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PubMed1986

[Pressure measurements of pneumatically driven artificial ventricles].

In the mock circulation are investigated methods for pressure measurement developed especially for the application on artificial ventricles. They require the in-vivo-confirmation in the long-term experiment. An exact analysis of the pressure curves gives information about the absolute measuring values and also about the function of the pump itself, such as about the points of reaching the final positions of the pump membrane. Via a control related to this in the "full stroke" mode with ejection of the complete stroke volume, when the stand-still times of the membrane are minimized, in addition to this the atrial pressures and the cardiac output can be determined. Eventual non-linearities in the lower pressure region (less than or equal to 0.5 kPa) are not essential in the measurement of the ventricular pressure with amplitudes of 20-25 kPa on the left side and are not investigated in detail.

Assisted Circulation↗
PubMed2001

Functional assessment of the circulation of the single kidney.

Functional alterations in the renal circulation that can contribute to abnormal renal perfusion have been demonstrated in various models of renal injury. To detect impairments in renal vascular function, renal flow reserve can be determined by repeated measurements of renal blood flow (RBF) during pharmacological challenge with short-acting vasodilators that should increase RBF in kidneys that are not severely damaged structurally. Among the invasive techniques for such measurements, the most readily available is probably the intravascular Doppler, which can be employed during renal angiography for rapid evaluation of changes in RBF during intrarenal injections of vasoactive substances. High-resolution tomographic imaging techniques, like electron-beam x-ray computed tomography, further offer the potential for noninvasive measurements of renal parenchymal perfusion and function, in association with either intrarenal or systemic injections of vasoactive substances. Acetylcholine is a potent short-acting renal vasodilator that can be useful to assess the response of the renal microcirculation, define renal flow reserve, and examine the endothelium-dependent responses of RBF. Such assessments of the function of the renal circulation can assist in evaluation of patients with systemic or renal disease for early detection and monitoring of renovascular injury.

Animals↗
PubMed1978

Total support of the circulation of a patient with post-cardiotomy stone-heart syndrome by a partial artificial heart (ALVAD) for 5 days followed by heart and kidney transplantation.

A patient with acute bacterial endocarditis in whom ischaemic contracture of the left ventricle (stone-heart syndrome) developed during aortic and mitral valve replacement had an emergency implantation of an intracorporeal partial artificial heart (an abdominal left-ventricular assist device of ALVAD). This device functioned as a total artificial heart for nearly 6 days, while a donor heart for transplantation was sought. The ALVAD was then removed, and the patient received allografts of a heart and a kidney. The transplanted heart functioned well, but the patient died 15 days later from gram-negative sepsis. There was no evidence of cardiac or renal allograft rejection.

Acute Disease↗
PubMed1980

Effectiveness of intra-aortic balloon counterpulsation on systolic unloading.

The therapeutic benefit of intra-aortic balloon pumping (IABP) is believed to result from the combined action of reducing myocardial demand (systolic unloading) while improving myocardial supply (diastolic augmentation). However, the relative importance of these aspects has not been fully understood. Accordingly, the systolic unloading responses to IABP were studied in 13 dogs on total coronary bypass. By perfusing the coronary circulation from an extracorporeal source at a controlled pressure the authors were able to analyse the systolic unloading responses without diastolic augmentation directly altering coronary flow. The results suggest that IABP is effective only in reducing myocardial demand at normotensive levels; IABP during hypotensive states did not assist the failing heart mechanically by systolic unloading. Therefore the therapeutic action of IABP must result from increases in coronary blood flow by diastolic augmentation.

Animals↗
PubMed1996

Mechanical circulatory assistance in paediatric patients with cardiac failure.

Extracorporeal membrane oxygenation (ECMO) was initially developed for respiratory failure. Its use, however, has evolved into an excellent method of preoperative and postoperative support in the treatment of infants and children with acquired and congenital heart disease. Along with ECMO, the left ventricular assist device (LVAD) and the intraaortic balloon pump (IABP) have also found a place in the management of paediatric patients with heart failure. This report documents 15 patients who were treated with one or a combination of these mechanical devices, either preoperatively or postoperatively. There is a 74% survival rate and the long-term outcome has been excellent in most cases. The use of heparin-coated devices and tight regulation of heparin has allowed the transfer of infants and children from standard cardiopulmonary bypass to assist devices in the operating room. Mechanical devices are an essential adjunct for the preoperative and postoperative treatment of infants and children with cardiac disease.

Anticoagulants↗
PubMedDate not supplied

A high capacity transcutaneous energy transmission system.

A transcutaneous energy transmission system is described that transmits up to 60 W for use by a mechanical circulatory support system or other internal device. It contains an input power conditioning circuit that permits it to sustain the required output with input voltages ranging from 10 to 16 V. The transcutaneous energy transmission system demonstrated a best overall efficiency of 77% when connected to a resistive load and 74% when connected to a mechanical circulatory support system pumping up to 8.0 L/min to a mock circulation system. These figures included the losses in the conditioning circuit, which, when operated separately, had an efficiency of 94%. By tuning the resonant frequency of the primary, an output with only a 10% variation was achieved with coils separated by between 0 and 25 mm. A model of the inductively coupled resonant circuits was analyzed and a closed form solution obtained that verified the equations reported by Galbraith et al. Additional useful results obtained included an expression for the efficiency of the power transfer through the coupled circuits and the ratio of the current circulating in the primary and secondary coils. These results indicate that information useful for control of the output voltage of the secondary may be available in the primary circuit.

Assisted Circulation↗
PubMed1997

Bridge experience with long-term implantable left ventricular assist devices. Are they an alternative to transplantation?

BACKGROUND: If long-term use of left ventricular assist devices (LVADs) as bridges to transplantation is successful, the issue of permanent device implantation in lieu of transplantation could be addressed through the creation of appropriately designed trials. Our medium-term experience with both pneumatically and electrically powered ThermoCardiosystems LVADs is presented to outline the benefits and limitations of device support in lieu of transplantation. METHODS AND RESULTS: Detailed records were kept prospectively for all patients undergoing LVAD insertion. Fifty-eight LVADs were inserted over 5 years, with a survival rate of 74%. Mean patient age was 50 years, and duration of support averaged 98 days. Although common, both preexisting infection and infection during LVAD support were not associated with increased mortality or decreased rate of successful transplantation. Thromboembolic complications were rare, occurring in only three patients (5%) despite the absence of anticoagulation. Ventricular arrhythmias were well tolerated in all patients except in cases of early perioperative right ventricular failure, with no deaths. Right ventricular failure occurred in one third of patients and was managed in a small percentage by right ventricular assist device (RVAD) support and/or inhaled nitric oxide therapy. There were no serious device malfunctions, but five graft-related hemorrhages resulted in two deaths. Finally, a variety of noncardiac surgical procedures were performed in LVAD recipients, with no major morbidity and mortality. CONCLUSIONS: Over all, our medium-term experience with implantable LVAD support is encouraging. Although additional areas of investigation exist, improvements in patients selection and management together with device alterations that have reduced the thromboembolic incidence and facilitated patient rehabilitation lead us to believe that a prospective, randomized trial is indicated to study the role that LVADs may have as an alternative to medical management.

Aged↗
PubMedDate not supplied

New assist method for orthotopic heart transplantation in the dog.

We used cross circulation as an assist method for orthotopic heart transplantation in eight dogs. Seven of the eight dogs could be extubated on the first to third postoperative day and were able to eat and walk several hours after extubation. The survival times and the causes of death in these eight dogs were as follows: 436 days (alive), 5 days (sudden death), 17 days (rejection), 17 days (pyothorax), 3 days (accidental death), 59 days (rejection), 19 days (pneumothorax), and 188 days (alive). None of the dogs died of any problems related to the use of cross circulation. Hematologic and biochemical studies revealed that the CK, CK-MB, LDH, GOT, GPT, and lactate levels increased shortly after the operation and returned to the preoperative values within 14 days. The blood urea nitrogen, creatinine, amylase, hematocrit, and total protein levels remained almost unchanged. No free hemoglobin was detected. These findings indicated that no severe damage occurred to the recipient's organs. The key factors for performing successful cross circulation are as follows: (1) The body weight of the support dog should be at least three times that of the recipient. (2) The systolic pressure of the support dog and the pressure gradient between the support and the recipient should be kept above 150 mm Hg and 50 mm Hg, respectively. (3) The flow rate in the arterial tube should be maintained at between 30% and 50% of the basal cardiac output of the recipient. In conclusion, cross circulation is a suitable assist method for orthotopic heart transplantation in the dog.

Animals↗
PubMed2000

Cerebral tissue oxygen saturation during percutaneous cardiopulmonary support in a canine model of respiratory failure.

Percutaneous cardiopulmonary support (PCPS) has come to be applied for cardiopulmonary resuscitation and in the management of severe respiratory failure as well as severe heart failure. We investigated cerebral tissue oxygen saturation during PCPS in a canine model of respiratory failure using near-infrared spectroscopy. Animals were mechanically ventilated with 10% oxygen to make a respiratory failure model. Perfusion with PCPS was performed via the left femoral artery and switched to that via the right axillary artery. Cerebral tissue oxygen saturation was 54.2 +/- 3.4% during PCPS via the femoral artery and was 82.3 +/- 4.6% during PCPS via the axillary artery (p = 0.001). Hepatic tissue oxygen saturation was not significantly different. LV dP/dt max increased significantly after switching to the axillary blood supply (p = 0.001). Conventional PCPS may not have the capability of supporting cerebral circulation under severe respiratory failure without organic heart disease.

Analysis of Variance↗
PubMed2006

Intravascular ultrasound for intracranial angioplasty and stent placement: technical case report.

OBJECTIVE: Intravascular ultrasound (IVUS) imaging has been used extensively in coronary artery interventions and has provided invaluable information for the understanding and treatment of coronary arterial disease. We present here the first description, to our knowledge, of IVUS-guided intracranial arterial interventions in the clinical setting. CLINICAL PRESENTATION: Two patients underwent intracranial angioplasty and stent placement with the assistance of IVUS for the evaluation of their lesions. One patient underwent stenting to treat an occlusive dissection of the left internal carotid artery that occurred during arteriovenous malformation embolization. Another patient underwent angioplasty and stenting for high-grade restenosis of a basilar artery atherosclerotic lesion. RESULTS: Both patients underwent successful revascularization procedures. The patient with the dissection had a small intraventricular and parenchymal hemorrhage documented by computed tomography 4 hours after treatment, but did not develop hydrocephalus or further hemorrhage. Both patients did well clinically and had no permanent neurological deficits. IVUS provided important information in terms of lesion evaluation, stent selection, and stent placement in each case. CONCLUSION: IVUS of the intracranial circulation may assist the performance of intracranial angioplasty and stenting. It provides useful information that can affect clinical decisions. It may prove to be a valuable tool in clinical use and enhance our understanding of vascular disease of the intracranial circulation, as it has in the coronary circulation.

Aged↗
PubMed1983

Improvement in intra-aortic balloon pumping and evaluation of its efficacy by electrode methods of control.

A basically new design for the reversing balloon pump has been proposed for increasing the efficacy of intra-aortic balloon pumping (IABP). The device not only causes a significant increase in discharge, but also permits control of the central and peripheral circulation within the desired limits owing to back-and-forth movements (like a piston) of the balloon pump. Standard one- and two-chamber balloon pumps were compared. In addition to traditional hemodynamic and biochemical indexes, the efficacy of IABP was assessed based on electrode monitor control of PO2 and pH in the myocardium, peripheral tissues, and circulating blood. Based on 54 experiments on dogs, it was found that IABP with reversing balloon pumps in synchronous pulsation resulted in survival of 69% of the cases; PO2 and pH levels in the myocardium, tissues, and blood in the coronary sinus were close to normal, and coronary blood flow and peripheral circulation were increased. With standard one-chamber balloon pumps, the survival rate did not exceed 33.4%; PO2 and pH in the peripheral tissues reached critical levels.

Animals↗
PubMedDate not supplied

Axial reciprocation of rotating impeller: a new concept of antithrombogenecity in centrifugal pump.

For long-term application, rotary pumps have to solve the problems of bearing wear and thrombosis along the bearing. Most 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. The authors have tried and found, however, that it is difficult to apply a magnetic bearing to the rotary pump without disturbing its simplicity, reliability and implantability, and have therefor developed a much simpler and much more creative approach to achieve the same results. Instead of using a sliding bearing, a rolling bearing has been devised for the pump, and its friction is about 1/15 of the sliding bearing. Furthermore, a wear-proof material of ultra-high-molecular weight polythene has been adopted to make the rollers, and its anti-wear property is 8 times better than metal. Thereby, the service life of the bearing has been prolonged to ten years according to the documents provided by the producer. In order to prevent the thrombus formation along the bearing, the impeller reciprocates axiallly as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is the 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 a piston pump, the oscillating impeller can make the blood flow in and out of the bearing, resulting in wash-out once a circle. This obviously helps to prevent thombosis along the bearing and in the pump. The endurance tests with saline of this novel pump demonstrated the durabililty of the device. It promises to be able to assist the circulation of patients permanently, and to be able to replace heart transplantation in the future.

Equipment Design↗
PubMedDate not supplied

[Enoximone in weaning from mechanical circulation support in pediatric patients].

OBJECTIVE: To assess and record the response to continuous infusion of the phosphodiesterase inhibitor enoximone during weaning from mechanical circulatory support (MCS) and to verify the possibility of success with this indication in pediatric patients. DESIGN: Retrospective study. SETTING: Pediatric cardiac surgery intensive care unit. PATIENTS: Two pediatric patients operated for complex congenital heart disease with low cardiac output syndrome in the immediate postoperative period, evolved in cardiocirculatory arrest despite massive inotropic pharmacological support, and then assisted by mechanical circulatory support. INTERVENTIONS: Weaning from mechanical circulatory support with continuous infusion of enoximone, only in one case preceded by a loading dose and associated with catecholamine infusion. MEASUREMENTS AND MAIN RESULTS: During weaning hemodynamic parameters (LAP, CVP, MAP, HR), SvO2, diuresis, rectal and cutaneous temperatures were assessed and recorded. A serial echocardiographic assessment of left ventricular systolic and diastolic diameters and ejection fraction (EF%) has also been performed every 12 hours. Weaning from MCS using enoximone as inotropic support was possible in both cases. CONCLUSIONS: Enoximone proved to be useful in weaning from MCS in two pediatric patients, despite the difficulty to assess its effect in one of the two cases in which enoximone was used together with high dosages of other inotropic drugs. These initial positive results urge us to further investigate applications of this drug in pediatric patients.

Assisted Circulation↗
PubMed1989

Skeletal muscle ventricles: improved performance at physiologic preloads.

We attempted to construct skeletal muscle ventricles (SMVs) so that they would develop optimal stroke work at physiologic preloads of 5 to 15 mm Hg. Thirty-one SMVs were constructed in mongrel dogs. The effects of electrical preconditioning with 2 Hz continuous and 25 Hz burst patterns were evaluated, as well as the application of passive stretch to the muscle fibers during preconditioning. We evaluated the stroke work developed by these SMVs at afterloads of 30 mm Hg and 80 mm Hg in vivo, using a mock circulation device. During mock circulation studies, the SMVs were stimulated via the thoracodorsal nerve with either a 25 Hz or 85 Hz burst pattern. SMVs with 2 Hz preconditioning developed significantly higher stroke work than SMVs with 25 Hz preconditioning under all conditions of afterload, preload, and stimulation frequency (p less than or equal to 0.001). Under these conditions, for the 2 Hz preconditioned SMVs, passive stretch during preconditioning resulted in a further significant increase in developed stroke work (p less than 0.05). For these SMVs, with an 85 Hz stimulation frequency, stroke work averaged 410% of canine RV stroke work, and 59% of canine LV stroke work at physiologic preloads and afterloads.

Animals↗
PubMed2001

[Ventricular assist support of the failing heart after surgery with extracorporeal circulation].

OBJECTIVE: To communicate our experience implanting ventricular assist devices; we report the incidence of refractory heart failure after extracorporeal circulatory support and discuss clinical course after support. PATIENTS AND METHOD: Retrospective study of 14 cases of ventricular assistance required when refractory heart failure developed after extracorporeal circulation. The patients were 10 males and 4 females aged between 12 and 70 years. Four underwent coronary revascularization, 2 required valve replacement, and 8 received heart transplants. Two left, 2 right and 6 bilateral ventricular assist devices were implanted. RESULTS: The incidence of refractory heart failure after extracorporeal mechanical circulation requiring ventricular assist devices among our patients was 0.48%, with left ventricular failure occurring in 21.42%, right ventricular failure in 42.85% and biventricular failure in 35.71%. The main complications were infection, renal insufficiency, coagulation disorder, hemorrhage with repeated surgery. One patient received a second transplant. The device was successfully withdrawn from 35.7% of the patients. Survival upon discharge was 7.1%. CONCLUSION: Refractory heart failure after extracorporeal circulation is a life-threatening event requiring rapid response and resolution. The decision to implant a ventricular assist device is a difficult one, requiring immediate assessment of the causes of heart failure, its reversibility and the possibility of performing a heart transplant. The study of large series of patients experiencing this event and implanted with ventricular assist devices would facilitate decision making.

Adolescent↗
PubMed1976

Removal of intraaortic balloon without vascular complications.

A technique for inserting and removing the intraaortic balloon pump without vascular complications is descirbed. Prevention of clot formation at the graft-arterial junction, preservation of collateral circulation by insertion in the common femoral artery, removal of potentially infected graft material, and enlargement of the common femoral artery by patch angioplasty are important factors.

Adult↗
PubMed1991

Development and training of skeletal muscle ventricles with low preload.

One-layered skeletal muscle ventricles (SMV) were constructed from latissimus dorsi (LD) muscles extrathoracally in six calves and trained under electrical stimulation on totally implanted mock circulation systems. These ventricles had low preloads of about 5 mmHg. The results showed that training against a resistance similar to the human aorta does not create an effective blood pump. But conditioning against a highly complaint workload makes them six times more effective. Therefore, further research on this observation is mandatory. After a conditioning of 16 to 63 days, all implanted mock circulations became infected due to perforated skin, so these experiments had to be terminated. To avoid these infections, we developed and tested an intrathoracic implantable mock circulation system with a highly compliant workload. With a double-layered muscle pump, systolic pressure 120-140 mmHg was generated and an output of more than 31/min was obtained. SMVs with a low end-diastolic pressure seem to be suitable for construction of an effective blood pump between the left atrium and the aorta as a left heart assist device.

Animals↗