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PubMedDate not supplied

Clinical experience with centrifugal pump ventricular support at UCLA Medical Center.

The experience using the vortex centrifugal pump as a ventricular assist device at The University of California, Los Angeles and Wadsworth V.A. Medical Centers is reviewed. Thirteen adult and one pediatric patients were supported postcardiotomy, 10 LVAD, 3 BIVAD, and 1 RVAD. There were no equipment failures over a mean perfusion time of 52 hr (range 12-140 hr). Seven of thirteen adult patients were supported and weaned from 6 LVAD and 1 BIVAD. Three patients underwent orthotopic heart transplantation, and the other four recovered ventricular function, of whom five are longterm survivors at a mean followup time of 16 months. In one patient bridged to transplantation, a prior infection caused the patient to succumb after successful transplantation. All patients assisted for transplantation are carefully screened, and would be excluded from transplantation if they developed significant infection, or irreversible renal or neurologic limitations.

Aged↗
PubMedDate not supplied

Ferromagnetic artificial cells for artificial circulation.

It is known that deoxygenated blood is paramagnetic. A ferrofluidic actuator for an implantable artificial heart has been studied. The magnetic fluid consists of ferromagnetic magnetite particles (10 nm). If artificial cells encapsulating ferromagnetic particles are mixed in blood, the circulation is maintained by applying a magnetic field to the blood. An array of two poles of ring solenoids with a gap of 10 mm was mounted near the glass tube (7.60 mm inner diameter). The flux density was 0.236 Tesla. Two experiments were conducted using models of artificial cells: 1) the magnetic fluid and 2) the magnetic fluid and an iron cylinder (6.67 mm in diameter and 28.7 mm in length). A flow of 38 to 8 ml/min was obtained against a pressure of 12.5 to 16.3 mmHg in experiment 1, and 80 to 24 ml/min against a pressure of 53 to 240 mmHg in experiment 2. Calculation showed that magnetic fluids could move against a pressure of 100 mmHg if they had a magnetization of 113 kA/m (B = 0.236 Tesla). The magnetic fluid has a magnetization of 35.6 kA/m, whereas the magnetite is 479 kA/m, and that of iron 1398 kA/m. Artificial circulation with ferromagnetic artificial cells could be feasible if artificial cells with a magnetization of 113 kA/m are developed.

Assisted Circulation↗
PubMed1978

Prolonged circulatory support with the intra-aortic balloon pump after myocardial infarction.

Circulation was supported by intra-aortic balloon counterpulsation for 30 and 38 days respectively in two patients with cardiogenic shock after acute myocardial infarction. One was flown 1400 km to Cape Town for heart transplantation but died after being weaned from the pump while awaiting a suitable donor. The other underwent successful surgical closure of a ruptured ventricular septum on the 30th day, allowing time for the edges of the ventricular septal defect to fibrose. Neither significant damage to circulating blood elements nor infection occurred, confirming the feasibility of prolonged circulatory support.

Acute Disease↗
PubMedDate not supplied

Bridge to cardiac transplantation: successful use of prosthetic biventricular support in a patient awaiting a donor heart.

A 33-year-old man with dilated cardiomyopathy was successfully "bridged" to cardiac transplantation, with the use of left and right prosthetic ventricles. The prostheses supported the pulmonary and systemic circulations for 87 h, at which time they were removed and orthotopic transplantation was performed. Heart transplantation is the only viable long-term therapy for end-stage dilated cardiomyopathy. In the case of sudden decompensation in a patient who requires cardiac transplantation, if a suitable allograft is not immediately available, a system of prosthetic ventricles can be used to provide hemodynamic support until a donor organ is located. In addition, the use of a prosthetic ventricle or ventricles does not preclude the possibility of recovery of ventricular function, an option that is removed if a total artificial heart is used.

Adult↗
PubMedDate not supplied

[Devices for temporary replacement of the pumping function of the heart].

The article gives the analysis of the authors' experience in developing the systems of mechanical maintenance of blood circulation: AvIK-9M, Sinus-BK, and the cylinder pump with an additional distal chamber, which has not only high hemodynamic efficiency but also, to a considerable extent, improves the bioenergetics of the myocardium. It also gives a detailed description of the device for the retrograde counterpulsation and periodic occlusion of the coronary sinus. All the systems have successfully undergone testing by experiment and in the clinic.

Assisted Circulation↗
PubMed1989

Surgical techniques for the implantation of heterotopic prosthetic ventricles.

Mechanical support of the failing heart is becoming an increasingly useful tool for bridging to cardiac transplantation and for recovery of the natural heart. Several options exist for cannulation sites during the implantation of the heterotopic prosthetic ventricles. These options include the left atrial appendage, the left ventricular apex, the interatrial groove, and the left atrial roof. The indications, contraindications, advantages, disadvantages, and surgical technique for each option are described. Operation of the drive console and postoperative care are also discussed.

Assisted Circulation↗
PubMed1998

Design and development strategy for the rotary blood pump.

Development of an antitraumatic antithrombogenic and durable blood pump is a very difficult task. Based upon this author's experience of over 35 years in the development of various types of cardiac prostheses, development strategies for a rotary blood pump are described. A step-by-step development strategy is thus proposed. Initially, the development of a 2 day antitraumatic pump (Phase 1) would be made. Then, conversion of this pump to a 2 week antithrombogenic pump (Phase 2) should be attempted. After the successful development of the Phase 2 pump, the conversion of this device to a durable, implantable, and long-term blood pump (Phase 3) should be established. Based upon this development strategy, 2 rotary blood pumps, namely, the axial flow blood pump and the centrifugal blood pump, have been developed in less than 6 years with modest development costs.

Adaptation, Physiological↗
PubMed1978

Mechanical circulatory support: evolving perspectives.

Mechanical circulatory support of the failing circulation is an emerging discipline. Prototype circulatory support services have been established in a few institutions but are spreading15. Intra-aortic balloon pumping, developmental only a decade ago, is now widespread. Pneumatically-actuated intra and extracorporeal left ventricular assist devices, federally-approved for clinical trials only 2 yrs ago, show encouraging early results. Efforts in West Germany, Austria, Switzerland, Russia and Japan are underway and a spirit of cooperation exists. There is a need to clarify and quantitate indications and timing for deployment, prior to the onset of multiple organ failure. Electrically and nuclear-activated LVAD's16--18 are being developed. Clarification of projected patient populations are needed and the role of the right heart in left ventricular assist device function requires further investigation. There is a need to define a reasonable clinical role for the much discussed and rather elusive total artificial heart. Many problems remain with actuation, energy conversion, percutaneous leads, compliance devices and biomaterials. The challenges are many and welcomed.

Assisted Circulation↗
PubMed2003

[A new approach for improving antithrombogenicity in centrifugal pump].

For long-term application of the rotary pumps, it is necessary to solve the problems of bearing wear and thrombosis along the bearing. Currently, many investigators choose the magnetic bearing to realize zero-friction and no contact between the rotor and stator; the former avoids the mechanical wear and the latter eliminates the possibility of thrombus formation. We tried and found that it is difficult to apply a magnetic bearing to rotary pump without disturbing its simplicity, reliability and implantable; therefore, we have developed a much simpler and much more creative approach to achieving the same results. Instead of the sliding bearing, a rolling bearing has been devised for the pump; its friction is about 1/15 of the sliding bearing. Furthermore, a wear-proof material of ultra-high-molecular weight polythene has been adopted in making the rollers, their anti-wear property in 8 times better than that of metal. Thereby, the service life of the bearing has extended to several years. For preventing the thrombus formation along the bearing, the impeller reciprocation axially as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is a result of the effects of a magnetic force between the motor rotor and stator, and a hydraulic force between the blood flow and the impeller. Similar to piston pump, the oscillating impeller can make the blood in and out of the bearing, resulting in wash-out once a circle. This is obviously beneficial to preventing thrombosis along the bearing and in the pump. The endurance tests with saline of this novel pump demonstrated a durability of the device. It promises to be able to assist the circulation of the patients permanently and to be able to replace the heart transplantation in the future.

Heart-Assist Devices↗
PubMed1980

Recovery of cardiac function with total transapical left ventricular bypass.

Transapical left ventricular bypass which withdraws blood directly from the left ventricular apex through a roller pump and outflow filter with return to the femoral artery has been applied in 6 patients with cardiac failure. All patients required total TALVB (with the aortic valve closed) for periods of one to 144 hrs, and 2 patients had recovery of life-sustaining myocardial function, allowing removal of the TALVB system. One patient had complete recovery without other organ dysfunction. Total TALVB continuously decompresses and unloads the left ventricle throughout systole and diastole, and maintains the circulation in otherwise terminal circumstances.

Adult↗
PubMed1992

Mechanical circulatory assist using heparin-coated tube and roller pump system.

We have invented a mechanical circulatory assist system that uses a heparin-coated tube and a roller pump. Experimental left heart bypass was performed on 13 mongrel dogs for 24 hours without systemic heparinization. There were no significant changes in coagulation variables during the experiment, and pathological examination of internal organs after bypass revealed no evidence of thromboembolism. We applied this assist system to 13 patients who could not be weaned from cardiopulmonary bypass after an open heart operation. Left heart bypass was performed on 7 patients, right heart bypass on 1 patient, combined left and right heart bypass on 2, and venoarterial bypass without oxygenation on 3. Duration of support ranged from 5 hours to 21 days, and the pump flow rate ranged from 0.8 to 3.2 L/min. Eight patients were successfully weaned from this support, and 6 were discharged from the hospital. Examination of the tubes in the assist system revealed excellent antithrombogenicity for at least 3 days without systemic heparinization. There was no evidence of thromboembolism in brain, kidneys, lungs, or other organs. Because of its simplicity and antithrombogenicity, this mechanical assist system is beneficial for patients who cannot be weaned from cardiopulmonary bypass after open heart operations.

Adult↗
PubMed1979

Reduction of myocardial infarct size: comparison between left atrial and left ventricular bypass.

A controlled study was undertaken to quantitate and compare the effect of left ventricular bypass (LVB) and left atrial bypass (LAB on left ventricular infarct volume (LVIV). After baseline studies, the left anterior descending coronary artery in each of 30 mongrel dogs was ligated 1-1.5 cm from its origin. After baseline ischemic studies, control dogs (group 1--10 dogs), LAB dogs (group 2--10 dogs), and LVB dogs (group 3--10 dogs) were monitored for four hours. Final infarct size was determined by the nitroblue tetrazolium staining technique. Heart rate, mean arterial pressure, and total systemic flow (TSF) showed no significant difference between control and left heart bypass groups. In group 1, the LVIV was 27.7 +/- 6.5 g/100 g left ventricle (LV). In group 2, left heart bypass (LHB) flow was 90 +/- 4% of TSF. The pressure time index (PTI) was 2845 +/- 52 mm Hg-sec/min. The PTI demonstrated no significant difference from cntrols. In group 2, LVIV was 22.5 +/- 6.0 g/100 g LV. LVIV was reduced 18.8% from controls (p less than 0.08). In group 2, LHB was complete. Left ventricular decompression (group 3) resulted in a PTI of 328 +/- 76 mm Hg-sec/min. The PTI was significantly different (p less than 0.001) from groups 1 and 2. The LVIV was 12.6 +/- 5.1 g/100 g LV. LVIV was reduced 54.5% from controls (p less than 0.001) and 44.0% from group 2 (p less than 0.001). These results suggest that LVB may be useful, not only in supporting the circulation in the patient with myocardial infarct and cardiogenic shock, but also in limiting infarct size.

Animals↗
PubMed1988

Heterotopic prosthetic ventricles as a bridge to cardiac transplantation. A multicenter study in 29 patients.

Heterotopic prosthetic ventricles were used to support the circulation in 29 candidates for heart transplantation who were expected to die before procurement of a donor heart. Twenty-one of these patients (average age, 36 years) underwent successful transplantation after 8 hours to 31 days of circulatory support. The other eight patients died because their condition could not be stabilized for transplantation, despite restoration of blood flow. Fourteen patients received biventricular support; 15 received only left ventricular support, with pharmacologic assistance of right heart function. Before transplantation, blood flow from the left prosthetic ventricle averaged 2.8 +/- 0.4 liters per minute per square meter of body-surface area, and from the right prosthesis 2.4 +/- 0.4 liters, as compared with an average flow of 1.6 +/- 0.5 liters per minute per square meter before implantation. Of the 21 patients who received heart transplants, 20 were discharged from the hospital after a median of 31 days. Nineteen patients were alive at 7 to 39 months, and 11 of the first 12 were alive at one year. We conclude that heterotopic placement of prosthetic ventricles as a bridge to transplantation provides an effective method of temporarily supporting cardiac function in critically ill patients without removing the natural heart. The early survival rate after transplantation is similar to that with elective cardiac transplantation.

Adolescent↗
PubMed1988

[Current status of use of the artificial heart in combination with heart transplantation].

Acute and therapeutically uncontrollable cardiac insufficiency in a case of chronic heart disease with acute risk of rejection and with a record of previous transplantation or during a heart operation should be considered as an indication for implantation of an artificial heart or a ventricle-supporting system, if a donor heart is not available. Two results are expected from such an approach, restoration of adequate circulation and improvement of organ functionally providing a chance for later transplantation. Attention should be given, according to the authors' own experience, to effective surgical haemostasis. Infections have quite often proved to be incurable after implantation of an artificial heart and, consequently, provide a clear-cut contraindication to implantation.

Assisted Circulation↗
PubMed1986

The current status of mechanical circulatory support.

In summary, techniques for support of a failing circulation have advanced steadily over the past thirty years. Just as the use of the intra-aortic balloon pump has permitted successful treatment of certain groups of high-risk patients, so increasing application of more invasive techniques of mechanical circulatory support has extended the range of surgical endeavour. Nevertheless, it is evident that further advances in the design and construction of mechanical circulatory support devices are most likely to occur in conjunction with developments in bioengineering technology. These advances will in turn demand analysis by means of careful animal and clinical investigations. Although the general clinical use of an off-the-shelf mechanical ventricular support will give rise to major financial and ethical problems it is likely that application of these devices may herald a new era in the field of artificial organ replacement.

Assisted Circulation↗