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S A Hayashida

Publications and source records attributed to S A Hayashida.

8 recordsLinked to original sources
PubMed2001

Pulsatile ventricular assist device with pericardial inner lining.

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.

Biocompatible Materials↗
PubMed1997

A virilizing Leydig cell tumor of the ovary associated with stromal hyperplasia under gonadotropin control.

A 34-yr-old nulliparous black woman presented with hair loss, facial hirsutism, irregular menses and infertility associated with greatly increased serum total testosterone levels. The adrenal glands and the ovaries were normal on radiological and ultrasonographic investigation. Catheterization of the veins draining from the adrenal glands and the ovaries yielded testosterone levels of 20.3 nmol/L and 20.0 nmol/L in the right and the left adrenal veins, respectively, and 17.9 nmol/L and 27.4 nmol/L in the right and left ovaries venous plexus, respectively. Sequencial dexamethasone and ethynyl estradiol suppression test showed a decrease in cortisol level with no change in total testosterone level on dexamethasone while an increase in testosterone from 10.5 nmol/L to 20.1 nmol/L was observed ten days after ethynil estradiol had been associated to dexamethasone. When a gonadotropin-releasing hormone agonist (gonadorelin 3.5 mg i.m.) was administered for 2 months, serum gonadotropins levels decreased to less than 2 IU/L, total testosterone to 3.8 nmol/L and estradiol to less than 36 pmol/L. The patient was submitted to a pelvic exploratory laparotomy and a left salpingo-oophorectomy was performed. A solid and circumscribed ovarian tumor of 1.0 cm in diameter was found. The pathological diagnosis was a Leydig cell tumor with surrounding stromal hyperplasia. These findings may suggest that this tumor was gonadotropin-dependent being indirectly stimulated by ethynil estradiol, through a sensitization of the pituitary gonadotropes and increase in gonadotropin levels and suppressed by a gonadotropin-releasing hormone agonist.

Adult↗
PubMed1995

Design, manufacturing, and testing of a paracorporeal pulsatile ventricular assist device: São Paulo Heart Institute VAD.

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.

Animals↗
PubMed1995

Extracorporeal circulation with autogenous oxygenation: hemodynamic and gasometric parameters.

Ten experimental perfusions with autogenous oxygenation were performed in mongrel dogs to evaluate the efficacy of the procedure in maintaining normal hemodynamic 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 FiO2 of 50% were used in 5 animals and with an FiO2 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.

Animals↗
PubMed1994

[Design, manufacturing, and testing of a pulsatile ventricular assist device].

PURPOSE: To describe the design of a ventricular assist device (VAD), its manufacturing and testing. METHODS: The VAD is pulsatile, with a free floating membrane, smooth internal surfaces, and pericardium valves. It comprises also a pneumatic driving unit capable of operating in the "full to empty", EKG synchronized or asynchronous modes. The system was tested "in vitro" to assess its mechanical durability, hydrodynamic performance and hemolysis. "In vivo" tests were performed in 22 sheep and 8 calves aiming at optimizing cannulas and implant techniques. In these experiments, hemolysis and the device's capacity of restoring to normal hemodynamic parameters during induced cardiac failure were evaluated. RESULTS: The device was worked 4,000 hours without failure in a mock circulatory loop. Hydrodynamic performance was satisfactory for adult circulatory support. In "full to empty" mode it displayed a frequency mediated "Starling like" performance. Optimum output was achieved with a systole duration of 40% of the cycle. "In vitro" hemolysis index was 6.7 +/- 2.1. Hemolysis in animal experiments was clinically non significant. In calves under induced cardiac failure the VAD was able to normalize hemodynamic parameters within 120 minutes. CONCLUSION: This VAD is capable to circulatory assist for cardiogenic shock in conditions needed for an adult patient and the average time span anticipated for bridge to transplantation or post cardiotomy cardiogenic shock.

Animals↗
PubMed1991

Alternative parameters for evaluating the performance of skeletal muscle in cardiac assistance.

This article describes a system designed to study the force, intramuscular pressure (IP), thickening (TH), and electromyographic (EMG) activity of the latissimus dorsi muscle in response to electrical stimulation. Experiments were carried out on fresh unconditioned muscles freed from the left flank insertion and fixed to contract isometrically. Statistical analysis of the data obtained demonstrated that IP and EMG activity were linearly related to force. The thickening of the muscle was found to be sensitive only to large variations in force, in a linear fashion.

Animals↗
PubMedDate not supplied

A non-conventional reniform heart valve bioprosthesis with improved performance.

Conventional bioprosthetic heart valves have been designed with circular mounting rings. This article describes a mitral bioprosthetic valve consisting of three bovine pericardial leaflets with a "reniform" base. Its shape resembles that of the mitral anulus, and therefore, it provides a better anatomic fit. Hydrodynamic comparisons were made between conventional valves (CV) and equivalent sized reniform valves (ERV) that would adapt to the same anulus. Under steady flow of 30 L/min, pressure drops were compared in CVs and ERVs. For CV sizes 27, 29, and 31mm, the ratios of pressure drops compared with ERVs were 2, 1.49, and 1.30, respectively. With the same flow rate, the ratios of effective orifice areas (EOA) for CVs and ERVs in sizes 27, 29, and 31mm were 1.41, 1.21, and 1.14, respectively. Under pulsatile flow (mean flow, 5 L/min, 100 beats/min [bpm]), the pressure drop across CVs was averaged for sizes 27, 29, and 31mm, and found to be 1.51-fold the averaged pressure drops for ERVs. In addition, ERV sizes 27, 29, and 31mm had EOAs averaging 1.24-fold those of CVs. Similarly, for an 80 bpm frequency, the pressure drops across CVs for the three sizes averaged 1.48-fold that of ERVs. The EOAs of ERVs were 1.22-fold those of CVs averaged for the three sizes.

Animals↗