Parameter-Optimized Model of Cardiovascular–Rotary Blood Pump Interactions

Lim, Einly; Dokos, Socrates; Cloherty, Shaun L.; Salamonsen, Robert F.; Mason, D. G.; Reizes, John; Lovell, Nigel H.

doi:10.1109/tbme.2009.2031629

Cited by 67 publications

(68 citation statements)

References 24 publications

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“…We consider optimal motor settings for different levels of LV assistance, the effects of the iRBP on the right heart, septum, and pulmonary circulation. Our model results align with those reported in [1]-[2]. Improvement in cardiac output, pulmonary congestion, and heart work are seen with the iRBP.…”

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confidence: 90%

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Modeling study of the failing heart and its interaction with an implantable rotary blood pump

Ramachandran

Luo

Tony³

et al. 2011

2011 Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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The effectiveness of clinical diagnosis and treatment of heart failure is a direct function of clinical signs that can be measured in a patient within cost and safety constraints. Large-scale mathematical modeling can be a key tool in revealing important, measurable clinical signs of heart failure, furthering medical understanding and development of treatment. In the first part of this study we have created two models of left heart failure diastolic and systolic, using our human cardiovascular-respiratory system (H-CRS) model, and we present a comparison of the two types with emphasis on novel and differentiating clinical signs, such as tricuspid flow and septal motion. In the event of compromised left ventricular performance, mechanical left ventricular assist devices (LVAD) are often implanted to augment or completely replace the pumping action of the left ventricle (LV). One such type is the implantable rotary blood pump (iRBP). Several design issues related to the iRBP are difficult to study experimentally due to procedure complexity and limitations in animal models of heart failure [2]. Therefore, modeling has become a key tool in iRBP development. In the second part of this study, we have introduced an iRBP model based on [1]-[2] in the systolic failing heart to study the interactions. We consider optimal motor settings for different levels of LV assistance, the effects of the iRBP on the right heart, septum, and pulmonary circulation. Our model results align with those reported in [1]-[2]. Improvement in cardiac output, pulmonary congestion, and heart work are seen with the iRBP. We observe lowered septal assistance to RV and LV ejection with increasing pump speeds, elevating right ventricular (RV) work, reducing LVET, and causing ventricular mechanical dyssynchrony in ejection. These results suggest right heart compromise via the septum s reduced role with the introduction of an iRBP. This work emphasizes the critical role of modeling in heart failure and treatment studies.

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confidence: 90%

“…Therefore, modeling has become a key tool in iRBP development. In the second part of this study, we have introduced an iRBP model based on [1]-[2] in the systolic failing heart to study the interactions. We consider optimal motor settings for different levels of LV assistance, the effects of the iRBP on the right heart, septum, and pulmonary circulation.…”

mentioning

confidence: 99%

Modeling study of the failing heart and its interaction with an implantable rotary blood pump

Ramachandran

Luo

Tony³

et al. 2011

2011 Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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“…The proposed model was also used to design a control algorithm for continuous and pulsatile flow [2]. A parameter-optimised model for the cardiovascular system assisted by an IRBP was verified in [3].The problem of noninvasive estimation of inlet pressure (P in ) in an IRBP has not been frequently studied, possibly because of its highly variable nature especially during abnormal pumping states such as ventricular collapse where, for example, the inlet pressure (P in ) during the diastolic period in VentrAssist TM (Ventracor Limited, Sydney, Australia) left ventricular assist device (LVAD) may be as low as 2160 mmHg, and varies between +10 mmHg during normal pump operation. During diastole, inlet pressure (P in ) and left ventricular (LV) end diastolic pressure, i.e.…”

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confidence: 99%

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confidence: 99%

Sensorless estimation of inlet pressure in implantable rotary blood pump for heart failure patients

et al. 2010

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A dynamical model for mean inlet pressure estimation in an implantable rotary blood pump is proposed. Noninvasive measurements of pump motor power (P), pulse width modulation, and impeller rotational speed (v) were used as inputs to the model. Linear regression analysis between estimated and measured inlet pressures obtained from in vivo greyhound data (N ¼ 3) resulted in a highly significant correlation (R 2 ¼ 0.957) and a mean absolute error (e) of 2.292 mmHg. Furthermore, the proposed model was stable which allowed accurate study and estimation of the transient response and the dynamics of the pump inlet pressure (P in ).Introduction: The shortage of donor organs for heart transplantation has led to a variety of treatment options for heart failure patients. Implantable rotary blood pumps (IRBPs) are emerging not only as a bridge to the transplant option but also as a means of long-term support.Noninvasive estimation of hemodynamic parameters of an IRBP plays a crucial role in designing an automatic, robust and responsive noninvasive control system that effectively copes with the body's physiological demands and perturbations. The implantation of additional sensors is not a preferred option as they result in thrombus formation and require regular calibration owing to measurement drifts. A stable dynamical model for noninvasive estimation of pulsatile flow and differential pressure in an IRBP was proposed and verified in [1]. The proposed model was also used to design a control algorithm for continuous and pulsatile flow [2]. A parameter-optimised model for the cardiovascular system assisted by an IRBP was verified in [3].The problem of noninvasive estimation of inlet pressure (P in ) in an IRBP has not been frequently studied, possibly because of its highly variable nature especially during abnormal pumping states such as ventricular collapse where, for example, the inlet pressure (P in ) during the diastolic period in VentrAssist TM (Ventracor Limited, Sydney, Australia) left ventricular assist device (LVAD) may be as low as 2160 mmHg, and varies between +10 mmHg during normal pump operation. During diastole, inlet pressure (P in ) and left ventricular (LV) end diastolic pressure, i.e. preload to the LV, are closely related. In normal humans, the operation of the heart satisfies the FrankStarling mechanism, i.e. the stroke volume depends on LV end diastolic volume. Therefore, one design requirement of IRBPs is to simulate the Frank-Starling law. On the other hand, in heart failure patients with an LV assisted by an IRBP, when the volume in the LV is low, inlet pressure (P in ) will automatically decrease and this may cause suction if the same target speed were to be maintained. To ensure patient safety, a control system that effectively detects and thus avoids such undesired pumping states is needed. This shows one example that makes the noninvasive estimation of inlet pressure of utmost importance for a pump control strategy. For instance, the proposed model could provide a definitive input for a controller t...

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“…CARDIOVASCULAR SYSTEM [60]. 14 FIGURE 1.12: EXAMPLE OF A TIME-VARYING ELASTANCE FUNCTION [63] 15 [63].…”

Section: Figure 111: Example Of a Lumped Parameter Model Of An Lvad mentioning

confidence: 99%

Automatic control of dual left ventricular assist devices as a biventricular assist device

Stevens¹

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In this thesis, we investigate automated methods for the control of rotary blood pumps in the treatment of heart failure. Heart failure is a common end-point for many forms of cardiovascular disease resulting in significant morbidity and mortality. Ventricular assist devices (VADs) are blood pumps designed to assist a failing heart and are used both to support patients whilst they are awaiting a heart transplant, or as an alternative to transplantation. Small rotary VADs can provide long-term support of the left ventricle (LVAD), right ventricle (RVAD) or both ventricles of the heart simultaneously.Unfortunately, the lack of a commercially available rotary RVAD has led to the implantation of two rotary LVADs as an ad hoc biventricular assist device (BiVAD). Clinicians currently operate such dual LVADs at a constant speed, which ensures balanced left and right pump flows for inactive patients.However, changes in levels of patient activity will lead to altered cardiac output requirements, which may disturb this balance. In turn, this can lead to undesirable events such as pulmonary venous congestion or ventricular suction. A control system that automatically adjusts pump speed with changes in the required cardiac output could alleviate such events and so offer significant benefits. However, while such physiological control systems have been investigated for single LVADs, limited work has been completed on dual LVAD control. In addition, there is no generally accepted framework for the evaluation of these systems that encompasses a broad range of patient scenarios, activity levels and heart conditions. Therefore, the primary aim of this thesis was to develop and evaluate a number of physiological control systems suitable for dual rotary LVADs.The first objective was to characterise the methods that are currently used to operate dual LVADs in the clinic. Using both in-vitro and in-vivo methods, it was shown that balanced left and right flow rates could be obtained by operating the RVAD slower than the LVAD, albeit at speeds below the manufacturer's recommendations (1400 -1800 RPM), which, according to other investigators, may adversely affect impeller washout. Operating both at the same design speed is only possible in patients with high pulmonary vascular resistance (PVR), high left ventricular contractility or high RVAD outflow cannula resistance. This thesis demonstrates that if the RVAD outflow cannula is restricted to a diameter between 6.5 and 8.1 mm, suitable steady-state haemodynamics (systemic flow rate 5 L.min -1 , MAP 90mmHg and LAP less than 25mmHg) can be achieved while maintaining impeller stability and optimal device washout. It was also established that changes in pump speed or outflow graft diameter were required to overcome elevations in pulmonary vascular resistance, thereby justifying the necessity of a physiological control system for dual LVADs.The second objective was to develop an in vitro evaluation protocol for control system testing utilising a mock circulation loop (MCL). The test...

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Parameter-Optimized Model of Cardiovascular–Rotary Blood Pump Interactions

Cited by 67 publications

References 24 publications

Modeling study of the failing heart and its interaction with an implantable rotary blood pump

Modeling study of the failing heart and its interaction with an implantable rotary blood pump

Sensorless estimation of inlet pressure in implantable rotary blood pump for heart failure patients

Automatic control of dual left ventricular assist devices as a biventricular assist device

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