Continuous Flow Pumps Research Articles

Continuous flow pumps and total artificial hearts: management issues

Feasibility studies are underway for new axial flow ventricular assist systems and with a total artificial heart (TAH). The axial flow pumps provide continuous flow from the left ventricle (LV) to the aorta; the TAH provides pulsatile flow to the pulmonary and systemic circulation. Understanding the differences between these systems is necessary for appropriate patient selection and management. We compared the Jarvik 2000 axial-flow pump and the AbioCor TAH. The Jarvik 2000 pump is placed in the LV with its outflow graft anastomosed to the aorta. This system is used for bridge-to-transplantation and destination therapy. The AbioCor TAH provides complete circulatory support. The AbioCor is used for destination therapy in patients expected to die in less than 30 days. Worldwide, 45 patients have received the Jarvik 2000 as a bridge to transplantation (n = 34) or destination therapy (n = 11) for an average duration of support of 132.8 days (5 to 853 days). In 30 bridge-to-transplantation cases, 14 patients (47%) have undergone heart transplantation, 5 (17%) continue to be supported with the Jarvik 2000 device, and 11 (37%) have died. Five of 7 patients supported by the AbioCor TAH survived beyond the perioperative period; 4 were ambulatory, 2 were discharged from the hospital, and 1 is at home 13 months after implantation. Anticoagulation therapy and infection management are necessary for both systems. Therapy with inotropic agents, vasoactive drugs, a pacemaker, and electrolyte normalization is necessary for Jarvik patients. AbioCor-supported patients do not require medications to support heart function. Vasoactive agents may be useful for controlling blood pressure.

BASIC STUDY OF THE ROTARY UNDULATION PUMP

The rotary undulation pump is a continuous flow pump with a new principle. The pump is composed of a disk having a pair of convex shape on both side and pump housing having the shape that one side is narrow and the other side is wide. The disk nutates and at the same time rotates with half the speed of nutation. With this motion of the disk, the disk can rotate through the narrow part of the pump housing and pump mechanism occurs. The first prototype model was developed using 4 permanent magnets built in the disk and every 6 electromagnets built in both side of the pump housing. In this model the disk could be driven from both side. To drive the model, a special drive circuit was developed. In this circuit, each electromagnet was driven individually with a pulse width modulation (PWM) method. Using this circuit, several drive methods were tested. Owing to the wide and unstable gap distance between the permanent magnet and electromagnet, the output was not enough when the load was high. The results showed that it was important to make the gap distance stable and narrow for designing the pump. The second prototype model was newly designed based on the results. This model is constructed with 8 permanent magnets built in the ring shaped disk and 12 electromagnets fixed to the housing and situated at the center of the disk. Now, the second prototype model and a drive circuit for this model are being developed.

Ventricular assist devices

Recent advances in technology as well as new indications for implantation have appeared in the field of ventricular assist devices. Progress has also been made in the understanding of the underlying mechanisms of myocardial recovery after ventricular assist device support. Technological progress includes the development of fully implantable pulsatile and continuous flow pumps, either axial flow or centrifugal, for left ventricular and total heart assistance. Among the new indications for ventricular assist device support, the most important is the use of the device as permanent treatment for end-stage cardiac failure patients. Increased knowledge has been acquired regarding the effects of mechanical assistance and of unloading of the heart on haemodynamics, as well as on the cellular, molecular and electrophysiological characteristics of the failing heart. All these findings suggest that depressed myocardial function can sometimes recover with ventricular assist device therapy. Ventricular assist device support, however, still carries a high rate of complications: the device itself can fail, bleeding and thromboembolism are common, immunity is disturbed and the incidence of infection remains high. In patients with end-stage heart failure, ventricular assist devices can be used as a bridge to transplantation or to recovery, but they are now also considered as a long-term myocardial replacement therapy. Which device is the most appropriate for each indication, however, remains to be defined. Even if the underlying mechanisms of myocardial recovery are progressively clarified, the use of ventricular assist devices as a bridge to recovery still has limited clinical success. Clinical trials with the fully implantable devices are in their early stages, but these pumps appear promising in terms of efficacy, reliability and complication rate, as well as being easy to implant. Because more patients will benefit from ventricular assist device placement in the future, anaesthesiologists must be prepared to manage patients undergoing ventricular assist device placement or presenting for noncardiac surgery while under ventricular assist device support.

Usefulness of percutaneous left ventricular assistance to support high-risk percutaneous coronary interventions

Percutaneous coronary intervention (PCI) has been proposed as a measure to alleviate symptoms and improve prognosis in patients with atherosclerotic heart disease and depressed heart function. Nonetheless, the risk of ischemic complications during or after the procedure is potentially increased in these patients. A number of supportive techniques have been described for high-risk angioplasty 1 Shawl F.A. Quyyumi A.A. Bajaj S. Hoff S.B. Dougherty K.G. Percutaneous cardiopulmonary bypass-supported coronary angioplasty in patients with unstable angina pectoris or myocardial infarction and a left ventricular ejection fraction ≤25%. Am J Cardiol. 1996; 77: 14-19 Abstract Full Text PDF PubMed Scopus (25) Google Scholar , 2 Scholz K.H. Dubois-Rande J.L. Urban P. Morice M.C. Loisance D. Smalling R.W. Figulla H.R. Clinical experience with the percutaneous hemopump during high-risk coronary angioplasty. Am J Cardiol. 1998; 82: 1107-1110 Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar , 3 Dubois-Rande J.L. Teiger E. Garot J. Aptecar E. Pernes J.M. Tixier D. Gueret P. Loisance D. Dupouy P. Effects of the 14F hemopump on coronary hemodynamics in patients undergoing high-risk coronary angioplasty. Am Heart J. 1998; 135: 844-849 Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar , 4 Schreiber T.L. Kodali U.R. O’Neill W.W. Gangadharan V. Puchrowicz-Ochocki S.B. Grines C.L. Comparison of acute results of prophylactic intraaortic balloon pumping with cardiopulmonary support for percutaneous transluminal coronary angioplasty (PCTA). Cathet Cardiovasc Diagn. 1998; 45: 115-119 Crossref PubMed Scopus (22) Google Scholar , 5 Kaul U. Sahay S. Bahl V.K. Sharma S. Wasir H.S. Venugopal P. Coronary angioplasty in high risk patients comparison of elective intraaortic balloon pump and percutaneous cardiopulmonary bypass support—a randomized study. J Interv Cardiol. 1995; 8: 199-205 Crossref PubMed Scopus (18) Google Scholar ; however, no single approach has achieved wide acceptance. Limited effectiveness in the actual support 6 Taguchi I. Ogawa K. Oida A. Abe S. Kaneko N. Sakio H. Comparison of hemodynamic effects of enhanced external counterpulsation and intra-aortic balloon pumping in patients with acute myocardial infarction. Am J Cardiol. 2000; 86: 1139-1141 Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar and device-related complications 2 Scholz K.H. Dubois-Rande J.L. Urban P. Morice M.C. Loisance D. Smalling R.W. Figulla H.R. Clinical experience with the percutaneous hemopump during high-risk coronary angioplasty. Am J Cardiol. 1998; 82: 1107-1110 Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar , 4 Schreiber T.L. Kodali U.R. O’Neill W.W. Gangadharan V. Puchrowicz-Ochocki S.B. Grines C.L. Comparison of acute results of prophylactic intraaortic balloon pumping with cardiopulmonary support for percutaneous transluminal coronary angioplasty (PCTA). Cathet Cardiovasc Diagn. 1998; 45: 115-119 Crossref PubMed Scopus (22) Google Scholar , 7 Alderman J.D. Gabliani G.I. McCabe C.H. Brewer C.C. Lorell B.H. Pasternak R.C. Skillman J.J. Steer M.L. Baim D.S. Incidence and management of limb ischemia with percutaneous wire-guided intraaortic balloon catheters. J Am Coll Cardiol. 1987; 9: 524-530 Abstract Full Text PDF PubMed Scopus (87) Google Scholar have hampered a more widespread use of these methods. Recently, a newly developed percutaneous left ventricular assist device (pVAD) has been demonstrated to effectively reverse cardiogenic shock after myocardial infarction (Tandem Heart pVAD; Cardiac Assist Technologies, Inc., Ithaca, New York). 8 Thiele H. Lauer B. Hambrecht R. Boudriot E. Cohen H.A. Schuler G. Reversal of cardiogenic shock by percutaneous left atrial-to-femoral arterial bypass assistance. Circulation. 2001; 104: 2917-2922 Crossref PubMed Scopus (233) Google Scholar This system is readily deployed by percutaneous approach in the catheterization laboratory and is able to provide a systemic output of up to 4 L/min. An inflow cannula is inserted into the left atrium via transseptal puncture and the oxygenated blood is diverted to the femoral artery by a low-speed centrifugal continuous-flow pump. In this study, we report on a series of patients who underwent high-risk PCI supported by the Tandem Heart pVAD.

Significant reduction in major LVAD device failures: comparison of the heartmate® VE and XVE LVAS

Background: Left ventricular assist device (LVAD) is an established surgical therapy for patients with end-stage heart failure (HF) as a bridge to heart transplantation (HTx). Pulsatile LVAD clinical application is limited by large dimensions, noise and major complications as bleeding, thromboembolism and infection. We report our clinical experiences with the DeBakey VAD continuous axial flow pump as bridge to HTx (BTT). Patients and Methods: Since April 2000, 12 patients with end-stage HF have been supported with the DeBakey VAD at our Institution (8 male, 42 14 years, range 12-57 y; 8 dilated idiopathic cardiomyopathy, 3 ischemic cardiomyopathy, 1 for major device failure of a pulsatile LVAD implanted at another institution). Before implant all patients suffered for severe heart failure (NYHA IV) despite of maximal pharmacological support and were put on the waiting list for HTx. All patients signed written informed consent. Mean cardiac index was 1,58 0,52 l/min/m2. Results: Total support time amounts to 607 patient/days. Nine patients (75%) were successfully transplanted after 51 49 days (range 11 -141 days). Two patients (16.6%) died during assistance due to multiorgan failure. One patient is still on VAD. No patients needed right-VAD. Bleeding complications required rethoracotomy in 2 patients (16.6%), neurologic event occurred in 1 patient, left ventricle/LVAD thrombosis occurred in one patient and was succesfully conservatively treated with endoventricular thrombolysis delivering rTPA into the left ventricle. No clinically relevant elevation of plasma-free hemoglobin was detected. No device, driveline or abdominal pocket infection occurred. No device failure occurred. Conclusions: In our clinical experience the axial continuous flow DeBakey VAD obtained an elevated rate of success associated with low risk for bleeding, hemolysis, thromboembolic and infectious complications.

A new technique for assessing myocardial improvement using pressure-volume loops during mechanical circulatory assistance

Background: Successful mechanical circulatory support (MCS) for end-stage heart failure may lead to LVAD removal without transplantation if cardiac function can be accurately assessed. End-systolic pressure-volume ratio (ESPVR), a load-independent index of myocardial contractility, may be used to predict myocardial improvement. Preload manipulation, required to calculate ESPVR, can be achieved by changing LVAD unloading rate (rpm or beat rate, for continuous flow or pulsatile pumps, respectively).

Nitric oxide inhalation prompts weaning from the right ventricular assist device: Evaluation under continuous-flow biventricular assistance

Objective: The objective of this study was to investigate the effect of nitric oxide on the recovery of right heart function under global ischemia with a continuous-flow biventricular assist device support. Methods: Fifteen piglets were divided into three groups: continuous-flow biventricular assist support only (control group), global ischemia with continuous-flow biventricular assist support (ischemia only group), and global ischemia with continuous-flow biventricular assist support plus nitric oxide inhalation (nitric oxide group). Two continuous-flow pumps were used as left and right ventricular assist devices. In the ischemic groups (ischemia only group and nitric oxide group), global ischemia was induced for 30 minutes and followed by a 6-hour reperfusion period; the nonischemic control group underwent a 6-hour perfusion period only. The left ventricular assist device was driven at a flow rate of more than 75 to 80 mL/(min · kg). The right ventricular assist device was driven so as to sustain the left ventricular assist device flow, and the animal was weaned from it in accordance with the objective of cardiac recovery. Results: Mean pulmonary arterial pressure remained low in the nitric oxide group (mean 23 mm Hg), whereas it rose from 19.9 mm Hg to 39.3 mm Hg in the ischemia group and to 26.2 mm Hg in the control group. Mixed venous saturation was maintained at more than 60% in all cases. Although no piglets in the ischemia group were able to survive without continuous-flow biventricular assist support, the right ventricular assist device flow ratio (device flow/total systemic flow) in the nitric oxide group could be reduced in all cases, and it was possible to wean the piglets from right ventricular assist device support in 4 of 5 cases. Conclusion: Inhalation of 40-ppm nitric oxide enabled smoother maintenance of the left ventricular assist device flow and prompted the weaning from right ventricular assist device support on continuous-flow biventricular assist.J Thorac Cardiovasc Surg 2002;124:739-49

Wound Infiltration with Ropivacaine Using a Continuous-Flow Infusion Pump Reduces Pain and Opioid Requirement in Patients after Major Shoulder Surgery

Wound Infiltration with Ropivacaine Using a Continuous-Flow Infusion Pump Reduces Pain and Opioid Requirement in Patients after Major Shoulder Surgery

Principle of the rotary undulation pump

The undulation pump is a unique continuous-flow displacement-type blood pump with high performance. However, the undulation pump has limited mechanical durability. To eliminate this limitation, the principle of the rotary undulation pump was developed. The rotary undulation pump is composed of a disk having a pair of convex shapes on both side and pump housing having a shape such that one side is narrow and the other side is wide. The disk nutates and at the same time rotates at half the speed of nutation. With this movement of the disk, the disk can rotate through the narrow part of the pump housing and pump mechanism occurs. Between the disk and the pump housing, four pump rooms are created. The four outputs are added at the outlet port, and continuous flow is generated. The practical shape was designed with computer graphics. The motion of the disk was calculated accurately with the computer, and the principle was confirmed. The inlet and outlet port areas were also calculated. Models were developed to demonstrate the principle. With the magnetic coupling method, up to about 6 l/min of output could be measured against 100 mmHg of pressure load, and the principle was demonstrated to work. An experimental model to study an electromagnetic drive method, including a magnetically suspended drive, is being developed for the next step. Although many objectives remain, the basic principle of the rotary undulation pump was confirmed.

Mechanical circulatory support: New advances, new pumps, new ideas

Mechanical circulatory support (MCS) is a viable therapy for severe end-stage heart disease. Most obstacles to long-term MCS therapy have been overcome, and a number of clinical trials, including the recent REMATCH trial, have shown a clear benefit in terms of survival and improved quality of life. MCS should therefore no longer be considered as simply a temporary bridge to other therapies, but also a destination therapy whose potential should continue to expand through the development and use of newer, more innovative devices such as continuous flow pumps, next-generation centrifugal pumps, and total artificial hearts. The homebound heart failure patient and the patient facing imminent death from massive myocardial infarction receive little statistical benefit from current therapies, and the new and evolving MCS technologies offer the potential for effective therapy to these desperately ill patients. Copyright 2002, Elsevier Science (USA). All rights reserved.

Interaction of the cardiovascular system with an implanted rotary assist device: simulation study with a refined computer model.

In recent years, implanted rotary pumps have achieved the level of extended clinical application including complete mobilization and physical exercise of the recipients. A computer model was developed to study the interaction between a continuous-flow pump and the recovering cardiovascular system, the effects of changing pre- and afterloads, and the possibilities for indirect estimation of hemodynamic parameters and pump control. A numerical model of the cardiovascular system using Matlab Simulink simulation software was established. Data of circulatory system modules were derived from patients, our own in vitro and in vivo experiments, and the literature. Special care was taken to simulate properly the dynamic pressure-volume characteristics of both left and right ventricle, the Frank-Starling behavior, and the impedance of the proximal vessels. Excellent correlation with measured data was achieved including pressure and flow patterns within the time domain, response to varying loads, and effects of previously observed pressure-flow hysteresis in rotary pumps. Potential energy, external work, pressure-volume area, and other derived heart work parameters could be calculated. The model offers the possibility to perform parameter variations to study the effects of changing patient condition and therapy and to display them with three-dimensional graphics (demonstrated with the effects on right ventricular work and efficiency). The presented model gives an improved understanding of the interaction between the pump and both ventricles. It can be used for the investigation of various clinical and control questions in normal and pathological conditions of the left ventricular assist device recipient.

Analysis of the relationship between left ventricular pressure and motor current for evaluation of native cardiac function during left ventricular support with a centrifugal blood pump

Control of the ventricular assist device (VAD) for native heart preservation should be attempted, and the VAD could be one strategy for dealing with the shortage of donors in the future. In the application of nonpulsatile blood pumps for ventricular assistance from the ventricular apex to the aorta, bypass flow and hence the motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous-flow pumps, in this study we investigated whether motor current could be used as an index for continuous monitoring of native cardiac function. In study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mmHg, afterload of 40 mmHg, and LV systolic pressure of 40 mmHg was used. The pump speed was fixed at 1300, 1500, and 1700 rpm, and LV systolic pressure was increased up to 140 mmHg by steps of 20 mmHg while the changes in LV pressure, motor current, pump flow, and aortic pressure were observed. In study 2, an in vivo experiment was performed using three sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LVP was varied through administration of dopamine while the changes in LV pressure, pump flow, and motor current at 1500 and 1700 rpm were observed. An excellent correlation was observed in both in vitro and in vivo studies in the relationship between motor current and LV pressure. In study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1300, 1500, and 1700 rpm, respectively. In study 2, they were 0.88 (animal no. 1), 0.83 (animal no. 2), and 0.88 (animal no. 3) for 1500 rpm, and 0.95 (animal no. 2) and 0.93 (animal no. 3) for 1700 rpm. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VAD for native heart preservation.

The index of motor current amplitude has feasibility in control for continuous flow pumps and evaluation of left ventricular function.

The index of motor current amplitude (ICA) has feasibility in continuous-flow ventricular assist device control. It can demonstrate the safe range of pump speed, which exists between the starting point of total assistance (t-point) and the starting point of sucking (s-point). The objective of this study was to investigate how the ICA characteristic curve changes with each condition of contractility, preload, and afterload changes. We changed preload, afterload, and contractility of closed-mock circulation and plotted the change of the ICA value against pump speed. Then the shift of ICA characteristic curve against the change of each condition was considered. When preload increased, ICA characteristic curves showed the expansion of a safe range. When afterload increased, ICA characteristic curves were shifted to the high rotation side, slightly narrowing a safe range. When contractility increased, ICA characteristic curves showed the shift of a convex above to narrowing of a safe range. As these shift patterns were observed even when the driving conditions of a circuit changed, reproducibility was checked. Understanding the feature of a shift pattern of ICA characteristic curves correctly, a possibility that change of the heart function could be predicted by change of ICA value and a possibility for a flexible control method based on ICA, according to hemodynamic state, were suggested.

Motor Current Waveforms as an Index for Evaluation of Native Cardiac Function During Left Ventricular Support with a Centrifugal Blood Pump

Control of ventricular assist devices (VADs) for native heart preservation should be attempted, and it could be one strategy for dealing with the shortage of donors in the future. In the application of a nonpulsatile blood pump for ventricular assistance from its apex to the aorta, the bypass flow and hence motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous flow pumps, this study investigated whether or not motor current could be used as an index for continuous monitoring of native cardiac function. In Study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mm Hg, afterload of 40 mm Hg, and left ventricular (LV) systolic pressure of 40 mm Hg was used. The pump rpm were fixed at 1,300, 1,500, and 1,700, and LV systolic pressure was increased up to 140 mm Hg by a step of 20 mm Hg while observing the changes in LV pressure, motor current, pump flow, and aortic pressure. In Study 2, in vivo experiments were performed using 5 sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LV pressure was varied through administration of dopamine while observing the changes in LV pressure, pump flow, motor current, and aortic pressure at 1,500 and 1,700 rpm. An excellent correlation was observed both in vitro and in vivo studies in the relationship between motor current and LV pressure. In Study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1,300, 1,500, and 1,700 rpm, respectively. In Study 2, they were 0.90 (Animal 1), 0.82 (Animal 2), 0.89 (Animal 3), 0.93 (Animal 4), and 0.70 (Animal 5) respectively for 1,500 rpm, and 0.94 (Animal 2), 0.85 (Animal 3), 0.94 (Animal 4), and 0.89 (Animal 5) respectively, for 1,700 rpm. The relationship between motor current and pump flow and LV pressure showed an unstable correlation in an in vivo study. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VADs for native heart preservation.

The Past 50 Years of Cardiovascular Surgery

The Past 50 Years of Cardiovascular Surgery

DEVELOPMENT OF A MIXED-FLOW CARDIAC ASSIST DEVICE

A new type of continuous flow pump, the mixed flow pump (MFP), featuring smaller size and higher efficiency than a centrifugal pump, while achieving lower hemolysis than an axial flow pump, was reported by us at the 44thASAIO congress. These advantages prompted us to develop a MFP for cardiopulmonary bypass (CPB), extracorporeal membrane oxygenation, or ventricular assistance. In an attempt to reduce the hemolysis of an MFP, we studied the influence on hemolysis of decreasing pump speed, by changes of impeller size. Four MFPs (A: 32-mm; B: 36-mm; C: 40-mm; and D: 44-mm impeller diameter) were compared in this study. These MFPs developed a pump flow of 51/min against a 100-mmHg pressure head, at 3450, 3000, 2550, and 2200 rpm, respectively. In vitro hemolysis tests were performed under three different driving conditions, defined by pressure heads of 100, 200, and 300 mmHg, all with a pump flow rate of 51/min, using fresh bovine blood.TableThese results showed that the lowest hemolysis was achieved in pump D at 100 mmHg, and in pump C at over 200 mmHg. It was concluded that a lower level of hemolysis is associated with decreasing pump speed, commensurate with enlargement of pump size; however, over-enlargement of the impeller increased hemolysis again. Among the pumps evaluated, the 40 mm-impeller MFP was deemed best-suited for CPB, because of its low hemolysis at afterloads over 200 mmHg, and is now thought to be the minimum size for commercial applications of the MFP as a CPB pump.

A pulsatile flow model for in vitro quantitative evaluation of prosthetic valve regurgitation.

A pulsatile pressure-flow model was developed for in vitro quantitative color Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors controlled by a computer. The piston was connected to acrylic chambers designed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventricular" chamber, a prosthetic heart valve was placed at the inflow connection with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reservoir arranged to mimic the peripheral circulation. The flow model was filled with a 0.25% corn starch/water suspension to improve Doppler imaging. A continuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosthetic valves. This pulsatile flow model was able to generate pressure and flow in the physiological human range, with independent adjustment of pulse duration and rate as well as of stroke volume. This model mimics flow profiles observed in patients with regurgitant prosthetic valves.

PATHOPHYSIOLOGICAL CHANGES AFTER CONTINUOUS FLOW VAD IMPLANTATION VERSUS SHAM-IMPLANTATION IN CALVES

Since 1996, 55 calves have been chronically implanted with various continuous flow blood pumps at the University of Pittsburgh. Pathophysiological changes seen in the testing of these devices include decreased hematocrit, post-surgical hypokalemia, renal infarction, and altered platelet function. To further determine the effect of the implantation surgery and the device on the calves, 3 calves were sham-implanted (SI). SI calves had a short length of graft anastomosed to the aorta, the left ventricle incised, and received post-surgical anticoagulation and blood withdrawals as with pump-implanted (PI) calves. SI calves were monitored for 90 days prior to sacrifice. PI and SI calves experienced a significant decrease in hematocrit post surgery (p < 0.01) which stabilized at a lower level than baseline (p < 0.01) after 28 days for the remainder of the experimental period. In both PI and SI calves, there was a transient post-surgical hypokalemia, which was more severe in PI calves. A significant correlation (r=0.58, p < 0.001) was found between the pulse pressure (systolic-diastolic) in the immediate period after implantation and the serum potassium 8 hours later. At this time point, SI calves had a significantly greater serum potassium than PI calves (3.13 ± 0.20 vs. 2.62 ± 0.07 mmol/L, p < 0.05). In summary, the results provide a valuable insight into pathophysiological changes seen due to continuous flow pump implantation, and could have clinical implications for human implantation.

Investigation of the Methods of Controlling the Biventricular Assist Device with Continuous Flow Pumps

Investigation of the Methods of Controlling the Biventricular Assist Device with Continuous Flow Pumps

Implantation of the undulation pump total artificial heart in the goat.

The undulation pump total artificial heart (UPTAH) was developed by using small-size continuous-flow displacement-type blood pumps (undulation pump). To clarify and improve the problems accompanied by the implantation in the chest, 14 animal experiments were performed on goats weighing 41.3-79.2 kg. The UPTAH could be implanted in the chest of all goats and was driven with a modulation pulsatile mode. The first problem was the atrial suction effect. This problem could be prevented to some extent by developing the soft disk and by improving atrial cuffs. An automatic detection and releasing of the atrial suction effect was also tried. The next problem was acute lung edema accompanied by the postural change of the animal. Development of the automatic control of left atrial pressure could prevent this problem. Small blood leakage from a pinpoint hole in the seal membrane was the next problem. Improvement of the manufacturing procedure of the membrane prevented this. With these improvements, a 10 day survival could be obtained with this unique implantable total artificial heart.