We have previously developed a native heart load control system for a continuous-flow left ventricular assist device (LVAD) ((EVAHEART
®
; Sun Medical) and demonstrated that the rotational speed (RS) ...in synchronization with the cardiac cycle can alter pulsatility and left ventricular (LV) load under general anesthesia. In this study, we assessed the effects of different levels of increase in RS on pulsatility and LV load in the chronic awake phase. We implanted the EVAHEART via left thoracotomy in 7 normal goats (59.3 ± 4.6 kg). Two weeks after implantation, we examined the effects of co-pulse mode (increased RS in the systolic phase) and counter-pulse mode (increased RS in the diastolic phase), as well as shifting the change in RS from 250 to 500 rpm, and 750 rpm in both modes on pulsatility and LV load. Pulsatility was assessed using pulse pressure and mean dP/dt max of aortic pressure. LV load was assessed using stroke work and left ventricle end-diastolic volume determined from LV pressure–volume loops. In the co-pulse mode, pulsatility values increased as the change in RS increased. By contrast, in the counter-pulse mode, these values decreased as the change in RS increased. LV load increased significantly in the co-pulse mode compared with the counter-pulse mode, but there were no significant differences among the three levels of RS increase in either mode. Increasing RS to varying degrees with our newly developed system could contribute to pulsatility. However, it appeared to have little effect on LV load in normal hearts.
Background: A novel control system for the EVAHEART left ventricular assist device (LVAD), known as the Native Heart Load Control System (NHLCS), can change the device’s rotational speed (RS) in ...synchrony with the heartbeat. The system enhanced coronary flow (CoF) with the counter-pulse mode in normal goats’ hearts, so we examined the change in CoF in goats with acute ischemic heart failure (HF). Methods and Results: We studied 14 goats (56.1±6.9kg) with acute ischemic HF induced by coronary microsphere embolization. We installed EVAHEART and ran the device in 4 modes continuous support, circuit-clamp, counter-pulse (raise RS in diastole), and co-pulse (raise RS in systole) with 50% or 100% bypass in each mode. In comparison with the circuit-clamp mode, CoF was 121.0±14.1% in the counter-pulse mode and 102.9±7.9% in the co-pulse mode, whereas it was 113.5±10.6% in the continuous mode, with 100% bypass (P<0.05). The same difference was confirmed with 50% bypass. The results indicated that a LVAD in an acute ischemic heart enhanced CoF, and that CoF was greater in the counter-pulse mode and smaller in the co-pulse mode relative to the continuous mode. Conclusions: By using NHLCS to change CoF, recovery of native heart function with a LVAD has a better prognosis. (Circ J 2013; 77: 995–1000)
Although the outcomes of patients with end-stage heart failure treated with implantable left ventricular assist devices have improved, extracorporeal left ventricular assist devices continue to play ...an important role, especially in pediatric patients. The present study aimed to examine the long-term biocompatibility of a small-sized extracorporeal pneumatic left ventricular assist device (NIPRO-LVAD) used in a 30- to 90-day animal experiment. The NIPRO-LVAD was designed for pediatric patients or small-sized adults. The left ventricular assist device system was installed in four adult Shiba goats weighing 25.7 ± 4.78 kg via a left thoracotomy. The outflow graft was sewn to the descending aorta and the inflow cannula was placed in the left ventricle through the left ventricular apex. Oral antiplatelet (aspirin) and oral anticoagulation therapies (warfarin) were also administered. Three out of four animals survived for a 30-day period and two goats survived for 90 days. One animal was killed early because of low pump flow due to obstruction of the inflow cannula by a left ventricular endocardial vegetation. The blood pump exhibited sufficient hydrodynamic performance with blood flows of 1.5–2.0 L/min. The animals’ laboratory values were within normal limits by postoperative day 7. There was no significant thrombus formation on the housing, diaphragm, or valves of the explanted pumps. Based on the biocompatibility demonstrated in this animal study, the explanted small-sized pump may be suitable for use in left ventricular assist device systems for pediatric patients.
An extracorporeal centrifugal blood pump with a hydrodynamically levitated impeller was developed for use in a durable extracorporeal membrane oxygenation (ECMO) system. The present study examined ...the biocompatibility of the blood pump during long-term use by conducting a series of 30-day chronic animal experiments. The ECMO system was used to produce a percutaneous venoarterial bypass between the venae cavae and carotid artery in adult goats. No anticoagulation or antiplatelet therapy was administered during the experiments. Three out of four animals survived for the scheduled 30-day period, and the blood pumps and membrane oxygenators both exhibited sufficient hydrodynamic performance and good antithrombogenicity, while one animal died of massive bleeding from the outflow cannulation site. The animals’ plasma free hemoglobin had returned to within the normal range by 1 week after the surgical intervention, and their hemodynamic and biochemistry parameters remained within their normal ranges throughout the experiment. The explanted centrifugal blood pumps did not display any trace of thrombus formation. Based on the biocompatibility demonstrated in this study, the examined centrifugal blood pump, which includes a hydrodynamically levitated impeller, is suitable for use in durable ECMO systems.
There are many reports comparing pulsatile and continuous-flow left ventricular assist devices (LVAD). But continuous-flow LVAD with the pulsatile driving technique had not been tried or discussed ...before our group’s report. We have previously developed and introduced a power-control unit for a centrifugal LVAD (EVAHEART®; Sun Medical), which can change the speed of rotation so it is synchronized with the heart beat. By use of this unit we analyzed the end-diastolic volume (EDV) to determine whether it is possible to change the native heart load. We studied 5 goats with normal hearts and 5 goats with acute LV dysfunction because of micro-embolization of the coronary artery. We used 4 modes, “circuit-clamp”, “continuous”, “counter-pulse”, and “co-pulse”, with the bypass rate (BR) 100%. We raised the speed of rotation of the LVAD in the diastolic phase with the counter-pulse mode, and raised it in the systolic phase with the co-pulse mode. As a result, the EDV decreased in the counter-pulse mode and increased in the co-pulse mode, compared with the continuous mode (
p
< 0.05), in both the normal and acute-heart-failure models. This result means it may be possible to achieve favorable EDV and native heart load by controlling the rotation of continuous-flow LVAD, so it is synchronized with the cardiac beat. This novel driving system may be of great benefit to patients with end-stage heart failure, especially those with ischemic etiology.
The management of heart failure patients presenting in a moribund state remains challenging, despite significant advances in the field of ventricular assist systems. Bridge to decision involves using ...temporary devices to stabilize the hemodynamic state of such patients while further assessment is performed and a decision can be made regarding patient management. We developed a new temporary left ventricular assist system employing a disposable centrifugal pump with a hydrodynamically levitated bearing. We used three adult goats (body weight, 58–68 kg) to investigate the 30-day performance and hemocompatibility of the newly developed left ventricular assist system, which included the pump, inflow and outflow cannulas, the extracorporeal circuit, and connectors. Hemodynamic, hematologic, and blood chemistry measurements were investigated as well as end-organ effect on necropsy. All goats survived for 30 days in good general condition. The blood pump was operated at a rotational speed of 3000–4500 rpm and a mean pump flow of 3.2 ± 0.6 L min. Excess hemolysis, observed in one goat, was due to the inadequate increase in pump rotational speed in response to drainage insufficiency caused by continuous contact of the inflow cannula tip with the left ventricular septal wall in the early days after surgery. At necropsy, no thrombus was noted in the pump, and no damage caused by mechanical contact was found on the bearing. The newly developed temporary left ventricular assist system using a disposable centrifugal pump with hydrodynamic bearing demonstrated consistent and satisfactory hemodynamic performance and hemocompatibility in the goat model.
Our research institute has been working on the development of a compact wearable drive unit for an extracorporeal ventricular assist device (VAD) with a pneumatically driven pump. A method for ...checking the pump blood flow on the side of the drive unit without modifying the existing blood pump and impairing the portability of it will be useful. In this study, to calculate the pump flow rate indirectly from measuring the flow rate of the driving air of the VAD air chamber, we conducted experiments using a mock circuit to investigate the correlation between the air flow rate and the pump flow rate as well as its accuracy and error factors. The pump flow rate was measured using an ultrasonic flow meter at the inflow and outflow tube, and the air flow was measured using a thermal mass flow meter at the driveline. Similarity in the instantaneous waveform was confirmed between the air flow rate in the driveline and the pump flow rate. Some limitations of this technique were indicated by consideration of the error factors. A significant correlation was found between the average pump flow rate in the ejecting direction and the average air flow rate in the ejecting direction (
R
2
= 0.704–0.856), and the air flow rate in the filling direction (
R
2
= 0.947–0.971). It was demonstrated that the average pump flow rate was estimated exactly in a wide range of drive conditions using the air flow of the filling phase.
We developed a novel controller for a continuous-flow left ventricular assist device (EVAHEART) that can change the pump’s rotational speed (RS) in synchronization with a patient’s myocardial ...electrocardiogram (ECG) with the aim of facilitating cardiac recovery. We previously presented various applications of this system in animal models, but there remained a concern that the repeated acceleration and deceleration of the impeller may induce additional hemolysis. In this study, we evaluated the blood trauma and motor power consumption induced by our system in a mock circulation. We evaluated our system with a 60-bpm pulse frequency and a variance between the high and low RSs of 500 rpm (EVA-P;
n
= 4). The continuous modes of EVAHEART (EVA-C;
n
= 4) and ROTAFLOW (
n
= 4) were used as controls. The pumps were examined at a mean flow rate of 5.0 ± 0.2 L/min against a mean pressure head of 100 ± 3 mmHg for a 4-h period. As a result, the normalized indexes of the hemolysis levels of EVA-P and EVA-C were 0.0023 ± 0.0019 and 0.0023 ± 0.0025, respectively, and their difference was not significant. The estimated mean motor power consumptions of EVA-C and EVA-P were 6.24 ± 0.33 and 7.19 ± 0.93 W, respectively. When a novel ECG-synchronized RS-change system was applied to EVAHEART, the periodic RS change with a 500-rpm RS variance did not affect the hemolysis at a 60-bpm pulse frequency.
Axial flow blood pumps are widely used for mechanical circulatory support including implantable left ventricular assist device and peripheral intra-aortic ventricular assist device. The ...miniaturization of the devices plays more and more important role in extending the treatable therapeutic options using these blood pumps. On the other hand, miniaturization will be accompanied with higher motor speed and lower energy efficiency, and blood compatibility of the devices must be taken special care in their developmental stage.
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