New-generation valved conduit: an experimental study

Bovine valved jugular vein (Contegra™) to reconstruct the right ventricular outflow tract

The right ventricular outflow tract (RVOT) is the part of the circulation located between the right ventricle and the bifurcation of the pulmonary artery. The most cranial part of the right ventriculum infundibulum, the pulmonary anulus, the valve and finally the main trunk of the pulmonary artery are the most important structures. The RVOT is frequently affected in congenital heart diseases, either isolated, or in combination with other cardiac malformations. Current techniques for surgical correction of anomalies of the RVOT include repair and/or replacement of the pulmonary valve often combined with sub- or supravalvular reconstruction. The use of extracardiac conduits (homografts, stented or stentless xenografts) to re-establish continuity between the pulmonary ventricle and pulmonary artery has been an important advance in repair of complex congenital malformations. The Contegra (Medtronic) conduit was introduced as a xenograft tissue for RVOT reconstruction. This conduit has some advantages over homografts including availability for pediatric and adult patient sizes and proximal and distal cuffs allowing for extended reconstruction. The principal late problem related to extracardiac conduit operations is the inevitable need for one or more conduit replacements due to patient somatic growth or progressive conduit degeneration and calcification leading to stenosis.

Right Ventricular Outflow Tract Reconstruction With Contegra Monocuspid Transannular Patch in Tetralogy of Fallot

BACKGROUND

Pediatric diminutive right ventricular outflow tract (RVOT) reconstruction with homografts or porcine xenografts remains challenging because of limited availability, early degeneration, tissue ingrowth, and child growth. The objective of this study was to assess whether Contegra valved bovine conduit, implanted as monocuspid transannular patch, might be an interesting alternative to overcome these problems.

METHODS

We reconstructed the RVOT of 12 patients with tetralogy of Fallot, by the use of a Contegra conduit, tailored as a monocuspid valved transannular patch. The patients were 4 females and 8 males, with a mean age of 12.8 +/- 15.1 months and a mean weight of 7.2 +/- 1.9 kg. The mean pulmonary artery annulus size was 8.2 +/- 1.6 mm.

RESULTS

The Contegra tissue was suitable for suturing and for reconstruction of even severely hypoplasic RVOT. We did not observe any sign of conduit or valve degeneration during the follow-up of 28.1 +/- 17.1 months. There were no early or late deaths, and no device-related adverse events. A peak transvalvular gradient of 36.5 +/- 4.7 mm Hg was measured by echocardiography in 4 patients postoperatively, and it decreased during the follow-up to 20 +/- 7.6 mm Hg. Pulmonary valve incompetence was grade 3 in 2 patients and grade 4 in 2 patients.

CONCLUSIONS

The Contegra monocuspid transannular patch is widely applicable to RVOT reconstruction with satisfactory midterm results, particularly in patients with small pulmonary annulus. Its main advantage is to reduce the potential risk of supravalvular stenosis due to the narrowing at the distal suture line, as demonstrated when used as conduits, especially in the smaller sizes.

Expandable right ventricular-to-pulmonary artery conduit: an animal study

This study was performed to assess a new vascular stent graft as an expandable valved conduit for right ventricular outflow tract (RVOT) reconstruction in sheep. Conduits were constructed by sewing an 18-mm valved conduit inside a stent. Crimped to 16 mm, they were implanted either under or without extracorporeal circulation in seven (group A) and in five (group B) sheep, respectively. Six weeks and 3 mo after their insertion, conduits were dilated intraluminally. A valved stent was implanted percutaneously into conduits before they were killed. Two animals from group A recovered normally, whereas five animals had a complicated postoperative course. In group B, one died acutely due to kinking of the conduit. Balloon dilatations were performed in all surviving animals. First dilatations had a slight impact on valvular function in all animals but one, whereas second dilatations led to significant PR in all. Transcatheter valve implantation was performed successfully. When animals were killed, no bleeding was found around the surgically implanted device. In conclusion, we designed a biologic valved conduit for RVOT reconstruction that can be dilated sequentially to follow animal growth. This new device can have tremendous applications in children with congenital heart diseases involving the RVOT.

Adverse Mid-Term Outcome Following RVOT Reconstruction Using the Contegra Valved Bovine Jugular Vein

BACKGROUND

Current techniques for repair of the right ventricular outflow tract (RVOT) may require interposition of a valved conduit between the right ventricle and the pulmonary artery bifurcation. Recently, the Contegra conduit (Medtronic, Inc.) was introduced as an alternative xenograft tissue for RVOT reconstruction. Promising early hemodynamic and clinical results have been reported so far, but still less is known about mid-term adverse outcome.

METHODS

A total of 38 Contegra valved conduits (12 to 22 mm) were implanted from October 1999 to June 2004, in 36 children less than 5 years old and in 2 patients 8 and 21 years old. Diagnosis included the following: tetralogy of Fallot (n = 21); pulmonary atresia (n = 4); double outlet right ventricle + pulmonary stenosis (n = 3); d-transposition of the great arteries, ventricular septal defect, and pulmonary stenosis (n = 3); truncus arteriosus (n = 3); and other complex malformations (n = 4).

RESULTS

There was no mortality following initial surgery and no valved-conduit-related early morbidity. Early postoperative echocardiographic assessment after 3 months demonstrated favorable hemodynamics in all patients. However, during further follow-up, 5 conduits had to be replaced because of severe stenosis at the level of the distal anastomosis (2 of them had moderate to severe dilatation of the conduit proximally to the valve). Excessive intimal peel formation and severe perigraft scarring reaction were observed in all cases. One child died before surgery.

CONCLUSIONS

The Contegra valved conduit is an interesting concept for reconstruction of the RVOT. However, because of unpredictable incidence of supravalvar stenosis during mid-term results, we cannot recommend routine use of this material.

Bovine Valved Xenograft in Pulmonary Position: Medium-Term Follow-Up With Excellent Hemodynamics and Freedom From Calcification

BACKGROUND

This study was designed to evaluate the outcome of Contegra xenograft valved conduit (Contegra, Medtronic Inc, Minneapolis, MN).

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.

Heparin coupling in inhibition of calcification of vascular bioprostheses

Inhibitory effect of heparin coupling on calcification of bioprosthetic vascular grafts of different origin was studied. Heparin-bonded (Hep) and 0.625% glutaraldehyde-cross-linked (GA) segments of porcine thoracic aorta (AO), pulmonary artery (PA), jugular vein (JV) and rabbit aorta (RA) were implanted subcutaneously in weanling rats for 5 months. Heparin bonding is ineffective in prevention of calcification of JV (Hep: Ca, 159 +/- 32.26 mg g-1; GA: Ca, 193.55 +/- 17.81; p = 0.075) and RA (Hep: Ca, 150.17 +/- 14.78; GA: Ca, 192.12 +/- 26.61; p = 0.015). Calcium content of heparin-coupled PA and AO was significantly less when compared with their GA-treated counterparts. Calcification inhibition was achieved to a greater extent in heparin-bonded PA (Hep: Ca = 22.62 +/- 5.72, GA: Ca = 115.99 +/- 21.91, p < 0.0001) than in the AO coupled to heparin (Hep: Ca = 63.77 +/- 22.75, GA: Ca = 150.40 +/- 35.21, p < 0.0001). Elastin fibers were the predominant site of calcification in all explanted vascular grafts. Heparin-bonded porcine pulmonary artery is seemed to be the best among all vascular bioprostheses in this study.