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Biomedical subjects

L K Fujimoto

Publications and source records attributed to L K Fujimoto.

18 recordsLinked to original sources
PubMed1988

The E4T electric powered total artificial heart (TAH).

The E4T is a totally implantable total artificial heart (TAH) resulting from many years of research work at the Cleveland Clinic Foundation (CCF) and Nimbus, Inc. It consists of four implanted subsystems: the pumping unit, the variable volume device, the transcutaneous transformer, and the internal battery. The pumping unit consists of two CCF biolized pusher plate pumps, and a Nimbus electrohydraulic energy converter. The control logic is based on a left master, alternating beating scheme. The timing difference between end right eject and end left fill determines the actuator speed adjustment. The pumps free fill, so left-right flow differences are easily accommodated. A prototype system has been built and begun testing to validate and refine the design details.

Electric Power Supplies↗
PubMed1987

A technique for apex cannulation without extracorporeal circulation.

A simple, fast, and highly reliable technique for apex cannulation without extracorporeal circulation is presented as a result of more than 30 left ventricle assist device implants performed in calves in the last 4 years at the Cleveland Clinic Foundation. Minimal bleeding and reduced risk of ventricular fibrillation, air emboli, muscle flap, and trauma to the heart have made this technique very unique and highly applicable to any investigative laboratory, as no special tools or expensive apparatus are required. The practicality of the technique is immediately applicable to the clinical level to avoid potential complications with cannula insertion.

Animals↗
PubMed1985

Anatomical considerations in the design of a long-term implantable human left ventricle assist system.

A permanently implantable left ventricle assist system (LVAS) is being developed and is planned to be implanted in the left chest cavity against the chest wall with the electrohydraulic energy converter placed in a resected rib space. The inflow and outflow pump ports are connected to the left ventricle (LV) apex and to the descending aorta, respectively. Three additional major components of this system consist of the transcutaneous energy transmission system (TETS) (Thermedics), the variable volume device (VVD), and the internal battery. To finalize the design of this integrated system, key anatomical information was obtained by a special radiographic and angiographic study of 31 adult men with a varying degree of coronary artery disease and myocardial dysfunction. These data were combined with the previous computed tomography study by using a standard vertical reference system. The resultant integrated data, which consist of the three-dimensional chest model, the LV apex and axis orientation, rib orientation, chest wall thickness, and the descending aorta location, were used to define the design and anatomical locations of the inflow and outflow pump ports, the VVD, the pump and energy converter orientation, the TETS, and the internal battery. The most critical component for the design was found to be the inflow system. With regard to the average coronary disease patient, an anatomically practical configuration was demonstrated to exist for the presently proposed LVAS. Design flexibility was allowed for some of the critical components in order to fit the system in a large number of patients regardless of the stage and type of the underlying disease.

Adult↗
PubMed1984

Human thoracic anatomy based on computed tomography for development of a totally implantable left ventricular assist system.

Human thoracic anatomy was studied using computed tomography (CT) for the development of a totally implantable electrohydraulic left ventricular system [Nimbus, Inc., and The Cleveland Clinic Foundation (CCF)]. To obtain statistical dimensional information for the chest wall, apex of the heart, and aorta, routine calibrated CT scans of 18 men and 17 women were analyzed. A special radiopaque vest was worn by the patient just prior to the scanning and X-ray procedures, so that each transverse scan could be assigned to a specific chest level after combination with a standard vertical referencing system set on the patient's radiogram. A polar coordinate system and direct measurement of transverse distances from the vertical column to points on the chest wall were employed to define collectively the shape and size of the intrathoracic surface of the chest wall. Locations of the aorta and apex were described by measuring their normalized distances from the midline and vertical column to the intrathoracic surface of the lateral and anterior chest wall. The radius of curvature of the intrathoracic wall lateral to the left ventricle was determined to be approximately 10.4 cm for the average adult male chest. The present CCF intrathoracic pump with this curvature fits fairly well in both the average and individual thoraxes of these adult males. The location of the aorta, particularly of the descending aorta, was used to determine the optimal outlet design. The most critical anatomical area was the apex location. For adult males, an average distance of 2.8 cm from the apex to the internal chest wall was found. Because of this small dimension, careful design of the inflow port is being performed to avoid anatomical mismatch.

Adult↗
PubMedDate not supplied

A biolized implantable ventricular assist device compatible with IABP console.

A low pressure pneumatic pusher plate blood pump was developed for temporary right, left, or biventricular assist. Important features of this pump are its 1) driveability by the standard, easily available intraaortic balloon pump (IABP) console; 2) gelatin coated internal surface for blood compatibility; 3) essentially flat disc shape, 3 cm thick and 11 cm in diameter, for optimal anatomic fit; and 4) unique pusher plate guide mechanism to ensure linear motion without deflections of the diaphragm, and consequent uniform flow distribution into the pump. The guide telescopes into itself to avoid a housing protrusion for easy implantability; this controlled movement also provides a number of performance, control, and diagnostic benefits. The pump's 60 ml displacement gives up to 4.7 L/min at 80 bpm and 6.7 L/min at 120 bpm outputs in a mock loop. This VAD has been implanted in two calves for 43 to 84 days, continuously driven by a Datascope IABP console. An average 5 L/min pump output has been observed in both synchronous and fixed rate modes. No anticoagulation was required. We expect extensive clinical use of this VAD, based on its reliability, low cost, and simplicity.

Animals↗
PubMedDate not supplied

Sustained heart failure induced by repeated microsphere injections for left ventricular assist device testing.

A subacute to chronic heart failure model was established to test left ventricular assist device (LVAD) systems. Five calves were anesthetized and instrumented. Heart failure was induced by daily injection of polystyrene microspheres (37-70 microns) into a left coronary catheter. The last three animals had an atrio-aortic pulsatile LVAD implanted. Cardiac output (CO) decreased from 12 to 5.5 L/min, and SV from 120 to 60 ml, whereas left atrial pressure (LAP) increased from 12 to 25 mmHg within 10 to 20 days in the two animals without LVAD support. Both animals stopped eating and drinking. The LVAD experiments were terminated after 5, 10, and 11 days. Cardiac function was determined during daily pump-off tests. After repeated microsphere injections, LAP increased to 30 and 50 mmHg, and CO decreased to 4 and 6 L/min without pump support. Daily stepwise microsphere injections induce a sclerotic cardiomyopathy in a safe and reliable manner.

Animals↗
PubMedDate not supplied

Long-term in vivo study of gas diffusion in bilaminar compliance chambers.

The problem of gas diffusion from compliance chambers in long-term pulsatile blood pump implantation continues. To evaluate and predict gas diffusion at the intrathoracic tissue interface, eight air-filled static bilaminar compliance chambers were implanted in four calves for a mean duration of 191 days. Mean volume loss was 40.3 +/- 6.2 ml (0.2 ml/day) compared with previous results of 1.2 ml/day for pure Hexsyn diaphragms. The residual gas in the chamber was analyzed as nitrogen = 89.6 +/- 0.6%; oxygen = 1.5 +/- 1.1%; and carbon dioxide = 8.8 +/- 0.6%. The resulting gas composition is assumed equivalent to that of the tissue interface and was used in developing a diffusion model. For a complete left ventricular assist system (LVAS), gas diffusion at the arterial blood and tissue interface was simulated. The predicted time to reach a minimum volume of 90 ml (compliance volume equal to full pump stroke volume) was in excess of 1 year.

Animals↗
PubMedDate not supplied

Methods for volume assessment of an air filled compliance chamber.

The air-filled (120 ml) compliance chamber employs a Dacron covered Hexsyn-butyl bilaminar diaphragm to minimize gas diffusion. Finite permeability dictates the need for a means to detect the remaining air volume and a refill port for gas addition. X-ray studies were used to detect radiopaque chamber markers in cadavers. Tangential X-ray cinematography enabled detection of chamber volumes less than 100 ml and diaphragm center deflection predicted volume to within +/- 6 ml of the actual volume. An electrically driven left ventricular assist pump (90 cc) was used to evaluate motor current (MC) and intracompliance pressure (IP) as indicators of low compliance volume. Peak MC was a function of both hemodynamic output power and compliance volume. Thus, if the peak current for a given hemodynamic output is known, variances may be indicative of low compliance volumes. The cyclic minimum IP vs. volume was +1, -3, and -13 mmHg for compliance volumes of 120, 90, and 80 cc, respectively. Ejection velocity did not significantly affect IP. In conclusion, X-ray studies and MC are useful as noninvasive means of assessing the need for compliance refill. IP, though measured invasively, is the most sensitive volume-dependent parameter.

Cineradiography↗
PubMedDate not supplied

Systemic and local effects of heat dissipation in the thermally powered LVAS.

A thermally powered left ventricular assist system (LVAS) requires 20 W of heat dissipation either to the blood or to the surrounding tissues, such as the lung subcutaneous tissues. Postoperative systemic and local effects of heat dissipation were studied in 5 thermally powered LVASs and 2 heated blood pumps implanted in calves, and compared with 10 pneumatically powered left ventricular assist devices (LVADs). Postoperative mean temperatures of the heat dissipation group were as follows: 1. rectal (RT), 39.1 x 0.4 degrees C (NS versus control); 2. Lung interface, 41.6 +/- 0.6 degrees C (P less than 0.01 versus RT); 3. tissue interface, 40.2 +/- 1.2 degrees C (P less than 0.01 versus RT); and 4. blood, 39.2 +/- 0.8 degrees C (NS versus RT). There was no significant postoperative change in heart rate, respiratory rate, or rectal temperature between the two groups. No difference was shown between the two groups in hematologic parameters, plasma free hemoglobin, liver and renal function, fibrinogen levels, or coagulation processes at the same postoperative time. Heat dissipation to the pump-blood interface promoted a thinner neointima when compared with the nonheated surface. Angioneogenesis was observed in the tissue capsule adjacent to the heat dissipating surface. These results indicated that the thermal LVAS induced no deleterious local or systemic effects on recipient animals.

Air↗
PubMedDate not supplied

Development of an epicardial circulatory assist device.

The overall purpose of this project was to develop a circulatory assist device that could be used as a bridge to heart transplantation. Although heart muscle damage was one of the disadvantages with the original epicardial assist devices, as long as no bleeding occurs, such trauma would be of secondary importance in this particular application. The development of the proposed epicardial circulatory assist device (ECAD) was evolutionary in nature, with the second prototype design based on the lessons learned from that of the first. In vivo results from both phases of the project are reported. ECAD prototype 1 (ECAD-1) was composed of a flexible outer housing and two driving balloons. Fixation to the heart was adjustable for various heart sizes using Velcro fasteners. The design of the ECAD prototype 2 (ECAD-2) was based on the results of ECAD-1. Fixation to the heart was accomplished by suturing the outer housing onto the heart along the anterior descending artery and at the posterior atrioventricular groove. Each device was tested in five dogs. ECAD-1 was able to maintain the systemic circulation for 5 hours. However, unstable fixation and myocardial damage due to rubbing were the major problems. ECAD-2 passive effects on natural heart filling were acceptable. Under conditions of severe heart failure, a flow of more than 85% of control was obtained with a driving rate of 90-110 beats/min and 30% systole. The longest pumping was conducted for 8 hours. The ECAD was demonstrated to be a device useful in assisting the failing heart for short periods. Proper design will play a fundamental role in successful extended use.

Animals↗
PubMedDate not supplied

Development of a completely implantable total artificial heart.

In conjunction with engineering and physiologic requirements, anatomic fit is a fundamental problem that must be carefully addressed in the design of a truly feasible implantable total circulatory support system. To facilitate the conceptualization, a three-dimensional anatomic model of an average adult thorax was developed from a data bank of 14 human cadavers, 100 radiographs, 18 computerized tomographs, 4 nuclear magnetic resonance (NMR) studies, and 31 cineangiograms. The location and orientation of the valves, the atrial chambers, venae cavae, and pulmonary hili were found to be the most critical information. As a result, configuration of a one piece, completely implantable total artificial heart (E4T system) with the hydraulic actuator placed between the two ventricles was defined and sized to provide an output of 8 L/min at 120 beats/min. The device was designed to be positioned through a midsternotomy similar to the natural ventricles (in the pericardial sac toward the left chest cavity), and the ports were carefully designed to eliminate the risk of compression of critical cardiovascular structures. Validation of the design was conducted with an E4T model implanted in three human adult cadavers, two of which were submitted to NMR imaging after the device was implanted and the incision closed. Excellent fit was observed in all cadavers, and analysis of the several sagittal, transverse, and coronal NMR images showed no compression of the natural internal structures.

Heart, Artificial↗