Flow Left Ventricular Assist Device Research Articles

Impact of an Accessory for Left Ventricular Assist Devices on Device Flow and Pressure Head In Vitro.

A novel accessory directing the blood from the outflow of a left ventricular assist device (LVAD) back through the left ventricular apex and across the aortic valve allows LVAD implantation via the left ventricular apex solely but may affect the LVAD performance. We quantified the effect of the accessory on LVAD flow and pressure head in vitro. In a mock circulatory loop, a centrifugal-flow LVAD (HeartMate 3, Abbott, Abbott Park, IL, USA) with (Accessory) and without the accessory (Control) was compared under physiological conditions using a water/glycerol solution as a blood substitute. The pump was operated at 4000, 5200, and 6400 rpm and 5 different resistance levels. Flow, inlet, and outlet pressure were measured, and pressure head was calculated. Compared to the Control, flow and pressure head in the Accessory group were reduced by an overall average of 0.26 L/min and 9.9 mmHg (all speeds and resistance levels). The highest decline in flow and pressure head occurred at the lowest resistance levels. In conclusion, the accessory leads to a reduction of LVAD flow and pressure head that is enhanced by decreases in resistance. Future developments in the LVAD accessory's design may reduce these effects and allow unimpaired LVAD performance and minimally invasive device implantation.

Self-care behaviours of patients with left ventricular assist devices in Israel: changes during the COVID-19 pandemic.

Left ventricular assist devices (LVADs) support the hearts of patients with advanced heart failure. Following LVAD implantation, patients face a complex regimen of self-care behaviours including self-care maintenance, self-care monitoring and self-care management. However, during the COVID-19 pandemic, symptoms of anxiety and depression may have interfered with their self-care. Currently, little is known on how specific self-care behaviours of LVAD-implanted patients changed during the COVID-19 pandemic. We aim to describe the changes in self-care behaviours among patients with an implanted LVAD in Israel during the COVID-19 pandemic and explore the factors related to self-care behaviour change. A prospective observational cross-sectional study design. A convenience sample of 27 Israeli LVAD-implanted patients (mean age 62.4±9, 86% male, 78.6% living with a partner) completed the LVAD Self-Care Behaviour Scale (1=never to 5=always) and Hospital Anxiety and Depression Scale (0=not at all to 3=most of the time). Data were collected before and after the onset of the COVID-19 pandemic in Israel. Statistical analyses included paired t-tests, Pearson's correlations, and one-way repeated measures ANOVAs. During the COVID-19 pandemic, a significant decrease was found in patients' adherence to checking and recording their LVAD speed, flow, power and PI (Pulsatility Index) (P=0.05), checking their INR (P=0.01), and daily weighing (P<0.01). The prevalence of some behaviours (e.g. regularly exercising) increased in some patients and decreased in others. Patients living without a partner worsened their adherence to some of the self-care behaviours (e.g. taking medicines as prescribed), compared with those living with a partner (Mb =5.0±0 and Md =5.0±0, delta=0 vs. Mb =5.0±0 and Md =4.6±0.9, delta=-0.4, respectively; F=4.9, P=0.04). Women, and not men, tended to improve their adherence to the self-care behaviour such as avoiding kinking, pulling, or moving the LVAD driveline at the exit site (Mb =4.0±1.0 and Md =5.0±0, delta=1.0 vs. Mb =4.5±0.9 and Md =4.4±1.2, delta=-0.1, F=4.7, P=0.04, respectively). In total, 41% (11) patients reported neither anxiety nor depression, 11% (3) reported anxiety, 15% (4) reported depression, and 44% (12) reported both anxiety and depression. No associations between anxiety and/or depression and self-care behaviours were found. Priorities in self-care behaviours among patients with implanted LVAD changed after the onset of the COVID-19 pandemic. Factors that assisted with adherence to self-care behaviours included living with a partner and being female. The current results may guide further research on identifying behaviours that are at risk of not being maintained during a time of emergency.

(735) Impact of Asynchronous Rotational Speed Modulation of Continuous Flow Left Ventricular Assist Device on Cardiac Condition

(735) Impact of Asynchronous Rotational Speed Modulation of Continuous Flow Left Ventricular Assist Device on Cardiac Condition

18F-FDG PET/CT In The Characterization And Management Of Continuous Flow Left Ventricular Assist Device Infection

18F-FDG PET/CT In The Characterization And Management Of Continuous Flow Left Ventricular Assist Device Infection

(836) Is There a Relationship Between Cannula Position and Right Ventricular Failure Outcome in Patients with Centrifugal Flow Left Ventricular Assist Devices?

(836) Is There a Relationship Between Cannula Position and Right Ventricular Failure Outcome in Patients with Centrifugal Flow Left Ventricular Assist Devices?

(772) Fully Magnetically Levitated Continuous Flow Left Ventricular Assist Device: Are We There Yet?

(772) Fully Magnetically Levitated Continuous Flow Left Ventricular Assist Device: Are We There Yet?

Meta-Analysis on the Impact of Ventricular Arrhythmias on Mortality in Patients With Continuous Flow Left Ventricular Assist Devices

Patients with continuous flow left ventricular assist devices (CFLVADs) have an increased risk of ventricular arrhythmias (VA), but the impact of VA on survival is unclear. A systematic search of electronic databases was conducted to identify studies that reported the impact of VA on all-cause mortality and right ventricular failure (RVF) in patients with CFLVAD. The Mantel-Haenszel method was used to calculate the 95% confidence interval (CI) and pooled risk ratio (RR) with a random-effects model. A total of 19 observational studies with 4,544 patients and a median follow-up of 18.5months (interquartile range 11.5 to 26.4) were included. There was statistically significantly higher mortality in patients with any VA than in those with no VA after CFLVAD implantation (RR 1.33, 95% CI 1.01 to 1.75, p=0.04, I2=78%). On sensitivity analysis, after removing the largest study by Rehorn etal,10 the association between overall mortality and VA was lost, suggesting that these results should be interpreted with caution. Early VA developing within 30days after implantation was associated with a higher risk of mortality (RR 1.37, 95% CI 1.15 to 1.63, p <0.01, I2=52%), whereas late VA developing after 30days after CFLVAD implantation was not associated with any significant difference in mortality (RR: 1.00; 95% CI: 0.80 to 1.24; p=0.98, I2=35%). In addition, there was a statistically significant higher risk of RVF in patients with VA than in those with no VA (RR 1.58, 95% CI 1.20 to 2.08, p <0.01, I2=0%). In conclusion, in patients with CFLVAD, the development of any VA was associated with a 33% higher risk of all-cause mortality. Early VA developing within 30days after implantation was significantly associated with a higher risk of mortality, whereas late VA was not associated with mortality. VA after left ventricular assist device was significantly associated with a higher risk of developing RVF.

Patient-specific, echocardiography compatible flow loop model of aortic valve regurgitation in the setting of a mechanical assist device.

Aortic regurgitation (AR) occurs commonly in patients with continuous-flow left ventricular assist devices (LVAD). No gold standard is available to assess AR severity in this setting. Aim of this study was to create a patient-specific model of AR-LVAD with tailored AR flow assessed by Doppler echocardiography. An echo-compatible flow loop incorporating a 3D printed left heart of a Heart Mate II (HMII) recipient with known significant AR was created. Forward flow and LVAD flow at different LVAD speed were directly measured and AR regurgitant volume (RegVol) obtained by subtraction. Doppler parameters of AR were simultaneously measured at each LVAD speed. We reproduced hemodynamics in a LVAD recipient with AR. AR in the model replicated accurately the AR in the index patient by comparable Color Doppler assessment. Forward flow increased from 4.09 to 5.61 L/min with LVAD speed increasing from 8,800 to 11,000 RPM while RegVol increased by 0.5 L/min (2.01 to 2.5 L/min). Our circulatory flow loop was able to accurately replicate AR severity and flow hemodynamics in an LVAD recipient. This model can be reliably used to study echo parameters and aid clinical management of patients with LVAD.

Abstract WP228: Stroke Risk Quantification For Patients With A Left Ventricular Assist Device

Introduction: Stroke is a leading cause of death and disability and a significant complication for heart failure patients on Left Ventricular Assist Device (LVAD) support. Most of these stroke cases are embolic in nature. Yet, specifics of embolus transport to the brain by the flow driven by an LVAD are poorly understood; precluding a clear understanding of post-implant stroke risks in these patients. Here we demonstrate an innovative stroke risk descriptor using in silico embolus transport analysis. Methods: Cardiac gated CTA images with LVAD graft were obtained for 6 patients. 3 patients reported post-LVAD stroke and the other 3 did not. 3D computer models of the LVAD graft, aortic arch, and branch vessels to the head were created using SimVascular. Blood flow from LVAD was computed for each model using LVAD flow rate and mean blood pressure as inputs. A custom fluid-particle interaction model for embolus transport was used to obtain the distribution of emboli entering the arch from the LVAD. A combination of normalized embolus distribution was used to create a stroke risk descriptor and compared across the stroke and non-stroke cases. Two sets of descriptors were defined using: (a) embolus distribution to the head; and (b) distribution to the head as well as accumulation at aortic root near the dysfunctional aortic valve. Results: We present results from 5,000 different embolism scenarios using representative thromboembolic particles of 1 mm diameter. For descriptor category (a) defined in Methods, the computed average for post-LVAD stroke cases was 0.35 as compared to 0.24 for those without post-LVAD stroke. For risk of embolic events in the brain including embolus accumulation in aortic root (i.e. descriptor category (b) in Methods) the reported averages were 0.38 and 0.27 for stroke vs no-stroke cases. Conclusions: The results indicate that our descriptor is a good surrogate for identifying stroke risks post-LVAD implantation, with stroke cases correlated with high values of the descriptor. The results also indicate that emboli traveling from LVAD graft into the arch, as well as emboli accumulating in regions of stasis at the aortic root may both contribute to stroke risks in patients with an LVAD. Continued investigations with bigger patient cohorts are needed.

Quantitative Assessment of Aortic Hemodynamics for Varying Left Ventricular Assist Device Outflow Graft Angles and Flow Pulsation.

Left ventricular assist devices (LVADs) comprise a primary treatment choice for advanced heart failure patients. Treatment with LVAD is commonly associated with complications like stroke and gastro-intestinal (GI) bleeding, which adversely impacts treatment outcomes, and causes fatalities. The etiology and mechanisms of these complications can be linked to the fact that LVAD outflow jet leads to an altered state of hemodynamics in the aorta as compared to baseline flow driven by aortic jet during ventricular systole. Here, we present a framework for quantitative assessment of aortic hemodynamics in LVAD flows realistic human vasculature, with a focus on quantifying the differences between flow driven by LVAD jet and the physiological aortic jet when no LVAD is present. We model hemodynamics in the aortic arch proximal to the LVAD outflow graft, as well as in the abdominal aorta away from the LVAD region. We characterize hemodynamics using quantitative descriptors of flow velocity, stasis, helicity, vorticity and mixing, and wall shear stress. These are used on a set of 27 LVAD scenarios obtained by parametrically varying LVAD outflow graft anastomosis angles, and LVAD flow pulse modulation. Computed descriptors for each of these scenarios are compared against the baseline flow, and a detailed quantitative characterization of the altered state of hemodynamics due to LVAD operation (when compared to baseline aortic flow) is compiled. These are interpreted using a conceptual model for LVAD flow that distinguishes between flow originating from the LVAD outflow jet (and its impingement on the aorta wall), and flow originating from aortic jet during aortic valve opening in normal physiological state.

Clinical Validation of a Neointima-Inducing Inflow Cannula in a Continuous Flow Left Ventricular Assist Device.

Wedge thrombus formation around the inflow cannula of a continuous left ventricular assist device (LVAD) is a source of systemic thromboemboli. We previously reported the potential advantages of a new inflow cannula wrapped with titanium mesh (GU30) over the standard smooth surface oblique cut cannula (GU10). The objective of the present study was to clinically validate this new cannula. A retrospective cohort analysis of patients with implanted LVAD (EVAHEART) comparing the GU10 to the GU30 was conducted. Clinical outcomes, including survival, the incidence of thromboembolism, and bleeding events, were compared. Gross and histopathological analyses of explanted GU30 cannula were conducted following transplant or patient death. No significant differences in the survival rate, severe emboli, or cerebral bleeding were observed during the LVAD implantation. However, severe emboli occurred earlier after LVAD implantation when using the GU30 cannula compared with the GU10. In cases of long LVAD support, the neointima fully covered the inflow of the GU30 cannulae without wedge thrombus formation. The titanium mesh-wrapped inflow cannulae did not reduce the overall incidence of neurological events significantly. However, the titanium mesh-wrapped inflow cannula induced autologous neointimal growth over the cannula and prevented wedge thrombus formation in late-phase LVAD implantation.

Abstract 15045: Impact of Left Ventricular Assist Device (LVAD) Type on Arrhythmic Outcomes in Patients With Continuous Flow LVADs

Introduction: Cardiac arrhythmias are common in continuous flow left ventricular assist device (LVAD) recipients. The impact of axial vs. intrapericardial centrifugal LVAD pumps on arrhythmia incidence and associated clinical outcomes is unclear. Hypothesis: This multicenter study evaluated the impact of LVAD type (axial vs. centrifugal) on incidence of atrial and ventricular arrhythmias, ICD shocks and mortality in LVAD patients. Methods: Analysis was done on 536 patients who underwent LVAD implantation at 5 US centers from 2008 to 2016. The groups were divided based on their LVAD type (axial - HeartMate II [HMII, n=433] vs. centrifugal - HeartWare (HW, n=103). Baseline characteristics as well as incidence of post-LVAD atrial arrhythmias (PL-AA), ventricular arrhythmias (PL-VA) and ICD shocks were analyzed in these groups. Multivariable Cox Regression analysis was used to identify predictors of survival. Results: Of 536 patients, 433 had HMII axial LVAD and 103 had HW centrifugal VAD implant. At baseline, HMII group had more males, higher proportion of CRT-D and higher prevalence of AA (Table 1A). Left ventricular dimensions were similar between groups. During a median follow-up of 537 days of LVAD support, incidence of PL-VA and ICD shocks were significantly higher in the HM2 group compared to HW group whereas incidence of PL-AA was not significantly different (Table 1A). In multivariable Cox Regression analysis, LVAD indication was the only variable that predicted survival (Table 1B). Type of LVAD (axial vs. centrifugal) was not associated with survival (HMII vs. HW - HR 1.04, P=0.48). Conclusions: In this multi-center continuous flow LVAD cohort, axial HM2 VAD patients had a higher incidence of PL-VA and ICD shocks. Type of LVAD (axial vs. centrifugal) was not associated with survival.

Hemodynamic Aberrancies in Left Ventricular Assist Device–Associated Heart Failure Syndromes

Hemodynamic Aberrancies in Left Ventricular Assist Device–Associated Heart Failure Syndromes

Non-intrusive PODI-ROM for patient-specific aortic blood flow in presence of a LVAD device.

Left ventricular assist devices (LVADs) are used to provide haemodynamic support to patients with critical cardiac failure. Severe complications can occur because of the modifications of the blood flow in the aortic region. In this work, the effect of a continuous flow LVAD device on the aortic flow is investigated by means of a non-intrusive reduced order model (ROM) built using the proper orthogonal decomposition with interpolation (PODI) method based on radial basis functions (RBF). The full order model (FOM) is represented by the incompressible Navier-Stokes equationsdiscretized by using a Finite Volume (FV) technique, coupled with three-element Windkessel models to enforce outlet boundary conditions in a multi-scale approach. A patient-specific framework is proposed: a personalized geometry reconstructed from Computed Tomography (CT) images is used and the individualization of the coefficients of the three-element Windkessel models is based on experimental data provided by the Right Heart Catheterization (RHC) and Echocardiography (ECHO) tests. At FOM level, we also consider the pre-surgery configuration in order to further validate the predictive capabilities of the model in several contexts. The ROM has been tested by considering a parametric setting with respect to the LVAD flow, which is a crucial parameter of the problem. We consider a parameter range that covers typical clinical values. The accuracy of the ROM is assessed against results obtained with the FOM both for primal, velocity and pressure, and derived quantities, wall shear stress (WSS). Finally, we briefly discuss the efficiency of our ROM approach.

Science, Medicine, and the Anesthesiologist

Science, Medicine, and the Anesthesiologist

A Computational Hemodynamics Approach to Left Ventricular Assist Device (LVAD) Optimization Validated in a Large Patient Cohort.

With increasing use of left ventricular assist devices (LVAD) it is critical to devise strategies to optimize LVAD speed while controlling mean arterial pressure (MAP) and flow according to patient physiology. The complex interdependency between LVAD speed, MAP, and flow frequently makes optimization difficult under clinical conditions. We propose a method to guide this procedure in silico, narrowing the conditions to test clinically. A computational model of the circulatory network that simulates HF and LVAD support, incorporating LVAD pressure-flow curves was applied retrospectively to anonymized patient hemodynamics data from the University of Washington Medical Center. MAP management on 61 patient-specific computational models with a target of 70 mm Hg, resulting flow for a given LVAD speed was analyzed, and compared to a target output of 5 L/min. Before performing virtual MAP management, 51% had a MAP>70 mm Hg and CO>5 L/min, and 33% had a MAP>70 mm Hg and CO<5 L/min. After changing systemic resistance to meet the MAP target (without adjusting LVAD speed), 84% of cases resulted in CO higher than 5 L/min, with a median CO of 6.79 L/min, using the computational predictive model. Blood pressure management alone is insufficient in meeting both MAP and CO targets, due to the risk of hypervolemia, and requires appropriate LVAD speed optimization to achieve both targets, while preserving right heart health. Such computational tools can narrow down conditions to be tested for each patient, providing significant insight into the pump-patient interplay. LVAD hemodynamic optimization has the potential to reduce complications and improve outcomes.

Impact of Continuous Flow Left Ventricular Assist Device on Heart Transplant Candidates: A Multi-State Survival Analysis.

(1) Objectives: The aim of this study was to investigate the impact of the prolonged use of continuous-flow left ventricular assist devices (LVADs) on heart transplant (HTx) candidates. (2) Methods: Between January 2012 and December 2019, we included all consecutive patients diagnosed with end-stage heart failure considered for HTx at our institution, who were also eligible for LVAD therapy as a bridge to transplant (BTT). Patients were divided into two groups: those who received an LVAD as BTT (LVAD group) and those who were listed without durable support (No-LVAD group). (3) Results: A total of 250 patients were analyzed. Of these, 70 patients (28%) were directly implanted with an LVAD as BTT, 11 (4.4%) received delayed LVAD implantation, and 169 (67%) were never assisted with an implantable device. The mean follow-up time was 36 ± 29 months. In the multivariate analysis of survival before HTx, LVAD implantation showed a protective effect: LVAD vs. No-LVAD HR 0.01 (p < 0.01) and LVAD vs. LVAD delayed HR 0.13 (p = 0.02). Mortality and adverse events after HTx were similar between LVAD and No-LVAD (p = 0.65 and p = 0.39, respectively). The multi-state survival analysis showed a significantly higher probability of death for No-LVAD vs. LVAD patients with (p = 0.03) or without (p = 0.04) HTx. (4) Conclusions: The use of LVAD as a bridge to transplant was associated with an overall survival benefit, compared to patients listed without LVAD support.

CARC19: Endovascular Axial Flow Left Ventricular Assist Device as a Bridge to Orthotopic Heart Transplantation

CARC19: Endovascular Axial Flow Left Ventricular Assist Device as a Bridge to Orthotopic Heart Transplantation

CARD27: The Effect of Permissive Hypertension on Cerebral Perfusion in VAD Patients with Embolic Stroke

Study: This study aims to investigate the effect of permissive hypertension, a deliberate rise in Mean Arterial Pressure (MAP), on cerebral perfusion in Left Ventricular Assist Device (LVAD) patients with embolic stroke. Methods: A previously published Lumped Parameter Model (LPM) of the human circulation, including pulmonary and systemic circulation, as well as all four cardiac chambers and an LVAD, is divided into circulation of the upper and lower body. The upper circulation is further divided into extracranial and intracranial vessels to study brain perfusion as a function of MAP, as well as peripheral and intracranial resistance. Actual LVAD H-Q characteristic curves model the instantaneous LVAD response to a rise in MAP and the differential increase in resistance between the intracranial region suffering a stroke and the remaining circulation. The resulting changes in intracranial flow rate as MAP increases and vascular resistance is altered are analyzed. Increased resistance in intracranial vasculature is incorporated into a model of a typical embolic stroke, and its influence on cerebral perfusion is studied for a range of LVAD speeds and MAP values. Results: In LVAD patients with embolic stroke, intracranial flow significantly decreases as MAP is allowed to rise. These findings are robust at any LVAD speed, consistent with a significant reduction in LVAD flow with increased afterload. This counterintuitive result of permissive hypertension in LVAD patients is captured by the LPM model of embolic stroke, whereby the increase in intracranial resistance decreases cerebral perfusion even further via a decrease in total cardiac output associated with the increase in MAP. Third-generation LVADs are known to be afterload sensitive. Our results show that a mere increase in MAP from 70 to 80 mmHg decreases cerebral blood flow by a commensurate 15%, thus increasing infarct size, which is quite deleterious (see Fig. 1). Our study confirms there is no role for permissive hypertension in LVAD patients with embolic stroke. Figure 1. Cranial flow rate (Qcranial) as a function of MAP for no embolism (purple) and embolism (teal) cases and for 2400 RPM (circles) and 2800 RPM (squares) LVAD speeds.

Flow dynamics during the HeartWare HVAD to HeartMate 3 exchange: A computational study assessing differential graft lengths and surgical techniques.

Flow dynamics during the HeartWare HVAD to HeartMate 3 exchange: A computational study assessing differential graft lengths and surgical techniques.