Control of ventricular unloading using an electrocardiogram-synchronized Thoratec paracorporeal ventricular assist device

Amacher, Raffael; Weber, Alberto; Brinks, Henriette; Axiak, Shannon; Ferreira, Antonio; Guzzella, Lino; Carrel, Thierry; Antaki, James F.; Vandenberghe, Stijn

doi:10.1016/j.jtcvs.2012.12.048

Cited by 30 publications

(27 citation statements)

References 25 publications

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“…The effect of the timing of the ejection phase of such a pulsatile volume-displacement VAD on the stroke work and the aortic valve flow was demonstrated earlier in vivo [43]. Similarly to the results in the current paper, that analysis shows that a change in phase shift is required when the maximization of the aortic valve flow was assigned preference over the minimization of the left ventricular stroke work.…”

Section: Constant Speed Solutionsupporting

confidence: 81%

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

et al. 2013

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Abstract:The current paper presents a methodology for the derivation of optimal operating strategies for turbo dynamic ventricular assist devices (tVADs). In current clinical practice, tVADs are typically operated at a constant rotational speed, resulting in a blood flow with a low pulsatility. Recent research in the field has aimed at optimizing the interaction between the tVAD and the cardiovascular system by using predefined periodic speed profiles. In the current paper, we avoid the limitation of using predefined profiles by formulating an optimal-control problem based on a mathematical model of the cardiovascular system and the tVAD. The optimal-control problem is solved numerically, leading to cycle-synchronized speed profiles, which are optimal with respect to an arbitrary objective. Here, an adjustable trade-off between the maximization of the flow through the aortic valve and the minimization of the left-ventricular stroke work is chosen. The optimal solutions perform better than constant-speed or sinusoidal-speed profiles for all cases studied. The analysis of optimized solutions provides insight into the optimized Bioengineering 2014, 1 23 interaction between the tVAD and the cardiovascular system. The numerical approach to the optimization of this interaction represents a powerful tool with applications in research related to tVAD control. Furthermore, patient-specific, optimized VAD actuation strategies can potentially be derived from this approach.

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Section: Constant Speed Solutionsupporting

confidence: 81%

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

et al. 2013

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“…Previous studies have investigated synchronization ratios (1:2 and 1:4) lower than the HR under one given phase-shift setting [24] with the intention of establishing a weaning protocol. The importance of considering the pump timing and systolic fraction as an integral part of the investigation has been shown in vivo by [2] for pVADs and by [1,3,4,26,33,34] both in silico and in vivo for tVADs.…”

Section: Discussionmentioning

confidence: 99%

“…They found the best ventricular unloading in terms of hydraulic stroke work (SW) during asynchronous operation with the stroke frequency in the same range as the patient's HR. This investigation was further assessed by Heredero et al [14] and Amacher et al [2], who found that under synchronous operation the timing between ventricle and pump systole has a remarkable impact on the unloading of the left ventricle in terms of hydraulic SW. This influence was not investigated in [24].…”

Section: Introductionmentioning

confidence: 97%

High-frequency operation of a pulsatile VAD – a simulation study

Rebholz

Amacher

Petrou

et al. 2017

Biomedical Engineering / Biomedizinische Technik

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Ventricular assist devices (VADs) are mechanical blood pumps that are clinically used to treat severe heart failure. Pulsatile VADs (pVADs) were initially used, but are today in most cases replaced by turbodynamic VADs (tVADs). The major concern with the pVADs is their size, which prohibits full pump body implantation for a majority of patients. A reduction of the necessary stroke volume can be achieved by increasing the stroke frequency, while maintaining the same level of support capability. This reduction in stroke volume in turn offers the possibility to reduce the pump's overall dimensions. We simulated a human cardiovascular system (CVS) supported by a pVAD with three different stroke rates that were equal, two-or threefold the heart rate (HR). The pVAD was additionally synchronized to the HR for better control over the hemodynamics and the ventricular unloading. The simulation results with a HR of 90 bpm showed that a pVAD stroke volume can be reduced by 71%, while maintaining an aortic pulse pressure (PP) of 30 mm Hg, avoiding suction events, reducing the ventricular stroke work (SW) and allowing the aortic valve to open. A reduction by 67% offers the additional possibility to tune the interaction between the pVAD and the CVS. These findings allow a major reduction of the pVAD's body size, while allowing the physician to tune the pVAD according to the patient's needs.

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“…52/09). Eight adult, female, mixed breed sheep (59 -83 kg) were implanted with a Thoratec PVAD (Thoratec, Pleasanton, CA) via left thoracotomy as described in detail previously (3). A custom-made cannula was inserted in the LV apex of the beating heart, and an outflow graft was anastomosed end-to-side on the aorta.…”

Section: Animals This Study Was Approved By the Commission Of Animalmentioning

confidence: 99%

“…In addition to being used as a bridge-to-transplantation, the use of VADs as a bridge-to-recovery and as an alternative to heart transplantation is becoming increasingly important (14). The impact of VADs on the hemodynamics and on the mechanical unloading of the heart has been analyzed previously (3,7,12,16,26). In cases where the duration of VAD support is in the order of years, its impact on the peripheral circulation and potentially induced structural changes (8,11,22) needs more research.…”

mentioning

confidence: 99%

Effects of Thoratec pulsatile ventricular assist device timing on the abdominal aortic wave intensity pattern

Jahren

Amacher

Weber

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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Jahren SE, Amacher R, Weber A, Most H, Flammer SA, Traupe T, Stoller M, de Marchi S, Vandenberghe S. Effects of Thoratec pulsatile ventricular assist device timing on the abdominal aortic wave intensity pattern. Am J Physiol Heart Circ Physiol 307: H1243-H1251, 2014. First published August 22, 2014; doi:10.1152/ajpheart.00085.2014.-Arterial waves are seen as possible independent mediators of cardiovascular risks, and the wave intensity analysis (WIA) has therefore been proposed as a method for patient selection for ventricular assist device (VAD) implantation. Interpreting measured wave intensity (WI) is challenging, and complexity is increased by the implantation of a VAD. The waves generated by the VAD interact with the waves generated by the native heart, and this interaction varies with changing VAD settings. Eight sheep were implanted with a pulsatile VAD (PVAD) through ventriculoaortic cannulation. The start of PVAD ejection was synchronized to the native R wave and delayed between 0 and 90% of the cardiac cycle in 10% steps or phase shifts (PS). Pressure and velocity signals were registered, with the use of a combined Doppler and pressure wire positioned in the abdominal aorta, and used to calculate the WI. Depending on the PS, different wave interference phenomena occurred. Maximum unloading of the left ventricle (LV) coincided with constructive interference and maximum blood flow pulsatility, and maximum loading of the LV coincided with destructive interference and minimum blood flow pulsatility. We believe that noninvasive WIA could potentially be used clinically to assess the mechanical load of the LV and to monitor the peripheral hemodynamics such as blood flow pulsatility and risk of intestinal bleeding.arterial wave interference; heart-ventricular assist device interaction; pulsatility; ventricular assist device; wave intensity analysis VENTRICULAR ASSIST DEVICES (VADs) are clinically used blood pumps to treat end-stage heart failure (28). In addition to being used as a bridge-to-transplantation, the use of VADs as a bridge-to-recovery and as an alternative to heart transplantation is becoming increasingly important (14). The impact of VADs on the hemodynamics and on the mechanical unloading of the heart has been analyzed previously (3,7,12,16,26). In cases where the duration of VAD support is in the order of years, its impact on the peripheral circulation and potentially induced structural changes (8,11,22) needs more research.Wave intensity analysis (WIA) is a relatively new method to evaluate arterial wave transmission phenomena. WIA has received increased attention because arterial waves are seen as possible independent mediators of cardiovascular risks (10). WIA is based on conservation of mass and momentum in elastic vessels and uses the simultaneous measurement of arterial pressure and blood flow velocity (20, 31). Previously, WIA has been used to analyze the performance of intra-aortic balloon pumps (IABPs) (4, 5, 15, 17), para-aortic counterpulsation devices (18), or pusher-plate pulsatil...

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Control of ventricular unloading using an electrocardiogram-synchronized Thoratec paracorporeal ventricular assist device

Cited by 30 publications

References 25 publications

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

High-frequency operation of a pulsatile VAD – a simulation study

Effects of Thoratec pulsatile ventricular assist device timing on the abdominal aortic wave intensity pattern

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