Experimental observation on a new chimney-shaped mechanical valve completely implanted above the mitral annulus in animals

Current commercially available prosthetic valves suffer from limited size, high requirements for implantation technique, subvalvular structural destruction, and valve dysfunction due to proliferation of fibrous endothelial tissue. This study aims to perform the preclinical large animal experiments for surgically implanting a chimney-shaped artificial mechanical heart valve with zero left ventricular occupancy, which fully accommodates the movement of the valve leaflets in the valve frame and realizes completely supra-annular surgical implantation. A total of 7 sheep underwent the replacement of artificial valve, and 5 sheep survived normally until anatomical examination. The mechanical properties of these artificial mitral valves remain functionally normal. There was no obvious thromboembolism around the artificial valve and in the important organs. The tissue layer of suture ring was completely organized and endothelialized, and the thickness of tissue layer was about 0.6-1.0 mm. The follow-up of echocardiography showed that the left ventricular ejection fraction was normal (60-70%) before and 6 months after operation. The results of transvalvular pressure gradient and blood flow velocity of artificial valve were normal. Left ventricular retrograde angiography showed that the artificial valve was completely located in the left atrium with good position and normal opening and closing. There was no obvious perivalvular leakage and other abnormalities. At 3 and 6 months, there were no obvious abnormalities in blood routine test, liver and kidney function, and other indexes. The new chimney-shaped artificial mechanical valve implanted completely above the mitral annulus had good wear resistance, histocompatibility, and antithrombotic and hemodynamic performance.