Flow Ventricular Assist Device Research Articles

Nonlinear control of a hybrid pneumo‐hydraulic mock circuit of the cardiovascular system

AbstractHybrid cardiovascular mock circuits (HMC), designed for dynamic testing of Ventricular Assist Devices (VAD), offer physiologic accuracy by sequestering model complexity in silico and ease of construction by reducing number of model elements in vitro. Despite superior response time and precision, pneumatic actuation is avoided in HMCs due to nonlinear dynamics and noise. We tested the hypothesis that a HMC consisting of a variable elastance‐driven numerical cardiovascular circuit (CVS) coupled to a pneumo‐hydraulic physical circuit can be controlled without linearizing system dynamics. Reference left ventricular and aortic pressures were generated in silico in a seventh‐order electrical analogue of the CVS and transmitted via an electro‐hydraulic interface to the physical circuit. There, they were tracked in in vitro preload and afterload pneumo‐hydraulic reservoirs, respectively. The nonlinear pneumatic dynamics in the reservoirs was controlled using the Lyapunov stability criterion. A centrifugal pump, the speed (i.e., flow) of which was adjusted manually or using PID control, was interposed between the reservoirs and mimicked the VAD under evaluation. The flow of a recirculating gear pump was controlled by an integral backstepping method to equalize reservoir fluid volumes by rejecting pressure and flow disturbances. Sensor noise was reduced with discrete‐time Kalman filtering. Our results showed that normal, failing, and assisted cardiovascular physiologies simulated in silico were commensurate with clinical data obtained from subjects with similar pathologies. The numerical pressure references were tracked with high accuracy at the physical VAD terminals. Reservoir volumes remained stable at various combinations of heart rate, pressure, and VAD flow for prolonged durations with negligible steady‐state error. The HMC described here offers a stable performance testing platform for VAD prototypes.

Tailoring left ventricular assist device cannula implantation using coupled multi-scale multi-objective optimization

BackgroundThe frequent occurrence of thromboembolic cerebral events continues to limit the widespread implementation of Ventricular Assist Devices (VAD) despite continued advancements in VAD design and anti-coagulation treatments. Recent studies point to the optimal positioning of the outflow graft (OG) as a potential mitigator of post implantation thromboembolism. ObjectiveThis study aims to examine the tailoring of the OG implantation orientation with the goal of minimizing the number of thrombi reaching the cerebral vessels by means of a formal shape optimization scheme incorporated into a multi-scale hemodynamics analysis. MethodsA 3-D patient-specific computational fluid dynamics model is loosely coupled in a two-way manner to a 0-D lumped parameter model of the peripheral circulation. A Lagrangian particle-tracking scheme models and tracks thrombi as non-interacting solid spheres. The loose coupling between CFD and LPM is integrated into a geometric shape optimization scheme which aims to optimize an objective function that targets a drop in cerebral embolization, and an overall reduction in particle residence times. ResultsThe results elucidate the importance of OG anastomosis orientation and placement particularly in the case that studied particle release from the OG, as a fivefold decrease in cerebral embolization was observed between the optimal and non-optimal implantations. Another case considered particle release from the ventricle and aortic root walls, in which optimal implantation was achieved with a shallow insertion angle. Particle release from all three origins was investigated in the third case, demonstrating that the optimal configurations were generally characterized by VAD flow directed along the central lumen of the aortic arch. Because optimal configurations depended on the anatomic origin of the thrombus, it is important to determine, in clinical studies, the most likely sites of thrombus formation in VAD patients.

Percutaneous left ventricular assist devices in refractory cardiac arrest: The role of chest compressions

Recent studies describe an emerging role for percutaneous left ventricular assist devices such as Impella CP® as rescue therapy for refractory cardiac arrest. We hypothesized that the addition of mechanical chest compressions to percutaneous left ventricular assist device assisted CPR would improve hemodynamics by compressing the right ventricle and augmenting pulmonary blood flow and left ventricular filling. We performed a pilot study to test this hypothesis using a swine model of prolonged cardiac arrest. Eight Yorkshire swine were anesthetized, intubated, and instrumented for hemodynamic monitoring. They were subjected to untreated ventricular fibrillation for 5.75 (SD 2.90) minutes followed by mechanical chest compressions for a mean of 20.0 (SD 5.0) minutes before initiation of percutaneous left ventricular assist device. After percutaneous left ventricular assist device initiation, mechanical chest compressions was stopped (n=4) or continued (n=4). Defibrillation was attempted 4, 8 and 12 minutes after initiating percutaneous left ventricular assist device circulatory support. The percutaneous left ventricular assist device+mechanical chest compressions group had significantly higher percutaneous left ventricular assist device flow prior to return of spontaneous heartbeat at four- and twelve-minutes after percutaneous left ventricular assist device initiation, and significantly higher end tidal CO2 at 4-minutes after percutaneous left ventricular assist device initiation, when compared with the percutaneous left ventricular assist device alone group. Carotid artery flow was not significantly different between the two groups. The addition of mechanical chest compressions to percutaneous left ventricular assist device support during cardiac arrest may generate higher percutaneous left ventricular assist device and carotid artery flow prior to return of spontaneous heartbeat compared to percutaneous left ventricular assist device alone. Further studies are needed to determine if this approach improves other hemodynamic parameters or outcomes after prolonged cardiac arrest.

P75: In Vivo Evaluation of a Paracorporeal Pulsatile Ventricular Assist Device in an Ovine Model

Background: Ventricular assist devices (VAD) have undergone numerous changes and improvements since their conception. One of the most notable advances was the paradigm change from pulsatile to non-pulsatile, continuous-flow (CF) rotary pumps, which are smaller and more durable. Despite these improvements, the price of CF-VADs makes them challenging to access in developing countries. Hence, an easily implantable, cost-effective VAD has the potential to increase access to life-saving procedures around the world. In this study, we performed two 30-day experiments to assess the safety and durability of the final version of the Vitalmex Paracorporeal Pulsatile Ventricular Assist Device (PPVAD). Methods: The device was implanted in two healthy sheep for 31 and 32 days. Implantation was performed by inserting the inflow cannula into the left ventricular apex and suturing the outflow graft to the descending aorta. Hemodynamic data, such as VAD pulse rate, flow, and pressures, were recorded. Bloodwork, including chemistry, hematology/coagulation profile, and plasma-free hemoglobin, was taken. A necropsy was performed at the end of the study. Values are reported as means with standard deviations. Results: Both animals reached the intended endpoint without any unexpected device-related problems. A fixed VAD rate of 65 bpm was maintained throughout most of the study duration. The average VAD flow was 3.14 ± 0.9 L/min. Plasma-free hemoglobin values were 10.15 ± 3.95 mg/dL. The histopathologic evaluation reported interstitial nephritis and mild cortical fibrosis of the adrenal glands. Thromboembolic incidents were observed in the liver and lungs; these were not clinically significant. The tissue changes surrounding the implant site at the left ventricle and descending aorta were within the expected degree of inflammation and fibrosis. Conclusion: The PPVAD can provide safe pulsatile mechanical circulatory support for 30 days. This device can offer an easily implantable, cost-effective alternative to currently available VADs.

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.

Science, Medicine, and the Anesthesiologist

Science, Medicine, and the Anesthesiologist

Neonatal ventricular assist device implantation for high-risk hypoplastic left heart syndrome: How we do it.

Neonatal ventricular assist device implantation for high-risk hypoplastic left heart syndrome: How we do it.

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.

Baseline Ventricular Assist Device (VAD) Flow as a Potential Marker of Increased Morbidity and Mortality Risk During Blood Stream Infection (BSIs) in Patients with Fixed Pump Speed

<h3>Purpose</h3> Patients with VADs are at risk of adverse outcomes following sepsis due to limited ability to augment cardiac output at fixed pump speed. This study aimed to profile VAD hemodynamic profiles around BSIs as potential markers of hemodynamic response, intensive care unit (ICU) requirements, time to transplant and mortality. <h3>Methods</h3> This was a single center retrospective study of patients with Medtronic HVAD implants as bridge-to-transplant from November 2007 to December 2020 with available log file data for flow (mL/min) and power (mW). All patients with BSIs whilst on pump were included and used as own controls. Baseline data was defined as the 24-hour period 7 days after VAD implant, and BSI data being the 48-hour period up to and following a positive blood culture. <h3>Results</h3> A total of 62 patients (52 males, 83.9%) were studied (51 LVADs, 11 BiVADs). Average age at implant was 50.0±12.7 years and INTERMACS score 2±0.7. There was a significant increase in pump flow from a baseline median of 4719.9 (IQR 4158.3- 5487.9) to 5230.0 (IQR 4401.8-5831.4) (p<0.001) at time of BSI, and 33 (53%) patients were managed in ICU. This increase in baseline flow was observed across all patients managed on the wards, ICU or required ICU transfer. There was a trend towards lower baseline flow in the ICU group at 4609.0 (IQR 4150.9-5322.7) compared with ward-managed patients at 4807.5 (IQR 4332.4-5474.7) (p=0.577). When compared to ward patients, ICU patients had increased incidence of death or progression to transplant (log-rank=0.028) (Figure). There was a distinct trend towards increased mortality for those in ICU. <h3>Conclusion</h3> In this study, baseline VAD flow measures following a positive blood culture could potentially reflect less cardiovascular reserve in patients requiring more intensive support. It may potentially be a marker of increased susceptibility to death or urgency to transplant assessment in light of a hemodynamic insult.

Design of a Hydrodynamic Performance Bench for Ventricular Assist Devices

This work presents the design of a hydrodynamic performance bench (HPB) of Ventricular Assist Devices (VADs) for evaluations of developed prototypes. VADs are used for the treatment of patients with Congestive Heart Failure (CHF), either as a bridge to recovery, for transplantation or as destination therapy. HPB is required for the performance evaluation of VADs that are under development in Brazil. The performance evaluation of a VAD considers the rotation speed [rpm], flow rate [L/min], pressure [mmHg] and power [W]. The project consists in choosing an actuator and transducers from HPB, and developing the mechanical components, supervisory control and modules. The HPB mechanical components were designed in SolidWorks® following rapid prototyping and built by additive manufacturing. The HPB supervisory program was developed in graphic language through the Labview® program and implemented in a development and application platform with data acquisition system. The manipulated variable of the supervisory system is the motor speed [rpm] acting via an Escon 50/4 EC-S power controller on the BLDC EC45 N339281 motor. The controlled variable is the “VAD flow” [L/min] provided by an HT-110 flow transducer. A particle image velocimetry (PIV) module was developed for flow analysis. All process data are stored in spreadsheets for later consultation. HPB could assist in a satisfactory way in the analysis of the developed VADs prototypes, demonstrating the technical success of the project.

Mechanical support for the failing single ventricle after Fontan

Mechanical support for the failing single ventricle after Fontan

Hemodynamic Response to Device Titration in the Shunted Single Ventricle Circulation: A Patient Cohort Modeling Study.

Clinical outcomes of ventricular assist device (VAD) support for shunted single ventricle patients trail the larger population due in part to the challenges in optimizing VAD support and balancing systemic and pulmonary circulations. We sought to understand the response to VAD titration in the shunted circulation using a lumped-parameter network modeling six patient-specific clinical cases. Hemodynamic data from six patients (mean body surface area = 0.30 m2) with a systemic-to-pulmonary shunt was used to construct simulated cases of heart failure and hemodynamic response to increasing VAD flow from 5 to 10 L/min/m2. With increasing VAD flow, the pulmonary arterial pressure stayed relatively constant in five patient cases and increased in one patient case. The mean VAD flow needed to attain an arterial-venous O2 saturation difference of 30% was 6.5 ± 1.2 L/min/m2, which is higher than that in the equivalent nonshunted scenario due to the partial diversion of flow to the pulmonary circulation. The hemodynamic responses to VAD support can vary significantly between specific patient cases; therefore hemodynamic modeling may help guide an individualized approach to perioperative VAD management in the shunted single-ventricle circulation and to understand the patients who may benefit the most from VAD support.

Vertical Ventricular Assist Device Placement to Systemic Right Ventricle for a Patient with Corrected Transposition of the Great Arteries and Mesocardia

Introduction Patients with physiologically repaired corrected transposition of the great arteries (cTGA) have morphological right ventricle (RV) as systemic ventricle. They may develop systemic RV failure in long-term and subsequently require heart transplantation with or without ventricular assist device (VAD) placement. However, VAD placement for systemic RV carries technical challenges, including trabeculated and diverse shapes of RV, close proximity to tricuspid valve and various apex positions. Case Report A case was 38-year-old female with cTGA and pulmonary stenosis. She had surgical history of physiological repair and redo pulmonary artery plasty at 10 and 19 years of age, respectively. She had history of heart failure symptoms with systemic RV dysfunction since 27 years of age. She was re-admitted for recurrent heart failure and listed for heart transplantation at 37 year of age. Her cardiac position was mesocardia and systemic RV was longitudinally elongated with severely dilated left atrium. The aorta was left anterior to the pulmonary trunk. Therefore, the standard VAD placement from cardiac apex may cause interference of sternal closure by pump body, inflow obstruction due to close proximity to the tricuspid valve, and difficult anastomosis to the short anterior ascending aorta. In contrast, the vertical VAD placement from diaphragmatic surface towards the aortic valve seemed to resolve these challenges. At the operation, a cardiopulmonary bypass was established through femoral cannulation. Under transesophageal echocardiogram guidance, the optimal inflow cannulation site was decided. After aortic cross-clamp, the systemic RV trabeculation was resected and the 3rd generation VAD pump was placed vertically from RV diaphragmatic surface. The outflow graft was laid along left side of the heart and anastomosed to left lateral ascending aorta. Postoperatively, the VAD flow had been stable with no evidence of sucking or thrombus formation. She was discharged and currently waiting for heart transplantation. Summary It is important to determine VAD placement technique with thorough understanding of unique characteristics of cTGA. Vertical VAD placement to systemic RV and anastomosis of outflow cannula to the left side of the aorta can be a good option for patients with systemic RV failure with mesocardia.

HVAD Decommission in a Failing Mustard: Making Virtue out of Necessity

Introduction Ventricular assist device (VAD) for systemic right ventricular failure (SRVF) in transposition of the great arteries (TGA) patients has proven useful to reduce transpulmonary gradient (TPG) and bridge-to-transplantation. Tricuspid valve replacement (TVR) at the time of implant to address severe tricuspid regurgitation (TR) may be beneficial to achieve optimal unloading of the systemic right ventricle (SRV). We report successful decommissioning of a SRV VAD following device thrombosis in a patient who underwent TVR at VAD implant. Case Report A 37-year-old man who underwent a Mustard procedure for TGA at 10 months of age presented with acute heart failure, triggered by leg cellulitis and pulmonary embolism. He was found to have a severely impaired SRV, severe TR and a dilated and moderately impaired subpulmonic left ventricle (LV). Despite medical management and anticoagulation, he worsened requiring admission to the ICU for inotropic support. A right heart catheter (RHC) showed a mean pulmonary artery (PA) pressure of 48 mmHg and TPG of 15 mmHg, therefore ineligible for heart transplant. He underwent successful HeartWare-VAD implantation into his failing SRV with concomitant systemic TVR. His post-operative course was uneventful and he was discharged after 25 days. After six months, his TPG came down to 4 mmHg and he was listed for heart transplantation. He remained stable and free from VAD complications until he presented with thrombosis of the outflow graft after 27 months. Anticoagulation with bivalirudin was started without success and persistent reduced VAD flow of Summary VAD implantation is a feasible strategy for those with SRVF. Concomitant TVR to address severe TR may have additional benefit and in this particular case, likely to have contributed to successful VAD decommissioning following device thrombosis.

Turbulence and turbulent flow structures in a ventricular assist device-A numerical study using the large-eddy simulation.

Numerical flow simulations that analyze the turbulent flow characteristics within a turbopump are important for optimizing the efficiency of such machines. In the case of ventricular assist devices (VADs), turbulent flow characteristics must be also examined in order to improve hemocompatibility. Turbulence increases the shear stresses in the VAD flow, which can lead to an increased damage to the transported blood components. Therefore, an understanding of the turbulent flow patterns and their significance for the numerical blood damage prediction is particularly important for flow optimizations in VADs in order to identify and thus minimize flow regions where blood could be damaged due to high turbulent stresses. Nevertheless, the turbulence occurring in VADs and the local turbulent structures that lead to increased turbulent stresses have not yet been analyzed in detail in these machines. Therefore, this study aims to investigate the turbulence in an axial VAD in a comprehensive and double tracked way. First, the flow in an axial VAD was computed using the large-eddy simulation method, and it was verified that the majority of the turbulence was directly resolved by the simulation. Then, the turbulent flow state of the VAD was quantified globally. For this purpose, a self-designed evaluation method, the power loss analysis, was used. Subsequently, local flow regions and flow structures were identified where significant turbulent stresses prevail. It will be shown that the identified regions are universal and will also occur in other axial blood pumps as well, for example, in the HeartMate II.

Argatroban versus heparin for the treatment of pump thrombosis in patients with ventricular assist device

Abstract Background/Introduction Pump thrombosis (PT) is a major complication from ventricular assist device (VAD) and the best therapy remains unknown. The diagnosis of PT is challenging and, based on the ISHLT (International Society of Heart and Lung Transplantation) guidelines, consists of signs of hemolysis and impaired pump function. Purpose We aimed to compare the outcomes of PT treated with continuous infusion of argatroban (ARG) versus heparin. Methods This is a retrospective cohort study including patients &amp;gt;15 years-old with VAD implanted between 2009 and 2017 and who developed PT during follow up. PT events were managed with ARG or heparin based on physician preference at our institution, and patients were grouped based on the anticoagulation treatment received. Variables of interest were survival at 1, 3 and 5 years, stroke, right heart failure (RHF), infection, laboratory data and VAD parameters before and after anticoagulation treatment, baseline characteristics and comorbidities. We used Chi-square test to analyze categorical data and the Wilcoxon signed rank test for continuous data in related samples to compare laboratory and VAD parameters pre and post anticoagulation in both groups. Kaplan Meier survival analysis was performed using the log rank statistics. Non-parametric results were reported as median and interquartile range (IQR). A 95% confidence interval (CI) was adopted. Results There were 193 VADs implanted in 170 patients. Of those, 30 patients had 47 episodes of PT, 34 treated with ARG and 13 with heparin. Of patients with PT, 73% had a HeartMate II and 27% had a HeartWare device, the median age at implantation was 48 years old (IQR 40.2, 60.2) and 90% were males; African Americans were 50%, followed by Hispanics (30%) and Caucasians (20%). The median follow-up was 2.5 years (IQR 1, 3.4). In the ARG group, there was a statistically significant reduction at the time of discharge in LDH (p&amp;lt;0.001), AST (p&amp;lt;0.001), total bilirubin (p=0.001), platelet count (p=0.046), VAD flow (p=0.011) and VAD power (p=0.004) compared with admission parameters, while no statistically significant change was present in the heparin group. ARG led to a numerically higher, but not statistically significant, survival when compared with heparin (53% vs 38%, p=0.237). One-year, 3-year and 5-year survival were not significantly different between anticoagulation strategies (p=0.23, p=0.9 and p=0.89, respectively). There was no difference in the number of VAD re-implants, RHF, stroke or infection between groups. Conclusions ARG therapy led to a statistically significant improvement in hemolysis parameters and pump function when compared to heparin therapy for PT in VAD recipients, but no survival benefit was demonstrated, which could be due to the small sample size. Other limitations were the retrospective and non-randomized data. ARG therapy must be tested in larger trials to confirm its benefits for PT. Funding Acknowledgement Type of funding source: None

Rotary Ventricular Assist Device Control With a Fiber Bragg Grating Pressure Sensor

Current ventricular assist devices (VADs) are rotary blood pumps used to treat end-stage heart failure. VADs are operated at a constant speed that is manually adjusted by a clinician based on the patient's cardiac demand during routine medical examinations. VADs operated at a constant speed have inadequate passive flow regulation due to the inherent mechanical pressure-flow characteristics of the pump; this can lead to harmful situations where the VAD is overpumping or underpumping. Typically, patients on long-term VAD support are discharged to an outpatient setting where the VAD speed can remain the same for weeks or months at a time, impacting patient safety and quality of life. Previously, physiological controllers for VADs have been proposed, which automatically adjust VAD speed to meet patient cardiac demand. Clinical implementation of physiological control is currently hindered by the lack of clinically available, implantable, and continuous hemodynamic sensors. This study describes the physiological control of a VAD using a fiber Bragg grating (FBG) sensor previously developed for measuring VAD inlet pressure. The FBG sensor was used as a feedback to a Starling-like physiological controller, and the control quality was compared against the same controller with feedback from a nonimplantable industrial pressure sensor (Omega sensor). Experiments were conducted in a bench-top cardiovascular simulator under various simulated patient scenarios. The average steady-state difference in VAD flow across all experiments was 0.1 L/min with a maximum difference of -0.4 L/min. Similarly, the average steady-state difference in left ventricular end-diastolic pressure was 0.02 mmHg with a maximum difference of -0.2 mmHg. The clinically insignificant differences found between the two feedback methods indicate that the FBG pressure sensor is viable for the physiological control of VADs.

Designing an Active Valvulated Outflow Conduit for a Continuous-Flow Left Ventricular Assist Device to Increase Pulsatility: A Simulation Study.

The purpose of this work was to investigate, using a lumped parameter model, the feasibility of increasing the pulsatility of a continuous-flow ventricular assist device (VAD) by implanting an active valvulated outflow cannula. A lumped parameter model was adopted for this study. VAD was modeled, starting from its pressure-flow characteristics. The valvulated outflow conduit was modeled as an active resistance described by a square function. Starting from pathologic condition, the following simulations were performed: VAD, VAD and valvulated outflow conduit in copulsation and counterpulsation with different ratios between the VAD valve opening rate and the heart rate, and asynchrony work with the heart with different VAD valve opening intervals. The copulsation 1:1 configuration and the asynchrony 0.3s-close-0.7s-open configurations permit to maximize the hemodynamic benefits provided by the presence of the active VAD outflow valvulated conduit providing an increase of arterial pulsatility from 1.86% to 14.98% without the presence of left ventricular output. The presence of the active VAD valve in the outflow conduit causes a decrement of the left ventricular unloading and of VAD flow and, that can be counteracted by increasing the VAD speed without affecting arterial pulsatility. The valvulated outflow tube provides an increase in arterial pulsatility; it can be driven in different working modality and can be potentially applicable to all types of VADs. However, the valvulated outflow conduit causes a decrement of left ventricular unloading and of the VAD flow that can be counteracted, increasing the VAD speed.

Advances in Hemodynamic Monitoring in Heart Failure Patients

Abnormal hemodynamics are associated with poor clinical outcomes in patients with heart failure. Given the invasiveness and unfeasibility of routine right heart catheterization, non-invasive methodologies to monitor hemodynamics are needed. The CardioMEMS™ device is a recently developed technology that enables remote monitoring of pulmonary artery pressures via an implanted sensor located in the distal left pulmonary artery. Along with the CardioMEMS™, a remote dielectric system might be another promising device that reports indirect intra-thoracic filling pressures associated with pulmonary congestion. In patients with advanced heart failure who require left ventricular assist devices, non-invasive hemodynamic monitoring is particularly necessary, given the increased procedural risks of invasive assessments. The HeartWare ventricular assist device flow waveform is a variable under active investigation that might also provide an estimation of filling pressures. This methodology is expected to lead to the development of a smart pump that can adjust its own settings, including the pump speed, automatically by monitoring the hemodynamics.

HVAD Flow Waveform Estimates Left Ventricular Filling Pressure

HVAD left ventricular assist device flow waveforms provides graphical real-time information linking device performance with invasive hemodynamics. Previous studies have demonstrated a good correlation between the slopes of the ventricular filling phase slope (VFPS) and directly measured pulmonary capillary wedge pressure (PCWP). We aimed to validate the utility of VFPS to estimate PCWP and predict clinical outcomes. In this prospective blinded study, screenshots from the HVAD monitor and simultaneous invasive hemodynamic measurements were obtained. Each screenshot was digitized and the VFPS was calculated by 2 independent reviewers who were blinded to the hemodynamic results. The equation PCWP = 7.053 +1.365 × (VFPS) was derived from a previously published dataset and the estimated PCWP was correlated to the actually measured PCWP. One hundred thirty-one sets of simultaneous measurements (VFPS and PCWP) were obtained from 27 HVAD patients (mean age 55 years, 47% male). A previously proposed cutoff of VFPS ≥5.8 L/min/s predicted PCWP ≥ 18 mmHg with 91.5% sensitivity and 95.2% specificity with the area under curve of 0.987. The estimated PCWP significantly correlated with measured PCWP (R2 = 0.65, P < .001) and showed acceptable agreement with measured PCWP. Patients with VFPS ≥ 5.8 L/min/s experienced significantly higher heart failure readmission rates than those without (0.24 vs 0.05 events/y, P < .001). VFPS of the HVAD flow waveform is a novel noninvasive parameter that can estimate PCWP.