Histological study of right ventricle-pulmonary artery valved conduit implantation (RPVC) in dogs with pulmonic stenosis.

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 microm, 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.

Cardiovascular effects of right ventricle-pulmonary artery valved conduit implantation in experimental pulmonic stenosis.

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.

Successful surgical correction of supravalvular pulmonary stenosis under beating heart using a cardiopulmonary bypass system in a dog.

A male Pomeranian dog aged 1 year and 8 months was presented for evaluation of severe systolic ejection, cardiac murmur and syncope on excitation. Supravalvular pulmonary stenosis was diagnosed. An echocardiogram showed a supravalvular membranous stricture and a severely increased pulmonary arterial velocity in the stricture (6.49 m/s, pressure gradient of 169 mmHg). The supravalvular stricture was surgically removed by pulmonary arteriotomy with the heart beating using a cardiopulmonary bypass system. The postoperative pulmonary arterial velocity at the narrow area decreased to 3.80 m/s, and the pressure gradient decreased to 57.7 mmHg. Six months after the operation, there were no signs of restenosis, and the dog was in good condition without syncope. Surgical correction of pulmonary stenosis with the heart beating using a cardiopulmonary bypass system is useful because of the improvement it brings in safety and reliability.

Hydrodynamic characteristics of porcine aortic valves cross-linked with glutaraldehyde and polyepoxy compounds.

Porcine aortic valve (AoF) tissues cross-linked with glutaraldehyde and epoxy compounds were reported to have high anticalcification properties, but their hydrodynamic characteristics have not been evaluated. The aim of the present study was to investigate the hydrodynamic differences between porcine AoFs, cross-linked with concomitant use of an epoxy compound and glutaraldehyde, at different fixation periods. The valves were mounted on a pulsatile flow circulation mimicking a left heart. The left atrial and left ventricular pressures and mitral and aortic flows were measured at every 0.002 seconds, and the hydrodynamic factor of the valves mounted on the mitral position was estimated. Effective orifice area and the regurgitation volume, which are used as indicators of valve efficiency, failed to detect significant differences due to glutaraldehyde fixation time. In addition, the pressure gradient across the bioprosthetic valve and the variation of mitral flow also had no significant differences. The flow circuit model of the present study was mimicking of a left heart. The evaluation of the mitral valvular function with different glutaraldehyde fixation times was accomplished by relating the pressure with the flow, and by estimating the time lag between valve motion and transvalvular flow.

The effect of 7.2% hypertonic saline solution with 6% dextran 70 on cardiac contractility as observed by an echocardiography in normovolemic and anesthetized dogs.

We studied the effect of a small volume of 7.2% hypertonic saline solution (HSS) or HSS with 6% dextran 70 (HSD) on hemodynamic status, especially on cardiac contractility, in anesthetized dogs using the left ventricular end-systolic volume index (ESVI) and ejection fraction (EF), which can be obtained in noninvasive echocardiography. In the present study, the mean values of ESVI were unaffected by HSS and HSD infusion, whereas the left ventricular end-diastolic volume index (EDVI) was markedly and significant increased. As a result of the changes in EDVI but not in ESVI, EF increased transiently and significantly in the HSS and HSD group, whereas no such significant change was observed in the dogs that received isotonic saline solution. In addition, as a result of the increases in cardiac index but not arterial pressure, system vascular resistances (SVR) decreased transiently and significantly in the HSS and HSD groups, whereas no such significant change was observed in the ISS group. Therefore, the positive inotropic effects of HSS and HSD may be attributable to the increase in left ventricular preload and decreases in SVR rather than direct changes in myocardial contractility.

Evaluation of the efficacy and safety of coil occlusion for patent ductus arteriosus in dogs.

We performed a retrospective study of 56 dogs with Patent Ductus Arteriosus (PDA) to evaluate the indications for and efficacy of transarterial PDA coil embolization. Transarterial PDA coil embolization was conducted in 37 cases (66.1%) and surgical ligation was conducted in 16 cases (28.6%). Three cases (5.4%) were diagnosed as pulmonary hypertension and were excluded from surgical intervention. Although coil dislodgement was observed in the pulmonary artery in one case, no death occurred during coil embolization or surgical ligation. Echocardiography showed that fractional shortening decreased from 35.4 +/- 6.8% to 30.2 +/- 5.9% (P<0.05) after transarterial PDA coil embolization. Although slight residual shunts were observed in 18 cases, transarterial PDA coil embolization was effective treatment of PDA.

Surgical correction of pulmonic stenosis using transventricular pulmonic dilation valvuloplasty (Brock) in a dog.

A two-month-old male long coated Chihuahua, which had symptoms including anorexia and decreased growth, was diagnosed with pulmonic valvular stenosis. Echocardiography showed the severe progression of pulmonary arterial velocity (6.29 m/s, Pressure gradient (PG); 158 mmHg). Transventricular pulmonic dilation valvuloplasty (Brock) was conducted, and stenosed valve was dilated by the oto forceps. Pleural effusion was observed postoperatively, however, it was diminished under the intensive care for five days after the surgery. The right ventricular systolic pressure was decreased to 60 mmHg in angiocardiography conducted two months postoperatively and the dog has kept a good general condition with recovered vigor and appetite.

Effect of long-term administration of a prostacyclin analogue (beraprost sodium) on myocardial fibrosis in Dahl rats.

Beraprost sodium (BPS) is an orally active prostacyclin analogue. The effects of BPS on the heart, including coronary circulation improvement, myocardial and vascular protection and anti-fibrosis effect on myocardium interstitium, have previously been demonstrated. However, the effects of BPS on hemodynamics, cardiac function and myocardial contractility in patients in the hypertrophic phase have not been clarified. Therefore, in the present study, the effects of BPS under long-term administration were investigated using the hypertension model of salt-sensitive Dahl rats. Six-week-old Dahl rats were divided into three groups, an 8% high salt diet group treated with BPS (BPS group), an untreated 8% high salt diet group (HHF group) and an untreated 0.3% low salt diet group (Control group), and observations were conducted until 17 weeks of age. In the BPS and HHF groups, the survival rates after 11 weeks of high salt diet intake were 87.5% and 47.1%, respectively (p<0.05). At 17 weeks of age, the atrial systolic peak velocity/early diastolic peak velocity and heart weight index of the BPS group decreased significantly compared with the HHF group (p<0.05). The HHF group exhibited significantly more severe myocardial fibrosis mainly in the endocardial layer of the left and right ventricles compared with the BPS and Control groups (p<0.05). In the present study, long-term BPS administration preserved diastolic function and prevented myocardial interstitial fibrosis in the non-compensatory phase. The results of the present study suggest that BPS is effective for treatment of hypertensive cardiac hypertrophy.