Biomedical subjects

S Nitta

Publications and source records attributed to S Nitta.

277 records · Page 16Linked to original sources

PubMedDate not supplied

Multi-institutional evaluation of the Tokyo University Ventricular Assist System.

A total of 61 VASs developed in Tokyo University were evaluated at 21 institutions in the period 1985-1989 for determination of its reliability and effectiveness. The system is comprised of a pneumatic sack-type pump (Nippon Zeon Co.), and its driving console (Aishin Seiki Co.). The stroke volume of the pump is 40 ml and blood contacting surfaces are coated with Cardiothane. Ages of the patients (pts) ranged from 12-82 yrs (mean 58 yrs). VASs were used in the assist mode of LVAD (54 pts), RVAD (5 pts) and BVAD (2 pts). Most of the cases (58 pts) included postocardiotomy cardiogenic shock after surgery for ischemic (28 pts), valvular (22 pts), both ischemic and valvular (7 pts) and congenital (1 pt) heart diseases. Average duration of the assist ranged from 1 hr-20 days (mean 5.6 dys). The VADs could be weaned in 34 cases (56%) and among these, 13 cases (21%) survived to discharge from the hospital. Causes of death in cases which could be weaned from the VAD included multiple organ failure/due to delayed institution of adequate circulatory support, renal failure and systemic infection. Small and minute thrombus formations were noted in 7 cases however, no pump originated thromboembolism were complicated. No troubles of the pump including leakage nor breakage, no mechanical failures of the driving consoles were experienced in any of the cases. Thus, it is concluded that the system was proved to be clinically effective and reliable.

Adolescent↗

PubMedDate not supplied

Antithrombogenicity of ventricular assist devices for postoperative myocardial dysfunction.

Antithrombogenicity of pneumatic ventricular assist devices (VAD) for postoperative ventricular failure was evaluated macroscopically and microscopically in relation to VAD flow, coagulation parameters, and other potentially thrombogenic factors. A total of 12 sack type pumps were used in nine cases after operations for ischemic heart diseases (4 cases), valvular diseases (3 cases), and congenital anomalies (2 cases). Durations of pumping of each device ranged from 18 hours to 37 days (mean, 10.9 days). The clinical protocol for antithrombogenicity of the device indicates maintenance of ACT around 150 sec and keeping VAD flow more than 2.0 L/min. In our clinical series, however, heparin was given only in most cases to maintain activated clotting times (ACT) at 120-140 sec for the first three postoperative days. Minute ringlike thrombi were noted at connectors of cannula in two pumps after low flow (1.5 L/min) pumping for 5 days or after frequent on/off studies for weaning. A small thrombus (2 X 2 mm) and fine granular thrombi were noted on actuating bladders in two pumps that were used with frequent on/off studies or in a patient with severe sepsis during VAD pumping. Other VAD pumps were macroscopically free of thrombus. SEM analyses on surfaces of actuating bladders demonstrated mild to moderate platelet adhesions, which were correlated with platelet count, but not with other coagulation parameters including platelet agglutination and pumping duration. In cases with leucocytosis during VAD uses, leucocyte adhesion was noted as well without correlation to the coagulation parameters.

Adolescent↗

PubMedDate not supplied

Real time sound spectral analysis for diagnosis of thrombosed prosthetic valves.

A real time sound spectral analyzer was developed at the authors' institute and has been used for diagnosis of thrombosed valves for 15 years. The analyzer consists of a wider frequency microphone, a digital signal processor with multiple bandpass filters, and displays. To quantify the high frequency component in section pattern of opening and closing clicks, maximal frequency at -30 dB level was used at a diagnostic parameter (normalized maximal frequency, NMF). A total of 17 thrombosed valves with or without pannus formations have been experienced and SSA showed abnormality in 13 valves, which comprised of Björk-Shiley (N = 6), Starr-Edwards 2320, 6120, 6520 (N = 5) and Kay-Shiley (N = 2). The abnormal findings included NMF of opening or closing clicks lower than normal range of each type of prosthesis, and significant decrease of NMF more than 450 Hz from the value previously obtained. All diagnoses of thrombus formations and their locations were confirmed by operative or autopsy findings. The SSA failed to diagnose in four valves, which comprised of Starr-Edwards 6520 (N = 3) and Björk-Shiley (N = 1). Operative findings revealed that thrombi were formed in a manner that permitted direct collision of disc and valvular ring causing clicks with high frequency component. No pseudo-positive diagnosis for thrombosed valve was experienced in the authors series, and SSA is thought to be a reliable noninvasive technique that enables early diagnosis of a thrombosed valve.

Adult↗

PubMedDate not supplied

Valve replacement of childhood: follow-up results and complications.

This study concerned 18 cases of value replacement in patients than 15 years, between 1964 and 1980. In this period, there was a total of 30 such cases, but there were eight hospital deaths and four cases with less than two years postoperative observation. These 12 cases were excluded from the study. The average follow-up period of the 18 cases was eight years and nine months. During this period, six cases were associated with postoperative complications, which consisted of three cerebral emboli, two malfunctions of the implanted prostheses and one congestive heart failure. Three cases involved prosthesis-related death. Secondary implantations were performed in two cases; one for relative stenosis of the prosthesis and the other for calcification of the porcine xenograft. Physical activity in the 15 survivors has been excellent in all but two cases with arrhythmia and sequelae of cerebral damage due to surgery.

Adolescent↗

PubMedDate not supplied

Deterministic chaos in the hemodynamics of an artificial heart.

To analyze the hemodynamic parameters during prosthetic circulation as an entity, non linear mathematical techniques were used. To compare natural and prosthetic circulation, two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses in chronic animal experiments using adult goats to consitute the biventricular bypass complete prosthetic circulation model with ventricular fibrillation. After implantation, these goats were placed in a cage and extubated after waking. All hemodynamic parameters with the natural circulation without biventricular bypass pumping, and the artificial circulation with biventricular bypass pumping under ventricular fibrillation were recorded under awake conditions. By the use of a non linear mathematical technique, the arterial blood pressure waveform was embedded into a four dimensional phase space and projected into three dimensional phase space. The Lyapunov numeric method is used as an adjunct to the graphic analysis of the state space. A phase portrait of the attractor showed a high dimension complex structure, with three dimensional solid torus suggesting deterministic chaos during natural circulation. However, a simple attractor, such as a limit cycle attractor, was observed during artificial circulation. Positive Lyapunov exponents during artificial circulation suggest the lower dimensional chaotic system. Thus, hemodynamic parameters during prosthetic circulation must be carefully controlled when unexpected stimuli are fed from outside.

Animals↗

PubMedDate not supplied

[Chaotic attractor of the left ventricular wall motion in normal heart healthy subject].

To analyze the entire left ventricular wall motion, not the decomposed motion, nonlinear mathematical techniques were used to describe graphically time series data for the left ventricular contraction. Time series data of the left ventricular wall motion were recorded by M-mode echocardiography, and embedded into three-dimensional phase space. The largest Lyapunov exponents, a measure of the rate of divergence in phase space, were calculated to detect the sensitive dependence on initial conditions. The reconstructed attractor of the left ventricular contraction showed a lower dimensional strange attractor, and calculation of the Lyapunov exponents indicated sensitivity to initial conditions. These results suggest that time series data of the left ventricular contraction show the characteristics of deterministic chaos. The chaotic system can provide an intelligent and flexible control system. Our results suggest that the circulatory control system, which mediates the cardiac contractility, may be a flexible dynamic compatible with deterministic chaos.

Echocardiography↗

PubMedDate not supplied

Necrotizing pancreatitis and gizzard erosion associated with adenovirus infection in chickens.

Cases of focal necrotic pancreatitis and gizzard erosion in chickens are reported. Intranuclear inclusion bodies were seen in necrotic pancreatic acinar cells and necrotic epithelial cells of the gizzard, and electron microscopy demonstrated virus particles in affected gizzard epithelium. Adenovirus antigens were detected immunohistochemically in these intranuclear inclusion bodies. These findings suggest that the necrotizing pancreatitis and gizzard erosion were associated with adenovirus infection.

Adenoviridae Infections↗