Percutaneous establishment of tricuspid regurgitation: an experimental model for transcatheter tricuspid valve replacement / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Valve replacement or repair is recommended in patients with tricuspid regurgitation when deterioration of their clinical status occurs as a consequence of right ventricular dysfunction. Percutaneous valve replacement was developed in recent years. To investigate the feasibility, effectiveness and long-term results of percutaneous tricuspid valve replacement, an experimental model with tricuspid regurgitation is needed. We developed a simple and reproducible percutaneous approach for the creation of tricuspid regurgitation in sheep.</p><p><b>METHODS</b>A specially designed grasping forceps were used to grasp chordae tendineae or the tricuspid valve leaflets through a catheter. Transcatheter creation of tricuspid regurgitation was performed on 7 healthy sheep. These sheep were followed up shortly after the procedure and at 6th month post-procedure with echocardiography. Additionally, all the sheep were sacrificed for anatomic evaluation at 6th month after the procedure.</p><p><b>RESULTS</b>Creation of tricuspid regurgitation was successfully accomplished in all sheep. Necropsy confirmed that damage was done to the tricuspid valve apparatus in all animals (tearing of the anterior leaflet of the tricuspid valve in five animals and posterior leaflet of the tricuspid valve in two animals). At the six-month follow-up, there was no significant increase in the right ventricle dimension and ejection fraction measured by echocardiography. Autopsy examinations demonstrated the tearing of tricuspid valve leaflets.</p><p><b>CONCLUSIONS</b>The creation of an animal model of tricuspid regurgitation via a percutaneous approach using forceps to sever one or more tricuspid leaflets is feasible and will allow investigation of devices designed replace the tricuspid valve via a percutaneous approach. Despite significant tricuspid regurgitation, the hemodynamics did not change during the follow-up period in this model.</p>

Percutaneous valve stent insertion to correct the pulmonary regurgitation: an animal feasibility study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Pulmonary regurgitation leads to progressive right ventricular dysfunction, susceptibility to arrhythmias, and sudden cardiac death. Percutaneous valve replacement has been developed in recent years, providing patients with an alternative option. Percutaneous pulmonary valve replacement has been recently introduced into clinical practice. The goal of this study was to evaluate the feasibility of percutaneous valve stent insertion to correct the pulmonary regurgitation in sheep using a cup-shaped valve stent.</p><p><b>METHODS</b>Pulmonary regurgitation was created by percutaneous cylindrical stent insertion in native pulmonary annulus of 8 sheep. One month after the initial procedure, the sheep with previous cylindrical stent implanted underwent the same implantation procedure of pulmonary valve stent. The valve stent consisted of a cup-shaped stent and pericardial valves. Hemodynamic assessments of the bioprosthetic pulmonary valve were obtained by echocardiography at immediately post-implant and at 2 months follow up.</p><p><b>RESULTS</b>Successful transcatheter cylindrical stent insertion was performed in 7 sheep but failed in 1 sheep because the cylindrical stent was released to right ventricle outflow tract. After one month the 7 sheep with pulmonary regurgitation underwent valve stent implantation successfully. Echocardiography confirmed the stents were in desired position during the follow-up. No evidence of pulmonary valve insufficiency occurred in any animals. Echocardiography showed all heart function markers were normal.</p><p><b>CONCLUSIONS</b>Percutaneous cylindrical stent insertion to induce significant pulmonary regurgitation in sheep was feasible, simple and reproducible. Percutaneous pulmonary valve stent implantation can reduce pulmonary regurgitation in a sheep model. Further development of animal model and clinical trials are warranted.</p>

Preparation of valved mitral stent and in vitro experimental implantation to mitral position through catheter / 第二军医大学学报

Objective: To prepare valved mitral stent and to discuss the feasibility of transcatheter implantation of the valved mitral stent in vitro. Methods: We designed a self-expandable stent made of super-elastic Ni-Ti shape memory alloy. The stent was composed of double disks with tubular linkage between them. A valvular ring made of nitinol wire was sutured on the tubular part. Fresh sheep pericardium was cross-linked with a 0.6% glutaraldehyde solution for 36 hours then sutured into a valvular ring; the latter was sutured onto the nitinol self-expandable stent. Through a sheath across the interatrial septum positioned in the left ventricle of isolated sheep heart via vena cava, the device was delivered into the native mitral valve position. When the left ventricle disk was deployed, it was applied to the mitral annulus by pulling back the external sheath. The waist and the left atrial disk were deployed by pulling the sheath in the annulus and left atrium, respectively. Thus the whole device was deployed in the mitral native. Water was injected into the pulmonary veins and left ventricle to test competence of the prosthetic heart valves. Results: The prepared valved mitral stent could be stably positioned at the native valves. There was no stent migration when it was repeatedly pulled. The two disks sandwiched the native mitral valve with one disk lying in the left ventricle and the other one in the left atrium. The prosthetic heart valves showed satisfactory function without structure damage. Conclusion: This self-expandable stent is well designed and can be safely implanted in the mitral valve position via transcatheter approach, and the function of the stent is satisfactory.

Percutaneous aortic valve replacement using a W-model valved stent: a preliminary feasibility study in sheep / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Percutaneous aortic valve replacement is a promising strategy in the treatment of patients with aortic valve stenosis. And many kinds of valved stents have been implanted in selected patients worldwide. However, the clinical experience is still limited. We developed a W-model valved stent and evaluated the feasibility and safety of percutaneous implantation of the device in the native aortic valve position.</p><p><b>METHODS</b>A self expanding nitinol stent with W-model, containing porcine pericardium valves in its proximal part, was implanted in six sheep by means of a 14 French catheter through the right common iliac artery under guidance of fluoroscopy. During stent deployment the original aortic valve was pushed against the aortic wall by the self expanding force of the stent while the new valve was expanded. These sheep were followed up shortly after procedure with supra-aortic angiogram and left ventriculography. Additionally, one sheep was sacrificed after the procedure for anatomic evaluation.</p><p><b>RESULTS</b>It was possible to replace the aortic valve in the beating heart in four sheep. The procedure failed in two sheep due to coronary orifice occlusion in one case and severe aortic valve regurgitation in the other case. One sheep was killed one hour after percutaneous aortic valve replacement for anatomic evaluation. There were no signs of damage of the aortic intima, or of obstruction of the coronary orifice.</p><p><b>CONCLUSIONS</b>Percutaneous aortic valve replacement with a W-model valved stent in the beating heart is possible. Further studies are mandatory to assess safety and efficacy of this kind of valved stent in larger sample size and by longer follow-up period.</p>

Transcatheter pulmonary valve replacement in sheep: 6-month evaluation of self-expanding valved stents / 中华心血管病杂志

<p><b>OBJECTIVE</b>The purpose of this study was to determine the feasibility of transcatheter pulmonary valve replacement in sheep up to 6 months post procedure.</p><p><b>METHODS</b>Fresh sheep pericardium treated with a 0.6% glutaraldehyde solution for 36 hours was sutured to a valvular ring and then fixed onto a newly designed nitinol self-expandable stent. Thoracotomy was performed in sheep (23.5 +/- 3.1) kg under general anesthesia and the device was delivered into the native pulmonary valve of the sheep via the anterior wall of right ventricle by catheter and fooled for 6 months.</p><p><b>RESULTS</b>One sheep died 4 months after the procedure due to in-stent thrombosis. Another 4 animals survived the 6-month observing period. Angiographic and hemodynamic measurements confirmed good positioning and function of the stents with a competent valve immediately post procedure and 6 months post the procedure in surviving animals.</p><p><b>CONCLUSION</b>Implantation of the nitinol self-expandable stent in the pulmonary valve position by a transcatheter approach is feasible and good function of transcatheter implanted memory nitinol valved stents was shown after 6 months of implantation in sheep.</p>