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

Author(s):  
Clemens Zeile ◽  
Thomas Rauwolf ◽  
Alexander Schmeisser ◽  
Jeremi Kaj Mizerski ◽  
Rüdiger C. Braun-Dullaeus ◽  
...  

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.

Author(s):  
Clemens Zeile ◽  
Thomas Rauwolf ◽  
Alexander Schmeisser ◽  
Jeremi Kaj Mizerski ◽  
Rüdiger C. Braun-Dullaeus ◽  
...  

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.


2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Jeongeun Son ◽  
Dongping Du ◽  
Yuncheng Du

Left ventricular assist devices (LVADs) have been used for end-stage heart failure patients as a therapeutic option. The aortic valve plays a critical role in heart failure and its treatment with a LVAD. The cardiovascular-LVAD model is often used to investigate the physiological demands required by patients and predict the hemodynamic of the native heart supported with a LVAD. As it is a “bridge-to-recovery” treatment, it is important to maintain appropriate and active dynamics of the aortic valve and the cardiac output of the native heart, which requires that the LVAD pump be adjusted so that a proper balance between the blood contributed through the aortic valve and the pump is maintained. In this paper, we investigate how the pump power of the LVAD pump can affect the dynamic behaviors of the aortic valve for different levels of activity and different severities of heart failure. Our objective is to identify a critical value of the pump power (i.e., breakpoint) to ensure that the LVAD pump does not take over the pumping function in the cardiovascular-pump system and share the ejected blood with the left ventricle to help the heart to recover. In addition, the hemodynamic often involves variability due to patients’ heterogeneity and the stochastic nature of the cardiovascular system. The variability poses significant challenges to understanding dynamic behaviors of the aortic valve and cardiac output. A generalized polynomial chaos (gPC) expansion is used in this work to develop a stochastic cardiovascular-pump model for efficient uncertainty propagation, from which it is possible to rapidly calculate the variance in the aortic valve opening duration and the cardiac output in the presence of variability. The simulation results show that the gPC-based cardiovascular-pump model is a reliable platform that can provide useful information to understand the effect of the LVAD pump on the hemodynamic of the heart.


2020 ◽  
pp. 039139882092702
Author(s):  
Hernan G Marcos-Abdala ◽  
Ana S Cruz-Solbes ◽  
Imad Hussain ◽  
Barry Trachtenberg ◽  
Guha Ashrith ◽  
...  

While Doppler and cuff blood pressure techniques are prevalent methods of assessing blood pressure in patients with continuous flow left ventricular assist devices, the impact of pulsatility on measurement is not well established. Retrospective chart analysis of clinical variables including pulse perception, blood pressure (Doppler and standard cuff), and aortic valve opening on echo at clinic visit were abstracted. Stable outpatients on continuous flow left ventricular assist devices support with concomitant portable echo assessment were included. Mean average difference was calculated and Pearson’s correlation performed for all those patients who had both Doppler and cuff pressure obtained. In all, 74 Heartmate-II patients with a median time from implant of 380 days were analyzed. A pulse was perceived in 82% of patients with persistent aortic valve opening on portable echo and also in 30% of those who had a persistently closed aortic valve. The mean average difference between the Doppler and systolic cuff pressure was ~13 mmHg ( r = 0.5, p = 0.004) when a pulse was present and ~11 mmHg when aortic valve was open ( r = 0.68, p < 0.0001). Pulse presence seems to reflect aortic valve opening a majority of the time but not always. In the presence of a prominent pulse or persistent aortic valve opening, the Doppler pressure seems to be more reflective of a systolic pressure than mean perfusion pressure. Hence, assessment of pulsatility needs to be incorporated into blood pressure measurement methods for patients with continuous flow left ventricular assist devices.


2020 ◽  
Vol 21 (Supplement_1) ◽  
Author(s):  
N Solowjowa ◽  
D Zimpfer ◽  
M Mueller ◽  
H Krastev ◽  
V Falk ◽  
...  

Abstract Background Twist of the outflow graft (OG) of the HeartMate 3 left ventricular (LV) assist device (HM3) with subsequent occlusion is a rare, but life-threatening complication. Purpose We evaluated if potential implantation technique dependent mechanisms of OG twist can be predicted by multislice computed tomography (MSCT). Methods We retrospectively analyzed clinical, echocardiographic and MSCT data of 7 patients with angiographically proven and surgically corrected OG twist and of 11 consecutive patients without any type of pump obstruction. MSCT parameters were: position of inflow cannula related to anatomical LV apex (1), angulation of axis of inflow cannula related to LV axis (2), orientation of outflow channel of the pump housing related to LV axis (3), OG course (4). Echocardiographic parameters were LV end-diastolic diameter (LVEDD) and aortic valve opening. Results Mean time from implantation to twist was 563 ± 161 days. Preoperative LVEDD (64.6 ± 9.8 mm vs. 67.4 ± 10.2 mm, p = 0.563) was similar. LVEDD reduction after implantation (20% vs. 28%) and prevalence of aortic valve opening was higher in the twist group (71% vs. 45%). The MSCT measurements showed a high degree of heterogeneity in both groups: (1) differed from superior to infero-lateral; (2) varied from cranial to caudal, lateral and medial; (3) varied from antero-septal to inferior. (4) showed an incidence of non-obstructive kinking of 29% and 36%, respectively. Conclusion Marked heterogeneity of the measured MSCT parameters was observed in both groups. No specific pattern or geometric relation could be attributed to the OG twist phenomenon.


Angiology ◽  
2020 ◽  
Vol 72 (1) ◽  
pp. 9-15
Author(s):  
Pavel Poredos ◽  
Mateja K. Jezovnik ◽  
Rajko Radovancevic ◽  
Igor D. Gregoric

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.


2018 ◽  
Vol 2018 ◽  
pp. 1-2 ◽  
Author(s):  
Katharina Huenges ◽  
Bernd Panholzer ◽  
Jochen Cremer ◽  
Assad Haneya

Left ventricular assist device (LVAD) is nowadays a routine therapy for patients with advanced heart failure. We present the case of a 74-year-old male patient who was admitted to our center with terminal heart failure in dilated cardiomyopathy and ascending aortic aneurysm with aortic valve regurgitation. The LVAD implantation with simultaneous aortic valve and supracoronary ascending aortic replacement was successfully performed.


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