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At least 19 recordsLinked to original sources
PubMed1986

Concepts in assisted circulation.

Assisted circulation by extracorporeal and extracardiac bypass techniques must be based on the requirements of the heart and of the total body, though these may differ. The cardiac problem in cardiogenic shock is more likely to be a biventricular problem demanding decompression of both sides. Extra pulmonary oxygenation should be avoided because of complexity in long-term use. Principles of assisted circulation may be applied in an extra-thoracic temporary manner or as an intracorporeal long-term device without removal of the heart. We have compared a number of extracorporeal mechanical bypass techniques (left ventricular bypass, left atrial bypass, right atrial plus left ventrical bypass, and right atrial plus left atrial bypass) in dogs at different flow rates with control groups (nitroprusside, metabolic substrates, and no therapy) for survival during and after 4-hour treatment periods in a standard severe myocardial infarction preparation with biventricular failure. The left ventricle was cannulated in a retrograde manner. Right atrial bypass was mixed with oxygenated left ventricular blood before return without oxygenation. Results in 50 dogs revealed that without treatment 20% survived; left ventricular plus right atrial bypass provided 100% survival during the 4-hour treatment, whereas left ventricular bypass and nitroprusside were intermediate with approximately 70% survival. Respiration and acid-base balance were not significantly altered by right atrial bypass, which provided adequate decompression of the right ventricle. Flow rates of 50% of control levels were adequate to provide normal or increased peripheral circulation as well as decompression of both ventricles and maintenance of sinus or nodal rhythm. Left atrial or left ventricular bypass alone was unable to support the heart or circulation in severe failure. Hemodynamics, including total body perfusion, atrial pressures, and dP/dt were improved significantly only by left ventricular plus right atrial bypass, even though reduced rates of flow were used. Similar findings were seen in lactic acid, CPK, and oxygen consumption. The addition of metabolic substrates currently does not improve survival though they appear to act as metabolic modulators. We conclude that the principle of a low flow left ventricular plus right atrial bypass without an oxygenator offers a technique for long- or short-term assistance.

Journal Article↗
PubMedDate not supplied

[Axial micro-pump system of assisted circulation].

An assisted circulation system having a HART-02 axial-flow micropump has been developed. The diameter of the micropump is 7 mm and its length is 20 mm, which allows it to be introduced into the ascending aorta through a peripheral artery. The system has a good biocompatibility, a low hemolysis and its productivity is as much as 3.5 liter/min.

Assisted Circulation↗
PubMedDate not supplied

[Methods of cardiac synchronization in assisted circulation].

In assisted circulation cardiosynchronization should be regarded as a process of monitoring the arterial blood pressure within the limits of the cardiac cycle and changes of its form with the aim of improving the energy balance of the heart. The coordination of the pumping function and that of the cardio-vascular system comes to a problem of shaping the monitoring action that depends upon three variables, viz. the time lag tepsilon, actuation of the unit relative to the base cardiosignal, duration of the pumping phase tpi and the signal level at the pump's inlet U(t). A number of researchers consider tepsilon and tpi to be a function of the cardiac contractions period and determine them in different ways, employing for this purpose extrapolation, stochastic characteristics, etc. Of late, in addition to the period of cardiac contractions extremal, mean integral values of the systolic and diastolic pressure, the level of pressure at the instant of the cardiac valves closure and others have also come in use. There are shortcomings in the proposed cardiosynchronization algorhythms: their empiric nature and also the fact that the monitoring action includes merely variables tepsilon and tpi and does not carry function U(t), which reflects the intensity of the pump's operation.

Assisted Circulation↗
PubMedDate not supplied

[Feasibility of increasing the high-speed response of the electromechanical drive in assisted circulation devices].

The conditions in assisted circulation, especially with ballooned aorta, place high demands on the speed of the intraortal pump-balloon response. The salient feature of the described assisted circulation unit consists in that the intraortal pump-balloon is connected to the pneumotract via a commutative air-operated valve. A block diagram of the assisted circulation unit "Biopulso-4" based on the use of the electric drive, designed at the All-Union Scientific-Research Institute of Medical Equipment and Instruments, stress diagrams and a scheme explaining the operation of the apparatus, are described. The results obtained show the possibility of the balloon's resetting and opening in 70 ms, with the triggering synchronous pulse delay of 10 ms prior to response (with air use as power gas). These results are not any worse than those obtained with the pneumatic drive-based assisted circulation apparatus.

Assisted Circulation↗
PubMed1998

[Microcirculation of kidney and skin during left ventricular assisted circulation--comparative studies of pulsatile and nonpulsatile assists].

We examined microcirculation of the kidney and skin over a six-hour period in an acute myocardial infarction model in pigs. The outflow cannula was placed in the ascending aorta, the inflow cannula was placed the in left atrium, and a pump was connected to each (pulsatile group, Zeon Medical pneumatic pump; nonpulsatile group, Nikkiso HPM-15). Items examined included the regional blood flow of the cortex and medulla in the kidney and skin, renal and carotid arterial flow, arterial ketone body ratio (AKBR), lactate/pyruvic acid (L/P), BUN, creatinine, and beta 2-microglobulin. After the experimental study, the major organs were removed and a pathological study was performed. The mean aortic pressure after the assist could be maintained at about 100 mmHg. There were no significant differences between the two groups in mean aortic pressure and total cardiac output. Under assisted circulation, the pulse pressure was maintained at about 15 mmHg in the nonpulsatile group and about 40 mmHg in the pulsatile group. After the assist, there were no significant differences in the carotid arterial blood flow between the two groups. However, there were significant differences between the two groups in the renal arterial, renal cortical, and regional skin blood flows. In the laboratory data, there were significant differences between the two groups in AKBR, L/P, and beta 2-microglobulin. Pathological findings on the kidney in the nonpulsatile group showed expansion of the proximal tubes, retention of red blood cells, and expansion of blood capillaries within the glomerulus. On the other hand, the pulsatile group showed almost normal formation. In the lungs, the nonpulsatile group showed edematous change in the air cells and the pulsatile group showed almost normal formation. The results of the previous and current study indicated that the pulsatile assist produced superior circulation in the kidney and peripheral organs and superior cellular metabolism in the early treatment of acute left cardiac failure. On the other hand, nonpulsatile assisted circulation was found to be ineffective in maintaining the circulation in the body, and to be potentially capable of causing irreversible damage of major organs if continuous for more than three hours. The results also indicated that pulsatility was necessary to maintain normal circulation in the peripheral organs and cellular metabolism in the early treatment of acute left cardiac failure.

Animals↗
PubMed1990

[Experimental studies of assisted circulation using left-ventricular assist devices with the pneumatic system (LVAD)].

The results of short-term (acute) studies of assisting artificially produced (reversible) left ventricle insufficiency with an artificial, pneumatically driven left ventricle are discussed. Both mechanical left ventricle and driving devices are of Polish manufacture. The studies involved mongrel dogs and sheep and were fully hemodynamically and biochemically monitored. The results obtained with each design of the device were given to the producers. It seems that recent models are near to clinically acceptable ones and enable to assist left cardiac ventricle for a short time preceding elective transplantation of the heart.

Animals↗
PubMedDate not supplied

Direct measurement of pulmonary and systemic flow during assisted circulation.

During biventricular assistance as a bridge to cardiac transplantation, the flow data provided by the pumping systems were compared with flow data obtained with the Fick method. There was a difference between the data sets only in the first 20 hr of observation, with the Fick method giving higher values. During the same period, analysis of the arterial and pulmonary pressure traces showed pulsatile activity to be related with the electrocardiogram's T waves. In the long run, the flow data provided by both methods were no different and the T wave-related pulsatile activity disappeared. The authors concluded that the Fick method represents a useful tool when measuring total flow during biventricular support.

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PubMed1998

Measures to control blood activation during assisted circulation.

Major improvements in heart assist devices have allowed prolonged mechanical circulatory support with successful subsequent weaning or heart transplantation. The contact of blood with biomaterials used in life-sustaining devices and numerous biomaterial-independent factors elicit a systemic inflammatory response, which involves activation of various plasma protein systems and blood cells. Prolonged mechanical circulatory support elicits a systemic inflammatory response and hemostatic perturbations similar to that reported during cardiopulmonary bypass. However, in the setting of prolonged assistance, time has a complex and ill-known influence on blood activation. Methods to reduce blood activation during prolonged assisted circulation are derived from cardiopulmonary bypass investigations. Improving the biocompatibility of artificial devices can be achieved either by biomaterial surface modifications, by inhibition of biologic cascades leading to blood activation, or by controlling end points of biologic cascades. However, the necessity to respect the integrity of the organism during prolonged assistance precludes most systemic interventions and limits the control of blood activation to the area of the device.

Assisted Circulation↗
PubMedDate not supplied

[Assisted circulation during electrostimulation of the heart].

In the course of the assisted circulation combined with the electrocardiostimulation the comparative study has been carried out to estimate the following conditions of the cardiosynchronization for an assisted circulation device: a) at the R-wave on the patient's electrocardiogram, b) at the R-wave on the ECG when an artefact from the electrocardiostimulation is previously "cut", c) when the electrocardiostimulation pulse is used as that of the cardiosynchronization. A system for the assisted circulation is proposed where the cardiosynchronization is realized by a separator of the R-waves for the ECS, thus providing consistent cardiosynchronization under conditions of both electrocardiostimulation and restoration of the cardiac rhythm.

Animals↗
PubMed1990

[The most frequently used methods of assisted circulation].

An account of the most widely used mechanical synchronized types of assisted circulation for the control and management of circulatory failure. Intraaortal ballon counterpulsation is in specialized departments already a routine method. When comparing intraaortal ballon counterpulsation with the bypass method of volume relief of the ventricle, based on the bioenergetic index, the latter method of assisted circulation is more effective. The authors draw attention to the bypass method of assisted circulation involving transdiaphragmatic cannulation of the left ventricle--aorta by laparotomy, without thoracotomy.

Assisted Circulation↗
PubMedDate not supplied

[Methods and modern apparatus for assisted circulation. The basic trends in their development].

A systematization of methods for assisted circulation, based on the formulation of a concrete procedure, the nature of the deranged or lost function substitution and conditions for effective realization of such a substitution, is offered. This made it possible to classify the equipment for assisted circulation and to analyze the current trends of its further development. The most characteristic automation levels of the equipment under consideration and of generations of some apparatus, differing in the degree of automation, control and monitoring the process of assisted circulation, are presented in the form of tables and pictures.

Assisted Circulation↗
PubMed1991

Vital organ perfusion during assisted circulation by manipulation of intrathoracic pressure.

BACKGROUND: We have previously shown, in dogs with severe cardiac depression, that modest cyclic increases in intrathoracic pressure, starting synchronously with left ventricular isovolumic contraction, significantly increase aortic flow and pressure. However, little is known of changes in vital organ perfusion during this technique of assisted circulation. METHODS AND RESULTS: We studied regional organ flow using radioactive labeled microspheres in 13 20-25-kg mongrel dogs. In the control group, after chemical induction of cardiac depression with verapamil and propranolol, coronary flow fell from 129.1 +/- 14.4 to 51.6 +/- 11.3 ml/100 g/min (p less than 0.005) and continued to decline over a 14-minute time period (flow was 32.2 +/- 11.5 ml/100 g/min at 7 minutes and 20.7 +/- 9.5 ml/100 g/min at 14 minutes [n = 6]; all p less than 0.05). In the intervention group, regional blood flow was evaluated before and after the induction of cardiac depression and also during assisted circulation using 400-msec, 20-25-mm Hg intrathoracic pressure increases delivered by a circumthoracic pneumatic vest, starting synchronously with left ventricular isovolumic contraction. In the intervention group, coronary flow fell from 119 +/- 26.7 to 47.9 +/- 13.1 ml/100 g/min 1 minute after the induction of cardiac depression (p less than 0.005). With the initiation of assisted circulation, coronary flow increased to 55.8 +/- 19.2 ml/100 g/min at 7 minutes and fell to 23.1 +/- 15.9 ml/100 g/min on termination of assisted circulation at 14 minutes (p less than 0.05 and p = NS versus control group flows at 1 and 14 minutes, respectively). During assisted circulation, cerebral, renal, and small intestinal flows also increased (all p less than 0.05 versus flows during myocardial depression). No significant increase in hepatic flow was observed. CONCLUSIONS: In the canine model, manipulation of intrathoracic pressure appears to be an effective, short-term, noninvasive means of not only increasing aortic pressure but also increasing vital organ perfusion during cardiogenic shock. Further studies are needed to assess the usefulness of this technique of assisted circulation in humans.

Animals↗