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Ann Thorac Surg 2006;82:1308-1315
© 2006 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Heart Center, University of Leipzig, Germany
b Department of Pediatric Cardiology, Heart Center, University of Leipzig, Germany
Accepted for publication April 18, 2006.
* Address correspondence to Dr Rastan, University of Leipzig, Department of Cardiac Surgery, Heart Center Leipzig, Struempellstr 39, Leipzig, 04289 Germany (Email: rastan{at}rz.uni-leipzig.de).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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METHODS: Seventy-eight bovine jugular vein implantations were performed over 5 years. Follow-up averaged 31 ± 17 months. Risk factor and adverse event analyses for graft dysfunction were performed by multivariate logistic regression and Kaplan-Meier analysis.
RESULTS: There was no early mortality. Two late deaths occurred after 9 and 15 months. Early postoperative echocardiography revealed bovine jugular vein regurgitation greater than 2+ in 10 patients, all of which had conduit dilatation, had received a 12-mm conduit, and had a right-ventricular-to-left ventricular pressure ratio greater than 0.6. Two additional patients had severe conduit incompetence develop at the 2-year follow-up. During follow-up, mean gradients increased from 15 to 23 mm Hg (p = 0.03) and stenosis at the distal anastomosis occurred in 25% of patients. Percutaneous interventions were performed in 19 patients (24.4%). Conduit exchange was required in 10 patients (12.8%) after a mean of 14.9 months for severe graft incompetence (8 patients) and progressive supravalvular stenosis (2 patients). Freedom from reoperation was 77.6% and 59.3% at 1 and 4 years for patients less than 1 year of age compared with 93.5% and 87.4% for patients older than 1 year of age (p < 0.001). Risk factors for reoperation were age less than 1 year, correction of truncus arteriosus, conduit size of 12 mm, and persistently elevated right-ventricular-to-left ventricular pressure ratio greater than 0.6 (p = 0.001 each).
CONCLUSIONS: Bovine jugular vein implantation is associated with low reoperation and acceptable reintervention rate in patients older than 1 year of age. In infants with persistently elevated right ventricular pressure, reoperation rate was high and had to be compared with other established surgical options.
There is no gold standard for right ventricular outflow tract (RVOT) reconstruction in surgical correction for congenital cardiac malformations. Homografts have been used for decades, however, limited availability and premature calcific stenosis, particularly in smaller sizes, led to the search for alternative biological conduits [1–4]. Since its clinical introduction in 1999, the valved bovine jugular vein graft (BJV, Contegra [Medtronic Inc, Minneapolis, MN]) has been proposed for RVOT reconstruction [5, 6]. The BJV has gained widespread application in pediatric patients with implantation in more than 500 patients reported in the literature thus far [7–17].
The BJV consists of a bovine jugular vein with a naturally integrated three-leaflet valve. It is fixed under low pressure (< 3 mm Hg) using 0.25% buffered glutaraldehyde solution and is sterilized in a formulation of glutaraldehyde, isopropyl alcohol, and other components with no additional anti-calcification treatment. The main advantages are the structural continuity between the lumen of the conduit and the valve, the availability of pediatric and adult sizes in consistent quality, and the generous proximal and distal cuffs for extended reconstructive procedures.
There are conflicting reports regarding performance and durability of the BJV for RVOT reconstruction. The majority of investigators found good early and mid-term conduit function, but there is also increasing evidence for the development of premature valve incompetence, aneurysm formation, and supravalvular fibrotic stenosis [9, 10, 13, 18, 19]. However, meaningful comparison of different studies is difficult due to limited patient numbers, different patient ages, variations in the underlying cardiac malformations, varying follow-up periods, and different end point definitions. Therefore we performed a systematic analysis of our experience with the BJV conduit, particularly with respect to younger patients, small conduit sizes, and the relation to persistently high postoperative right ventricular (RV) pressure to identify risk factors for early graft dysfunction and reinterventions.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Implanted sizes (mean 16.6 ± 3.9 mm), congenital cardiac malformations, and patients characteristics are displayed in Table 1. Thirty-four patients were female and 38 were male. Patient age was 9.2 ± 12.9 years (range, 7 days to 45.1 years), and median age was 3.8 years. Twenty-three patients (29.4%) were infants (< 1 year of age), 14 patients were between 1 and 3 years, and 41 patients were older than 3 years. Body weight was 25 ± 24 kg, and body surface area was 0.83 ± 0.58 m2.
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Surgical Technique
All operations were performed under moderate hypothermia of 24°C to 32°C, except 4 patients who had concomitant aortic arch pathology. Ultrafiltration was used in all infants and children. Cardioplegic arrest was induced in 62 of the operations (79.5%) using St. Thomas cardioplegic solution (30 mL/kgBW). The conduit was rinsed 3 times for 5 minutes using physiological saline solution before surgical tailoring. In all cases the valve was placed as close as possible to the pulmonary bifurcation to prevent sternal distortion or compression of this high profile venous valve. Only unsupported, not ring-reinforced conduits were used. The distal anastomosis was completed in an oblique fashion with conduit material only, and a running polypropylene 7-0 suture. The RV hood was constructed with a running suture, using the appropriately tailored proximal tubular extension of the conduit without additional patch material. In 27 patients who required additional peripheral pulmonary artery reconstruction, thin-walled Gore-Tex (W.L. Gore & Assoc, Flagstaff, AZ) was used. Other associated procedures were resection of the modified Blalock-Taussig shunt in 16 patients, Waterston shunt resection in 3, tricuspid valve reconstruction in 16, residual ventricular septal defect (VSD) closure in 5, VSD enlargement in 2, secundum atrial septal defect closure in 13, persistent ductus arteriosus resection in 5, unifocalization in 3, and aortic arch reconstruction in 1.
Postoperative anticoagulation consisted of low-dose intravenous heparin (100 IU/kg/d) followed by oral aspirin medication (3 to 5 mg/kg/d) for the first 3 months. Baseline conduit performance was assessed by intraoperative transesophageal and postoperative transthoracic echocardiography in the intensive care unit and prior to hospital discharge.
Follow-up
Follow-up was performed at 1, 3, and 6 months, and every half year thereafter, which included routine echocardiographic examinations. All data related to level and extent of RVOT gradients were prospectively recorded using the modified Bernoulli equation. Right ventricular pressure was quantitatively estimated by tricuspid insufficiency velocity and RV function was graded as good, moderate, or poor. Bovine jugular vein regurgitation was assessed by onset and area of regurgitation. Conduit insufficiency was scaled by color flow Doppler as absent (grade 0), trivial (1+), mild (2+), moderate (3+, backflow starting from the bifurcation level), and severe (4+, backflow starting from the peripheral pulmonary artery branches). Conduit gradients were classified as subvalvular, transvalvular, or supravalvular (at the level of the distal anastomosis). Bovine jugular vein conduit regurgitation greater than 2+ and gradient greater than 30 mm Hg was judged as functionally significant. Conduit aneurysm formation was defined as conduit dilatation more than 1.5-fold of initial diameter. All given data were based on the echocardiographic findings. Two foreign patients were lost to follow-up. Mean follow-up for all others was 31.2 ± 16.8 months (median, 38.4 months) corresponding to a total of 202.8 patient years (range, 0.3 to 5.4 years). All given data were based on the echocardiographic examinations. Cardiac catheterization was performed only when indicated by clinical and echocardiographic findings, except for pulmonary atresia plus VSD patients who had an elective catheter at 6 months postoperatively.
Data Analysis
For statistical analyses, redo operations were defined as redo surgery on the RVOT after failed previously performed correction. Continuous variables are expressed as mean ± standard deviation, and categorical data are expressed as proportions throughout the article. Categorical variables were compared using the 
2 test, and independent continuous variables were compared by using the two-tailed Student's t test or Mann–Whitney U test as appropriate at a level of significance of p < 0.05. Comparisons of related variables were performed by the Wilcoxon test and paired samples t test. Univariate and multivariate logistic regression was performed to assess BJV regurgitation greater than 2+, distal gradient greater than 30 mm Hg, reoperation, percutaneous reinterventions, and overall reinterventions. Nine dichotomous variables analyzed as possible predictors of outcomes were BJV size of 12 mm, male gender, age less than 1 year at the time of operation, RVOT redo procedure, concomitant pulmonary artery enlargement, correction of truncus arteriosus communis (TAC), primary correction of tetralogy of Fallot and pulmonary atresia plus VSD, cardiopulmonary bypass time greater than 2 hours, and postoperatively elevated right-ventricular-to-left ventricular (RV-to-LV) pressure ratio greater than 0.6. Analyses were carried out by using logistic regression models with stepwise backward procedure. Results are described as odds ratios (ORs) and 95%-confidence intervals (CIs).
Event-free survival was calculated by the Kaplan-Meier method with 95% confidence limits and the log-rank test. The p values less than 0.05 were considered statistically significant. The statistical analyses were performed using SPSS 13.0 software package (SPSS Inc, Chicago, IL).
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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At discharge, the maximal RVOT gradient was 15 ± 13 mm Hg. As given in Table 2, there were no significant gradient differences regarding patient age, implanted conduit size, or underlying cardiac malformation. Two infants and 1 adult had early postoperative gradients higher than 30 mm Hg.
Follow-up
Neither episodes of endocarditis or thromboembolism were noticed in the early postoperative course and during follow-up, respectively. Two late deaths (2.6%) occurred after 9 and 15 months postoperatively, because of persisting severe pulmonary hypertension and recurrent fungal septicaemia, respectively. All other patients were in functional class I or II at follow-up, with the exception of 2 patients who had TAC and transposition of the great arteries with VSD and pulmonary stenosis, who were in New York Heart Association functional class III.
In the 9 patients discharged with conduit regurgitation greater than 2+, an increase in conduit regurgitation from mean grade of 3.1 to 3.6 was observed, and conduit dilatation progressed to 6.2 ± 2.9 mm (p = 0.03), resulting in aneurysmal formation in 4 patients.
Two more patients had significant conduit regurgitation develop during follow-up (1 with TAC and 1 with PA plus VSD). All 12 patients with significant conduit regurgitation had RV-to-LV pressure ratio greater than 0.6 (mean, 0.81 ± 0.13). Reasons for high RV pressure were diminutive pulmonary vasculature in 4 patients, peripheral pulmonary artery stenosis in 3, pulmonary hypertension in 4, and distal anastomotic stenosis in 3. Therefore 6 of these patients received percutaneous angioplasty of the peripheral pulmonary arteries and distal anastomoses, respectively. Multivariate analysis revealed that predictors for conduit regurgitation greater than 2+ were BJV conduit size 12 mm (OR, 57.2; CI, 6.6–194; p < 0.001), infancy at the time of operation (OR, 51.0; CI, 5.9–237; p = 0.001), TAC correction (OR, 39.3; CI, 7.4–108; p = 0.001), and persistently elevated RV-to-LV pressure ratio greater than 0.6 (OR, 15.7; CI, 3.7–66; p = 0.001). One-year and 4-year freedom from conduit regurgitation is displayed in Table 2 and Figure 1a. Freedom from greater than 2+ conduit regurgitation was significantly worse for age less than 1 year during implantation (p = 0.001), TAC correction (p = 0.01), primary tetralogy of Fallot and pulmonary atresia plus VSD correction (p = 0.04), and conduit size of 12 mm (p = 0.002).
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Histologic examination of the explanted conduits revealed excessive intimal peel formation, not related to the suture line, forming an annular membrane at the level of the distal anastomosis in 3 patients. The membrane was formed by fibrous tissue covered with granulation tissue and infiltrated by a varying number of lymphocytes and macrophages. In all patients with severe regurgitation, conduits were significantly dilated and the valve leaflets had completely vanished in 6 of 8 patients, presenting only rudiments of the commissures. No conduit calcification was identified.
A total of 44.9% of patients underwent cardiac catheterization at 17.4 ± 13.5 months after implantation (range, 9 to 1,773 days). Percutaneous RVOT reinterventions were performed in 19 patients (24.4%) after a mean of 12.9 ± 9.0 months post surgery. Interventions included dilatation of the distal anastomosis in 18 patients (7 with stents), subvalvular conduit dilatation in 1, and concomitant major aortopulmonary collateral arteries coil occlusion in 3 patients. Risk factors for percutaneous RVOT reintervention were BJV conduit size 12 mm (OR, 4.1; CI, 1.4–12.0; p = 0.009), and TAC correction (OR 4.8; CI, 1.3–17.2; p = 0.02). Overall surgical and percutaneous reintervention rate was 29.5% with a 70% rate in children operated on during newborn age, 47.8% in infants less than 1 year of age, 58.3% after primary TAC correction, and 47.8% in BJV conduits of 12-mm size. One-year and 4-year freedom from overall reintervention is given in Figure 1d and Table 2. There was a significantly higher rate for patients aged less than 1 year at the time of operation (p = 0.002), for TAC correction (p = 0.01), and for 12-mm conduits (p = 0.02).
Gender, RVOT redo procedure, reconstruction of the peripheral pulmonary arteries, and cardiopulmonary bypass time longer than 2 hours did not significantly affect the early or mid-term conduit function.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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We currently report a series of 78 BJV conduit implantations, which is one of the largest series in the literature, along with length and detailed follow-up. The inclusion of almost 30% of patients less than 1 year of age at implantation, as well as a sufficient number of small (12 mm) BJV conduit sizes and complex underlying cardiac malformations, allowed us to perform specific-risk factor analyses of varying end points using multivariate techniques.
One of the most interesting findings of our study was the high rate of moderate to severe conduit valve regurgitation arising in the early postoperative course, and it was associated with significant conduit dilatation in all patients. All of these cases occurred in infants less than 1 year of age with persistently elevated RV pressure after the operation. Reasons for persistently elevated RV-to-LV pressure ratios varied between pulmonary hypertension, peripheral pulmonary artery stenosis, and diminutive pulmonary vasculature. Truncus arteriosus communis was the most frequent underlying cardiac anomaly within this subgroup. However, in 3 patients, BJV conduit dilatation resulted in a distortion of the distal anastomosis leading to a significant distal anastomotic stenosis and RV dysfunction. These stenoses were successfully treated by percutaneous dilatation and elective reoperation was scheduled.
The incidence and risk factors for early and follow-up BJV regurgitation in infants has not been addressed in detail so far. Breymann and coworkers [7] found an association between conduit valve incompetence and higher RV pressures, with a critical RV pressure of approximately 100 mm Hg. The incidence of moderate to severe valve incompetence was low in this study with little progression over time, even though the number of infants with TAC and BJV (size 12 mm) were comparable with our study population. Conduit dilatation was reported in 5.6% of their patients, but no RV pressure-related analysis was available. With the finding of more than 30% of moderate conduit valve regurgitation in that series, it can be speculated that discrepancies between their results and ours were probably related to different assessments of regurgitation volume. Tiete and coworkers [13] found significant regurgitation in 8 of 29 patients (27.6%) and aneurysm formation in 1 patient. In a recently published series, Shebani and coworkers [25] reported significant conduit dilatation and consecutive severe regurgitation in 16 of 62 patients (27.5%). In the majority of these patients, a high RV-to-LV pressure ratio was found, and 3 patients needed urgent conduit replacement. This experience is similar to ours, as pulmonary atresia plus VSD with persistently high RV pressure and elevated RV-to-LV pressure ratio greater than 0.6 was significantly related to conduit dilatation and secondary BJV regurgitation. Interestingly, they also found a small number of unpredictable conduit dilatations in the absence of raised intra-conduit pressure. Their findings as well as our findings suggest that the BJV conduit performs poorly under higher pressure conditions, and the conduit should be used with caution in patients in whom a high postoperative RV pressure is anticipated.
During follow-up we also found a tendency toward progression of regurgitation and dilatation of the RV hood that has rarely been described so far [26].
To avoid conduit dilatation, it has been suggested to position the high profile valve as near as possible to the pulmonary bifurcation to reduce the portion that is exposed to high pressures during diastole. However, this strategy does not completely avoid aneurysm formation in this low pressure substitute, as shown in our series and others [25]. To avoid aneurysm formation in risk patients, techniques such as inclusion of reinforced segments of the conduit by heterologous or synthetic materials should be considered.
It is well known that the region of the distal anastomosis is the most common location for BJV stenosis [8, 9, 19, 21]. Histologic examinations reveal severe peel formation leading to progressive distal anastomotic stenosis [9, 10, 25], which was confirmed by our study. Several reasons for intimal proliferation have been hypothesized, including hemodynamic factors like turbulent blood blow due to abrupt diameter mismatch from the conduit to diminutive pulmonary vasculature [9, 17, 26–28]. In our cohort, initial maximum gradient at the level of distal anastomosis was 15 mm Hg and comparable with other reports [7, 8, 15, 16]. During follow-up there was a significant increase in the distal anastomosis gradient over time. This observation is different from other investigators who showed stable pressure gradients during follow-up. Possible reasons for this discrepancy include varying number of included patients and different follow-up periods. Comparable with our findings, Breymann and coworkers [7] demonstrated an increase of maximal pressure gradient at the distal anastomosis from 17 to 35 mm Hg in 108 patients after a mean follow-up of 2.1 years. We found no significant correlation between younger age at implant, underlying cardiac malformation, or BJV conduit size, and the RVOT gradient at discharge and during follow-up [13]. By contrast, two other series described increased distal anastomotic gradients for small sized conduits and younger patients [8, 9]. Meyns and coworkers [9] even found a 55% risk of an elevated gradient (> 50 mm Hg) for small size conduits 1 year postoperatively.
In our series, postoperative percutaneous reinterventions at the distal anastomosis were common, noting that most did not meet routine surgical indications yet. However, this incidence is comparable with others [25]. Most of the moderate stenoses could be successfully treated by percutaneous balloon interventions, even in small patients. This may explain that compared with other reports the indication for conduit replacement due to isolated conduit stenosis was rare in our series [7, 17]. The optimal timing of reintervention in conduit stenosis is still a matter of debate as the benefit of early RV unloading must be compared with the risk of reintervention. However, the relatively low risk of percutaneous procedures has lead to more liberal decisions for reintervention, but the benefit of early percutaneous procedures on RV function and functional class have to be proven in the future.
One-year and 4-year freedom from reoperation was 93.5% and 87.4%, respectively, in our series and comparable with other studies [8, 24]. In the series of Corno and colleagues [24], patient age less than 1 year at the time of implantation was found to be a risk factor for reoperation. By multivariate analysis we also identified infancy, as well as small conduit size, TAC, and RV-to-LV pressure ratio greater than 0.6 as independent risk factors for reoperation.
Freedom from reoperation was 100% after 1-year and 4-years for patients older than 1 year of age in our series, demonstrating good graft function in young children and adults. For patients less than 1 year, freedom from reoperation was only 77.6% as also experienced by others [17, 25].
In conclusion, BJV RVOT conduit implantation leads to good mid-term results in children and adults with congenital heart defects with low reoperation rate and acceptable reintervention rate. However, results are suboptimal in infants less than 1 year of age at risk of persistently elevated postoperative RV pressures (eg, pulmonary hypertension, diminutive pulmonary vasculature, or peripheral pulmonary stenosis). The significant risk of aneurysmal dilatation and early conduit valve incompetence in these patients makes close echocardiographic examinations mandatory. Although graft failure for infants and neonates is still an ongoing and unsolved problem for all other valved conduits [29, 30], the BJV conduit remains a viable surgical option in these challenging patients. Further analyses on a larger series and longer follow-up should be better focused on infants to identify risk factors for graft failure or reoperation and to elucidate the advantage of BJV implantation over homografts and other surgical options for this patient population. A multicenter BJV registry will be helpful for better data analysis and will allow defining optimal implant indications [30].
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