In Vivo Evaluation of Physiologic Control Algorithms for Left Ventricular Assist Devices Based on Left Ventricular Volume or Pressure.

Turbodynamic left ventricular assist devices (LVADs) provide a continuous flow depending on the speed at which the pump is set, and do not adapt to the changing requirements of the patient. The limited adaptation of the pump flow (PF) to the amount of venous return can lead to ventricular suction or overload. Physiologic control may compensate such situations by an automatic adaptation of the PF to the volume status of the left ventricle.

Control of the Fluid Viscosity in a Mock Circulation.

A mock circulation allows the in vitro investigation, development, and testing of ventricular assist devices. An aqueous-glycerol solution is commonly used to mimic the viscosity of blood. Due to evaporation and temperature changes, the viscosity of the solution drifts from its initial value and therefore, deviates substantially from the targeted viscosity of blood.

Left Ventricular Assist Devices: Challenges Toward Sustaining Long-Term Patient Care.

Over the last few decades, the left ventricular assist device (LVAD) technology has been tremendously improved transitioning from large and noisy paracorporeal volume displacement pumps to small implantable turbodynamic devices with only a single transcutaneous element, the driveline. Nevertheless, there remains a great demand for further improvements to meet the challenge of having a robust and safe device for long-term therapy. Here, we review the state of the art and highlight four key areas of needed improvement targeting long-term, sustainable LVAD function: (1) LVADs available today still have a high risk of thromboembolic and bleeding events that could be addressed by the rational fabrication of novel surface structures and endothelialization approaches aiming at improving the device hemocompatibility.

A Novel Mean-Value Model of the Cardiovascular System Including a Left Ventricular Assist Device.

Time-varying elastance models (TVEMs) are often used for simulation studies of the cardiovascular system with a left ventricular assist device (LVAD). Because these models are computationally expensive, they cannot be used for long-term simulation studies. In addition, their equilibria are periodic solutions, which prevent the extraction of a linear time-invariant model that could be used e.

Response of a physiological controller for ventricular assist devices during acute patho-physiological events: an in vitro study.

The current paper analyzes the performance of a physiological controller for turbodynamic ventricular assist devices (tVADs) during acute patho-physiological events. The numerical model of the human blood circulation implemented on our hybrid mock circulation was extended in order to simulate the Valsalva maneuver (VM) and premature ventricular contractions (PVCs). The performance of an end-diastolic volume (EDV)-based physiological controller for VADs, named preload responsive speed (PRS) controller was evaluated under VM and PVCs.

A Physiological Controller for Turbodynamic Ventricular Assist Devices Based on Left Ventricular Systolic Pressure.

The current article presents a novel physiological feedback controller for turbodynamic ventricular assist devices (tVADs). This controller is based on the recording of the left ventricular (LV) pressure measured at the inlet cannula of a tVAD thus requiring only one pressure sensor. The LV systolic pressure (SP) is proposed as an indicator to determine the varying perfusion requirements.

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

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.

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

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.

Synchronized pulsatile speed control of turbodynamic left ventricular assist devices: review and prospects.

Turbodynamic blood pumps are used clinically as ventricular assist devices (VADs). They are mostly operated at a constant rotational speed, which results in a reduced pulsatility. Previous research has analyzed pulsing pump speeds (speed modulation) to alter the interaction between the cardiovascular system and the blood pump.

A physiological controller for turbodynamic ventricular assist devices based on a measurement of the left ventricular volume.

The current article presents a novel physiological control algorithm for ventricular assist devices (VADs), which is inspired by the preload recruitable stroke work. This controller adapts the hydraulic power output of the VAD to the end-diastolic volume of the left ventricle. We tested this controller on a hybrid mock circulation where the left ventricular volume (LVV) is known, i.

Analysis of pressure head-flow loops of pulsatile rotodynamic blood pumps.

The clinical importance of pulsatility is a recurring topic of debate in mechanical circulatory support. Lack of pulsatility has been identified as a possible factor responsible for adverse events and has also demonstrated a role in myocardial perfusion and cardiac recovery. A commonly used method for restoring pulsatility with rotodynamic blood pumps (RBPs) is to modulate the speed profile, synchronized to the cardiac cycle.

A robust reference signal generator for synchronized ventricular assist devices.

Ventricular assist devices (VADs) are blood pumps that offer an option to support the circulation of patients with severe heart failure. Since a failing heart has a remaining pump function, its interaction with the VAD influences the hemodynamics. Ideally, the heart's action is taken into account for actuating the device such that the device is synchronized to the natural cardiac cycle.

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

Objective: Current pulsatile ventricular assist devices operate asynchronous with the left ventricle in fixed-rate or fill-to-empty modes because electrocardiogram-triggered modes have been abandoned. We hypothesize that varying the ejection delay in the synchronized mode yields more precise control of hemodynamics and left ventricular loading. This allows for a refined management that may be clinically beneficial.

A novel interface for hybrid mock circulations to evaluate ventricular assist devices.

This paper presents a novel mock circulation for the evaluation of ventricular assist devices (VADs), which is based on a hardware-in-the-loop concept. A numerical model of the human blood circulation runs in real time and computes instantaneous pressure, volume, and flow rate values. The VAD to be tested is connected to a numerical-hydraulic interface, which allows the interaction between the VAD and the numerical model of the circulation.