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Biomedical subjects

H Harasaki

Publications and source records attributed to H Harasaki.

At least 55 records · Page 3Linked to original sources
PubMed1988

Heat dissipation through the blood contacting surface of a thermally driven LVAS.

A heat exchanger for a totally implantable heat driven LVAD is an essential element in overall system thermal management. The heat exchange is accomplished by supplying cooling water from a pusher-plate driven water pump to the engine and then to the heat exchanger on the pump housing. The temperature of the interface between the blood and pump surface is of critical importance for clinically acceptable operation of the system. Temperatures were measured by instrumenting a pump housing with thermocouples and an electric heater on a mock circulatory loop. Flows were varied from 1 to 8 l/min and heat input was 20 watts. At 1.0 l/min pump flow the maximum inner surface temperature rise is 4.5 degrees C. In vitro tests were conducted to examine the effect of elevated temperature on platelete function. Both platelet aggregation and adhesion were reduced at elevated temperatures of 42 and 47 degrees C indicating a potential benefit of reduced thrombogenesis on the heated housing surface.

Assisted Circulation↗
PubMed1988

Biological performance of TiNi shape memory alloy vascular ring prostheses: a two year study.

A method was developed for the noninvasive insertion of a vascular ring prostheses aimed at preserving arterial patency and preventing restenosis following angioplasty. Using a specially designed 7F catheter 22 nitinol (TiNi) wire prostheses (I.D. 5 mm; 0.25 mm thickness) were torsion reduced in diameter and inserted under fluoroscopy into both carotid (n = 2) and iliac-femoral arteries (n = 20) of dogs. Aspirin (650 mg BID) and Persantin (200 mg BID) were given for only 30 days postoperatively. Angiography of all rings at 1, 6, 12 months exhibited excellent biocompatibility and long term patency 91% (20/22) as reported in Trans ASAIO 32:30, 1986. Four rings inserted in the right and left common iliac arteries and femoral artery were followed for up to 2 years and exhibited 100% patency. Angiography demonstrated that the anchorage of the prostheses was stable and the lumen was uniformly covered by a thin neointimal layer of endothelial like cells. The prostheses were patent with no evidence of thrombosis or inflammation. In view of the problem of recurrent stenosis occurring during the healing period after balloon angioplasty (PTA or PTCA), this approach may lead to a new means of clinical intervention in atherosclerosis.

Alloys↗
PubMed1988

Biomaterial-associated calcification: pathology, mechanisms, and strategies for prevention.

Deposition of calcium-containing apatite mineral occurs widely in association with cardiovascular and noncardiovascular medical devices and biomaterials, is the leading cause of failure of contemporary bioprosthetic heart valves, and limits the functional lifetime of experimental (and potentially clinical) mechanical blood pumps and polymeric heart valves. Calcification of bioprosthetic tissue is primarily intrinsic, related to cuspal connective tissue cells and fragments, and collagen. In contrast, the predominant site of calcific crystals on flexing polymeric surfaces in blood pumps or valve prostheses is extrinsic, associated with adherent cells, thrombus, or pseudointima. Pathologic calcification shares key features with physiologic skeletal mineralization, including crystal initiation through the mediation of cell membranes, usually in the form of extracellular vesicles. This suggests a unified hypothesis for normal and abnormal mineralization. Several approaches are being studied experimentally for the inhibition of bioprosthetic heart valve calcification. Controlled-release diphosphonate therapy, perhaps in conjunction with an anticalcification cuspal pretreatment, appears most effective. Research objectives in biomaterial-associated calcification include (1) development of animal models, (2) determination of initial crystal nucleation events and sites, (3) elucidation of the relative roles of host, implant, and mechanical determinants, and (4) development of approaches for the inhibition of mineralization.

Assisted Circulation↗
PubMed1985

Anatomicomechanical study for the hydraulic line of a thermal left ventricular assist system.

A thermal left ventricular assist system currently under development consists of two separate major components, i.e., a pump/actuator module and an engine/thermal battery module. The possible implantation site of the engine/battery module is tentatively determined to be the iliac fossa, which requires a flexible interconnecting line to the pump/actuator module. A quantitative and biomechanical study was done on the effect of the implanted hydraulic line on the bendability of the torso. It revealed that the semirigid interconnecting line would not severely restrict the movement of the patient provided it has the proper prebend configuration. The cadaver fitting study proved the anatomical feasibility of the retroperitoneal iliac fossa as the implant site of the Thermal Ventricular Assist System 8 (TVAS 8) engine/battery module. The location and configuration of the interconnecting line of the TVAS 8 were determined using biomechanical analysis so that the restriction of the body movement due to the line could be minimized. The main route of the line was the left side of the trunk, and the line is W shaped in configuration. The line elongation is the most critical resistive factor and accordingly there may still be rigidity during lateral flexion.

Assisted Circulation↗
PubMed1985

Experimental evaluation of complete electrically powered ventricular assist system.

The LVAS utilizing an intrathoracic blood pump and a parathoracic, electrohydraulic energy converter has a number of promising features. These include: transcutaneous energy transmission and an implanted variable volume device which eliminate the need for percutaneous access; utilization of an intrathoracic blood pump and variable volume device which allow the diaphragm and abdominal cavity to remain intact; parathoracic or subcutaneous location of the transformer secondary, energy converter, internal battery and interconnecting elements allowing replacement with a minor surgical procedure; employment of the "biolized" continuous blood contacting surface which has the potential of long-term use without anticoagulants and utilization of an electrohydraulic energy converter which provides synchronization without requiring transducers and associated electronics and which provides lubrication of mechanical components. The development effort, which began separately in 1977 and has been conducted jointly by Nimbus and the Cleveland Clinic since 1980, has demonstrated that the above features can be incorporated in a reliable LVAS. In particular, the system in vivo test series have demonstrated the soundness of the basic concepts and led to refinements which were demonstrated in the 6-1/2 mo test. All elements of the system have been utilized during the in vivo test program. Component tests of significance include: LVAS and total heart blood pump in vivo experiments of up to 7 mos duration which demonstrate the blood compatibility of the biolized surface without the use of long-term anticoagulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Successful acute heart-lung transplantation after six hours preservation.

The lack of an appropriate and effective technique for prolonged heart-lung preservation has been one of the factors limiting the use of this therapeutic modality. Presently, the donor is transported to the transplant center, which is often an unacceptable burden to the donor's family. A reliable preservation technique that would allow long-distance procurement would markedly increase the use of heart-lung transplantation. Using a dog, a successful heart-lung transplantation was achieved following six hours of preservation of the graft. The experiment was terminated when the animal was able to maintain normal blood gases following extubation.

Animals↗
PubMed1984

A simple method for extended heart-lung preservation by autoperfusion.

A modification of Robicsek's autoperfusing heart-lung preparation preserved normal structure in the canine lung for 8 hrs and in the heart for 12 hrs. Applicable to both heart and heart-lung transplantation, the system would permit a safe extension of preservation time limits.

Animals↗