Alternation of left ventricular load by a continuous-flow left ventricular assist device with a native heart load control system in a chronic heart failure model

Arakawa, Mamoru; Nishimura, Takashi; Takewa, Yoshiaki; Umeki, Akihide; Ando, Masahiko; Adachi, Hideo; Tatsumi, Eisuke

doi:10.1016/j.jtcvs.2013.12.049

Cited by 20 publications

(15 citation statements)

References 27 publications

(34 reference statements)

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“…We developed a rotational speed (RS) modulation system for EVAHEART that can change the RS in synchronization with the cardiac cycle of the native heart. We have previously reported that this system can change the native heart load, alter arterial pulsatility, enhance myocardial perfusion, and may be able to prevent aortic insufficiency without harmful effects on hemolysis . Although these properties can be beneficial to patients under CF‐LVAD, there remains a concern that the repeated acceleration and deceleration of an impeller may affect vWF dynamics.…”

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confidence: 99%

Influence of a Rotational Speed Modulation System Used With an Implantable Continuous‐Flow Left Ventricular Assist Device on von Willebrand Factor Dynamics

et al. 2016

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We have developed a rotational speed (RS) modulation system for a continuous-flow left ventricular assist device (EVAHEART) that can change RS in synchronization with a patient's electrocardiogram. Although EVAHEART is considered not to cause significant acquired von Willebrand syndrome, there remains a concern that the repeated acceleration and deceleration of the impeller may degrade von Willebrand factor (vWF) multimers. Accordingly, we evaluated the influence of our RS modulation system on vWF dynamics. A simple mock circulation was used. The circulation was filled with whole bovine blood (650 mL), and the temperature was maintained at 37 ± 1°C. EVAHEART was operated using the electrocardiogram-synchronized RS modulation system with an RS variance of 500 rpm and a pulse frequency of 60 bpm (EVA-RSM; n = 4). The pumps were operated at a mean flow rate of 5.0 ± 0.2 L/min against a mean pressure head of 100 ± 3 mm Hg. The continuous-flow mode of EVAHEART (EVA-C; n = 4) and ROTAFLOW (ROTA; n = 4) was used as controls. Whole blood samples were collected at baseline and every 60 min for 6 h. Complete blood counts (CBCs), normalized indexes of hemolysis (NIH), vWF antigen (vWF:Ag), vWF ristocetin cofactor (vWF:Rco), the ratio of vWF:Rco to vWF:Ag (Rco/Ag), and high molecular weight multimers (HMWM) of vWF were evaluated. There were no significant changes in CBCs throughout the 6-h test period in any group. NIH levels of EVA-RSM, EVA-C, and ROTA were 0.0035 ± 0.0018, 0.0031 ± 0.0007, and 0.0022 ± 0.0011 g/100 L, respectively. Levels of vWF:Ag, vWF:Rco, and Rco/Ag did not change significantly during the test. Immunoblotting analysis of vWF multimers showed slight degradation of HMWM in all groups, but there were no significant differences between groups in the ratios of HMWM to low molecular weight multimers, calculated by densitometry. This study suggests that our RS modulation system used with EVAHEART does not have marked adverse influences on vWF dynamics. The low NIH and the absence of significant decreases in CBCs indicate that EVAHEART is hemocompatible, regardless of whether it is operated with the RS modulation system.

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Influence of a Rotational Speed Modulation System Used With an Implantable Continuous‐Flow Left Ventricular Assist Device on von Willebrand Factor Dynamics

et al. 2016

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“…Increasing the size of the system by adding a flow meter is also undesirable for portable extracorporeal RBPs. Furthermore, there is a need to measure the flow rate and the pressure in VADs for novel therapies that promote heart recovery, in which the flow rate of the VAD is controlled and the load to the biological heart deliberately increased .…”

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Sensorless Viscosity Measurement in a Magnetically‐Levitated Rotary Blood Pump

et al. 2015

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Controlling the flow rate in an implantable rotary blood pump based on the physiological demand made by the body is important. Even though various methods to estimate the flow rate without using a flow meter have been proposed, no adequate method for measuring the blood viscosity, which is necessary for an accurate estimate of the flow rate, without using additional sensors or mechanisms in a noninvasive way, has yet been realized. We have developed a sensorless method for measuring viscosity in magnetically levitated rotary blood pumps, which requires no additional sensors or mechanisms. By applying vibrational excitation to the impeller using a magnetic bearing, we measured the viscosity of the working fluid by measuring the phase difference between the current in the magnetic bearing and the displacement of the impeller. The measured viscosity showed a high correlation (R(2) > 0.992) with respect to a reference viscosity. The mean absolute deviation of the measured viscosity was 0.12 mPa·s for several working fluids with viscosities ranging from 1.18 to 5.12 mPa·s. The proposed sensorless measurement method has the possibility of being utilized for estimating flow rate.

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“…Our RS modulation control system can alter the native heart load , pulsatility , and blood flow of the coronary artery by changing the RS in the systolic and diastolic phases. Based on our previous protocol, the variance in the RS between systole and diastole was set at 500 rpm . Umeki et al used our RS modulation system in an acute ischemic heart model, and achieved a smaller LVEDV in the counter‐pulse mode and desirable LVEDV control.…”

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confidence: 99%

What Is the Optimal Setting for a Continuous‐Flow Left Ventricular Assist Device in Severe Mitral Regurgitation?

et al. 2016

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Excessive left ventricular (LV) volume unloading can affect right ventricular (RV) function by causing a leftward shift of the interventricular septum in patients with mitral regurgitation (MR) receiving left ventricular assist device (LVAD) support. Optimal settings for the LVAD should be chosen to appropriately control the MR without causing RV dysfunction. In this study, we assessed the utility of our electrocardiogram-synchronized rotational speed (RS) modulation system along with a continuous-flow LVAD in a goat model of MR. We implanted EVAHEART devices after left thoracotomy in six adult goats weighing 66.4 ± 10.7 kg. Severe MR was induced through inflation of a temporary inferior vena cava filter placed within the mitral valve. We evaluated total flow (TF; the sum of aortic flow and pump flow [PF]), RV fractional area change (RVFAC) calculated by echocardiography, left atrial pressure (LAP), LV end-diastolic pressure (LVEDP), LV end-diastolic volume (LVEDV), and LV stroke work (LVSW) with a bypass rate (PF divided by TF) of 100% under four conditions: circuit-clamp, continuous mode, co-pulse mode (increased RS during systole), and counter-pulse mode (increased RS during diastole). TF tended to be higher in the counter-pulse mode. Moreover, RVFAC was significantly higher in the counter-pulse mode than in the co-pulse mode, whereas LAP was significantly lower in all driving modes than in the circuit-clamp condition. Furthermore, LVEDP, LVEDV, and LVSW were significantly lower in the counter-pulse mode than in the circuit-clamp condition. The counter-pulse mode of our RS modulation system used with a continuous-flow LVAD may offer favorable control of MR while minimizing RV dysfunction.

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Alternation of left ventricular load by a continuous-flow left ventricular assist device with a native heart load control system in a chronic heart failure model

Cited by 20 publications

References 27 publications

Influence of a Rotational Speed Modulation System Used With an Implantable Continuous‐Flow Left Ventricular Assist Device on von Willebrand Factor Dynamics

Influence of a Rotational Speed Modulation System Used With an Implantable Continuous‐Flow Left Ventricular Assist Device on von Willebrand Factor Dynamics

Sensorless Viscosity Measurement in a Magnetically‐Levitated Rotary Blood Pump

What Is the Optimal Setting for a Continuous‐Flow Left Ventricular Assist Device in Severe Mitral Regurgitation?

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