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Ann Thorac Surg 2007;84:606-611
© 2007 The Society of Thoracic Surgeons
a Division of Cardiovascular Surgery, University Hospital of Geneva, Geneva, Switzerland
b Unit of Pediatric Cardiology, Department of Pediatrics, University Hospital of Geneva, Geneva, Switzerland
Accepted for publication March 20, 2007.
* Address correspondence to Dr Christenson, Department of Cardiovascular Surgery, University Hospital of Geneva, 24 rue Micheli-du-Crest, Geneva 14, CH-1211, Switzerland (Email: jan.christenson{at}hcuge.ch).
Presented at 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: Between 1993 and 2005, 88 aortic homografts (54 blood-group compatible, iso, and 34 nonblood-group compatible, non-iso) and 50 Contegra conduits were implanted for RVOT reconstruction. Mean age was 4.9 ± 3.6 years, ranging from 1 month to 15 years. The two important primary diagnoses were tetralogy of Fallot (61%), and double-outlet right ventricle with pulmonary stenosis (12%). There were no demographic differences between the groups. The mean graft diameter was 19 mm (homografts) and 15 mm (Contegra).
Results: There were no hospital deaths in the homograft group, whereas 1 patient died of graft unrelated causes in the Contegra group. Postoperative mean gradient was 14.5 ± 11.2 mm Hg (homografts) and 19.8 ± 11.5 mm Hg (Contegra). Freedom from graft dysfunction and reoperation at 2, 5, and 7 years was 88.9%, 87.6%, and 81.3% for all homografts; 100%, 97.4%, and 93.8% for homograft iso; 79.9%, 76.9%, and 66.6% for homograft non-iso; and 94.0%, 90.7%, and 90.7% for Contegra grafts. Moderate valvar regurgitation was seen in 3.4% (homografts) and 8.0% (Contegra). No supravalvar lesions were observed in either group.
Conclusions: Blood-group compatible cryopreserved homografts and Contegra conduits for RVOT reconstruction have very similar performance as long as 7 years postoperatively, and are significantly superior to nonblood-group compatible homografts.
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Introduction |
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The Contegra conduit (Medtronic, Minneapolis, MN) is a heterologous bovine jugular vein graft containing a trileaflet venous valve and a natural sinus slightly larger than its lumen. The bioprosthesis is preserved in buffered 0.6% glutaraldehyde solution under zero pressure condition, thus preserving the flexibility of the leaflets. In addition, the conduit is available in small sizes, 12 mm to 22 mm. Early animal trials showed excellent durability and low calcification rate [9, 10], and clinical reports with short- to mid-term follow-up have described excellent results [11–14]. This has led to an increasing use of Contegra conduits for RVOT reconstructions in the pediatric population. Pseudoaneurysm formation and supravalvar stenosis using the Contegra conduit have been reported [14, 15].
Only a few studies have been undertaken to compare the different conduits until now [11, 12, 16, 17]. Therefore, in the present study, we have compared long-term outcomes between cryopreserved aortic homografts (blood-group compatible and noncompatible) and Contegra conduits used for RVOT reconstruction in a pediatric population.
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Patients and Methods |
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Patient Characteristics
Eighty-eight pediatric patients who had cryopreserved aortic valved homografts implanted for RVOT reconstructions between June 1993 and December 2005 were compared with 50 patients who received Contegra conduits from September 2000 to December 2005. During the period when both conduits were available, the choice of conduit was based on the availability of correctly sized and biocompatible homografts. Age and sex distribution and primary diagnosis of their congenital lesions are described in Table 1. The only main difference between the two groups was that patients in the Contegra group were slightly younger. Twenty-three patients in the homograft group (26%) had undergone at least one earlier cardiac intervention compared with 12 patients (24%) in the Contegra group (Table 2). In the homograft group, 54 patients had the same blood group (ABO) as the homograft donor (iso group), and in 34 cases, there was blood group incompatibility (non-iso group). Fifty-eight valved cryopreserved homografts were obtained from two sources: 36 iso and 22 non-iso from the European Homograft Bank (Brussels Military Hospital, Belgium); and 18 iso and 12 non-iso from CryoLife (Marietta, GA). The procurement and preparation techniques used have been described earlier [18].
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The RVOT conduit was inserted between the extended pulmonary bifurcation and the infundibulotomy. The distal anastomoses were performed first; in some patients, bovine or autologous pericardium was used to enlarge the pulmonary arteries or to provide continuity between the pulmonary arteries. The proximal anastomoses were made to vertical infundibulectomies. In addition, a patch of bovine or autologous pericardium was inserted as a hood to cover the space between the anterior mitral leaflet attached to the homograft or Contegra graft and the remaining boarders of the infundibulotomy. No prosthetic material was used. Associated procedures performed simultaneously are shown in Table 3.
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Statistical Analysis
Data are presented as the mean ± SD. Continuous variables were analyzed with Student t test and categorical variables using 
2 test. Actuarial estimates were calculated using the Kaplan-Meier method.
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Results |
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Oversizing of homografts (Z-value approximately 2) was achieved in 90% (79 of 88) of the patients, and graft oversizing in the Contegra group was achieved in all patients. Of a total of 88 cryopreserved homografts, blood group compatibility between donor and receiver was achieved in 54 patients (61%).
Primary diagnosis, age and sex distribution, and previous surgical procedures did not reveal any statistically significant differences between the homograft group and the Contegra group, even though there were slightly more patients younger than 3 years of age at the time of surgery in the Contegra group. Sex, age, and primary diagnosis was also without difference between the iso and non-iso homograft groups. Mean gradient right ventricle (RV) to pulmonary artery (PA) was 14.5 ± 11.2 mm Hg, ranging from 0 to 49 mm Hg at 3 months after homograft implantation, whereas the mean gradient RV to PA in the Contegra group was significantly higher, 19.8 ± 11.5 mm Hg, ranging from 0 to 50 mm Hg (p < 0.001). In the homograft group, the mean gradient RV to PA did not significantly change over time, except in those patients who subsequently had severe to moderate calcifications. In the Contegra group, the mean RV to PA gradient showed a trend to diminish beyond 6 months after implantation (19.8 ± 11.5 mm Hg at 3 months versus 16.5 ± 10.8 mm Hg at 1 year).
During follow-up, 14 patients (16.1%) required a reoperation owing to stenosis and valvular dysfunction in the homograft group. The indications for reoperation were a RV to PA gradient of 50 mm Hg or greater, or a grade III pulmonary insufficiency with dilated RV. There were significantly more reoperations in the non-iso homograft subgroup, 11 of 34 (32.4%), compared with 3 of 54 in the iso homograft group (5.6%; p < 0.001). Four patients required a reoperation during the first postoperative year and another 3 during the second year after homograft implantation, all belonging to the non-iso homograft group. Another 4 patients in the non-iso homograft group underwent reoperation at 4, 7 (2 patients), and 10 years after homograft implantation, whereas the 3 iso homograft patients underwent reoperation at 5, 7, and 9 years after the primary operation.
In the Contegra group, 3 of 50 patients (6%) underwent reoperations. In 1 patient, reoperation due to severe distal anastomotic stenosis, with gradient of 110 mm Hg RV-PA due to a technical problem, required a refashioning of the distal anastomosis 1 day postoperatively, with immediate satisfactory result (RV-AP gradient of 21 mm Hg). In a second patient, a necrosis of a leaflet was diagnosed on the 28th postoperative day, and the conduit was replaced with a homograft. A third patient underwent reexploration owing to a peri-Contegra abscess, which was successfully healed by drainage and antibiotic therapy without need for replacement of the conduit. So far, there have not been any delayed reoperations in the Contegra group due to valvar or subvalvar stenosis, and in addition, supravalvar stenosis was not observed in this series. Moderate valvar regurgitation was seen in 3.4% of homografts and 8.0% of Contegra, a nonstatistically significant difference. No supravalvar lesions were observed in either group.
In terms of freedom from reoperation, the Contegra conduit compares well with blood-group compatible (iso) homografts, 6% versus 5.6%, and significantly better than blood-group noncompatible (non-iso) cryopreserved homografts, 8% versus 32.4% (p < 0.001).
The actuarial freedom from reoperations for Contegra conduits was 90.7% at 7 years compared with the overall freedom from reoperations for cryopreserved valved homografts of 81.3%, however, with a marked difference between the two homograft subgroups: blood-group compatible homografts, 93.8%, versus nonblood-group compatible homografts, 66.6% (Fig 1).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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However, the European Homograft Bank has stated that 10% of the requests cannot be satisfied [24], not taking into consideration either blood-group compatibility or homograft size. It has been clearly demonstrated that undersizing (small Z values) result in worse freedom from conduit dysfunction and need for reoperation [4, 17]. The practice of oversizing valves with a Z-value of approximately 2 to allow for growth was strictly observed for all patients in our series. An additional participating factor in homograft failure is related to the material used as hood to cover the infundibulotomy, as well as in patch enlargement of the pulmonary arteries [2, 8, 24]. We consistently used autologous or bovine pericardium for these patches, and that may have contributed to the good outcome observed in our series.
The Contegra valved bovine jugular vein has become an interesting alternative in RVOT reconstruction, with reported excellent early results [13, 16]. The Contegra conduit is biological inert, readily available in a broad spectrum of different sizes. Many of the limitations of the cryopreserved homograft have thus been avoided by introduction of the Contegra conduit. To evaluate the long-term results, the present study was undertaken. The homograft and Contegra group of patients were comparable. Anesthesia, cardiopulmonary bypass techniques, and surgical techniques were the same for the two groups. The need for reoperation was significantly higher in the homograft group compared with the Contegra group, but when blood-group compatibility was observed in the homograft group, reoperations were less common than in the Contegra group, clearly demonstrated by comparing freedom from reoperation, which was 93.8% for blood-group compatible homografts and 90.7% for Contegra conduits at 7 years after conduit implantation. The majority of the patients in this series had as primary diagnosis tetralogy of Fallot, which may explain the good results achieved in this series. These results are consistent with data reported by others [3, 25]. In our series, we observed no dilatation of the Contegra conduit or severe calcifications. Until now, no reoperations have been done for valvar or subvalvar stenosis, and in addition, distal anastomotic stenosis was not observed in this series. Only 3 patients underwent reoperations in the Contegra group; 1 patient had a leaflet necrosis, 1 patient had severe distal anastomotic stenosis, and a third patient had peri-Contegra abscess.
In conclusion, blood-group compatible cryopreserved homografts and Contegra conduits for RVOT reconstruction have very similar performance as long as 7 years after implantation and are clearly superior to nonblood-group compatible homografts. We conclude that the Contegra conduit, owing to its availability and its large range of sizes, is a valid alternative to homografts for RVOT reconstruction in the pediatric population.
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Discussion |
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DR CHRISTENSON: In the Contegra group, we did not observe any relationship between conduit failure and conduit size. The Contegra conduits are readily available in all sizes.
DR PIGULA: Down to 12 mm?
DR CHRISTENSON: That is correct.
DR JOHN W. BROWN (Indianapolis, IN): Very interesting study. I agree with your conclusions. However, were these aortic or pulmonary homografts that you used?
DR CHRISTENSON: In this series we used only aortic homografts.
DR BROWN: And why?
DR CHRISTENSON: Simply because it’s very difficult to find pulmonary homografts in adequate size as well as biocompatible.
DR BROWN: Do you think that pulmonary homografts would have fared better if they were iso compatible or do you have a comment?
DR CHRISTENSON: I can only speculate about that. However, there are some earlier studies showing that aortic homograft in pulmonary position have a higher risk of calcifications than pulmonary homograft. However, I have no data from this series that can demonstrate that.
DR BROWN: And I guess my final comment was, there’s nothing to indicate what the functionality of the two different groups is. When we compare conduits, we look at conduit dysfunction, which we would define as a gradient greater than 40 and greater than 2-plus regurgitation. And you didn’t really tell us, at least in the presentation, how the two groups compared at last follow-up.
DR CHRISTENSON: That is correct, I didn’t present these data in the presentation, owing to time restrain. However, it is available in the manuscript, and we followed exactly the same definition that you mentioned for conduit failure.
DR JOHN J. NIGRO (Phoenix, AZ): I really was interested in the blood grouping and the homografts that were matched and those that were nonmatched. I wondered if there was a difference in the mode of failure in these two groups, meaning when matched homografts failed, was failure due to predominantly stenosis or insufficiency? Was there a relationship between tissue matching and failure mode?
DR CHRISTENSON: No. What we have shown is that in the very young patients (younger than 3 years of age) significantly more accelerated fibrocalcifications occurred in the homograft when blood group compatibility was not achieved. This phenomenon was less frequent in older children.
So it looks like it’s during the very early phase after conduit implantation, when you still might have some viable cells in the homograft, that may trigger an early immune response leading to early and accelerated fibrocalcification in cases of bioincompatibility.
DR PIGULA: Can I just ask the audience? Do you use as a consideration for your homograft ABO compatibility when you select one? How many people do that? [A show of hands.] So the majority of the people disregard ABO compatibility and really focus on size; is that right?
[A show of hands.]
DR SERTAC CICEK (Istanbul, Turkey): Excellent study. More than 50% of the patients had the diagnosis of tetralogy of Fallot. What are your indications using RV to PA conduits in tetralogy of Fallot? Are you liberally using them? What number of the total patients among the tetralogy of Fallot diagnosis gets the RV to PA conduit?
DR CHRISTENSON: I am sorry, but I cannot recall from the top of my head how many patients with diagnosis tetralogy of Fallot receive RV to PA conduit at our institution.
DR CHRISTOPHER J. KNOTT-CRAIG (Birmingham, AL): There seems to be some controversy in this area of blood compatibility and homograft longevity; our analysis, which was presented at the AATS a few years ago, demonstrated no relationship between ABO compatibility and longevity; however, factors such as the time from harvesting to the time of cryopreservation may have influenced the long-term performance of the pulmonary homograft. How do you explain these differences in the literature?
DR CHRISTENSON: Well, first of all, we got our homografts from two sources, from the CryoLife in the United States and from the Homograft Bank in Brussels. And we have looked into the preparation time. There is no major difference between the two suppliers in ischemia time. I cannot for each individual patient give you a concrete answer to your question.
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