scholarly journals A Personalized Switched Systems Approach for the Optimal Control of Ventricular Assist Devices based on Atrioventricular Plane Displacement

2020 ◽  
Author(s):  
Clemens Zeile ◽  
Thomas Rauwolf ◽  
Alexander Schmeisser ◽  
Jeremi Kaj Mizerski ◽  
Rüdiger C. Braun-Dullaeus ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Mathematical Optimization ◽  
Left Ventricular ◽  
Rotor Speed ◽  
Ventricular Assist ◽  
Pump Speed ◽  
Atrioventricular Plane Displacement ◽  
Valve Opening ◽  
Plane Displacement

AbstractObjectiveA promising treatment for congestive heart failure is the implementation of a left ventricular assist device (LVAD) that works as a mechanical pump. Modern LVADs work with adjustable constant rotor speed and provide therefore continuous blood flow; however, recently undertaken efforts try to mimic pulsatile blood flow by oscillating the pump speed. This work proposes an algorithmic framework to construct and evaluate optimal pump speed policies.MethodsWe use a model that captures the atrioventricular plane displacement, which is a physiological indicator for heart failure. We employ mathematical optimization to adapt this model to patient specific data and to find optimal pump speed policies with respect to ventricular unloading and aortic valve opening. To this end, we reformulate the cardiovascular dynamics into a switched system and thereby reduce nonlinearities. We consider system switches that stem from varying the constant pump speed and that are state dependent such as valve opening or closing.ResultsAs a proof of concept study, we personalize the model to a selected patient with respect to ventricular pressure. The model fitting results in a root-mean-square deviation of about 6 mmHg. Optimized constant and piecewise constant rotor speed profiles improve the default initialized solution by 31% and 68% respectively.ConclusionThese in silico findings demon-strate the potential of personalized hemodynamical optimization for the LVAD therapy.SignificanceLVADs and their optimal configuration are active research fields. Mathematical optimization enhances our understanding of how LVADs should provide pulsatility.

scholarly journals An Intra-Cycle Optimal Control Framework for Ventricular Assist Devices Based on Atrioventricular Plane Displacement Modeling

2021 ◽  
Author(s):  
Clemens Zeile ◽  
Thomas Rauwolf ◽  
Alexander Schmeisser ◽  
Jeremi Kaj Mizerski ◽  
Rüdiger C. Braun-Dullaeus ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Aortic Valve ◽  
Left Ventricular ◽  
Patient Specific ◽  
Ventricular Assist ◽  
Pump Speed ◽  
Atrioventricular Plane Displacement ◽  
Valve Opening ◽  
Plane Displacement

AbstractA promising treatment for congestive heart failure is the implementation of a left ventricular assist device (LVAD) that works as a mechanical pump. Modern LVADs work with adjustable constant rotor speed and provide therefore continuous blood flow; however, recently undertaken efforts try to mimic pulsatile blood flow by oscillating the pump speed. This work proposes an algorithmic framework to construct and evaluate optimal pump speed policies with respect to generic objectives. We use a model that captures the atrioventricular plane displacement, which is a physiological indicator for heart failure. We employ mathematical optimization to adapt this model to patient specific data and to find optimal pump speed policies with respect to ventricular unloading and aortic valve opening. To this end, we reformulate the cardiovascular dynamics into a switched system and thereby reduce nonlinearities. We consider system switches that stem from varying the constant pump speed and that are state dependent such as valve opening or closing. As a proof of concept study, we personalize the model to a selected patient with respect to ventricular pressure. The model fitting results in a root-mean-square deviation of about 6 mmHg. The optimization that considers aortic valve opening and ventricular unloading results in speed modulation akin to counterpulsation. These in silico findings demonstrate the potential of personalized hemodynamical optimization for the LVAD therapy.

Endothelial Function in Patients With Continuous-Flow Left Ventricular Assist Devices

Angiology ◽  
2020 ◽  
Vol 72 (1) ◽  
pp. 9-15
Author(s):  
Pavel Poredos ◽  
Mateja K. Jezovnik ◽  
Rajko Radovancevic ◽  
Igor D. Gregoric
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Shear Stress ◽  
Continuous Flow ◽  
Tissue Perfusion ◽  
Left Ventricular ◽  
Ventricular Assist Devices ◽  
Left Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Left Ventricular Assist

The endothelium plays a crucial role in maintaining cardiovascular homeostasis. Shear stress generated by flowing blood regulates the release of substances that provide adequate tissue perfusion. The extent of damage to endothelial cells depends on locally disturbed shear stress caused by the deteriorated flow. Patients with heart failure have reduced cardiac output, which results in reduced blood flow and negative shear stress. Reduced shear stress also affects microcirculation and reduces tissue perfusion. Consequently, the production of free oxygen radicals is increased and bioavailability of nitric oxide is additionally decreased. Therefore, endothelial dysfunction is involved in the progression of heart failure and cardiovascular events. Left ventricular assist devices (LVAD) are used for the treatment of patients with advanced heart failure. Older pulsatile flow LVADs were mostly substituted by continuous-flow LVADs (cf-LVADs). Despite the advantages of the cf-LVADs, the loss of pulsatility leads to different complications on the micro- and macrovascular levels. One of the pathogenetic mechanisms of cardiovascular complications with cf-LVADs may be endothelial dysfunction, which after the implantation of the device does not improve and may even deteriorate. In contrast, the pulsatile pattern of LVADs on blood flow could preserve endothelial function.

scholarly journals Effects of Acute Pump Speed Changes on Cerebral Hemodynamics in Patients With an Implantable Continuous-Flow Left Ventricular Assist Devices

2021 ◽  
pp. 831-839
Author(s):  
M. Konarik ◽  
M. Sramko ◽  
Z. Dorazilova ◽  
M. Blaha ◽  
I. Netuka ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Pulse Pressure ◽  
Continuous Flow ◽  
Left Ventricular ◽  
Arterial Pulse ◽  
Ventricular Assist ◽  
Pump Speed ◽  
Left Ventricular Assist ◽  
Relative Change

Mechanical circulatory support (MCS) with an implantable left ventricular assist device (LVAD) is an established therapeutic option for advanced heart failure. Most of the currently used LVADs generate a continuous stream of blood that decreases arterial pulse pressure. This study investigated whether a change of the pulse pressure during different pump speed settings would affect cerebral autoregulation and thereby affect cerebral blood flow (CBF). The study included 21 haemodynamically stable outpatients with a continuous-flow LVAD (HeartMate II, Abbott, USA) implanted a median of 6 months before the study (interquartile range 3 to 14 months). Arterial blood pressure (measured by finger plethysmography) was recorded simultaneously with CBF (measured by transcranial Doppler ultrasound) during baseline pump speed (8900 rpm [IQR 8800; 9200]) and during minimum and maximum tolerated pump speeds (8000 rpm [IQR 8000; 8200] and 9800 rpm [IQR 9800; 10 000]). An increase in LVAD pump speed by 800 rpm [IQR 800; 1000] from the baseline lead to a significant decrease in arterial pulse pressure and cerebral blood flow pulsatility (relative change −24 % and −32 %, both p < 0.01), but it did not affect mean arterial pressure and mean CBF velocity (relative change 1 % and −1.7 %, p=0.1 and 0.7). In stable patients with a continuous-flow LVAD, changes of pump speed settings within a clinically used range did not impair static cerebral autoregulation and cerebral blood flow.

scholarly journals Cerebral blood flow responses to exercise are enhanced in left ventricular assist device patients after an exercise rehabilitation program

2020 ◽  
Vol 128 (1) ◽  
pp. 108-116 ◽  
Author(s):  
Kurt J. Smith ◽  
Ignacio Moreno-Suarez ◽  
Anna Scheer ◽  
Lawrence Dembo ◽  
Louise H. Naylor ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Exercise Training ◽  
Left Ventricular ◽  
Ventricular Assist Devices ◽  
Left Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Assist Devices ◽  
Cerebrovascular Function ◽  
Left Ventricular Assist

Cerebral blood flow during exercise is impaired in patients with heart failure implanted with left ventricular assist devices (LVADs). Our aim was to determine whether a 3-mo exercise training program could mitigate cerebrovascular dysfunction. Internal carotid artery (ICA) blood flow and intracranial middle (MCA v) and posterior cerebral (PCA v) artery velocities were measured continuously using Doppler ultrasound, alongside cardiorespiratory measures at rest and in response to an incremental cycle ergometer exercise protocol in 12 LVAD participants (5 female, 53.6 ± 11.8 yr; 84.2 ± 15.7 kg; 1.73 ± 0.08) pre- (PreTR) and post- (PostTR) completion of a 3-mo supervised exercise rehabilitation program. At rest, only PCAv was different PostTR (38.1 ± 10.4 cm/s) compared with PreTR (43.0 ± 10.8 cm/s; P < 0.05). PreTR, the reduction in PCAv observed from rest to exercise (5.2 ± 1.8%) was mitigated PostTR ( P < 0.001). Similarly, exercise training enhanced ICA flow during submaximal exercise (~8.6 ± 13.7%), resulting in increased ICA flow PostTR compared with a reduced flow PreTR ( P < 0.001). Although both end-tidal partial pressure of carbon dioxide and mean arterial pressure responses during incremental exercise were greater PostTR than PreTR, only the improved [Formula: see text] was related to the improved ICA flow ( R2 = 0.14; P < 0.05). Our findings suggest that short-term exercise training improves cerebrovascular function during exercise in patients with LVADs. This finding should encourage future studies investigating long-term exercise training and cerebral and peripheral vascular adaptation. NEW & NOTEWORTHY Left ventricular assist devices, now used as destination therapy in end-stage heart failure, enable patients to undertake rehabilitative exercise training. We show, for the first time in humans, that training improves cerebrovascular function during exercise in patients with left ventricular assist devices. This finding may have implications for cerebrovascular health in patients with heart failure.

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