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Ann Thorac Surg 2006;82:909-916
© 2006 The Society of Thoracic Surgeons
a Section of Cardiothoracic Surgery, James W. Riley Hospital for Children, Indiana University School of Medicine, Indianapolis, Indiana
b Section of Cardiology, James W. Riley Hospital for Children, Indiana University School of Medicine, Indianapolis, Indiana
Accepted for publication March 3, 2006.
* Address correspondence to Dr Brown, Section of Cardiothoracic Surgery, Indiana University School of Medicine, 545 Barnhill Dr., EH 215, Indianapolis, IN 46202-5123. (Email: jobrown{at}iupui.edu).
| Pediatric cardiac surgery:
The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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METHODS: The early results of RVOT reconstruction utilizing the Contegra conduit were retrospectively analyzed in 62 patients. This series consisted of 9 newborns with truncus arteriosus, 39 patients with failed PHs, 6 with pulmonary atresia and 2 with tetralogy of Fallot with absent pulmonary valve, 2 with transposition of great arteries with ventricular septal defect and pulmonary stenosis, and 4 undergoing a Ross procedure. The patients ages ranged from 2 weeks to 18 years (mean, 7.3 ± 6.0 years) and weights were from 2 to 83 kg (mean, 28.1 ± 22.3 kg). The Contegra conduit sizes varied in diameter between 12 and 22 mm (mean, 18.2 ± 4.1 mm).
RESULTS: There were two early (3%) and four (7%) late deaths and none of them was conduit related. There has been one conduit explantation, and seven patients have required reinterventions to relieve stenosis at or beyond the distal anastomosis of the conduit to pulmonary artery bifurcation (8 of 60; 13%). Six of the 7 patients had balloon dilatation of the branch pulmonary arteries for preexisting stenosis. One patient developed distal anastomotic stenosis that did not yield to balloon angioplasty and she underwent surgical patch arterioplasty of the distal anastomosis. The interval from conduit implantation to reintervention ranged from 3 to 27 months (mean, 11.1 ± 7.8 months). Of these, three patients required placement of a stent in the left (n = 1) or both branch pulmonary arteries (n = 2). During the short to intermediate follow-up in our series we have not observed, on echocardiography, shrinkage of the Contegra as we and others have reported with PHs.
CONCLUSIONS: The Contegra conduit offers a promising alternative for RVOT reconstruction. Early hemodynamic performance compares favorably with PHs. Clinical advantages are greater availability in sizes from 12 to 22 mm and natural continuity between the valve and conduit that allows proximal infundibular shaping without additional materials. The price of the bovine jugular venous valve is approximately one-half that of many PHs in the US. Short-term freedom from dysfunction is at least as good as PHs. Long-term durability must be determined for this new conduit. The Contegra conduit is currently our conduit of choice for RVOT reconstruction in infants, children, and young adults.
| Dr Brown discloses that he has a financial relationship with Medtronic, Inc.
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Right ventricular to pulmonary artery (RV-PA) conduits have made possible the repair of many complex congenital cardiac lesions involving atresia or hypoplasia of the right ventricular outflow tract (RVOT). These lesions include truncus arteriosus (TA), pulmonary atresia with ventricular septal defect (VSD), severe tetralogy of Fallot, transposition with ventricular septal defect and pulmonary atresia, and various forms of double outlet right ventricle. Conduits have also made possible the pulmonary autograft replacement of the aortic root with the pulmonary root (Ross procedure) [1].
Numerous valved conduits have been introduced since an aortic homograft was first used clinically in the mid-1960's [2–7]. Conduit types include bioprostheses in Dacron tubes, stented bovine or porcine xenografts in pericardial tubes, glutaraldehyde fixed aortic or pulmonary roots, nonvalved tissue or prosthetic conduits, and aortic and pulmonary homografts.
Aortic and pulmonary cryopreserved homografts have been the "gold standard" in the US since the mid-1980s [2, 3, 7]. Pulmonary homografts (PHs) have been favored over aortic homografts in most centers as they are less prone to obstruction and calcification [8]. Aortic homografts are usually more difficult to remove and(or) revise due to their propensity for dense calcification and adherence to surrounding structures.
Pulmonary homografts are in short supply particularly in small sizes (10 to 18 mm). PHs usually require the addition of prosthetic or pericardial skirts on the proximal end to facilitate connection to the right ventricle. Many PHs are prone to shrinkage, leading to conduit stenosis and the development of significant valve regurgitation within months of insertion especially when implanted as extracardiac conduits [9]. Their performance is significantly improved in the orthotopic position, as in the Ross aortic valve replacement patients, who are usually older and where an oversized PH can be easily accommodated. The focus of this report is to review our Institution's clinical experience with the bovine jugular vein conduit (BJVC).
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Patients and Methods |
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Parents of patients enrolled in this study had given informed consent for participation in accordance with the guidelines of the Institutional Review Board at Indiana University (IRB No. 0009-42). Five patients received a BJVC under Federal Drug Administration (FDA) emergency compassion exemption, while 59 patients are part of the United States BJVC clinical trial funded by Medtronic, Inc, Minneapolis, MN. Since November 2003, the BJVC is being used in the US under Humanitarian Device Exemption (HDE) approved by the FDA. Hospital records were retrospectively reviewed, including operative records, as well as preoperative and postoperative catheterization and echocardiography data and the data were submitted for analysis to a core laboratory.
Primary and secondary operations for conduit implant are shown in Table 1. The majority of patients underwent operation (38 of 62, 61%) for truncus arteriosus and pulmonary atresia with VSD as the most common indications for Contegra insertion.
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Cardiopulmonary bypass is established with bicaval cannulation and moderate hyperthermia (32°C). Aortic cross-clamping with intermittent cold potassium blood cardioplegia is employed for the intracardiac repair if indicated. The mean bypass and clamp times were 107 ± 67 and 31 ± 52 minutes, respectively. All conduit insertions, primary or reoperation, are performed with the heart beating.
The principles of conduit insertion include the following. (1) The conduit is rinsed for 5 minutes with continuous manual agitation in four 500 cc baths of normal saline or ringers lactate prior to implantation. (2) The conduit is positioned to the left of the midline to avoid sternal compression. (3) The outflow end of the conduit is cut so that the conduit valve is positioned as far distally as possible toward the PA bifurcation to avoid valve distortion with sternal closure. (4) The distal anastomosis is performed with monofilament suture (Ethicon, Inc, Summerville, NJ) as a continuous stitch posteriorly and interrupted suture anteriorly to minimize the potential for distal anastomotic narrowing. (5) The inflow end of the conduit is spatulated to form a hood over the incision in the right ventricle and sewn with continuous monofilament suture. A narrow strip of left-over Contegra tissue is used to reinforce the inflow ventriculotomy in neonates and younger children who might exhibit postoperative pulmonary hypertension. (6) Polytetrafluoroethylene (PTFE) pericardial membrane (0.1 mm) is sewn to the pericardial edges to facilitate sternal reentry if reoperation becomes necessary.
Conduits used in our series ranged from 12 to 22 mm (mean, 18.2 ± 4.1 mm). There were 9 ring-supported and 53 nonring supported conduits implanted. Postoperatively, all patients received aspirin (10 mg/kg/day) for 3 months.
Measurements
Intraoperative peak transconduit gradients were measured by transesophageal echocardiography or direct measurement prior to sternal closure. Postoperative surface echocardiography was performed by coinvestigators of the Contegra clinical trial at Indiana University. All patients had echocardiographic evaluation prior to discharge and at 1, 3, 6, and 12 months after surgery for the Investigational Device Exemption (IDE) study and yearly thereafter for both the IDE and HDE studies. The surgical data, preoperative and postoperative catheterization, and echocardiography data were sent to the Contegra Core Laboratory.
Definitions
Early death is defined as a death in the hospital or within 30 days of discharge. All other events are considered late.
Pulmonary hypertension was treated by systemic vasodilators and (or) nitric oxide if the pulmonary artery systolic pressure was greater than or equal to two-thirds of the systemic blood pressure. Conduit valve regurgitation is assessed by color Doppler imaging from the parasternal short-axis view at the level of the great arteries (RVOT view).
Conduit dysfunction is defined as a peak conduit gradient greater than 40 mm Hg or greater than 2+ regurgitation and conduit failure is defined as the need for conduit replacement or the need for cath lab conduit reintervention. As a general rule, the transconduit peak gradient obtained at catheterization under general anesthesia was less than the peak gradient obtained by surface echocardiography on an awake patient.
The severity of regurgitation is graded by visual comparison of the width of the regurgitant jet at its origin to the width of the annulus using the following criteria: none, no diastolic color flow visualized on the ventricular side of the leaflets; trace, pinhole color flow jet on the ventricular side of the leaflets; mild, a jet less than 20%; moderate, a jet of 20% to 40%; and severe, a jet greater than 40% of the pulmonary valve conduit width. Numerically, trace is equivalent to +1; mild +2; moderate +3; and severe +4 pulmonary insufficiency. Cardiac magnetic resonance imaging (MRI) has recently become available at our institution and it is a very valuable tool to evaluate RV volume, RV function, and valve regurgitation. No patient in this series has yet had MRI postoperatively.
Indications for conduit insertion included the following: (1) pulmonary atresia or stenosis with or without pulmonary insufficiency; (2) right ventricular pressure greater than or equal to two-thirds systemic pressure; or (3) RV to PA peak gradient greater than or equal to 40 mm Hg. Indications for bovine jugular vein conduit reintervention include the symptoms of RV failure, a RV to PA peak gradient equal to or greater than 40 mm Hg, or progressive dilatation of the RV with or without tricuspid valve regurgitation.
Statistical Analysis
Statistical software SPSS for Windows version 10 (SPSS Inc, Chicago, IL.) was used for data analysis. Actuarial survival was determined using the Kaplan-Meier method. For all tests, a p value of less than 0.05 was considered significant.
Follow-Up
Follow up was obtained in all hospital survivors for a mean of 29.6 ± 20.0 months (range, 3 to 80 months); a total of 1,744 patient-months.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Reintervention
The incidence of RVOT reinterventions was 8 of 60 (13%) and is shown in Table 3. The only conduit explanted was in a patient with pulmonary atresia, VSD, and multiple aortopulmonary collateral arteries to hypoplastic, but centrally confluent pulmonary arteries. Initial palliation (central shunt and coil embolization of multiple aortopulmonary collateral arteries) was performed at age 14 months. At age 2.5 years he underwent Dacron patch closure of the VSD and placement of a 12 mm Contegra conduit between the RV and main PA. His postrepair right ventricular to left ventricular ratio was 80%. At 3.5 years, he underwent implantation of two stents in the left PA due to preexisting persistent narrowing of the left pulmonary artery. At 4.3 years, he moved to another state and was found to have a RV suture line pseudoaneurysm and underwent resection of the RVOT pseudoaneurysm, BJVC explantation and insertion of a PH (23 mm), and right and left PA patch augmentation. A preoperative echocardiogram showed moderate left PA stenosis with a gradient of 50 mm Hg and well-functioning BJVC with mild plus insufficiency. At operation his BJVC grossly appeared normal.
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Six additional patients have required cath-lab interventions for preexisting peripheral pulmonary stenosis (PEPPS) which was not addressed at the time of initial surgical repair (Table 3). In all 6 cases, the reintervention was directed at relieving stenosis at or beyond the distal anastomosis of the conduit to PA bifurcation. The interval from conduit implantation to intervention ranged from 3 to 27 months with a mean of 12.9 ± 9.0 months. Six of 7 patients had peripheral pulmonary stenosis noted on their preoperative evaluation but the peripheral stenosis was not surgically addressed at the time of conduit insertion. One patient (No. 2) developed postoperative stenosis at the distal conduit anastomosis and is described above. Of the 6 patients who required cath-lab reintervention, three patients required placement of a stent in the left (n = 1) or both branch pulmonary arteries (n = 2). The mean distal anastomotic gradient post cath-lab reintervention was 16.8 ± 6.2 mm Hg.
Echocardiographic Analysis
At the time the 60 hospital survivors were discharged, the mean echo conduit gradient was 11.8 ± 13.8 mm Hg. Forty-one patients (68%) had no pulmonary insufficiency and each of the remaining 19 patients (32%) was judged echocardiographically to have trace to mild conduit valve insufficiency. At a mean follow up of 29.6 ± 20.0 months, the mean echo conduit gradient increased slightly to 14.4 ± 13.1 mm Hg, but this increase was not statistically significant (p = 0.18). Among the 56 late survivors, the degree of conduit valve insufficiency increased slightly as only 30 patients (54%) had none, but 26 patients (46%) had trace to mild and one patient has moderate regurgitation. Shrinkage of the BJVC has not been observed. Dilatation of the BJVC has not been observed by echocardiography in this series despite the 7 patients (13%) who had distal obstruction. It appears that the BJVC withstands high pressures without pathologic dilatation during our 30 months of follow-up.
Nine patients received ring-supported bovine jugular vein conduits in an attempt to maintain conduit valve geometry and competency. At the time of discharge and at follow-up, the degree of conduit valve insufficiency and the gradient across the conduit was not significantly different from the 51 patients who received nonring-supported BJVC. The gradient at last follow-up was slighter higher in the ring-supported BJVC (21.9 ± 12.7 vs 13.7 ± 12.3 mm Hg) but was not significantly different (p = 0.06).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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The limited availability and durability of homografts conduits, especially in smaller sizes, supported the search for an alternative conduit to reconstruct the RVOT in congenital heart defects and in the patients undergoing the Ross procedure. In 1999, the Contegra bovine jugular vein conduit was introduced as a potential alternative to homografts for RVOT reconstruction. Early animal studies by Ichikawa and colleagues [11] and our group [12] reported excellent results demonstrating good leaflet preservation and freedom from significant structural degeneration and valve regurgitation at 3 years. These animal studies were confirmed in human clinical trials with up to 27 months (mean, 1.2 years) follow-up reported by Breymann and colleagues [13] suggesting that the Contegra conduit might represent a promising alternative to homograft conduits. A report by Bove and colleagues [14] comparing bicuspid pulmonary homograft and Contegra supported these findings in 41 patients (mean age, 1.9 years) who underwent RVOT reconstruction. Their results demonstrated equivalent hemodynamics of the BJVC with their bicuspid homografts.
The first author of this report (JWB) was introduced to the glutaraldehyde-preserved bovine jugular vein with integral venous valve (BJVC) in the late 1980s and was able to test this conduit in an experimental animal (dog) model [12]. Other RV-PA conduit prototypes were being tested at that time in this model. The BJVC handled and performed in a superior manner in our model when compared with xenografts in prosthetic tubes or animal homografts preserved a number of different ways [12]. Interest in the BJVC grew slowly until clinical follow-up studies on pulmonary homografts began to demonstrate significant early regurgitation and stenosis (Table 4; Refs. 4, 7, 10, 15–17).
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Making the conduit too long can cause angulation at the distal anastomosis and cause turbulent flow and may become a major cause of conduit obstruction. We also believe that residual glutaraldehyde in the conduit wall or inclusion of conduit adventitia into the lumen may be responsible for some of the white cell and platelet deposition at the distal anastomotic stenosis and neointimal peel seen and reported by some investigators. Autologous tissue (eg, pericardium) soaked in glutaraldehyde contracts and shrinks before it is used for an intra or extra cardiac patch. Insufficient BJVC conduit rinsing may result in retained glutaraldehyde within the wall of the Contegra; retained glutaraldehyde could trigger the development of neointimal fibrosis and subsequent stenosis at the distal conduit anastomosis. We consistently use one additional 5 minute (500 cc) normal saline bath for conduit rinsing and avoid conduit adventitia being incorporated into the lumen at anastomotic sites. Additionally, all patients are kept on 10 mg/kg per day aspirin for 3 months to decrease potential platelet aggregation at suture lines.
We believe that suture technique at the distal anastomosis may be relevant. In our series, we employed a continuous suture posteriorly with every third stitch locked. Interrupted sutures were inserted anteriorly to avoid purse stringing and mechanical stenosis. Interestingly, in our series, the suture material (Prolene and PDS) were equally employed among the eight patients requiring reintervention, suggesting that the type of suture material is not an etiologic factor.
We and other investigators [20, 24] also believe that it is important to perform the distal conduit anastomosis leftward toward the proximal left PA. This prevents mechanical interaction between the lesser curvature of the ascending aorta and the distal Contegra anastomosis, which could potentially trigger mechanical narrowing.
Meyns and colleagues [25] noted neointimal proliferation at the distal anastomosis resulting in the need for endovascular intervention in 17 patients (29%) and conduit explantation in seven patients (12%) of their series. Pathologic findings in their explanted group demonstrated preserved conduit wall integrity with minimal calcification and the valve leaflets were intact and pliable. This study and others suggest that the Contegra conduit can withstand high distal pressures without the formation of aneurysm or conduit valve degeneration. In our series, the early performance of the Contegra has been satisfactory with 34 of 40 late survivors (85%) free of any intervention at a mean follow-up of 26 months. The RV to PA mean gradient has increased only slightly during this interval (16.6 mm Hg to 18.8 mm Hg), without any appreciable increase in conduit valve regurgitation. We have not seen neointimal proliferation at any anastomotic site. This lack of neointimal proliferation may be due to the routine use of aspirin in our patients. The price of the Contegra BJVC to our hospital is $4,000, and the average price of a pulmonary homograft (CryoLife/LifeNet) is $6,900.
In conclusion, the BJVC is a new RV-PA conduit clinically available in Europe and Asia and is in clinical trials in Europe and in the US in several major centers. In November 2003 BJVC was released by the FDA for HDE utilization in centers that obtain institutional review board approval and have appropriate informed patient consent.
The BJVC is very "surgeon friendly" and needs no additional material to facilitate connection to the RV. It is projected to be one-half the cost of many currently available cryopreserved PHs (ie, around $4,000). In this study its function early is comparable if not superior to the PH because it has developed less obstruction and regurgitation than has been reported with PHs at the same time interval [9]. We recommend keeping the posterior wall of the conduit short so it will not angulate and obstruct the conduit distal to the valve. Keeping the conduit valve distal and away from the sternum may prevent deforming the valve and preserve valve competency. We recommend a three month postoperative course of low dose aspirin and an interrupted distal suture line to prevent distal suture line stenosis. The Contegra BJVC has become the conduit of choice at our institution for RVOT reconstruction.
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References |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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A. C. Fiore, M. Rodefeld, M. Turrentine, P. Vijay, T. Reynolds, J. Standeven, K. Hill, J. Bost, D. Carpenter, C. Tobin, et al. Pulmonary Valve Replacement: A Comparison of Three Biological Valves Ann. Thorac. Surg., May 1, 2008; 85(5): 1712 - 1718. [Abstract] [Full Text] [PDF]
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