Phenotyping of Stable Left Ventricular Assist Device Patients Using Noninvasive Pump Flow Responses to Acute Loading Transients

HeartMate 3 Snoopy: Noninvasive cardiovascular diagnosis of patients with fully magnetically levitated blood pumps during echocardiographic speed ramp tests and Valsalva maneuvers

PURPOSE

The HeartMate 3 (HM3) left ventricular assist device (LVAD) has demonstrated excellent clinical outcomes; however, pump speed optimization is challenging with the available HM3 monitoring. Therefore, this study reports on clinical HM3 parameters collected with a noninvasive HM3 monitoring system (HM3 Snoopy) during echocardiographic speed ramp tests and Valsalva maneuvers.

METHODS

In this prospective, single-center study, the HM3 data communication between the controller and pump was recorded with a novel data acquisition system. Twelve pump parameters sampled every second (1 Hz) and clinical assessments (echocardiography, electrocardiogram (ECG), and blood pressure measurement) during speed ramp tests were analyzed using Pearson's correlation (r, median [IQR]). The cause for the occurrence of pulsatility index (PI)-events during ramp speed tests and valsalva maneuvers was investigated.

RESULTS

In 24 patients (age: 58.9 ± 8.8 years, body mass index: 28.1 ± 5.1 kg/m2, female: 20.8%), 35 speed ramp tests were performed with speed changes in the range of ±1000 rpm from a baseline speed of 5443 ± 244 rpm. Eight HM3 pump parameters from estimated flow, motor current, and LVAD speed together with blood pressure showed positive collinearities (r = 0.9 [0.1]). Negative collinearities were observed for pump flow pulsatility, pulsatility index, rotor noise, and left ventricular diameters (r = -0.8 [0.1]), whereas rotor displacement and heartrate showed absence of collinearities (r = -0.1 [0.08]).

CONCLUSIONS

In this study, the HM3 Snoopy was successfully used to acquire more parameters from the HM3 at a higher sampling rate. Analysis of HM3 per-second data provide additional clinical diagnostic information on heart-pump interactions and cause of PI-events.

Using pulsatility responses to breath-hold maneuvers to predict readmission rates in continuous-flow left ventricular assist device patients

BACKGROUND

Dynamic respiratory maneuvers induce heterogenous changes to flow-pulsatility in continuous-flow left ventricular assist device patients. We evaluated the association of these pulsatility responses with patient hemodynamics and outcomes.

METHODS

Responses obtained from HVAD (Medtronic) outpatients during successive weekly clinics were categorized into three ordinal groups according to the percentage reduction in flow-waveform pulsatility (peak-trough flow) upon inspiratory-breath-hold, (%∆P): (1) minimal change (%∆P ≤ 50), (2) reduced pulsatility (%∆P > 50 but <100), (3) flatline (%∆P = 100). Same-day echocardiography and right-heart-catheterization were performed. Readmissions were compared between patients with ≥1 flatline response (F-group) and those without (NF-group).

RESULTS

Overall, 712 responses were obtained from 55 patients (82% male, age 56.4 ± 11.5). When compared to minimal change, reduced pulsatility and flatline responses were associated with lower central venous pressure (14.2 vs. 11.4 vs. 9.0 mm Hg, p = 0.08) and pulmonary capillary wedge pressure (19.8 vs. 14.3 vs. 13.0 mm Hg, p = 0.03), lower rates of ≥moderate mitral regurgitation (48% vs. 13% vs. 10%, p = 0.01), lower rates of ≥moderate right ventricular impairment (62% vs. 25% vs. 27%, p = 0.03), and increased rates of aortic valve opening (32% vs. 50% vs. 75%, p = 0.03). The F-group (n = 28) experienced numerically lower all-cause readmissions (1.51 vs. 2.79 events-per-patient-year [EPPY], hazard-ratio [HR] = 0.67, p = 0.12), reduced heart failure readmissions (0.07 vs. 0.57 EPPY, HR = 0.15, p = 0.008), and superior readmission-free survival (HR = 0.47, log-rank p = 0.04). Syncopal readmissions occurred exclusively in the F-group (0.20 vs. 0 EPPY, p = 0.01).

CONCLUSION

Responses to inspiratory-breath-hold predicted hemodynamics and readmission risk. The impact of inspiratory-breath-hold on pulsatility can non-invasively guide hemodynamic management decisions, patient optimization, and readmission risk stratification.

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

Background

Contemporary 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.

Methods

A 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.

Results

A 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.

Conclusion

In 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 Registration

ClinicalTrials.gov, identifier: NCT04786236.