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

Bovine jugular vein conduit: What affects its elastomechanical properties and thermostability?

The aim of this study was to compare the mechanical properties and thermal stability of the venous wall depending on the treatment method used, and, accordingly, on those structural changes in the tissue that this treatment causes. Bovine jugular vein walls (BJVWs) cross-linked with glutaraldehyde (GA), ethylene glycol diglycidyl ether (DE), and Contegra commercial conduit were evaluated using uniaxial stretching [with and without pre-conditioning (PreC)], differential scanning calorimetry, amino acid analysis, and attenuated total reflection infrared spectroscopy. Fresh BJVW was used as a control. It was shown that failure stress in non-PreC GA-treated and DE-treated materials was lower than that in fresh and Contegra counterparts. Contegra samples were the stiffest among the tested materials. Cyclic preloading leads to distortion of the mechanical behavior of this material, which is heterogeneous in composition and structure. The denaturation temperatures (T_d ) of all cross-linked BJVWs were higher than the T_d of the fresh vein. The microstructures of the tested BJVWs did not exhibit any differences, but the cross-linking density and hydration of the DE-vein were the highest. GA-cross-linking or DE-cross-linking and isopropanol exposure (Contegra) changed the protein secondary structures of the tested materials in different ways. We hypothesized that the protein secondary structure and hydration degree are the main causes of differences in the mechanical properties and thermal stability of BJVW.

Globular chitosan treatment of bovine jugular veins: evidence of anticalcification efficacy in the subcutaneous rat model

Vascular xenografts are widely used in cardiovascular surgery as an alternative to autologous vessels and vascular allografts. Calcification is one of the main drawbacks of vascular grafts, especially among young patients and children. Among different anticalcification approaches, chitosan emerges as a highly promising candidate due to its versatility, natural origin, and biocompatibility. We investigated the anticalcification efficacy of globular chitosan ("Chitozol") as it demonstrated the improved rate of water solubility as compared with conventional linear macromolecules of chitosan. In addition, we supposed that compact globular form of "Chitozol" molecules could provide effective penetration of extracellular matrix of bovine jugular veins (BJVs). Our results revealed that "Chitozol" treatment mitigated calcification in the experimental groups as compared to the control groups (without any treatment, conventional treatment with glutaraldehyde, and commercially available Contegra conduit). Different concentrations of "Chitozol" (0.3% and 3%), as well as different incubation times (15 and 30min), were equally effective in the prevention of calcification. In addition, "Chitozol" treatment with decellularization of BJVs demonstrated slightly improved stress-strain properties of unimplanted samples. Thus, the filling of fresh BJV with globular chitosan is proposed as a promising emerging treatment for the mitigation of calcific degeneration in BJVs xenografts.

Percutaneous heart valve replacement: histology and calcification characteristics of biological valved stents in juvenile sheep

INTRODUCTION

Percutaneous techniques to replace the pulmonary valve are emerging as an alternative to congenital cardiac surgical procedures. Promising experimental and early clinical results have been reported so far, focusing on technical feasibility and valved stent function. The present study aimed to describe the micropathology after experimental percutaneous valve replacement.

METHODS

Self-expanding nitinol stents carrying a valved bovine jugular vein were transfemorally implanted into the pulmonary position of nine sheep. After 3 months of survival, macro- and micropathological examinations were carried out using standard staining techniques and immunohistochemistry. Additionally, calcification characteristics were determined by X-ray examinations and von Kossa stainings.

RESULTS

Six of nine animals survived the 3-month study time with good angiographic and echocardiographic function. All valves were grossly functional at the time of explantation. Slight fibrous overgrowth was seen at the inflow portions of two valved stents. No cuspal perforations or intracuspal hematomas were observed. Light microscopy proved the absence of cellular inflammatory infiltrates in any tissue samples. The myocardium directly proximal to the stent appeared structurally normal without calcification. The overall structure of the native pulmonary artery was well preserved with few mineral deposits spread diffusely throughout the wall distal to the stent. Massive calcification appeared in the bovine jugular-vein wall together with increased numbers of T lymphocytes. Neither calcific deposits in the cusps nor extrinsic mineralization was noted.

CONCLUSION

For the first time, micropathologic evaluation of percutaneously implanted heart valves is described. The results demonstrate that calcification of valved stents occurs in the wall portions without affecting the cusps. The cardiac structures in the vicinity had normal histology without inflammation.

Xenograft Transplantation in Congenital Cardiac Surgery at Baskent University: Midterm Results

OBJECTIVE

Xenograft valved conduits have been used in several cardiac pathologies. In this study we have presented our midterm results of pediatric patients pathologies who were operated with xenograft conduits.

PATIENTS AND METHODS

Between January 1999 and January 2005, 134 patients underwent open heart surgery with xenograft conduits. The conduits were used to establish the continuity of the right ventricle to the pulmonary artery or aorta, the left ventricle to the pulmonary artery, or aorta due to various types of complex cardiac anomalies. Patients were evaluated by transthoracic echocardiography (ECHO) at 6-month follow-ups. Cardiac catheterization was performed when ECHO demonstrated significant conduit failure.

RESULTS

Hospital mortality was observed in 28 patients (20.1%), and 13 patients died upon follow-up (9.7%). Mean follow-up was 24.6 +/- 4 months (range, 13 to 85 months). Among 93 survivors 20 patients (21.5%) were reoperated due to conduit failure. The main reasons for conduit failure were stenosis (n=13), valvular regurgitation (n=2), or both conditions in 5 cases. Mean pulmonary gradient before conduit re-replacement was 47.7 +/- 30.1 mmHg. The 1-, 3-, and 6-year actuarial survival rates were 95 +/- 2%, 91 +/- 3%, and 86 +/- 5%. The 1-, 3-, and 6-year actuarial freedom rates from reoperation were 95 +/- 1%, 90 +/- 3%, and 86 +/- 4%. An increased gradient between the pulmonary artery and the right ventricle and prolonged cardiopulmonary bypass times were observed to be significant risk factors for reoperation. There was no mortality among reoperated patients.

CONCLUSION

Xenograft conduits should be closely followed for calcification and stenosis. Conduit stenosis is the major risk factor for reoperation. In these patients, reoperation for conduit replacement can be performed safely before deterioration of cardiac performance.

Percutaneous replacement of pulmonary valve using the Edwards-Cribier percutaneous heart valve: first report in a human patient

We report on the use of the Edwards-Cribier percutaneous heart valve (PHV) in a stenotic right ventricle to pulmonary artery homograft in a 16-year old patient who underwent the Ross operation. Initially, the homograft was stented and at the same procedure, the PHV was deployed inside it. This is the first human case of the application of this valve in the pulmonary valve position.