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PubMed1989

Circulatory Support 1988. Weaning and bridging.

After a patient has been supported with a circulatory assist device, the expected outcomes are weaning, bridging, or discontinuation of support. An early insertion of the device will avoid deterioration of the heart and other organs to an irreversible condition. Cardiac assistance for a minimum of 24 hours is recommended with a mild dose of anticoagulant. It is necessary to monitor the hemodynamic functions during circulatory support and weaning. Most of the mechanical devices are quite reliable, and complications during ventricular assist are easily managed. The patient should be in the same condition as in ordinary elective transplant candidate before transplantation. Patients with an artificial heart or ventricular assist device should not be on the priority emergency list for cardiac transplantation. Patients suffering from cardiogenic shock can be stabilized with a ventricular assist device to allow the heart to recover or be provided with other treatment. A circulatory support device can also be used as a bridge for patients awaiting a cardiac transplant.

Assisted Circulation↗
PubMed2004

Mechanical assist devices as bridging systems to transplantation: A current review, possible risks, and perspectives.

Mechanical circulatory support is of increasing interest because of its considerable demographic importance concerning myocardial failure and because of stagnant transplantation volumes. This study offers an overview of the present state of the art. Institutions with a mechanical circulatory assist program usually dispose of a decision chart for the various systems. There are devices with intra- or extracorporeal pump positions and with long- or short-term application. The various possibilities of mechanical circulatory assistance are presented, along with their technical properties, indications, and results. Currently, the application is concerned with technical reliability and limited biocompatibility with thrombembolic, neurological, and infectious complications. With some further developments, the present state of the art is supposed to enable a widespread application as bridging systems and as long-term therapy of heart failure within the next few years.

Anticoagulants↗
PubMed2000

Implantable left ventricular assist systems (LVAS): recent results. A report from a series of meetings sponsored by the Study Group on Advanced Heart Failure of the Working Group on Heart Failure.

Implantable left ventricular assist systems (LVAS) consist of implantable pumps with small control consoles and power sources that can be worn externally. These systems provide far greater patient mobility and independence than external pumps with bulky control consoles. Patients with implantable LVAS can be discharged from hospital and are able to return to work and resume active sports. Most patients have received these systems as a bridge to heart transplantation. Clinical status and quality of life improve dramatically after device implantation and survival on support (60-70% after approx. 100 days of support) is acceptable compared with transplant candidates on medical therapy. Patient selection and adverse events, primarily bleeding, thromboembolism and infection, are important issues with LVAS. In the future, long-term support and bridging to myocardial recovery may become important indications for LVAS.

Adolescent↗
PubMedDate not supplied

Determinants of clinical results of mechanical circulatory support for ventricular failure after cardiotomy.

To clarify determinants of clinical results of circulatory support for ventricular failure after cardiotomy, we examined 53 patients (33 men and 20 women) who underwent circulatory support for post operative heart failure from 1984 to October 1995. Their ages ranged from 22 to 74 years (mean, 51 years). In 53 patients, 32 had valvular, 19 had ischemic, and 2 had congenital heart disease. After operation, 21 patients underwent venoarterial bypass, 20 underwent biventricular bypass, and 8 underwent left ventricular bypass. The remaining 4 patients received a pulsatile left ventricular assist device. Weaning and discharge rates of the patients by type of support were 52.4% and 28.6% with venoarterial bypass, 75.0% and 55.0% with biventricular bypass, 87.5% and 37.5% with left ventricular bypass, and 75.0% and 50.0% with left ventricular assist device, respectively. The results of this series (67.9% weaning rate and 41.5% discharge rate) were acceptable. Peri-operative variables before and during circulatory support were analyzed multivariately by logistic regression analysis. Selected independent determinants (odds ratio) of significant difference (p < .05) were type of support (7.547) for non weaning and pre support cardiogenic shock (17.246), and type of support (8.780) and support duration (1.487) for mortality. These results suggest that early application before profound shock and appropriate selection of type of support might be key factors in successful circulatory support for ventricular failure occurring after cardiotomy.

Adult↗
PubMedDate not supplied

Symbion acute ventricular assist device: nursing challenge.

A cardiac patient is rapidly deteriorating and facing imminent death. The medical team decides to insert an experimental ventricular assist device (VAD) to perform the work of the dying heart. How can the critical care nurse best care for a patient with this challenging and unyielding diagnosis?

Assisted Circulation↗
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↗
PubMed1987

Effect of left ventricular assist device (LVAD) on myocardial pH change after regional coronary occlusion.

To evaluate the effect of an assist pump on the metabolic viability of the ischemic myocardium, myocardial pH was continuously monitored using an ion-sensitive field-effect transistor (ISFET) pH sensor in 14 dogs after coronary occlusion. In seven dogs (control group), coronary occlusion (10-20 min) and successive reperfusion (30-60 min) were performed several times. In seven dogs [left ventricular assist device (LVAD) group], the LVAD was implanted between the left atrium and the aorta. Occlusion and reperfusion were performed first with the pump on and then with the pump off. In both groups, myocardial pH fell after occlusion, and increased after reperfusion. In the control group, the fall rate of pH in the later coronary occlusion decreased to 66 +/- 7% (mean +/- SEM) of that in the previous occlusion. Contrarily, in the LVAD group, the fall rate under LVAD-off increased to 174 +/- 32% of that under the preceding LVAD-on. This indicates that progressive cellular damage occurred in the control group, while the myocardium was preserved by the assist pump in the LVAD group. LVAD is effective for preserving the metabolic viability of the ischemic myocardium.

Animals↗
PubMed1994

Results of circulatory support for postoperative cardiogenic shock.

Over the last 5 years, 15 patients received ventricular assist devices (VADs) (Group 1) and 5 received percutaneous cardiopulmonary support (CPS) (Group 2) while in postoperative cardiogenic shock. Group 1 consisted of 8 men and 7 women ranging in age from 22 to 73 years (average age, 55 years). Nine of these patients underwent surgery for valve replacement, 5 for coronary artery bypass grafting, and 1 for closure of a ventricular septal rupture. The duration of VAD support ranged from 6 h to 9 days (mean, 3.9 days). Group 2 consisted of 4 men and 1 woman ranging in age from 49 to 68 years (average age, 57 years). One of these patients underwent surgery for valve replacement, 1 for coronary artery bypass grafting, 2 for replacement of a thoracic aneurysm, and 1 for left ventricular aneurysmectomy. The duration of CPS ranged from 4 h to 8 days (mean, 2.8 days). In Group 1, 13 patients were weaned from the VADs and 8 survived. Bleeding occurred in 5 patients, renal failure in 4, infection in 3, cardiac failure in 4, cerebral infarction in 1, perioperative myocardial infarction in 1, arrhythmia in 1, and ileus in 1. In Group 2, 4 patients were weaned from the CPS and 3 survived. Bleeding occurred in 3 patients, renal failure in 2, CNS injury in 2, and cardiopulmonary failure in 1. The 8 survivors in Group 1 have been followed for 2 to 56 months (mean, 28.7 months). Five patients were in NYHA class I, 2 were in class II and 1 was in class III.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

Long-term animal survival with an implantable axial flow pump as a left ventricular assist device.

We are developing an axial flow blood pump with Nimbus Inc. (AxiPump). For in vivo evaluation the AxiPump has been used as a left ventricular assist device with a left ventricular and descending aorta cannulation and implantation in a small pocket on the left lateral abdominal wall just posterior to the costal margin. Electrical and flow probe leads exit the body transcutaneously. A purge line that delivers the purge fluid for lubrication of the seal between the rotor and stator bodies in the purge fluid bearing system is tunneled with the other leads. Following acute animal studies, 3 animals have been supported for over 1 month with this AxiPump system. All laboratory results were within normal limits except during a recovery period from surgical damage. Hemolysis was not a serious problem. In the first case, the purge system failed at 28 days, and in the second and third cases, the nonpurge bearing system worked well for 57 and 52 days, respectively. Bearings are still under development in this kind of pump. However, this success encourages us to improve the AxiPump as a long-term assist device.

Animals↗
PubMed1988

Long-term neurostimulation of skeletal muscle: its potential for a tether-free biologic cardiac assist device.

Skeletal muscle has a tremendous capacity to adapt. This adaptive phenomenon is seen perhaps to the greatest extent when skeletal muscle is subjected to chronic low frequency stimulation via the motor nerve. There is a decrease in glycolytic enzymes and an increase in oxidative enzymes, as well as a change in the contractile proteins and an increase in the mitochondrial volume fraction of the muscle fiber. These adaptive changes result in a muscle that is considerably more fatigue-resistant. Specifically herein, we report on a pneumatic aortic counterpulsator device powered by skeletal muscle. These muscle pumps functioned continuously and pumped blood effectively in tether-free animals for several weeks.

Adaptation, Physiological↗
PubMed1987

An experimental study of Newtonian and non-Newtonian flow dynamics in a ventricular assist device.

The fluid dynamic behavior of a Newtonian water/glycerol solution, a non-Newtonian polymer (separan) solution, and bovine blood were compared in the Penn State Electrical Ventricular Assist Device (EVAD). Pulsed doppler ultrasound velocimetry was used to measure velocities in the near wall region (0.95-2.7 mm) along the perimeter of the pump. Mean velocity, turbulence intensity, local and convective acceleration, and shear rate were calculated from the PDU velocity measurements. Flow visualization provided qualitative information about the general flow patterns in the EVAD. Results indicate that water/glycerol does not accurately model the flow characteristics of bovine blood in the EVAD. The non-Newtonian separan solution produced results closer to those of the bovine blood than did the water/glycerol solution. Near wall velocity magnitudes for the separan were similar to those of the bovine blood, but the profile shapes differed for portions of the pump cycle. All three fluids exhibited periods of stagnation. Bovine blood results indicated the presence of a desired rotational washout pattern at midsystole, while results with the other fluids did not show this feature.

Animals↗
PubMed1987

Successful use of a right ventricular assist device.

Right ventricular failure caused by myocardial infarction may be refractory to treatment designed to support the systemic ventricle. A new type of right ventricular assist device driven by an impeller pump was successfully used for 79 hours after emergency revascularisation after right coronary occlusion. Despite renal failure requiring haemofiltration the patient has now fully recovered.

Acute Kidney Injury↗
PubMed1986

The human heart: vault of the soul or pump?

Medical causes that led to the development of artificial hearts are reviewed. Ventricular assist systems are compared with other designs. A discussion of the functioning and surgical implantation of Thermedics Corporation's ventricular assist pump provides a context for an analysis of technical challenges still to be solved.

Assisted Circulation↗