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PubMedDate not supplied

Latest developments in the field of assisted circulation.

The 51st Annual Meeting of the American Society for Artificial Internal Organs was held in Washington, DC, June 9 to 11, 2005. The abstract submission deadline for this meeting occurred on January 14, 2005. To ensure that the attendees were completely up-to-date with developments in the field of mechanical circulatory support, I was asked to provide a brief summary of developments or milestones that occurred after the abstract submission deadline. The list of highlights included in this manuscript was selected from an informal poll of colleagues and industry representatives, as well as a review of press releases and government- and industry-sponsored Web sites. Any omissions or errors in this summary of the latest developments in the field of mechanical circulatory support are entirely my responsibility. I also want the reader to understand that I have no financial interest in any of the device manufacturing companies to which I will refer.

Adult↗
PubMed2001

[Assisted circulation. I. Systems with short-term mechanical circulatory support].

The concept of artificial circulatory support has been established almost 200 years ago. It has only been within the last four decades that physicians and engineers have developed mechanical assist devices that can temporarily support the circulation until the native heart recovers from a reversible injury. If the heart does not recover sufficient function to maintain adequate hemodynamics, long-term circulatory support or permanent replace (biologically--heart transplant or permanent mechanical circulatory support) is needed. In this paper we describe the devices (intraaortic balloon pump, roller, centrifugal and axial pumps), that are in current clinical use for temporary (short-term) mechanical circulatory support.

Assisted Circulation↗
PubMedDate not supplied

The Windkesselventricle with guiding balloon as a new approach for assisted circulation.

A simple method was developed to aid the patient with low cardiac output syndrome following cardiac surgery. The concept was shown to be feasible in electric circulatory analog studies and verified in 20 dog experiments. A Dacron graft (end-to-side) through the right second intercostal space connects the ascending aorta to the subcutaneously implanted, ellipsoidal-shaped artifical ventricle. A spherical polyurethane balloon is positioned in the aorta distal to the Dacron graft via the femoral artery. The ventricle and balloon are pneumatically driven synchronously with the ECG. In natural systole the balloon is inflated, occluding the aorta, and the artificial ventricle sucks the entire stroke volume. In natural diastole the balloon deflates and the artificial ventricle ejects the blood into the peripheral arteries. With this system it is possible to maintain a normal systemic pressure and have high hemodynamic efficiency. The left ventricular systolic pressure is 85 percent unloaded. The systolic wave is turned 180 degrees to the natural. After treatment, the device can be removed without thoracotomy.

Animals↗
PubMed1992

[Clinical experience of continuous retrograde cerebral perfusion for assisted circulation during the surgical treatment of acute dissection of aorta: Stanford A type].

Surgical treatment of the dissection involving the ascending aorta or aortic arch represents one of the most complicated technical challenges. Recently continuous retrograde cerebral perfusion (CRCP) is sometimes applied in order to avoid cerebral complications. We compared two surgical groups, one of which was performed graft-replacement of ascending aorta using CRCP and another was utilized normograde cerebral circulation, about the technique of operation, total extracorporeal circulation (ECC) time, aortic clamp time, separate ECC time, total bleeding volume, and urination during operation. In the group using CRCP, separate ECC time was 53 min (mean), and intraoperative bleeding volume was only 1,170 ml. Good urination was obtained during operation. Postoperative courses were uneventful, and consciousness was smoothly and soon recovered. The new method of separate ECC has some advantages over the previously described methods, particularly for avoidance of cerebral complications. As it is not necessary to require dissecting, taping, and clamping of cephalic branches, operative procedure will be very simplified, easier and safer, leading to intraoperative bleeding is a fewer. It is our belief that this method should be widely applied in the operation of graft-replacement of ascending aorta or aortic arch in the near future.

Aged↗
PubMed1983

Prospects for using implanted systems of assisted circulation and artificial heart with a radioisotope power source (biomedical, thermal, and radiation aspects).

The capacity of dogs to diffuse heat (up to 50 W) from an artificial heart and to tolerate prolonged intracorporeal ionizing radiation from a radioisotope power source (238Pu) was investigated, using electrical models of vascular blood heat exchangers that permit reproduction of elimination and heat transmission in autonomous systems. It was shown that up to 50 W can be discharged at temperatures of the wall-blood interface that do not exceed 43 degrees C. Clotting indexes, concentration of total protein, hemolysis, and serum enzyme activity during 1-1.5 months of heating remained within physiologically normal limits. A specific power load of up to 1.5 W/kg at ambient temperatures of 18-20 degrees C revealed no evidence of changes in heat production. By measuring the distribution of power of the dose absorbed around a 45-W plutonium source it was possible to estimate dose loads on critical organs and to assess overall risk of death from malignant tumors induced by radiation over a 10-year period: 6-12% for males and 8-14% for females. It is not very probable that use of the artificial heart with a radioisotope power source will be limited by thermal and radiational effects.

Animals↗
PubMed1998

Effect of assisted circulation on left ventricular performance in a canine model.

BACKGROUND: Little is known about left ventricular performance during venoarterial bypass and left heart bypass (LHB) after cross-clamping the descending thoracic aorta. We evaluated the effects of venoarterial bypass and LHB on ventricular load optimization and left ventricular work efficiency. METHODS: We used the left ventricular conductance catheter and a micromanometer in 7 anesthetized mongrel dogs. We assessed preload by the end-diastolic volume, afterload by the effective arterial elastance, and left ventricular contractile properties by the slope of the end-systolic pressure-volume relationship. In addition, optimal ventricular arterial coupling (ratio of effective arterial elastance to slope of end-systolic pressure-volume relationship) and left ventricular work efficiency (ratio of external work to pressure-volume area) were calculated. RESULTS: The decrease in preload was much greater with LHB than venoarterial bypass. There were no significant differences in afterload and left ventricular contractility between venoarterial bypass and LHB. The ventricular arterial coupling during LHB was near 0.50 (0.69 +/- 0.16) in the "best heart" condition (effective arterial elastance = slope of end-systolic pressure-volume relationship/2), whereas the work efficiency during LHB was at maximum (0.73 +/- 0.12). CONCLUSIONS: We conclude that LHB has a more beneficial effect on left ventricular performance after cross-clamping of the descending thoracic aorta.

Animals↗
PubMedDate not supplied

[The postoperative control of the technical links in the biotechnical system of assisted circulation].

Presently, it is impossible to develop a completely implantable mechanical self-contained system of extracorporeal circulation that can maintain a patient's heart performance for a long time. In this connection, replacement of a mechanical assister by a biological one is promising as this may clear up a lot of troubles of the mechanical systems. The prominent example of successful realization of the completely implantable self-contained system of extracorporeal circulation is a biotechnological system (BTS) which is formed by dynamic cardiomyoplasty and includes the heart, a cardiac electrode, an implantable blood muscular pump pacemaker (BMPP). A muscular electrode, and muscle autograft that acts as an assister. The authors propose the formalized algorithms of noninvasive postoperative control of the technical links of BTS-BMPP and electrodes. The diagnostic algorithms of BTS containing one- and two-channel BMPP are different and based on electrocardiographic, X-ray, and other noninvasive findings.

Algorithms↗
PubMed1994

Assisted circulation without systemic heparinization.

The need for improvements in materials and equipment for extracorporeal circulation has been obvious for years. Among the surfaces with biologically active compounds, those with heparin binding have been found sufficiently thromboresistant and particularly suitable for different types of artificial perfusion. Partial left heart bypass (LHBP) was performed in 10 anesthetized, acutely instrumented, and open-chested mongrel dogs (weight 23 to 50 kg) with a servo-controlled roller pump. The pump flow was maintained at 50 mL/kg/min for 6 hours. Heparin surface-coated equipment was used without additional heparin. For LHBP with a standard circuit, the total amount of heparin during the study period was (mean +/- SD) 487 +/- 124 IU/kg. The right atrial, pulmonary artery, and left ventricular end-diastolic pressures, cardiac output, left ventricular output, right and left ventricular stroke work, pulmonary gas exchange, and acid-base balance changed similarly with both systems. Blood loss (204 +/- 78 v 1,240 +/- 586 mL, P < 0.0005), volume substitution requirements (647 +/- 48 v 1,860 +/- 764 mL, P < 0.0025), and oxygen extraction ratio (mean 25.4 to 32.0 v 25.4 to 56.4%, P < 0.025) were significantly lower, and mean aortic pressure (mean 65 to 69 v 62 to 38 mmHg, P < 0.025) and hemoglobin concentration (mean 9.1 to 8.1 v 9.4 to 3.9 g/dL, P < 0.05) were significantly higher during 6 hours of LHBP without systemic heparinization. Low but stable oxygen delivery was provided with heparin-coated LHBP, whereas it showed a descending trend (mean 14.0 to 10.8 v 13.4 to 5.5 mL/kg/min, P < 0.1) with the standard circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Pulsate regimes of the centrifugal pump operation for assisted circulation.

This paper focuses on the evaluation of dynamic pumps as an element of the assist unit from the standpoint of its capacity to pass and change the left ventricle's pulsations. Analyses of the dynamic equations of the pipelines and pump have been performed. The pump intensification capacity of the disc and blade pumps was computed. Theoretically it was determined and experimentally confirmed that the pump intensification capacity was defined by the performance of the pump head. It was also determined that the existing pumps (e.g., The BioMedicus Biopump and the Moscow Aviation Institute, OK) pass and attenuate the left ventricle pressure pulsations.

Heart-Assist Devices↗
PubMed1998

Assisted circulation for end-stage chronic heart failure.

Despite the trend in the use of electromechanical left ventricular assist devices (LVAD), the highly compact, long lasting, and endurance characteristics of the new pneumatic system has its place in the treatment of end-stage chronic heart failure. The ProCor Model 1 LVAD has an implantable pump which is small in size and has a double pusher plate design. The portable power pack is small, too. It is easy to carry, and it is synchronized to the ECG to pump during the patient's diastolic period. Constant driving conditions are set as follows: frequency rate, 60 bpm; systolic percentage, 25 (250 ms); dP/dt, 1,800 (45 ms) mm Hg.s; and driving pressure, 250 mm Hg to have a basic 3.500 L/min pump output for prolonged circulatory assistance. The 6 mm internal diameter (ID) percutaneous multipurpose pneumatic tube contains within its wall both a spiral of MP35N alloy wire connected to the myocardial lead for ECG sensing and a spiral serving as mass ready to be used for cardiac pacing with an external pacemaker when necessary. The aortic porcine bioprosthesis maintains the aortic root and the sinus ridge.

Animals↗
PubMed1994

[Hemodynamic and neurohormonal profile during assisted circulation with heterotopic artificial ventricle followed by heart transplantation].

We describe the hemodynamic and neurohormonal data during ventricular assistance device system support as a bridge to heart transplantation of one patient, 30 years old, with heart failure due to Chagas' heart disease in functional class IV. We determined the pressures in mmHg of right atrium (RA), pulmonary artery pressure (PAP), pulmonary wedge pressure (WEDGE), arterial blood pressure (AP), and the cardiac output (CO) in l/min. In addition, the blood levels of norepinephrine (Ne), renin (Re), epinephrine (Ep), lactate and the mixed venous oxygen pressure (pVO2) were determined. The CO increased from 2.14 to 3.9-4.2 l/min, the AD decreased from 26mmHg to 8mmHg, the MPAP reduced from 38mmHg to 14-24mmHg, the WEDGE reduced from 25 to 4mmHg and the AP become normal. The Ne reduced from 1927pg/ml to 983pg/ml, the lactate reduced from 99mg/dl to 22mg/dl and the pVO2 increased from 28mmHg to 43mmHg. The EP remained between 81pg/ml and 129pg/ml, the renin activity remained between 113ng/ml/hr and 136ng/ml/hr. Thus, during the ventricular assistance device system support there was a improvement in hemodynamic and neurohormonal conditions. The patient underwent successful heart transplantation.

Adult↗
PubMedDate not supplied

A sheep model for the study of hemorheology with assisted circulation. Effect of an axial flow blood pump.

Hemorheologic investigations were performed on nine sheep during the in vivo evaluation of a new axial flow ventricular assist device, the Nimbus AxiPump (Nimbus, Inc., Rancho Cordova, CA). Blood hematocrit, plasma and whole blood viscosity, red blood cell (RBC) deformability and aggregation, plasma fibrinogen, and free hemoglobin (hemolysis) levels were measured. Changes in the main rheologic parameters of sheep blood relative to the pre-implant values were minor and transient. The exception was RBC aggregation, which appeared on the third day of implantation. (Sheep blood does not normally demonstrate RBC aggregation.) Sheep RBCs started to form classic rouleaux typically on the third post-operative day simultaneously with increasing fibrinogen level. To investigate the relative effects of mechanical stress and elevated fibrinogen levels on RBC aggregability, in vitro studies were conducted with blood from control sheep. These studies indicated that neither mechanical trauma nor elevated fibrinogen alone caused RBC aggregation as seen in vivo. However, combined mechanical stress and elevated fibrinogen did cause this unusual effect for sheep blood.

Animals↗
PubMed1996

Comparison studies of major organ microcirculations under pulsatile- and nonpulsatile-assisted circulations.

In these comparison studies, we examined changes in major organ microcirculations during circulatory support using pulsatile and nonpulsatile pumps. Acute myocardial infarction was created by left anterior descending (LAD) branch ligation. After the animals in these studies fell into cardiogenic shock, they were supported by mechanical assist devices: a pulsatile ventricular assist device (VAD) in 4 pigs, a nonpulsatile VAD in 4 pigs, and an intraaortic balloon pumping (IABP) plus nonpulsatile VAD in 4 pigs. Each group was supported for 3 h with an identical mean aortic pressure being maintained. As for parameters, the stomach mucosa, liver regional blood flow, stomach mucosal pH, and arterial blood keton body ratio (AKBR) were measured. Both regional blood flow and AKBR increased in the pulsatile group as compared with the nonpulsatile group. There were no differences in the stomach mucosal pH among the 3 groups. These results suggest that pulsatile assist rather than the nonpulsatile assist plays a significant role in the recovery of deteriorated splanchnic organs due to cardiogenic shock.

Animals↗
PubMed2003

Postcardiotomy assisted circulation with roller pump--early and late results.

The incidence of postcardiotomy myocardial failure (PMF) requiring mechanical circulatory support beyond IABP is reported to be 0.2% to 1.2%. From Dec. 1989 through Dec. 1995, 18 patients (0.3% of the total pump cases) were supported with roller pump type of LVAD. Assisted flow ranged from 3.5 up to 5 L/min with average support time of 35.5 hours. Six (33.3%) patients died while on LVAD. The causes of additional seven deaths (pts weaned of LVAD) were: myocardial failure (4), stroke (2) and intractable bleeding during removal of the LVAD (1). Overall, five patients (27.8%) were successfully discharged from the hospital. Two out of five long-term survivors died later, 6 months and 4 years postoperatively, both of cardiac causes. The actuarial survival rate of long-term survivors was 60% at 7 years, all of them being in NYHA functional class II. These results have proved efficiency of roller pump driven LVAD for short-term circulatory support in pts with PMF. Results are comparable to so far published data on postcardiotomy support with the same, as well as other types of more versatile and costly devices.

Aged↗
PubMed1993

Assisted circulation using cardiomyoplasty together with aortomyoplasty.

Both dynamic cardiomyoplasty and counterpulsation by the synchronous paced contraction of skeletal muscles in aortomyoplasty can improve ventricular function. The goal of this study was to clarify the effect of cardiomyoplasty combined with aortomyoplasty on cardiac dysfunction in dogs. The percentage of increase in various hemodynamic parameters was calculated during assisted and unassisted cardiac cycles and was compared for three groups: cardiomyoplasty only (Group A), aortomyoplasty only (Group B), and both methods combined (Group C). In Group A, the left ventricular pressure (LVP), systolic aortic pressure (systolic AoP), and dp/dt of LVP (LV dp/dt) increased significantly; the diastolic aortic pressure (diastolic AoP) did not change; and the endocardial viability ration (EVR) decreased during assisted cardiac cycles. In Group B, the diastolic AoP and EVR were improved significantly, but the LVP, LV dp/dt, and systolic AoP were unchanged during assisted cardiac cycles. In contrast to Groups A and B, all parameters were improved in Group C during assisted cardiac cycles. Cardiac assistance using cardiomyoplasty together with aortomyoplasty was more effective than either procedure used alone.

Animals↗