22]. Tiete and colleagues [22] reported thrombus formation at the conduit valve leaflets in 2 small patients. With anticoagulation therapy, the thrombus disappeared in both cases. The authors recommend prophylactic anticoagulation in small patients with a greater mismatch between conduit size and normal valve size. In our series, thrombosis of one of the valve cusps was observed in 2 patients. One thrombosed cusp was accidently observed during reoperation for PA branch stenosis. Both Contegra conduits were replaced by a new one. No other cases of thrombus formation were present in our group.
In a series of 58 implants, Meyns and colleagues [11] observed an increasing rate of severe stenosis (peak gradient >50 mm Hg) located at the level of the distal anastomosis. In that series, freedom from severe stenosis at the distal anastomosis was 91% at 3 months, 68% at 12 months, and 49% at 24 months. Although they indicate the significant relation between graft size and the occurrence of stenosis, severe stenoses in the adult Contegra sizes were also observed. This group discouraged the use of the bovine jugular vein conduit. Göber and coworkers [12] presented a series of 38 patients operated on between 1999 and 2004. They focused on a small number of patients who developed severe stenosis at the distal anastomosis, leading to explantation of the conduit. Six of 38 patients required conduit replacement. The main intraoperative macroscopic finding was an excessive intimal peel formation in all 6 patients. Because of the unpredictable incidence of supravalvular stenosis during midterm results, these authors advised against routine use of the Contegra conduit.
In our group, the measured maximal echocardiographic gradients inside the Contegra conduit were less than 36 mm Hg in 98.4% of the patients. In only 2 patients were significant pressure gradients were noted, both due to external compression. Echocardiographic signs of distal stenosis were found in 25 patients, mainly in patients with preoperative diminutive PAs. Diagnosis of PA stenosis by echocardiograpy is based on two-dimensional information in combination with measurement of Doppler gradients. Stenosis of the distal anastomotic site generates elevation of right ventricle pressure and a pressure drop over the stenosis.
Patients were catheterized to define level and exact location of obstruction. In general, the maximum Doppler gradients tended to overestimate the catheterization gradients. Doppler gradients have to be interpreted cautiously, especially in cases of postoperative pulmonary branch stenosis [21]. Twenty-two of the 25 patients with high Doppler RVOT gradients underwent reintervention (conduit explantation/stent placement/balloon dilatation) because of distal stenosis. Particularly in cases with pulmonary atresia, VSD, and MAPCAs, preexisting hypoplastic PAs or unifocalized MAPCAs were associated with later high maximum Doppler gradients. High pressure gradients were also associated with younger age at operation. These findings motivated us to agree that, as noted by others as well, the echocardiographic gradient at the level of the distal anastomosis might be attributed to the mismatch between the end of the conduit (>12 mm) and the beginning of the pulmonary artery branches (<3 mm), especially in very young patients with small PAs [6, 22]. Reduction of the distal end of the conduit (from 12 to 8 mm) was sometimes necessary. Fish-mouthing the distal anastomosis may be a better technique but has not been used in this series. The local turbulence at the distal anastomosis, caused by the conduit–PA branch mismatch together with crowding of the conduit wall tissue, may be one of the most important factors responsible for the development of the stenosis.
In our young patient group, the freedom from explantation is comparable to the results of other studies with homografts and a similar patient group [23, 24]. Homografts are not free of wall calcification, shrinking, and valve degeneration, leading to conduit explantation. These adverse effects of the homograft conduits occur even more frequently among young children [4, 23–25]. Boethig and colleagues [24] reported the results of a comparison among homografts (n = 52), porcine xenografts (n = 30), and Contegras (n = 108). The median age of the three groups was 1.5 years, 0.3 years, and 1.8 years, respectively. The authors described the reoperations, stratified by problem zone (subvalvular, intravalvular, and supravalvular), and reported "the Contegra conduit not to be inferior to homografts concerning freedom from subvalvular and valvular reoperation reasons."
In our patient group, 13 patients needed explantation of the Contegra conduit. In 4 explanted conduits, fibrous pannus formation was noted at the distal anastomotic site. One thrombus formation was noted, leading to branch obstruction. Contegra endocarditis was diagnosed in 3 conduits, and 5 conduits were explanted to make relief of the PA obstruction technically easier. No signs of calcification have been observed in the explanted conduits. In contrast, as reported by Boethig and colleagues [24], severe calcification of conduit walls and valves, is frequently observed in explanted homografts and porcine xenografts.
The uncontrolled dilatation of the bovine jugular vein conduit is an occasional problem we have observed in 4 patients of our series. One of the dilated Contegra conduits, in presence of distal stenosis, was explanted and replaced by a pulmonary homograft. Within a short period of time, the homograft conduit diameter, measured during echocardiography, exceeded the diameter indicated at implantation. Dilatation is occasionally reported by others [6]. High graft pressure seems to be responsible for the observed dilatation in our patients.
Limitations
This is a retrospective study with a follow-up duration no longer than 5 years and only a few patients available for follow-up at 5 years.
After 5 years of follow-up, we can conclude that the Contegra bovine jugular vein grafts show good results with respect to valve sufficiency and gradients at valvular level. Obstruction at the distal anastomotic site and in the proximal parts of the PAs was observed in 20% of the patients. These stenoses led to explantations of the conduit and catheter reinterventions. However, we experienced that the stenosis was significantly related to mismatch between the conduit and the pulmonary artery branches. These mismatches were due to preoperatively diagnosed diminutive PAs or very young age at operation. We need to emphasize that our patient group has a young median age, forming a risk factor for early Contegra conduit failure. Despite the stenotic appearances, the Contegra conduit presents good handling characteristics, shows very low calcification rates, and remains a valuable alternative to homografts for RVOT reconstruction.
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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