A Study On The New Type Of Cardiac Valve Prosthesis: An All-pyrolytic Carbon Bileaflet Valve In Vivo

The new type of cardiac valve prosthesis is a low profile, bileaflet mechanical prosthesis with three flow orifices. Differing from other mechanical prosthetic valves, such as St. Jude and CarboMedics valve prostheses, coated with pyrolytic carbon, this new valve prosthesis is constructed entirely with pyrolytic carbon. In vitro studies have consistently demonstrated theoretical safety and superior hemodynamic performance. In vivo study was performed in accordance with the requirements recommended by the ISO 5840-96(E) and GB 12279-90 for testing of prosthetic valves, so as to evaluate the durability, hemodynamic performance, and biocompatibility of the prosthesis.1. Animal testMaterials and Methods: Fifteen sheep weighted about 50kg underwent mitral valve replacement with 21mm new cardiac valve prostheses under endotracheal anesthesia. Standard methods of cardiopulmonary bypass were utilized. Heparin was used in 3months since operation. Open cardiac catheterization was performed in six animalsafter mitral valve replacement. Left atrial pressure (PLA) and left ventricular pressure (PLv) were measured simultaneously by dual-catheter technique. Cardiac output (CO) was determined by thermodilution technique.Animals were put to death at 1,12 weeks and in 30 months postoperatively by barbiturate overdose following systemic heparinization. The heart, lungs and peripheral organs including the liver, spleen and kidney were excised and examined grossly to determine if thromboembolic phenomenon occurred. The hearts were examined to observe the new endocardium on the left atrial side and the left ventricular side of the valve. Photographs of atrial and ventricular view of the prosthesis were performed. The new endocardium was subjected to electron microscopic examination. Doppler echocardiography was performed in two sheep 30 months after implantation to measure CO and transvalvular gradients and to determine if thrombosis or paravalvular leakage occurred. The second open cardiac catheterization was performed to determinate the PLA. PLV and so on. CO was measured by thermodilution technique. The hemodynamic performance of the new cardiac prosthesis was evaluated by means of dobutamine stress catheterization technique. Dobutamine was administrated at the rate of 5ug 'kg'1 fmin~1 with the dose increased every 15 minutes. PLA, PLV and CO were measured under different dobutamine doses stress, respectively. Results: 5 sheep died within 24hr after operation, 5 sheep died during 24-48hr, 5 sheep survived. 5 of the 10 deaths resulted from the anulus tore. There was no evidence of embolic phenomenon, nor were there any mechanical valve failures. The transvalvular gradients were 5.2 + 1. 7mmHg during operation, and 6.1?.3mmHg 30 months after implantation respectively. There was a minimal increase in transvalvular gradient as CO7increased under different dobutamine doses stress. Transvalvular gradients were 6.8 + 0. 4mmHg measured by echocardiography, similar to the invasive gradients. 2. Clinical trialMaterials and Methods: Between January, 1996 and January, 2002,62 patients underwent valve replacement with the new type of prosthetic valves. Of the 62 patients, 24 were male and 38 female. The subjects ranged in age 20?2 years. The medical history ranged 2~26 years. Rheumatic valvular disease was the predominant lesion in 56 patients, mitral valve prolapse in 3 patients, infective endocarditis associated with MI or AI respectively in 2, Congenital valvular disease in 1 patient. Of these patients, 33 were associated with atrial fibrillation, 10 with left atrial thrombus, and 4 with hemiplegia. Preoperative functional status was 27 in class III(NYHA) and 35 in class IV.The surgical technique was similar in each case, standard cardiopulmonary bypass techniques were utilized. Of the 62 patients, 11 had AYR, 39 had MVR, and 12 had DVR. Associated procedures were performed, these included repair of congenital defect in 3 patients, the Cox Maz III procedure for treatment of atrial fibrillation i...