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Biomedical subjects

E Imamura

Publications and source records attributed to E Imamura.

At least 73 records · Page 4Linked to original sources
PubMed1982

Open versus closed position fixation of bioprosthesis. Comparative in vitro studies from the viewpoint of durability.

In an effort to normalize the dynamic leaflet behavior of a porcine bioprosthesis, an experimental attempt was made to treat a tissue heart valve with 0.625% glutaraldehyde in the open position ("open-type valve"). Eighteen open-type valves, having fixed openings of various sizes, were examined with our pulse simulators. Eight closed-type valves, which were treated in the closed position, were studied for comparison. The results showed that closed-type valve tended to offer an immobile cusp at a low flow state; at a pump pressure of 90 mm Hg in a pulsatile flow or under steady flows of no more than 10 L/min. By contrast, the open-type valve showed the symmetric cusps opening with circular orifices at any given flow rates. Analysis of the pressure loss coefficient revealed that the leaflets prepared in the open position produced only a minimal impediment to the forward flow. One half of the anatomic orifice of a valve was considered to be the optimal size for the fixed opening. It is concluded that open position fixation is expected to provide the bioprosthesis with improved fatigue durability in patients with low cardiac output syndrome and in small children.

Aortic Valve↗
PubMed1977

Radiographic assessment of leaflet motion of Gore-Tex laminate trileaflet valves and Hancock xenograft in tricuspid position of dogs.

Six samples of various thicknessess of Gore-Tex compounds were fashioned into trileaflet valves. A radiopaque marker was placed on the center of the free margin of each cusp, and the prostheses were implanted in the tricuspid position of dogs. Two Hancock valves were studied for comparison. Catheterization revealed that the hemodynamic function was normal in all valves tested. High-speed radiography permitted analysis of leaflet movement throughout the cardiac cycle. Of the six Gore-Tex valves, five opened completely. The cusps of these five valves were fabricated from 4, 6, 8, 10, and 12 layers of Gore-Tex film. The remaining valve, which was fabricated from 15 layers of Gore-Tex film, and both porcine xenograft aortic valves did not open completely. We postulate that the laminates of 12 layers or less of Gore-Tex film are suitable for further study to evaluate their potential applicability in trileaflet cardiac valve prostheses.

Animals↗
PubMed1977

Function of expanded-polytetrafluoroethylene laminated trileaflet valves in animals.

A stent-mounted trileaflet cardiac valve prosthesis has been developed in which the valve leaflets were fabricated from 0.003-mm films of expanded polytetrafluoroethylene laminated in 4 to 15 layers. A total of 28 valves of varying leaflet thickness were implanted in the tricuspid position in dogs. Cardiac catheterization performed during the follow-up period between 1 week and 15 months after valve replacement in 20 surviving animals showed that the initial good function was maintained in 12 dogs for up to 15 months, whereas valve dysfunction developed in 8 other dogs within 6 months. Autopsy revealed that the cause of valve dysfunction among the eight dogs was cusp stiffening with or without retraction in six, dehiscence of the suture ring in one, and strut entrapment in one. This study demonstrated that the thickness of the leaflet material is an important factor affecting the long-term function in vivo.

Animals↗
PubMed1977

Conduit repairs of transposition complexes. A report of 14 cases.

Of 14 patients with transposition complexes undergoing conduit repairs, 10 had complete transposition of the great arteries (TGA) and 4 double-outlet right ventricle. All 14 had ventricular septal defect (VSD). Ten had pulmonary stenosis, one had an atrial septal defect, and one had patent ductus arteriosus. The ages of the patients ranged from 13 months to 18 years. Six patients were treated with nine palliative operations: four systemic-pulmonary artery shunts, three atrioseptectomies, and two pulmonary banding procedures. Four patients died immediately after the operation. Among the 10 operative survivors, there were no late deaths during the follow-up periods from 5 months through 6 years. Review of the factors influencine the early operative results has stressed the importance of correct timing of operation with or without palliative treatment, increased surgical experience, and the critical evaluation of intracardiac anatomy.

Adolescent↗