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Biomedical subjects

R J Kiraly

Publications and source records attributed to R J Kiraly.

14 recordsLinked to original sources
PubMed1979

The dura mater valve: in vitro characteristics and pathological changes after implantation in calves.

Human dura mater valves of various sizes with rigid and flexible stents were tested in an in vitro pulsatile mock circulatory system. A 22-mm flexible stent valve incorporating a new fabrication technique showed almost the same pressure gradient as a 28-mm rigid stent valve. The backflow/stroke volume ratio was about 4% at a net flow of 10 L/min. One hundred and five rigid stent-mounted dura mater valves were used in 51 pump implantations for up to 316 days. Collagen fiber degeneration began three months after implantation. Microscopic and macroscopic calcification of the valve tissue was seen in eight out of 105 valves, giving an overall incidence of 7.6%. The calcified degeneration was dystrophic in nature, not accompanied by cellular reactions, and was seen in the areas of the valve under stress. The degenerative changes were more severe in the left side than in the right side of the total artificial heart. These findings suggest that mechanical damage to the tissue plays an important role in the pathogenesis of calcification.

Animals↗
PubMed1978

Human thoracic anatomy relevant to implantable artificial hearts.

The objective of this study is to define the human thorax in a quantitative statistical manner such that the information will be useful to the designers of cardiac prostheses, both total replacement and assist devices. This paper pertains specifically to anatomical parameters relevant to the total artificial heart. Methods were developed for generating an integrated, statistical model of the anatomical structures within the human thorax. These methods involve definition of the anatomy in four areas: chest wall, pericardium, vascular connection locations, and great vessels. Results are presented in three dimensional scale views of the human thorax showing the main features pertinent to cardiac prosthesis implantation. Statistical variability of this data is also included. Measurements were obtained from a number of sources and represent both normal and diseased patients. The ERDA total artificial heart was shown to successfully fit the fiftieth percentile adult male human.

Aorta↗
PubMed1977

Surface characteristics of the cardiac prostheses in vivo.

The pseudoneointima (PNI) deposited onto a cardiac prosthesis surface reflects many factors of biocompatibility, surface morphology, flow distribution, design, animal's physiological condition, and duration. In the evaluation of any prosthesis, the PNI is one of the prime considerations from both material and functional standpoints. Historically, Dacron fabric has been used as an internal lining for cardiac prostheses. However, we have observed cracks on the Dacron fibers, fiber fracture, fiber protrusion, and poor attachment to the diaphragm, which can cause potentially disastrous complications. In addition, there are basic differences in the PNI formation on aldehyde-treated pericardium and natural aortic valves as compared to the Dacron fabric. 1) Minimal degeneration takes place on the chemically treated natural tissue compared with the fabtic surface. Intact cells on the tissue suggest a greater compatibility. In later specimens (13 and 24 days), there is active cell infiltration onto the pericardium structure with capillary formation. 2) The deposits on natural tissue are mostly fibrin, with minimum cellular involvement and a trend toward reduction in thickness. 3) Fibroblast cells are found on the natural tissue as early as 7 days but were not observed on the Dacron fabrics. Based on these findings, the Dacron fabric-covered diaphragm studied was not favorable for use in long-term implantation of cardiac prostheses.

Adsorption↗
PubMed1977

An efficient, compact and simple-to-use blood gas exchanger for long-term use.

The CCF folded coil membrane oxygenator has demonstrated a high capability for mass transfer both in vitro and ex vivo. The membrane-gas net interaction currently under investigation has indicated improved transfer with more controlled blood film thickness. The gas net being evaluated at this time in 3 layers: an open weave inner layer and net number 024 as a direct membrane support structure. No serious adverse effects of ex vivo bypass were found in 4 trials, and in long-term experiments, no deterioration of oxygenator performances could be found. The position of the oxygenator on the pump console and the absence of auxiliary frames, motors or pumps simplify operation of this device. It is felt that, following further detail refinement and ex vivo and clinical testing, this device can be presented as a suitable answer to the need for an efficient, simple to use, and versatile membrane oxygenator.

Animals↗
PubMed1976

A simple in vitro screening test for blood compatibility of materials.

An in vitro closed-cell kinetic blood-coagulation test was developed and used to evaluate the blood compatibility of materials. The test compares the clotformation rate on a test surface to that of a control material, Silastic. This method avoids anticoagulants, blood flow variations, and the exposure to air and other foreign surfaces. Eight pairs of cells are sequentially evaluated as to the weight of thrombus formed, the amount of unclotted blood, and the reduction in platelet count of the blood exposed to both the test materials and the control. These data are used to calculate a relative index whereby materials can be rated quantitatively as to the rate of clot formation on their surface. The order of decreasing clot formation on one group of materials studied was as follows: biolized (Imai et al., Trans. Amer. Soc. Artif. Int. Organs, 17, 6, 1973) poly (ether urethane), segmented polyurethane, formaldehyde-treated pericardium, Hydron, glutaraldehyde-treated pericardium, biolized natural rubber, Hexsyn, heparinized natural rubber, Silastic, and natural rubber. Urethane and aldehyde-treated natural tissue had a lower percentage of red thrombus formation. These results generally correlate with in vivo observations.

Biocompatible Materials↗
PubMed1975

Biodegradable material for bladder reconstruction.

The objective of this study was to develop a biodegradable material for use in reconstructive surgery of the bladder to serve a temporary function until normal regrowth of the host's tissue is completed. The biodegradable material can serve as a base over which the new bladder can regenerate. At the conclusion of the regrowth of the new tissue, the temporary material could be consumed by the body and therefore not have to be removed. Material evaluation showed that 70% acetic anhydride treated bovine pericardium was digested and dissolved in 4 weeks when implanted subcutaneously in dogs. Based upon this, supplementation of the bladder using this material was performed on 5 dogs. One dog showed urinary leakage and was sacrificed after 1 week. In 3 dogs examined 4, 6, and 48 weeks after implantation, respectively, the implanted material had been dissolved. In one animal autopsied at 10.5 months, a small remnant of the material still remained. Post-operative observation of the animals, excretory pyelocystograms and cystometry confirmed that the material applied was useful for experimental urinary bladder supplementation.

Acetates↗
PubMedDate not supplied

Effects of mechanical ventilation and spontaneous respiration on hemodynamics in calves with total artificial hearts.

The effects of respiration on hemodynamics were evaluated in four Holstein calves with total artificial hearts (TAH). The electrohydraulic actuated E4T-TAH has a continuously reciprocating actuator packaged between two alternately ejecting blood pumps that passively fill. The hemodynamic parameters (right atrial pressure [RAP], left atrial pressure [LAP], pulmonary artery pressure [PAP], aortic pressure [AoP]), and right and left pump filling (Rt% fill and Lt% fill) were measured when the animal was intubated and mechanically ventilated. These measurements were repeated with spontaneous respiration after the animal was extubated. With mechanical ventilation, LAP, PAP, and AoP were significantly higher during inspiration than during expiration. However, RAP during inspiration was slightly lower than that during expiration. The Rt% fill during inspiration was significantly lower than during expiration, but Lt% fill during inspiration was significantly higher than during expiration. During spontaneous respiration, these changes were opposite to those observed during mechanical ventilation. That mechanical ventilation generates positive intrathoracic pressure during inspiration, but spontaneous respiration generates negative pressure may explain these results. The change in venous return to the right atrium caused the change in RAP to be opposite in direction to that of the other pressures.

Animals↗
PubMedDate not supplied

Anatomic study for in vivo evaluation of a total artificial heart in calves.

A poor fit will negate any physiologic evaluation of an implantable total artificial heart (TAH). Fifteen Holstein calves (weight, 65-111 kg) were used to measure intrathoracic dimensions for TAH design, to find correlations between intrathoracic and external parameters for preoperative animal selection, and to suggest minor modifications for fitting a TAH in calf chests. The following dimensions were found to be critical to avoid compromising venous return: 1) mitral annulus center (MVC)-sternum, 10.4 +/- 1.0 cm; 2) tricuspid annulus center (TVC)-sternum, 9.8 +/- 1.6 cm; 3) MVC-TVC, 5.5 +/- 0.4 cm; 4) MVC-diaphragm, 3.4 +/- 0.8 cm; 5) MVC-left chest wall, 4.5 +/- 0.9 cm; and 6) TVC-right chest wall, 4.5 +/- 1.0 cm. These dimensions had no statistically significant correlation with body weight, but three of them did with the following external parameters: 1) bronchial carina-sternum on chest radiograph, p less than 0.05; 2) dorsoventral dimension at xiphoid, p less than 0.05; and 3) circumference at the caudal end of the scapula, p less than 0.05. Based on these results, the port orientation of the left housing of this electrohydraulic TAH designed for humans was modified for in vivo evaluation in calves. No other pump features required change. These data should prove useful to others involved in TAH development.

Animals↗
PubMedDate not supplied

Development of the E4T electrohydraulic total artificial heart.

A completely implantable total artificial heart (TAH) is being developed based on many years of research performed at the Cleveland Clinic Foundation and Nimbus, Inc. The pumping unit consists of biolized surface-treated pusher plate blood pumps powered by an interventricular electrohydraulic energy converter. A variable volume device references the back side of the pusher plates to lung pressure. Electrical power is supplied by a transcutaneous energy transmission system, integrated with a wearable external battery pack. An implanted internal battery provides back-up power. System design and optimization efforts have resulted in a compact pumping unit package and an overall TAH that meets anatomic, physiologic, and engineering requirements. Overall pumping unit basic dimensions are 98 mm diameter and 80 mm thick. The blood pumps have a truncated conical shape and are separated by a thin interventricular septum 21 mm thick. Theoretical stroke volume is 64 ml, and maximum stroke length is 13.2 mm. Normal pump operation is at 90% of full stroke, which yields a net output of 53 ml, with valve regurgitation taken into account.

Cardiac Output↗
PubMedDate not supplied

An intrathoracic left ventricular assist system: utilization of results from a development program.

An intrathoracic, electrohydraulically actuated, left ventricular assist system (LVAS) was subjected to formal device readiness testing. Endurance testing was initiated on eight systems before testing was halted due to failure of four of the systems. Three failed due to environmental leakage. Solutions were straightforward, involving gasket changes and o-ring resizing. The fourth failure involved a magnetic coupling piston swelling and seizing. The failure was attributed, after long investigation, to hydrogen adsorption by the samarium-cobalt magnets. An unknown number of coupling magnets were affected in this fashion, necessitating complete replacement of magnets to resolve the problem. However, this was beyond the scope of the program, and no further endurance testing was accomplished. The test experience of the Nimbus/CCF LVAS has demonstrated all functional aspects of the complete LVAS, both in vitro and in vivo, and the endurance and reliability potential is indicated as well. Although the LVAS program is currently inactive, its legacy of technical innovations continue to drive the development of other medical devices.

Animals↗
PubMedDate not supplied

Biolized intrathoracic left ventricular assist device (LVAD).

The design of an intrathoracic left ventricular assist device (LVAD) is briefly described. The unique feature of the LVAD is that all blood-contacting surfaces are biolized, having either chemically treated natural tissues or protein coatings. The blood-contacting surface of the housing is glutaraldehyde-treated pericardium and is covered with natural rubber and polyurethane. Tri-leaflet valves fabricated from human dura mater are used at the pump inlet; glutaraldehyde-treated bovine aortic valves are used at the outlet. The pumping diaphragm, made of polyolefin rubber with a textured surface, is coated with gelatin and treated with glutaraldehyde. Anticoagulants are not used with this device. Extensive in vivo and in vitro testing in the development of the pumps led to the current configuration having good performance, long life, and improved blood compatibility.

Animals↗