Ten experimental perfusions with autogenous oxygenation were performed in mongrel dogs to evaluate the efficacy of the procedure in maintaining normal hemodynamic conditions and adequate blood gases for 1 h. Blood was drained from the right and left atria and pumped to the pulmonary artery and aorta, respectively. Two closed circuits containing compliant chambers and roller pumps were utilized. Artificial ventilation with an Fio, of 50% were used in 5 animals and with an Fio, level of 30% in the other 5. EKG, cardiac output, aortic, pulmonary artery, and left atrium pressures were registered. Pulmonary tissue was biopsied after perfusion. The heart was electrically fibrillated after perfusion was established and defibrillated at the end of the bypass. The procedure was able to maintain blood gases and pulmonary, aortic, and left atrial pressures within normal ranges during the perfusion. The mobility of the heart and the access to all coronary arteries was excellent. Clinical central nervous system evaluation, EKG tracings, and pulmonary histological exams showed no adverse effects of perfusion. We conclude that the technique employed may present a suitable proceeding for extracorporeal circulation in closed heart surgeries, and its clinical application should be evaluated as a safe and economical alternative. Leirner, Rua Pernambuco, 15-Apt. 41, Sio Paulo, 0124-020 Brazil. 16. Helmsworth JA, Shabetai R, Cole WR, Neely JC, Albers JE, Gonzales LL. A method of cardiac bypass with autogenous oxygenation. Surgery 1959;45: 129-37. 17. Atkins CW. Early and late results following elective isolated myocardial revascularization during hipothermic fibrillatory arrest. Circulation 1985;72 (Suppl 3):375. 40:237-52. 425-9.

This paper describes the design of a ventricular assist device (VAD), its manufacturing, and testing. The VAD presented is pulsatile, with a free-floating membrane, smooth internal surfaces, and pericardial valves. It comprehends also a pneumatic driving unit capable of operating in the "full to empty," EKG synchronized or asynchronous modes. In vitro tests were performed to assess its mechanical durability, hydrodynamic performance, and hemolysis. To optimize cannulas and implant techniques, we performed in vivo tests in 22 sheep and 8 calves. In these tests, we also evaluated hemolysis and the device's capacity to normalize hemodynamic parameters during induced cardiac failure. The VAD worked for 4,000 h without failure in a mock circulatory loop. In full to empty mode, it displayed a rate-mediated "Starling-like" performance. Optimum output was achieved with a systole duration of 40% of the cycle. The in vitro hemolysis index (IH) was 6.7 +/- 2.1. Hemolysis in animal experiments was clinically nonsignificant. In calves with induced cardiac failure, the VAD was able to normalize hemodynamic parameters within 120 min.

Avaliação do desempenho hemodinâmico do dispositivo de assistência ventricular InCor como substituto do coração esquerdo

Freeze-drying of biological tissues allows for dry storage and gamma ray sterilization, which may improve their use as a medical prosthesis. The objective of this study was to evaluate the rehydration characteristics and hydrodynamic performance of prosthetic valves before and after lyophilization. Two size 23 bovine pericardium aortic valve prostheses from different manufacturers were evaluated in a Shelhigh (Union, NJ, USA) pulse duplicator (80 ppm, 5 L/min) before and after lyophilization. Flow and transvalvular pressure gradient were registered in vitro and in vivo, and images of opening and closing of the prosthesis were obtained in the pulse duplicator in a digital camera. Rehydration was evaluated by comparison of dry valve weight with valve weight after 15 min, and 1, 24, 48, and 72 h in saline solution, inside the pulse duplicator. In vivo performance was assessed by surgical implantation in Santa Inês young male sheep in the pulmonary position after 30 min rehydration with 0.9% saline. Transvalvular pressure gradient and flow measurements were obtained immediately after implantation and 3 months after surgery when valves were explanted. Captured images showed a change in the profile opening and closing of valve prosthesis after lyophilization. The gradient measured (in vitro) in two valves was 17.08 ± 0.57 and 18.76 ± 0.70 mm Hg before lyophilization, and 34.24 ± 0.59 and 30.40 ± 0.97 mm Hg after lyophilization. Rehydration of both lyophilized valves was approximately 82%. Drying changed the profile of the opening and closing of valve prostheses, and increased on average by 83% the gradient in vitro tests. The result of the in vivo tests suggests maintaining pressure levels of the animal with the lyophilized prostheses within acceptable levels.

Preserved pericardium in contact with blood is not thrombogenic, therefore avoiding the use of anticoagulants, and has excellent mechanical properties. Our objective is to take advantage of these characteristics and build a pulsatile ventricular assist device (VAD) with pericardium used as the inner lining of the blood chamber. A mold is used for the tanning of the pericardium, rendering it with an exact shape. A flexible polymeric structure is designed to serve as a base for the pericardium, guiding it and limiting its rate of strain. It consists of two halves, which when outfitted with the interior pericardium lining and connected to each other, form the blood chamber. This assembly is housed in rigid polyvinyl chloride (PVC) shells making up the air chamber for the pneumatic activation. Valves are likewise made of pericardium. Sealing of the chambers was tested statically up to 300 mm Hg with no air or fluid leakage. The device was tested for 60 continuous days in a mock loop, demonstrating hydrodynamic performance adequate for ventricular assist. Micrographs (confocal laser and scanning electron microscopy) were obtained of several pericardium areas, especially on the flexing regions that are a transition between the wet and dry regions. No sign of damage to the pericardium was observed either with the naked eye or at the microscopic level. From the hydraulic performance and materials viewpoints, a completely pericardium-lined pulsatile VAD displaying a polymeric structure that avoids unpredictable bending and limits strain is feasible. The results warrant further studies regarding biocompatibility and strength advantages.