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Biomedical subjects

A Massiello

Publications and source records attributed to A Massiello.

18 recordsLinked to original sources
PubMed2006

Hemolysis evaluation of centrifugal pumps using microcapsule suspension.

OBJECTIVES: Bovine and human blood has been widely used for in vitro hemolysis testing to evaluate centrifugal cardiac assist pumps. However, results from such tests are complicated by variations in the susceptibility of individual red blood cells to shear. The objective of this study was to evaluate the use of microcapsule suspension as an alternative to bovine or human blood for hemolysis testing. METHODS: Microcapsule suspensions of 100 micro m maximal diameter (average 79.1 micro m) with a polyurethane membrane were used. Each microcapsule contained a leuco dye, which was used to measure "hemolysis" in the suspension after exposure to mechanical stress. Six centrifugal pumps were used to measure and compare the hemolysis values of microcapsule suspensions, bovine blood and human blood. RESULTS: Correlations were significant between the hemolysis values measured using microcapsule suspensions and those using bovine blood (R = 0.965, p = 0.002) and human blood (R = 0.940, p = 0.005). CONCLUSIONS: Microcapsule suspension can be successfully used instead of blood to compare the relative hemolytic performance of centrifugal blood pumps.

Animals↗
PubMed1998

Cleveland Clinic continuous flow blood pump: progress in development.

The Cleveland Clinic continuous flow blood pump is the central element of our innovative ventricular assist system (IVAS). Recent progress has been made in the design/fabrication of a pulsatile mock loop, journal bearing materials testing, and evaluation of a system control algorithm. These results have allowed an acceleration of our program.

Algorithms↗
PubMed1996

Chronic nonpulsatile blood flow. II. Hemodynamic responses to progressive exercise in calves with chronic nonpulsatile biventricular bypass.

We investigated the effects of stepwise treadmill exercise on animal (calf) hemodynamic variables during chronic nonpulsatile biventricular bypass with ventricular fibrillation. Seven days was allowed for recovery from the effects of anesthesia and surgery; each animal's natural heart was then fibrillated. The pump flows were maintained at nominal rates of 90, 100, and 120 ml.kg-1.min-1 for 1 week each, with the order varying from experiment to experiment. A total of 30 incremental exercise tests were performed on five animals. No significant changes in mean aortic pressure were observed during nonpulsatile perfusion at the three nominal flow rates of nonpulsatile flow either before or during exercise. The systemic vascular resistance decreased significantly during exercise (from 705 +/- 22 to 547 +/- 81 dyne.sec.cm-5, p < 0.01, and from 604 +/- 25 to 510 +/- 15 dyne.sec.cm-5, p < 0.05, at nominal flow rates of 100 and 120 ml.kg-1.min-1, respectively). There were also significant (analysis of variance, Scheffe test, p < 0.05) differences in systemic vascular resistance among three nominal flow rates both before and during exercise. These results suggest that the autonomic nerve reflex control of the cardiovascular system in physical exercise was functioning normally in animals with chronic nonpulsatile blood flow.

Animals↗
PubMed1996

Chronic nonpulsatile blood flow. III. Effects of pump flow rate on oxygen transport and utilization in chronic nonpulsatile biventricular bypass.

The relationship between blood flow and oxygen transport was studied in five calves with chronic nonpulsatile biventricular bypass. Seven days was allowed for recovery from the effects of anesthesia and operation; the natural heart was then fibrillated. Pump flows were maintained at nominal rates of 90, 100, or 120 ml.kg-1.min for 1 week each, with the sequence varied from experiment to experiment. Venous and arterial blood samples were taken at rest for blood gas analysis. Serum lactate analysis was done twice a week, on the third and seventh days after each pump flow change. Serum catecholamine levels were assayed on the seventh day of each flow rate. Progressive exercise tests were also conducted during each test segment. Basal oxygen consumption of a 4-month-old calf was 6.3 +/- 0.3 ml.kg-1.min-1. The mixed venous oxygen tension decreased when pump flow rate was reduced (29.6 +/- 1.0, 28.3 +/- 1.2, and 23.8 +/- 0.9 mm Hg at 120, 100, and 90 ml.kg-1.min-1 of pump flow, respectively), and oxygen extraction increased linearly when pump flow rate was reduced. Hemoglobin concentration significantly affected oxygen extraction rate. Serum lactate concentration increased significantly at a 90 ml.kg-1.min-1 perfusion compared with concentrations at other pump flow rates (7.81 +/- 2.42 mEq/L at 90 ml.kg-1.min-1 vs 0.71 +/- 0.19 and 0.73 +/- 0.81 mEq/L at 100 and 120 ml.kg-1.min-1, respectively; p < 0.01, analysis of variance, Scheffe F test). Maximum oxygen extraction during exercise was 78%. These results suggest that a critical flow level between 90 and 100 ml.kg-1.min-1 maintains oxidative metabolism in the calf with chronic nonpulsatile flow. The resulting oxygen delivery was slightly higher than that indicated in the literature. Maximal oxygen extraction was normal.

Animals↗
PubMed1994

Chronic nonpulsatile blood flow. I. Cerebral autoregulation in chronic nonpulsatile biventricular bypass: carotid blood flow response to hypercapnia.

To investigate the response of the carotid blood flow and general circulation to hypercapnia in chronic nonpulsatile blood flow, we performed 18 carbon dioxide gas inhalation studies on three calves undergoing a centrifugal biventricular bypass with ventricular fibrillation. An ultrasonic flow probe was put on the carotid artery during biventricular bypass pump implantation, and pump flows were maintained at 90, 100, and 120 ml/kg per minute for 1 week each. The carbon dioxide inhalation studies were performed twice a week. Hypercapnia was induced by administering pure carbon dioxide gas through a nasal tube at flow rates of 0, 5, 7.5, 10, 12.5, and 15 L/min for 5 minutes each at three different nominal pump flow rates, and the resultant arterial blood gas and hemodynamic changes were recorded. No significant correlation existed between the carotid blood flow and mean aortic pressure, which varied from 70 to 140 mm Hg, but the carotid blood flow correlated significantly (p < 0.01) with the systemic pump flow rate. A significant (p < 0.01) linear relationship was found between the carotid blood flow and arterial carbon dioxide tension. For each 1 mm Hg change in arterial carbon dioxide tension, there was a 2.8 % change in the carotid blood flow. The percent changes in the carotid blood flow in response to arterial carbon dioxide tension were calculated as 2.9%, 3.7%, and 2.5% for each 1 mm Hg change in arterial carbon dioxide tension at pump flows of 90, 100 and 120 ml/kg per minute. No significant differences in the carotid blood flow response to hypercapnia were detected among the three systemic pump flow rates. These results thus suggested that chronic nonpulsatile blood flow had no detrimental effects on cerebral autoregulation.

Animals↗
PubMed1994

The Cleveland Clinic-Nimbus total artificial heart. Design and in vitro function.

We describe the design and in vitro testing of the Cleveland Clinic-Nimbus electrohydraulic permanent total artificial heart as it nears completion of development. The total artificial heart uses an electric motor and hydraulic actuator to drive two diaphragm-type blood pumps. The interventricular space contains the pump control electronics and is vented to an air-filled compliance chamber. Pericardial tissue valves and biolized blood-contacting surfaces potentially eliminate the need for anticoagulation. In vitro studies on a mock circulatory circuit demonstrated preload-sensitive control of pump output over the operating range of the blood pump: 70 to 160 beats/min and 5 to 9.6 L/min at right and left atrial pressures of 1.0 to 7.0 mm Hg and 5.0 to 12.0 mm Hg, respectively. The pump output was found to be insensitive to afterload over a range of 15 to 40 mm Hg mean pulmonary artery pressure and 60 to 130 mm Hg mean systemic pressure. The left master alternate control mode balanced the ventricular outputs during simulated bronchial artery shunting of up to 20% of cardiac output. A 10% to 15% right-pump, stroke-volume limiter balanced ventricular outputs during maximum output of 9.6 L/min. In response to a sustained increase in systemic venous return, the pump increased output by 2 L/min (29%) in 35 seconds. Thus the Cleveland Clinic-Nimbus total artificial heart meets the National Heart, Lung, and Blood Institute hemodynamic performance goals for devices being developed for permanent heart replacement. The biolized blood-contacting surfaces should decrease the risk of thromboembolism associated with circulatory assist devices.

Cardiac Output↗
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

In vitro and in vivo performance evaluation of a totally implantable electrohydraulic left ventricular assist system.

The biolized electrohydraulic left ventricle assist devices were tested in 14 calves with an average survival time of 162 days and as long as 250 days without the use of anticoagulants. In vitro, the system pumped 4.1 L/min at a low 4.8 mmHg fill pressure with a mean afterload of 100 mmHg and rate of 46 bpm. A flow rate of 13.5 L/min was observed at 155 bpm and 110 mmHg afterload. Motor frequency and current increased with increasing flow rate (162 Hz, 0.67 amp at 2.5 L/min; 484 Hz, 2.43 amp at 13.5 L/min). Flow rate did not change significantly with afterload pressure. The complete system was implanted in a 100 kg calf. Synchronization of the blood pump with the natural heart was demonstrated at heart rates of 85 to 167 bpm. The synchronized flow rate varied from 6 to 10.5 L/min despite the considerable heart rate changes and stroke variations. The system hemodynamic performances were acceptable and met NIH requirements.

Animals↗
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

Initial in vivo tests of an electrohydraulic actuated total artificial heart.

The authors are involved in developing a total artificial heart (TAH) for permanent human use. This device was designed to fit human anatomy, and it has housings made of carbon fiber-epoxy composite and titanium. Tissue valves and protein coating of blood contacting surfaces minimize the need for anticoagulants. A continuously reciprocating electrohydraulic actuator is packaged between two alternately ejecting and passively filling ventricles. The control system varies the pump rate to maintain average left ventricular filling at 90%. This TAH in vivo successively progressed through 1, 5, 9, and 45 day implants in calves of 84, 94, 82, and 82 kg preoperative body weights. The operating modes include automatic and fixed rate. The chronic and acute effects of varying the right pump displaced stroke volume indicated the need for it to be limited to 85% of that of the left for stable hemodynamics at maximum flow. The pump exhibited afterload insensitive and preload sensitive performance. Pump output ranged from 4.0-9.5 L/min at left atrial pressures of 7-16 mmHg at pump rates of 80-160 beats/min in these four experiments. These data suggest that this device will meet clinical hemodynamic requirements; it has the potential for total implantable cardiac replacement.

Animals↗
PubMedDate not supplied

Adaptation of tissue to a chronic heat load.

Determination of the chronic effect of heat on tissue is one of the important issues facing mechanically actuated total artificial heart (TAH) development. In an effort to characterize this effect, implantations of heating devices producing constant heat fluxes of 0.04 watts/cm2, 0.06 W/cm2, and 0.08 W/cm2 were performed in 11 calves (H-series). Heated disks were implanted adjacent to lung and muscle tissue for a period of 7 weeks. Temperature sensors were placed at the surface as part of the heater assemblies. The results showed that initially, temperature elevations above body temperature (delta T) were 6.4 +/- 0.6 degrees C, 4.5 +/- 0.2 degrees C, and 1.8 +/- 0.5 degrees C at the muscle heater surface for 0.08, 0.06, and 0.04 W/cm2, respectively. At 2 weeks after implant delta T values changed to 5.5 +/- 0.6 degrees C, 3.4 +/- 0.2 degrees C, and 1.8 +/- 0.2 degrees C, respectively. Seven weeks after implant, delta T values decreased to 3.7 +/- 1.2 degrees C, 2.8 +/- 0.1 degrees C, and 0.8 degrees C for 0.08, 0.06, and 0.04 W/cm2, respectively. The authors think this change is attributable to an adaptive response of the tissue to increase heat dissipation through angiogenesis. Results from three TAH cases indicated that at two measured tissue interfaces, delta T decreased by 1 degrees C during a 15 day period. At the same time, the waste heat (volts x current in-flow x afterload to the blood) remained constant at 11.1 +/- 0.5 W during this period. This decrease in delta T corresponded to that observed for the H-series experiments at the higher heat fluxes. Thus, it appears that adaptation observed in the H-series experiments also is seen for tissues surrounding heat sources such as the TAH.

Adaptation, Physiological↗
PubMedDate not supplied

A comprehensive hematologic study in calves with total artificial hearts.

Thromboembolism and infection remain potential threats for long-term circulatory assist and replacement devices. The alteration of the hemostatic system and of blood cell functions caused by device implantation may predispose the recipient to these complications. Many sensitive coagulation assays and the technology of flow cytometry would be powerful tools for this investigation. The availability of such immunologic technologies for animal species other than humans has yet to be established. In a series of in vitro tests we found that the following assays, among others, are usable in calves: TAT, TxB2, platelet surface glycoprotein IIbIIIa, and membrane aminophospholipid. F1.2, D-dimer, beta TG, PF-4, and platelet surface expression of GMP-140 and receptors for fibronectin, thrombospondin, and vWF were not measurable. A sustained mild decrease in hematocrit levels in six calves with the Cleveland Clinic-Nimbus total artificial heart for 11-120 days was attributed to an increase in circulating blood volume, but not to red blood cell damage. Whole blood platelet aggregation was suppressed only for the first 3 post operative days, with decreased GPIIbIIIa expression. Polymorphonuclear phagocytosis, chemotaxis, and superoxide anion production were not altered. Device infection and thromboembolism occurred in one of 13 cases overall.

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

Continuing development of the Cleveland Clinic-Nimbus total artificial heart.

A completely implanted total artificial heart (TAH) is under development by Nimbus, Inc., and the Cleveland Clinic Foundation (CCF). Key features of the system include an electrohydraulic energy converter, an automatic control system that produces a Frank-Starling response, and dual ventricles composed of graphite-epoxy and titanium with gelatin blood contacting surfaces. The system is controlled by a single substrate, hybridized microcircuit (the hybrid). Fabrication of the TAH control hybrid has recently been completed and testing begun. Its design emphasizes simplicity, reliability, and efficiency. Particular attention was given to optimizing thermal management. Externally controlled TAH systems have been used in eight in vivo experiments of up to 120 days' duration. In the last two of these experiments, a variable volume device was also implanted with excellent results. In vivo use of the system has demonstrated the Frank-Starling pump response, but the systems quickly reach maximum output with the bovine animal models. Human fitting studies, including adult patients undergoing heart transplantation, demonstrated satisfactory fit of the pump within the pericardium without compression of the vascular structures or chest wall. Measurements of chest circumference, plain chest films, and transesophageal echocardiograms should provide reliable predictions of pump fit in the majority of patients.

Animals↗
PubMedDate not supplied

Progress in Cleveland Clinic-Nimbus total artificial heart development.

A totally implantable, Cleveland Clinic-Nimbus total artificial heart (TAH) uses electrohydraulic energy conversion and an automatic left master-alternate mode control scheme, with a filling sensitivity of 1.0 l/min/mmHg and a maximum output of 9.5 l/min. The TAHs were tested in 12 calves for 1-120 days with normal major organ and blood cell function. Post-operative suppression of platelet aggregation recovered by the second post-operative week. The gelatin-coated pump surface generally was clean without any anticoagulants and free from infection. Embolism, which occurred in two cases, was caused by complications attributable to fungal infection in a Dacron graft and by thrombus formed around a jugular vein catheter. A system with a hybridized microcircuit controller in the interventricular space has been tested successfully in the three most recent cases, with a peak device surface temperature elevation of 6.5 degrees C. Heat effects were confined to the tissues immediately adjacent to the hottest spots. The carbon fiber-reinforced epoxy housing and 60 ml butyl rubber compliance chamber showed good tissue compatibility with a thin, fibrous tissue capsule. The transcutaneous energy transmission system and the internal battery functioned well as designed in the most recent animal implant.

Animals↗