Cardiovascular Effects of Right Ventricle-Pulmonary Artery Valved Conduit Implantation in Experimental Pulmonic Stenosis

Abstract

ABSTRACT. Right ventricle (RV)-pulmonary artery (PA) valved conduit (RPVC) implantation decreases RV systolic pressure in pulmonic stenosis (PS) by forming a bypass route between the RV and the PA. The present study evaluates valved conduits derived from canine aortae in a canine model of PS produced by pulmonary artery banding (PAB). Pulmonary stenosis was elicited using PAB in 10 conditioned beagles aged 8 months. Twelve weeks after PAB, the dogs were assigned to one group that did not undergo surgical intervention and another that underwent RPVC using denacol-treated canine aortic valved grafts (PAB+RPVC). Twelve weeks later, the rate of change in the RV-PA systolic pressure gradient was significantly decreased in the PAB+RPVC, compared with the PAB group (60.5  16.7% vs. 108.9  22.9%; p<0.01). In addition, the end-diastolic RV free wall thickness (RVFWd) was significantly reduced in the PAB+RPVC, compared with the PAB group (8.2  0.2 vs. 9.4  0.7 mm; p<0.05). Thereafter, regurgitation was not evident beyond the conduit valve and the decrease in RV pressure overload induced by RPVC was confirmed. The present results indicate that RPVC can be performed under a beating heart without cardiopulmonary bypass and adapted to dogs with various types of PS, including "supra valvular" PS or PS accompanied by dysplasia of the pulmonary valve. Therefore, we consider that this method is useful for treating PS in small animals. KEY WORDS: angiocardiography, echocardiography, pulmonary artery banding, pulmonic stenosis, valved conduit.J. Vet. Med. Sci. 71(4): 477-483, 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 [10]. The three types of PS are supravalvular, subvalvular and infundibular, and the most frequent type in dogs is valvular dysplasia [11]. The obstruction causes increased resistance to right ventricle (RV) systolic outflow and a proportional increase in RV systolic pressure. The increase in systolic wall stress (tension) stimulates concentric muscular hypertrophy of the RV wall [34]. Doppler echocardiography can noninvasively identify and determine the severity of PS. Dogs with resting pressure gradients of > 80 mm Hg on echocardiograms between RV and pulmonary artery (PA) are at increased risk for syncope, congestive heart failure or sudden death, and surgical intervention is usually recommended [11,14,26,36]. Strategies for treating severe pulmonic stenosis include pulmonary valvulotomy or valvulectomy [13], transventricular pulmonic dilation valvuloplasty [9], closed patch-graft valvuloplasty [4,33], open patch-graft valvuloplasty [19] and balloon dilation valvuloplasty [5,7,20,21,30]. Although patch-graft valvuloplasty is an effective radical treatment for PS, circulation arrest time is limited using inflow occlusion [27] and cardiopulmonary bypass (CPB) is necessary for cardioplegic arrest [26]. On the other hand, although balloon dilation valvuloplasty is a popular strategy, the results in dogs wi...

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].…”