Histological Study of Right Ventricle-Pulmonary Artery Valved Conduit Implantation (RPVC) in Dogs with Pulmonic Stenosis

Abstract

ABSTRACT. We examined whether right ventricle-pulmonary artery valved conduit (RPVC) implantation can overcome the disadvantages of current procedures for pulmonic stenosis (PS). We histologically evaluated the feasibility of RPVC using a homograft in PS model dogs. Eight dogs underwent pulmonary artery banding (PAB) and then 12 weeks later were assigned to PAB (n=4) or PAB+RPVC (n=4) groups. Dogs in the PAB group received no treatment throughout the experimental period, whereas the PAB+RPVC group underwent RPVC. At 1 year after PAB, hearts and conduits were explanted from euthanized dogs and histologically evaluated. The ratios (%) of myocardial fibrosis on right ventricle (RV) epicardial, median and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. The ratio of myocardial fibrosis on left ventricular (LV) epicardial and endocardial layers were significantly lower in the PAB+RPVC, than in the PAB group. Neo-intimal thickness in the anastomosis areas of the Denacol and PAB+RPVC groups was 42.77  30.19 and 88.30  27.24 m, respectively, with no significant differences between the groups. Calcification and neo-intima hypertrophy were not obvious in the valve area. Immunohistological staining showed that the internal surface of the anastomosis and intermediate areas were positive for endothelial cells. We concluded that RPVC using a bioprosthetic graft can apparently overcome the disadvantages of current procedures for pulmonic stenosis. KEY WORDS: endotherialization, myocardial fibrosis, pulmonary artery banding, pulmonic stenosis, valved conduit.J. Vet. Med. Sci. 71(4): 409-415, 2009 Pulmonic stenosis (PS) is a relatively frequent congenital narrowing of the right ventricular outflow tract that occurs in about 0.1% of all dogs [9]. Strategies for treating severe pulmonic stenosis include transventricular pulmonic dilation [8], closed patch-graft [3,24], open patch-graft [12] and balloon dilation [4,6,14,15] valvuloplasty. Patch-graft valvuloplasty is an effective radical treatment for PS, but it requires a cardiopulmonary bypass to stabilize the circulation, which cannot be performed at many institutions [21]. On the other hand, although balloon dilation valvuloplasty is a popular strategy, the results are inferior in dogs with PS accompanied by dysplasia of the pulmonic annulus and main pulmonary artery to those in dogs with PS alone [6]. Thus, we considered right ventricle (RV)-pulmonary artery valved conduit (RPVC) implantation to overcome the disadvantages of the current procedures. Implantation with the RPVC decreases right ventricular systolic pressure by forming a bypass and the procedure is less invasive because it can be performed under the beating heart. A bioprosthetic valved conduit has been used for RVOT reconstruction in humans [2]. Denacol-treated bioprosthetic implanted conduits are better assimilated and organized with the blood vasculature [19]; they are also thrombo-resistant and do not provoke the immune response [13]. Furthermore, the valve in the condu...

Obstruction-Induced Pulmonary Vascular Remodeling

“…Several previous studies have investigated the changes in the right ventricle (RV), such as free wall thickness and cardiac fibrosis [8,9], while others have studied how specific isozymes contribute to cardiac remodeling [10]. In clinical situations, pulmonary stenosis can create a pressure gradient in the artery of around 20–60 mm Hg, and blood flow becomes turbulent distal to a stenosis [11,12].…”