RESUMEN
An electrohydraulic total artificial heart (EHTAH) has been developed and evaluated by long-term in vivo studies. The EHTAH is composed of blood pumps with an interatrial shunt (IAS), an energy converter, and electronics. The EHTAH with external electronics was implanted in four calves weighing from 81-90 kg. Two animals died on the 1st and 5th post operative days, the third animal survived for 32 days, and the fourth for 159 days. The IAS was free of thrombus at autopsy in all animals. The longest surviving animal increased in size from a pre operative weight of 81 kg to 134 kg on day 144. Cardiac output ranged from 9.3 to 10.5 L/min, whereas right and left atrial pressures increased with the calf's growth from 4-10 to 16-20 mmHg and from 8-14 to 18-22 mmHg, respectively. The animal favorably tolerated up to 3.4 km/hr of treadmill exercise, both hemodynamically and metabolically. The elevation of atrial pressures during treadmill exercise was significantly alleviated by employing an automatic control mode. It is concluded that the device has the potential to be a totally implantable system for permanent use.
Asunto(s)
Corazón Artificial , Hemodinámica/fisiología , Animales , Presión Sanguínea/fisiología , Peso Corporal/fisiología , Gasto Cardíaco/fisiología , Bovinos , Diseño de Equipo , Prueba de Esfuerzo , Masculino , Procesamiento de Señales Asistido por Computador/instrumentaciónRESUMEN
A recently designed blood pump subsystem for the completely implantable electrohydraulic total artificial heart (EHTAH) has been developed and is under evaluation. The subsystem consists of joined left and right ventricles, atrial cuffs with an interatrial shunt (IAS), and two outflow grafts. The ventricles were developed to fit within the pericardial space based on the results of anatomic fit trials. An optimized configuration for animal use, which was adaptable for human use with minimal modification, was identified. The core dimensions of the ventricles with an energy converter are approximately 10 x 11 x 7 cm. Maximum output and stroke volume are 9.2 L/min and 81 ml, respectively. The IAS is used to balance the volumetrically coupled EHTAH, and is made by forming an orifice in the common septum of the left and right atrial cuffs. Performance and durability of the IAS were examined in animal experiments for up to 9 days. The diameter of the IAS was 3.4-5.5 mm, and the left-right atrial pressure difference ranged from 2 to 10 mmHg, with 0.57-1.48 L/min of theoretically calculated shunt flow. No evidence of thrombus formation was found in or around the IAS at autopsy. The entire EHTAH system with a new blood pump is being assembled for long-term animal studies.
Asunto(s)
Corazón Artificial , Animales , Función Atrial , Ingeniería Biomédica , Bovinos , Circulación Coronaria , Electrónica Médica , Estudios de Evaluación como Asunto , Atrios Cardíacos/cirugía , Corazón Artificial/efectos adversos , Humanos , Técnicas In Vitro , Diseño de PrótesisRESUMEN
Since the early 1980s, a rapid increase in successful pediatric heart transplantation has improved the chance of survival for many children suffering from otherwise fatal cardiomyopathies or congenital cardiac defects. During the last 5 years, heart transplantation in neonates and infants (0-28 days and 1-12 months, respectively) has been the most rapidly growing area within the pediatric patient population. No adequate mechanical circulatory support system, designed to be used as a bridge to transplantation, is available for many of these pediatric patients. Neonates are the smallest candidates to potentially benefit from heart transplantation, and their often acute need for either heart transplantation or temporary circulatory support indicates that any new development of a pediatric bridging device should focus on this youngest group. Subsequently, such a device may be modified to any weight or age group. An innovative total artificial heart design was developed in an attempt to meet the anatomic and physiologic requirements of neonates and infants. This report discusses the rapidly growing pediatric heart transplantation patient population, as well as an innovative total artificial heart design.
Asunto(s)
Cardiopatías Congénitas/cirugía , Corazón Artificial , Hemodinámica/fisiología , Presión Sanguínea/fisiología , Gasto Cardíaco/fisiología , Diseño de Equipo , Humanos , Recién Nacido , Proyectos PilotoRESUMEN
In vitro tests were performed to evaluate the use of an interatrial shunt in balancing a dual energy converter, actively filled, volumetrically coupled, electrohydraulic total artificial heart. The in vitro atrial shunt was comprised of a 8 mm (PTFE) Teflon graft placed between the left and the right atrium. Other features under study were 1) cardiac output (CO) response to preload, 2) CO relationship to mean aortic pressure, and 3) balance of ventricular outputs. The tests were performed by varying the right filling pressure and monitoring ventricular output and inflow/outflow pressures. Effects of changes in afterload were simulated by varying the (AoP) pressure from 80 mmHg to 120 mmHg, and the (PAP) pressure from 15 mmHg to 40 mmHg. The test results indicated a rise in CO from 4 L/min to 9 L/min, with a change in mean right atrial pressure from 0 mmHg to 12 mmHg. No significant difference in CO was found as afterload pressures were varied. The interatrial shunt (IAS) was effective in establishing ventricular balance over a wide range of preload and afterload conditions, and a mean positive flow from left to right was maintained in the atrial shunt, even at conditions simulating an extreme left-right imbalance.
Asunto(s)
Atrios Cardíacos/fisiopatología , Corazón Artificial , Hemodinámica/fisiología , Velocidad del Flujo Sanguíneo/fisiología , Presión Sanguínea/fisiología , Prótesis Vascular , Gasto Cardíaco/fisiología , Diseño de Equipo , Humanos , Modelos Cardiovasculares , Transductores de PresiónRESUMEN
An electrohydraulic total artificial heart (EHTAH), using an interatrial shunt (IAS) for right-left heart balance, was evaluated in acute, in vivo, open-chested calves. The EHTAH system demonstrated physiologic autoregulation with Starling-like responsiveness to preload. Output varied from 4 to 9 L/min, as right atrial pressure increased from 3 to 15 mmHg. Device output was minimally influenced by afterload. The efficacy of an IAS to balance the EHTAH was demonstrated over a wide range of preload and afterload conditions. Interatrial shunt flow rates, reflective of the degree of right-left imbalance, varied from 2% to 14% (IAS flow from left to right) of cardiac output. Left atrial pressures typically did not exceed right atrial pressures by more than 6-8 mmHg using an instrumented vascular graft such as the IAS. The simplicity and distinct anatomic, surgical, and engineering advantages of the IAS approach to right-left balance of implanted electrically powered artificial hearts justify further development toward a reliable long-term design.
Asunto(s)
Suministros de Energía Eléctrica , Corazón Artificial , Hemodinámica/fisiología , Animales , Presión Sanguínea/fisiología , Gasto Cardíaco/fisiología , Bovinos , Diseño de EquipoRESUMEN
A new biocompatible hermetically sealed electric wire feedthrough has been developed for use in a totally implantable artificial heart (TAH) and ventricular assist device (VAD). This feedthrough allows electric current to pass through a rigid polyurethane (Isoplast 301, Dow Chemical U.S.A., Midland, MI) housing wall. The implantable housing is exposed externally to tissue and body fluids and is filled with low viscosity silicone oil (decamethyltetrasiloxane) which acts as a hydraulic fluid. The feedthrough prevents fluid transfer which caused early prototype devices to fail. The feedthrough consists of external and internal wires insulated with soft segmented polyurethane (Biomer, Ethicon, Somerville, NJ) and soldered to opposite ends of a conductive pin. The pin and the wire connections are encapsulated in Biomer, forming a leak-free barrier between the housing wall and the wire insulation. The pin soldered between the two wires prevents leakage from between the strands and the insulation.
Asunto(s)
Materiales Biocompatibles , Corazón Artificial , Animales , Bovinos , Electrónica , Diseño de EquipoRESUMEN
The in vitro development of automatic control of the actively filled, alternately pumped, volumetrically coupled, electrohydraulic total artificial heart was the goal of this investigation. Control features under study were (a) cardiac output (CO) response to preload; (b) CO relationship to mean aortic pressure (AoP); and (c) control of balanced ventricular outputs. A modified pulmonic valve to increase backflow was used as a balancing mechanism. Hydraulic fluid pressure transducers monitored diastolic pressures, and microprocessor control of motor speed maintained in a mild suction to yield filling rate dependent on atrial pressure. Results indicated a rise in CO from 5 to 9 L/min, with a change in mean right atrial pressure (RAP) from 0 to 7 mm Hg. No significant difference in CO was found as AoP was varied from 80 to 120 mm Hg with a maximum variation of +/- 0.5 L/min on CO and +/- 1 mm Hg on RAP. Balance was maintained for bronchial flows up to 50% with mean left atrial pressure never exceeding 15 mm Hg. An alternately pumped electrohydraulic heart was automatically controlled to respond sensitively to preload changes. Afterload changes did not alter the CO response curve. Automatically controlled, balanced ventricular outputs were maintained.