Biomedical subjects

H Hotei

Publications and source records attributed to H Hotei.

5 recordsLinked to original sources

PubMed1997

Development of a direct mechanical left ventricular assist device for left ventricular failure.

We have developed a direct mechanical left ventricular assist device (DMLVAD) for severe left ventricular failure. The DMLVAD was attached to the left ventricle and compressed the heart by a pneumatic driving unit. In a mock circulation model with an extracted nonbeating heart, a cardiac output (CO) of 1.93 L/min was obtained at a driving pressure of 200 mm Hg. In a canine left ventricular failure model induced by injection of sodium hydroxide into the myocardium, the systolic arterial pressure, systolic left ventricular pressure, maximum LV dP/dt, peak flow, and CO increased by 21, 24, 58, 144, and 37%, respectively. The mean left atrial pressure also decreased by 15% when the DMLVAD was driven. These effects were most prominent when the mean left atrial pressure was over 15 mm Hg, and the driving pressure was over 100 mm Hg. Compression at late systole was more effective in obtaining greater CO. We suggest that the DMLVAD could be an optional circulatory assist device for patients with left ventricular failure awaiting heart transplantation.

Animals↗

PubMed1997

Trial manufacture of eccentric roller type total artificial heart.

Working toward a completely implantable total artificial heart, we have designed an eccentric roller type total artificial heart. The actuator of this artificial heart is a drum type eccentric roller that squeezes the blood chambers. The blood chambers are made of silicone rubber and are torus in shape. The shape of the artificial heart is an almost circular cylinder, and its length and diameter are 10 cm and 8 cm, respectively. The 2 main characteristics of this artificial heart are that it discharges blood in a pulsatile mode and that it requires no reversing of the motor. Because we have not completed the artificial heart yet, we have tested the eccentric roller mechanism on the prototype with an overflow type mock circulation with a 100 mm Hg afterload. The prototype worked at the roller speeds of 50, 100, and 150 rpm with flow rates of 1.7, 3.7, and 5.4 L/min, respectively. Next the prototype was connected to a Donovan type mock circulatory system and worked at roller speeds of 88-214 rpm with flow rates of 3.0-8.4 L/min against mean afterloads of 82-120 mm Hg.

Biocompatible Materials↗

PubMed1996

Numerical simulation of nonpulsatile left ventricular bypass.

A computer simulation was carried out to investigate the influence of nonpulsatile left ventricular assistance on hemodynamics. A simulation circuit was constructed to represent the circulatory system. A source of current was added to denote the nonpulsatile blood pump. The left and right ventricles were replaced by variable compliances. Left heart failure was simulated by decreasing the amount of compliance change of the left ventricle. We introduced a pulsatility indicator (PI) to clarify the pulsatility characteristics in the hemodynamics; this PI was defined as the ratio of the pulse pressure (PP) to the mean aortic pressure (AoP). When nonpulsatile bypass flow increased, the mean AoP, tension time index (TTI), and diastolic pressure time index (DPTI) increased, and cardiac output, PP, and PI decreased. When assisted flow increased with the constant total flow rate, the mean AoP and DPTI changed little; the PP, TTI, and PI decreased, and the endocardial viability rate increased. The PI would be helpful in evaluating the effect of pulsatility.

Blood Pressure↗

PubMed1995

Pulsatile total artificial heart using a reversible rotary pump.

A pump circuit was assembled and examined for use as an implantable artificial heart. The circuit consisted of a gear pump and 4 artificial heart valves. Mitral and pulmonary arterial valves were placed at the inflow port of the pump, and aortic and tricuspid valves were placed at the outflow port. The mitral and the tricuspid valves were connected to each reservoir at 10 mm Hg, and the aortic and the pulmonary arterial valves were connected to the head tanks at 80 and 20 mm Hg, respectively. The pump discharged pulsatile flows into both systemic and pulmonary arteries alternately by switching the direction of rotation periodically. Because the rated discharge was 1.7 L/min for the gear pump used, the measured flow rate was 0.8-0.75 L/min at a heart rate of 60-110 bpm.

Aortic Valve↗

PubMed1988

[A case of right adrenal myelolipoma diagnosed preoperatively and review of literature in Japan].

Fifty-nine years old female who complained of right back pain was diagnosed as having right adrenal myelolipoma preoperatively by ultrasound, CT and other examinations. The patient was cured by surgery. The resected tumor was 11.5 X 10.5 X 8.5 cm in size and 470 g in weight. Histopathological diagnosis was myelolipoma of Soós's type 1. Sixteen cases of myelolipoma, including our case have been reported in Japanese literature. The age of patients ranged from 20 to 60 (average 49.1) and male-female ratio was 11:5. Most patients presented with abdominal pain and abdominal mass, and had complication of obesity and hypertension. The lesion was more common on the right side (11:5). Their size was 3-21 cm (average 10.9 cm) and their weight was 10-1, 930 g (average 823 g). Adrenal myelolipoma can be certainly diagnosed preoperatively by ultrasound, CT and other examinations. Adrenal tumors showing normal adrenal endocrine function and fat density on CT examination indicate that they could be myelolipoma in their nature.

Adrenal Gland Neoplasms↗