A bovine pericardial conduit was developed in the laboratory incorporating the principle of crimping used for synthetic vascular prostheses. The pericardium was processed in glutaraldehyde and the tube was crimped by a technique which preserves the integrity of collagen fibres. This vascular substitute presents a non-thrombogenic and non-porous inner surface which does not require preclotting and does not leak. The material is very soft, easy to handle and suture, coapts nicely to suture lines resulting in a hemostatic anastomosis. The crimping design provides longitudinal elasticity and resistance to collapsing, retains its shape with bending and avoids kinking. Crimping provides a circular tube which makes the construction of the anastomosis easier. Experimental studies in dogs demonstrated absence of thromboembolism with the conduit implanted in the abdominal aorta. Fibrin accumulation was not noted in the convexities of the crimps. This conduit was designed for aortic and pulmonary reconstruction and available in different sizes with or without a biological valve. Initial clinical experience included its use in 10 patients with aortic dissections or aortic aneurysms from August 1989 to March 1990. A reconstruction of the abdominal aorta was performed in 2 patients, the descending thoracic aorta in 2, the ascending aorta in 2 and the ascending aorta including the aortic valve and reimplantation of coronary arteries in 4. For the latter 4, composite crimped pericardial tubes containing a porcine bioprosthesis were used. An additional patient with a single ventricle underwent a Fontan type operation also employing a valved crimped pericardial conduit.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: A protective layer of endothelial cells (EC) of host origin on the entire surface of bioprosthetic heart valves has never been reported. Current commercial bioprosthetic heart valves are commonly preserved in glutaraldehyde (GA) and are cytotoxic to host cells preventing spontaneous endothelialization. The aim of this study is to demonstrate the potential for in vivo endothelialization of heart valves treated by the L.-Hydro™ preservation process.Method: L-Hydro™ preservation process consists of mild extraction of antigenic substances by the action of polyethyleneglycol and incorporation of an antiinflammatory and a anti-thrombotic agent. Seven stented porcine valves treated by the L-Hydro™ process and three GA-fixed porcine valves were implanted in the mitral position of juvenile sheep. The valves were evaluated by echocardiography and angiography prior to sacrifice at five months. Recovered valves were also histologically and histochemically evaluated.Results: There were no hemodynamic differences between the groups. However, scanning and transmission electron microscopy showed a nearly complete coverage of EC on the surfaces of all leaflets in the L-Hydro™ treated valves. The EC were in direct contact with the underlying collagen layer and expressed von Willebrand-related antigens (vW).The surfaces of the GA-treated valves were covered by fibrin deposition, macrophages, calcium and thrombotic material. Only sparse EC were observed and contact of the EC where the underlying tissue was incomplete.Conclusion: These data indicate that L-Hydro™ treated porcine valve tissues are capable of inducing spontaneous endothelialization with evidence of strong cell attachment of the new endothelium to the collagen matrix. Descriptors: Bioprosthesis. Heart valve prosthesis. glutaraldehyde. Endotelização in vivo das biopróteses cardíacas: preservação convencional versus não-aldeídica

As there is currently no suitable valved pulmonary conduit for small children, porcine conduits treated by the L-Hydro process were implanted into 9 newborn lambs to investigate growth potential. Of the 8 survivors, 7 were kept alive for 12 months after implantation. The diameter of the conduit and gradient across the valve were evaluated at surgery and at 3 and 9 months postoperatively using bidirectional echocardiographic and angiographic methods. After sacrifice, histological and radiological analyses were performed. The mean weight of the animals was 4.2 +/- 1.1 kg at implantation and 43.1 +/- 6.2 kg at sacrifice. There was a significant increase in mean valve area from 139.9 +/- 18.0 mm2 at implantation to 443.5 +/- 89.2 mm2 at 12 months. Pre-sacrifice angiography showed no transvalvular gradient, and radiographic analysis did not reveal significant conduit wall or leaflet calcification in any of the animals. Histological examination of the grafts demonstrated total integration, with native-like intact valve leaflets. Thus functional evaluation, echocardiography, and histology demonstrated growth of the grafts with completely endothelialized and apparently normal pulmonary valve leaflets without calcification.

Calcification of glutaraldehyde-treated bioprosthetic heart valves is a major cause of long-term failure. We studied porcine aortic valves treated by the L-Hydro process and implanted into 14 juvenile sheep (group 1). Another 10 sheep were implanted with glutaraldehyde-treated porcine bioprostheses (group 2). The animals were sacrificed after 150 days and the explanted valves were analyzed for calcification. Hemodynamic measurements by echocardiography and angiography were carried out prior to sacrifice. Macroscopic analysis showed calcification and loss of mobility of the leaflets in all group 2 implants and in one group 1 implant. Light microscopy showed foci of calcification in all group 2 implants and in 3 valves from group 1. A significant reduction in the level of calcification was found in porcine bioprostheses treated by the L-Hydro process and implanted into the juvenile sheep model.

This 12-year follow-up shows a very low incidence of primary allograft failure for patients older than 15 years undergoing mitral valve replacement, and much superior than our results with porcine bioprosthesis in the same age group. This supports our assumption that this investigational valve represents a new advance in cardiac valve surgery.