A Sensorless Modular Multiobjective Control Algorithm for Left Ventricular Assist Devices: A Clinical Pilot Study

Abstract

BackgroundContemporary Left Ventricular Assist Devices (LVADs) mainly operate at a constant speed, only insufficiently adapting to changes in patient demand. Automatic physiological speed control promises tighter integration of the LVAD into patient physiology, increasing the level of support during activity and decreasing support when it is excessive.MethodsA sensorless modular control algorithm was developed for a centrifugal LVAD (HVAD, Medtronic plc, MN, USA). It consists of a heart rate-, a pulsatility-, a suction reaction—and a supervisor module. These modules were embedded into a safe testing environment and investigated in a single-center, blinded, crossover, clinical pilot trial (clinicaltrials.gov, NCT04786236). Patients completed a protocol consisting of orthostatic changes, Valsalva maneuver and submaximal bicycle ergometry in constant speed and physiological control mode in randomized sequence. Endpoints for the study were reduction of suction burden, adequate pump speed and flowrate adaptations of the control algorithm for each protocol item and no necessity for intervention via the hardware safety systems.ResultsA total of six patients (median age 53.5, 100% male) completed 13 tests in the intermediate care unit or in an outpatient setting, without necessity for intervention during control mode operation. Physiological control reduced speed and flowrate during patient rest, in sitting by a median of −75 [Interquartile Range (IQR): −137, 65] rpm and in supine position by −130 [−150, 30] rpm, thereby reducing suction burden in scenarios prone to overpumping in most tests [0 [−10, 2] Suction events/minute] in orthostatic upwards transitions and by −2 [−6, 0] Suction events/min in Valsalva maneuver. During submaximal ergometry speed was increased by 86 [31, 193] rpm compared to constant speed for a median flow increase of 0.2 [0.1, 0.8] L/min. In 3 tests speed could not be increased above constant set speed due to recurring suction and in 3 tests speed could be increased by up to 500 rpm with a pump flowrate increase of up to 0.9 L/min.ConclusionIn this pilot study, safety, short-term efficacy, and physiological responsiveness of a sensorless automated speed control system for a centrifugal LVAD was established. Long term studies are needed to show improved clinical outcomes.Clinical Trial RegistrationClinicalTrials.gov, identifier: NCT04786236.

Estimation of Left Ventricular Stroke Work for Rotary Left Ventricular Assist Devices

“…This process could also potentially be built into physiological control systems in the long-term. 29,34,35 Aside from sensor errors, several other factors could have contributed to lower ex vivo accuracy demonstrated in this study, including higher overall AoV flow, progressive changes in the pressure drop across the graft caused by thrombus, and other movement artifacts. Another contributing factor to the lower accuracy was likely the wide variety of cardiac conditions evaluated in this study, which was more extensive than any previously published study.…”

“…This process could also potentially be built into physiological control systems in the long-term. 29,34,35…”

An in vitro model to study suction events by a ventricular assist device: validation with clinical data

“…The variability of suction phenomenology should be considered by companies and research groups when developing algorithms to detect and mitigate suction. ( Hatoh et al, 1999 ; Vollkron et al, 2004 ; Karantonis et al, 2006 ; Ferreira et al, 2007 ; Maw et al, 2021 ; Maw et al, 2022 ). This study has shed the light on how different ventricular properties (DCM and RCM) can induce very distinct suction patterns in case of hypovolemia.…”

“…Several research groups and companies are studying physiological pump controllers to change the LVAD speed to avoid suction. ( Hatoh et al, 1999 ; Vollkron et al, 2004 ; Karantonis et al, 2006 ; Ferreira et al, 2007 ; Maw et al, 2021 ; Maw et al, 2022 ). Therefore, there is a need for an in vitro test bench with high fidelity and versatility to capture the wide range of suction characteristics observed in the clinics and capable of providing repeatable test scenarios for pump controllers.…”

Sensor-Free Biosensing of Mitral and Aortic Valvular Function During Continuous Flow Left Ventricular Assist Device Support

“…Ventricular Assist Device Support control pump operating speed to adjust the level of CF-LVAD support according to physical activities [16]. The main advantages of sensor-free measurements for the physiological activity of heart, in terms of flow, over physical sensors [17], optical pressure sensors [18] and other sensing systems [19], [20] is that it avoids incorporation of an additional components within a device.…”