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Ann Thorac Surg 2004;78:1382-1388
© 2004 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, Lausanne, Switzerland
b Department of Radiology, Lausanne, Switzerland
c Department of Pediatrics, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
Accepted for publication February 10, 2004.
* Address reprint requests to Dr Corno, Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), 46 Rue du Bugnon, CH 1011, Lausanne, Switzerland
antonio.corno{at}chuv.hospvd.ch
Presented at the Fortieth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 26–28, 2004.
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Abstract |
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METHODS: From April 1999 to December 2003, 67 patients with a mean age of 16.1 ±15.0 years (2 months to 53 years) and a mean weight of 39.7 ± 27.1 kg (4 to 95 kg) were discharged after implantation of a Contegra conduit. The diagnosis contained the following: pulmonary valve replacement during Ross operation (n = 27), pulmonary valve regurgitation (n = 9), tetralogy of Fallot (n = 7), pulmonary atresia with ventricular septal defect (n = 7), double outlet right ventricle (n = 7), truncus arteriosus (n = 5), Taussig-Bing (n = 2), obstructed conduit (n = 2), and double discordance (n = 1). Conduit size was 14 mm in 2, 16 mm in 7, 18 mm in 12, 20 mm in 13, and 22 mm in 33 patients. Mean cardiopulmonary bypass was 155 ± 48 min (65 to 337 min) and mean aortic cross clamping was 69 ± 38 min (0 to 146 min). All patients underwent echocardiography, 23 of 67 (34%) patients had cardiac catheterization, and 23 of 67 (34%) patients had electrocardiograph-gated multislice computer tomography.
RESULTS: In a mean follow-up of 26.4 months (1 to 56 months) there was one late death (1 of 67 patients; 1.5% mortality) unrelated to the conduit. Five patients underwent reoperation; four were nonconduit-related and one was to replace a twisted conduit. Five patients underwent interventional cardiology; three were nonconduit-related and two were to stent a twisted or stenotic conduit. Echocardiography showed absent valve regurgitation in 30 of 67 (45%) patients, trivial in 21 of 67 (31%) patients, mild in 16 of 67 (24%) patients. The transconduit pressure gradient remained stable during follow-up, with peak pressure gradient 17 ± 11 mm Hg and mean gradient 8 ± 6 mm Hg. Internal diameters corresponded to 110% ± 20% of the implanted diameter at level of proximal anastomosis, 112% ± 18% at valve level, and 110% ± 14% at distal anastomosis. Calcifications were not found, with the exception of a minimal (2.3 mm) parietal calcification.
CONCLUSIONS: The Contegra valved conduit provided excellent morphology and hemodynamics, and freedom from calcification in a medium-term follow-up.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Contegra (Medtronic Inc, Minneapolis, MN), a biological valved conduit consisting of a zero-pressure glutaraldehyde preserved heterologous bovine jugular vein with a trileaflet venous valve with natural sinuses, provided encouraging data after experimental studies in animals [12–16] and in the first clinical series from our unit as well as from other hospitals [17–21]. The use of the Contegra valved conduit has also been successfully introduced by us for the pulmonary valve replacement during the Ross operation [22]. The medium term results of our prospective clinical study with this valved conduit have been evaluated, in particular regarding the morphologic and hemodynamic aspects and the occurrence of calcifications.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Two-dimensional (2D) and Doppler echocardiography was performed in all patients (67 of 67, 100% follow-up) at 1, 3, 6, and 12 months after surgery, and every 12 months afterwards. All data related to the peak and mean right ventricle to pulmonary artery pressure gradients in mm Hg have been recorded, as well as the presence and degree of conduit valve regurgitation, scaled as absent, trivial, mild, moderate, and severe. Cardiac catheterization with angiography has been performed in 23 of 67 (34%) patients; in 5 patients with associated procedures of interventional cardiology.
In order to evaluate the actual size of the conduit and the occurrence of calcifications, 23 of 67 (34%) patients electively underwent cardiac computerized tomography (CT) at least two years after conduit implantation. The CT scan consisted of an electrocardiographic (ECG-) gated multislice CT (MSCT) using 8-row detectors (Lightspeed Ultra; GE Medical Systems, Milwaukee, MN) or 16-row detectors platform (Lightspeed Pro 16; GE Medical Systems, Milwaukee, MN). Axial images of 1.25-mm slice thickness were retrospectively reconstructed from helical data at 70% of the RR cardiac cycle. Enhanced images were obtained after intravenous injection of a total of 1.5 mL/kg of iodinated contrast material at 4 mL/s. The obtained images were separately analyzed by two radiologists (SA and SDQ, who were unaware of the clinical data), including the axial images as well as volume rendering 3D reconstruction and 2D multiplanar reformations. The internal diameters were measured in all patients on the left anterior oblique 3D view corresponding to three levels: (1) proximal anastomosis of the Contegra conduit to the right ventricle; (2) conduit valve; (3) distal anastomosis of the conduit to the pulmonary artery (Fig 1). Any diameter smaller than the three diameters measured at the above levels was separately measured and recorded, as well as the presence of a conduit twist. The obtained values of the internal diameters were compared to the expected diameters (known diameter of the implanted conduit) and among them to evaluate the presence of any significant change in diameter within the three levels in the same patients. Presence, size, and location of calcifications were also recorded. Any adverse event requiring unscheduled treatment, either by percutaneous endovascular approach or by reoperation, was recorded and analyzed. Data have been expressed as mean ± standard deviation
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Results |
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During the entire follow-up one young adult patient underwent successful replacement of a 22-mm twisted conduit (16 months after surgery) because of a technical problem at implantation. In this patient the ECG-gated MSCT scan showed, very well, the conduit twisted between the valve and the distal anastomosis, with an internal diameter equal to 50% of the recorded proximal and distal values, corresponding to a peak pressure gradient of 27 mm Hg and a mean gradient of 24 mm Hg (Fig 2).
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Five patients underwent percutaneous endovascular procedures. One patient with a twisted 22-mm conduit underwent successful stent implantation in the conduit proximal to the valve one month after surgery. Another patient underwent stent implantation between the valve and the distal anastomosis, three months after surgery, because of extrinsic conduit (22 mm) compression (probably due to the presence of a hematoma, at least as we speculated). This patient, in whom the ECG-gated MSCT scan showed a 30% reduction of the internal diameter distal to the conduit valve, was the one in whom a small calcification (2.3 mm in diameter) was detected on the Contegra conduit wall (Fig 3). The other three interventional procedures were not conduit related: one in a child to close a residual muscular ventricular septal defect and in two children to balloon dilate a peripheral pulmonary artery stenosis. One child, admitted with endocarditis (Enterococcus phecalis) on the conduit valve 30 months after implantation of a 18-mm conduit, underwent successful medical treatment.
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The Contegra conduit internal diameters measured with ECG-gated MSCT scan were 110% ± 20% of the known diameter of the implanted conduit at the level of the proximal anastomosis, 112% ± 18% at the level of the valve, and 110% ± 14% at the level of the distal anastomosis. No significant differences were found among the internal diameters measured for each single patient at the three different levels, with a mean value of 112% ± 11% of the expected internal diameter (range, 105% to 126%) (Fig 1). No calcifications were found, with the exception of a minimal (2.3 mm in diameter) parietal calcification in a young adult 3 years after a Ross operation (Fig 3).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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The major limit of the biologic valved conduits is their relatively limited duration, with the need for replacement because of one or more of the following reasons: patient outgrowth (particularly in the pediatric age), calcification (again more frequent in the pediatric age and with aortic homografts), thrombosis, thromboembolism, conduit obstruction, and valve regurgitation [7–11]. The reported freedom from reoperation because of conduit related problems ranges between 79% and 98% at 5 years, 41% and 76% at 10 years, 7% and 41% at 15 years [7–11]. Of course the higher incidence of early reoperation was reported whenever the conduit was implanted in infancy because of the relatively small size allowed at this age. So far the best results have been provided by homografts, with occasional reports of very long duration (up to 21 to 22 years) [10, 23].
The Contegra valved conduit is always available in all sizes from 12 to 22 mm internal diameter. This constitutes a major advantage over conventional homografts because of the increasing shortage within recent years of the homograft, particularly for smaller sizes.
With respect to the problem of valved conduit calcification, particularly frequent in children because of the accelerated calcium metabolism, the Contegra valved conduit presents potential advantages over the conventional homograft because of the treatment with buffered zero-pressure glutaraldehyde in low concentration. The positive results observed in the experimental studies [14, 15] seem to be confirmed by our clinical observations. Even if the medium-term follow-up is relatively short, practically no calcifications were found, and never at the valvular level, in all patients screened with ECG-gated MSCT scan with more than a 2 year interval after conduit implantation.
The hemodynamic results provided by the Contegra seem to be quite favorable, with ECG showing absent or trivial valve regurgitation in 76% of the patients and mild in 24%; the transconduit pressure gradient was stable during follow-up, with acceptable mean values of peak and mean pressure gradient (respectively, 17 ± 11 mm Hg and 8 ± 6 mm Hg). In our study three patients (3 of 67, 4.5%) required unscheduled treatment: two patients with stent implantation and one surgical replacement; in two patients because of conduit twist due to technical problems at the moment of implantation and in one patient because of extrinsic compression between the conduit valve and the distal anastomosis. The observed twist of the conduit has to be correlated with the learning curve in the use of this type of conduit, which is much more soft and pliable than the conventional homograft and therefore less forgiving with regard to the potential twisting.
Despite the fact that only medium-term observations are available, because the Contegra valved conduit only became available for clinical trial in 1999, we did not observe, in our prospective study, any increase in the transconduit pressure gradient in a follow-up to 56 months, including the conduits of smaller size.
Recently, a case with aneurysm dilatation was reported in a Contegra valved conduit, revealed by angiography, with a still functioning conduit [24]. Within the group of 23 patients screened with elective ECG-gated MSCT scan with an interval of at least two years after conduit implantation, the measured internal diameters of the conduit have always corresponded to the expected measures at the moment of implantation.
In case of conduit obstruction, and in order to avoid a reoperation, an alternative option has been proposed with the percutaneous replacement of the pulmonary valve [25]. The major current limit of this technique is the mismatch between the size of the venous access and the size of the needed introducer (at least 18 Fr), restricting its use to only in older children ( > 25 kg of body weight), and the size of the implantable valve to an 18 mm internal diameter biological valve [25]. In order to overcome the limits of this alternative interventional option to the conventional conduit replacement on cardiopulmonary bypass, we recently proposed the encouraging results of an experimental study with off-bypass pulmonary valve implantation with a limited surgical access, but with the possibility of implanting a pulmonary valve of unlimited size [26].
Finally, another reported problem is the shorter duration of the second homograft implanted in the same patient, with a potential explanation arising from an increased reaction due to antigenic properties of the homograft [10]. In this regard, an inflammatory-immunologic reaction, also with the Contegra valved conduit, was recently reported by two separate observers [27, 28]. If these observations can be confirmed on a larger scale, an option might be to consider alternating conventional homografts with the Contegra valved conduit in order to avoid implantation of two consecutive conduits of the same type. This option should be considered particularly in children requiring their first valved conduit implantation during infancy, and who therefore will need at least another conduit replacement during their lifetime.
In conclusion, the Contegra valved conduit provided good hemodynamic results, together with consistent measures of internal diameters and absence of calcifications, in the first few years of clinical use. The claimed advantages of this conduit are constant off the shelf availability, a large variety of sizes available, easy tailoring and suturing, adequate hemodynamics thanks to a favorable effective orifice area, no need for proximal or distal extension, and reduced cost. Together with the results provided by the current study, these advantages make this conduit a valid and reliable alternative to the conventional homografts.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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DR CORNO: Yes, they were.
DR FIORE: The reason I ask is because it is unknown how high the pulmonary vascular resistance or pulmonary artery pressure can be and still safely implant this venous valve conduit. Can you provide any information relative to this from your experience?
DR CORNO: Well, what you are saying is not definitely coming from our experience. But as you have seen, we don't see a huge number of neonates, because the vast majority of the patients we have are coming from abroad, so they are late referral and not in the neonatal period.
I'm aware about colleagues who are having some problem with this type of conduit, particularly when implanting in a neonate and/or in a patient with very high pulmonary vascular resistances. Of course, this is a vein from a cow, so it's supposed to stay at low pressure.
I believe that, when you come off cardiopulmonary bypass with systemic pressure in the pulmonary artery, as it was the case in the cases reported by the colleagues with dilatation of this conduit, and therefore with pulmonary valve regurgitation, probably is due to the fact that this conduit is very pliable, not able to sustain systemic pressure.
As a matter of fact, there is a contraindication of using this conduit in the systemic circulation. And the company is also providing a stented conduit with a metal ring at the level of the valve. We have never used it, but probably this is a good indication for small kids to avoid dilatation of the conduit in correspondence of the valve.
DR JOSEPH AMATO (Chicago, IL): I wish to congratulate Dr. Corno and his colleagues not only on their excellent work but the great presentation. While my experience with the conduit is limited because of my retirement, I had placed four of these conduits in children, and I'm happy to report, at least in one case, with a now 4-year-old, a true ectopia cordis, who has one of these conduits, he's living well, alive, running around. The conduit is working absolutely well, no calcification, and no dysfunction of the conduit. Thank you again.
DR CORNO: Well, I have nothing to add to your comment. It's quite nice to have a retiring surgeon implanting conduits.
DR JOHN MAYER (Boston, MA): I'm just curious if you have any histology on the conduit—I assume you explanted the one that was twisted—and what the host response looked like, whether or not the conduit reendothelialized or was repopulated with any cells.
DR CORNO: Nice question. But, unfortunately, we haven't erformed any histology because we were sure the problem was due to the technically wrong implantation, of course, because of the twisting. And so unfortunately, we didn't perform any study, and it was the only conduit that was explanted up to now.
DR JOHN W. BROWN (Indianapolis, IN): We too have had a favorable experience with this conduit having implanted it in 41 neonates and children. About a third of our patient population are neonates. In newborns with truncus with elevated pulmonary vascular resistance, at least in the early postoperative period, and many with peripheral pulmonary stenosis, the size 12 conduit without stents holds up very well. We have not had a single conduit dilated. We have had, out of the series of 40, 2 or 3 who have developed some narrowing at the distal anastomosis were quite amenable to balloon dilatation. Distal anastomosis stenosis has been a concern of many investigators using this conduit. The incidence seems to be low and amenable to balloon dilatation.
We have had the occasion to re-operate on one child where the conduit was placed in a neonate, and the distal anastomotic constriction did not yield to balloon dilatation. We did a patch angioplasty of that anastomosis and that child has done very well without recurrence. The Contegra seems to be a conduit that is quite versatile for a wide patient, age range and distribution of pulmonary vascular resistance levels.
DR CORNO: You had a much larger experience in neonates compared to our experience, and this is confirming then that the conduit can sustain even high pressures and resistance.
I suspect that the colleagues reporting dilatation of the conduit and pulmonary valve regurgitation have possibly problems at the level, as you say, of the distal anastomosis. And to avoid this, we use technical maneuvers, and probably you do the same: first by cutting obliquely the distal conduit to increase the cross-sectional area; second we perform an incision on the pulmonary bifurcation, extended towards the left pulmonary artery to enlarge as much as possible the size of the distal anastomosis; finally we strictly avoid running sutures on the distal anastomosis, performing several interrupted sutures. Maybe the combination of these surgical details can reduce the risk of stenosis at the level of the distal anastomosis.
DR CHARLES FRASER (Houston, TX): One brief comment. We, in Houston, have also been very favorably impressed with this conduit. And I think as was indicated in our session yesterday, a lot of people are interested in the use of the Contegra as an option.
We put 40 in and have had a little bit of a different experience; and we're not quite sure what to make of it. We've had 3 patients in whom, with otherwise good conduit function and low pressures, a thrombus has developed in one of the sinuses. And this was picked up on routine post-op screening echoes, which had led us to conclude that we're not washing the conduit properly. Even though we were using the guidelines as indicated by the investigators, we wash them for a lot longer now, presuming that there was still residual glutaraldehyde or something that was causing this. So I'm pleased to see that you haven't seen that, but we have seen that in 3 patients.
DR CORNO: May I ask you if you are using any prophylactic antithrombotic treatment? What are you doing? Are you using heparin in the immediate postoperative period? Are you giving antiplatelets, anticoagulation? What is your treatment?
DR FRASER: We don't use heparin postop, but we do put our patients on aspirin long term.
DR CORNO: We use systematically heparin I.V. until the patient remains in intensive care unit. And from postoperative day one, we start prophylactic antiplatelets treatment with aspirin in all of them.
DR STEFANO MARIANESCHI (Milan, Italy): I don't have experience with this conduit, I just read the literature about it, but I have experience with another conduit, a xenograft, it's the Sheligh No-react® conduit. In the last three years, we implanted this conduit in 33 patients, mostly less than 6 months of age. And we had good results with this conduit. We explanted only two, one for patient outgrowth and another one for distal anastomosis narrowing, but we haven't any problem with valve or we haven't seen any calcification.
This is our conduit of choice. Thank you.
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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