Shear stress and blood trauma under constant and pulse-modulated speed CF-VAD operations: CFD analysis of the HVAD.

Modulation of pump speed has been proposed and implemented clinically to improve vascular pulsatility in continuous flow ventricular assist device patient. The flow dynamics of the HVAD with a promising asynchronous pump speed modulation and its potential risk for device-induced blood trauma was investigated numerically. The boundary conditions at the pump inlet and outlet were defined using the pressure waveforms adapted from the experimentally recorded ventricular and arterial pressure waveforms in a large animal ischemic heart failure (IHF) model supported by the HVAD operated at constant and modulated pump speeds.

Hemodynamic Benefits of Counterpulsation, Implantable, Percutaneous, and Intraaortic Rotary Blood Pumps: An In-Silico and In Vitro Study.

Mechanical circulatory support (MCS) devices have become a standard therapy for heart failure (HF) patients. MCS device designs may differ by level of support, inflow and/or outflow cannulation sites, and mechanism(s) of cardiac unloading and blood flow delivery. Investigation and direct comparison of hemodynamic parameters that help characterize performance of MCS devices has been limited.

Mechanistic insight of platelet apoptosis leading to non-surgical bleeding among heart failure patients supported by continuous-flow left ventricular assist devices.

Non-surgical bleeding (NSB) is the most common clinical complication in heart failure (HF) patients supported by continuous-flow left ventricular assist devices (CF-LVADs). In this study, oxidative stress and alteration of signal pathways leading to platelet apoptosis were investigated. Thirty-one HF patients supported by CF-LVADs were divided into bleeder (n = 12) and non-bleeder (n = 19) groups.

Continuous-Flow Left Ventricular Assist Device Support Improves Myocardial Supply:Demand in Chronic Heart Failure.

Continuous-flow left ventricular assist devices (CF LVADs) are rotary blood pumps that improve mean blood flow, but with potential limitations of non-physiological ventricular volume unloading and diminished vascular pulsatility. In this study, we tested the hypothesis that left ventricular unloading with increasing CF LVAD flow increases myocardial flow normalized to left ventricular work. Healthy (n = 8) and chronic ischemic heart failure (IHF, n = 7) calves were implanted with CF LVADs.

Surgical Technique for Ventricular Device Exchange: From HeartMate II to HVAD.

Implantable continuous-flow left ventricular assist devices (LVADs) have improved the survival of end-stage heart failure patients. Recent studies have shown an increased occurrence of device replacement in the axial flow pumps particularly for thrombosis. In some patients, to try and avoid recurrent pump thrombosis, it might be advantageous to switch from the axial flow LVAD to a newer generation centrifugal flow LVAD.

Efficacy of Subcutaneous Electrocardiogram Leads for Synchronous Timing During Chronic Counterpulsation Therapy.

Counterpulsation devices (CPDs) require an accurate, reliable electrocardiogram (ECG) waveform for triggering inflation and deflation. Surface electrodes are for short-term use, and transvenous/epicardial leads require invasive implant procedure. A subcutaneous ECG lead configuration was developed as an alternative approach for long-term use with timing mechanical circulatory support (MCS) devices.

Infection, Oxidative Stress, and Changes in Circulating Regulatory T Cells of Heart Failure Patients Supported by Continuous-Flow Ventricular Assist Devices.

The objective of this study was to investigate the changes in oxidative stress (OS) and circulating regulatory T cells (Tregs) of the immune system in patients supported by continuous-flow ventricular assist device (CF-VAD) with or without infection. We recruited 16 CF-VAD patients (5 with infection and 11 without infection) and 7 healthy volunteers. Generation of reactive oxygen species (ROS) from lymphocytes, superoxide dismutase (SOD) in erythrocyte, total antioxidant capacity (TAC), and oxidized low-density lipoprotein (oxLDL) in plasma were measured.

Feasibility of Pump Speed Modulation for Restoring Vascular Pulsatility with Rotary Blood Pumps.

Continuous flow (CF) left ventricular assist devices (LVAD) diminish vascular pressure pulsatility, which may be associated with clinically reported adverse events including gastrointestinal bleeding, aortic valve insufficiency, and hemorrhagic stroke. Three candidate CF LVAD pump speed modulation algorithms designed to augment aortic pulsatility were evaluated in mock flow loop and ischemic heart failure (IHF) bovine models by quantifying hemodynamic performance as a function of mean pump speed, modulation amplitude, and timing. Asynchronous and synchronous copulsation (high revolutions per minute [RPM] during systole, low RPM during diastole) and counterpulsation (low RPM during systole, high RPM during diastole) algorithms were tested for defined modulation amplitudes (±300, ±500, ±800, and ±1,100 RPM) and frequencies (18.

Feasibility Study of Pulsatile Left Ventricular Assist Device for Prolonged Ex Vivo Lung Perfusion.

Background: Ex vivo lung perfusion (EVLP) has the potential to increase the donor pool for lung transplantation by facilitating resuscitation and extended evaluation of marginal organs. Current EVLP methodology employs continuous flow (CF) pumps that produce non-pulsatile EVLP hemodynamics. In this feasibility study, we tested the hypothesis that a pulsatile flow (PF) pump will provide better EVLP support than a CF pump through delivery of physiologic hemodynamics.

Left Ventricular Assist Device-Associated Carbon Monoxide and Iron-Enhanced Hypercoagulation: Impact of Concurrent Disease.

Left ventricular assist device (LVAD) therapy is associated with thrombophilia despite anticoagulation. Of interest, LVAD patients have increased carboxyhemoglobin, a measure of upregulated heme oxygenase (Hmox) activity that releases carbon monoxide (CO) and iron. Given that CO and iron enhance plasmatic coagulation, we determined if LVAD patients had hypercoagulability and decreased fibrinolytic vulnerability with measurable CO and iron-mediated effects.

Left ventricular volume unloading with axial and centrifugal rotary blood pumps.

Axial (AX) and centrifugal (CFG) rotary blood pumps have gained clinical acceptance for the treatment of advanced heart failure. Differences between AX and CFG designs and mechanism of blood flow delivery may offer clinical advantages. In this study, pump characteristics, and acute physiologic responses during support with AX (HeartMate II) and CFG (HVAD) left ventricular assist devices (LVAD) were investigated in mock loop and chronic ischemic heart failure bovine models.

Hemodynamic changes and retrograde flow in LVAD failure.

In the event of left ventricular assist device (LVAD) failure, we hypothesized that rotary blood pumps will experience significant retrograde flow and induce adverse physiologic responses. Catastrophic LVAD failure was investigated in computer simulation with pulsatile, axial, and centrifugal LVAD, mock flow loop with pulsatile (PVAD) and centrifugal (ROTAFLOW), and healthy and chronic ischemic heart failure bovine models with pulsatile (PVAD), axial (HeartMate II), and centrifugal (HVAD) pumps. Simulated conditions were LVAD "off" with outflow graft clamped (baseline), LVAD "off" with outflow graft unclamped (LVAD failure), and LVAD "on" (5 L/min).

Rotary pump speed modulation for generating pulsatile flow and phasic left ventricular volume unloading in a bovine model of chronic ischemic heart failure.

Background: Rotary blood pumps operate at a constant speed (rpm) that diminishes vascular pulsatility and variation in ventricular end-systolic and end-diastolic volumes, which may contribute to adverse events, including aortic insufficiency and gastrointestinal bleeding. In this study, pump speed modulation algorithms for generating pulsatility and variation in ventricular end-systolic and end-diastolic volumes were investigated in an ischemic heart failure (IHF) bovine model (n = 10) using a clinically implanted centrifugal-flow left ventricular assist device (LVAD).

Methods: Hemodynamic and hematologic measurements were recorded during IHF baseline, constant pumps speeds, and asynchronous (19-60 cycles/min) and synchronous (copulse and counterpulse) pump speed modulation profiles using low relative pulse speed (±25%) of 3,200 ± 800 rpm and high relative pulse speed (±38%) of 2,900 ± 1,100 rpm.

Feasibility study of particulate extracellular matrix (P-ECM) and left ventricular assist device (HVAD) therapy in chronic ischemic heart failure bovine model.

Myocardial recovery with left ventricular assist device (LVAD) support is uncommon and unpredictable. We tested the hypothesis that injectable particulate extracellular matrix (P-ECM) with LVAD support promotes cell proliferation and improves cardiac function. LVAD, P-ECM, and P-ECM + LVAD therapies were investigated in chronic ischemic heart failure (IHF) calves induced using coronary embolization.

Early feasibility testing and engineering development of a sutureless beating heart connector for left ventricular assist devices.

APK Advanced Medical Technologies (Atlanta, GA) is developing a sutureless beating heart (SBH) left ventricular assist device (LVAD) connector system consisting of anchoring titanium coil, titanium cannula with integrated silicone hemostatic valve, coring and delivery tool, and LVAD locking mechanism to facilitate LVAD inflow surgical procedures. Feasibility testing was completed in human cadavers (n = 4) under simulated normal and hypertensive conditions using saline to observe seal quality in degraded human tissue and assess anatomic fit; acutely in ischemic heart failure bovine model (n = 2) to investigate short-term performance and ease of use; and chronically for 30 days in healthy calves (n = 2) implanted with HeartWare HVAD to evaluate performance and biocompatibility. Complete hemostasis was achieved in human cadavers and animals at LV pressures up to 170 mm Hg.

Development of an extracellular matrix delivery system for effective intramyocardial injection in ischemic tissue.

Biomaterials with direct intramyocardial injection devices have been developed and are being investigated as a potential cardiac regenerative therapy for end-stage ischemic heart failure. Decellularized extracellular matrix (ECM) has been shown to improve cardiac function and attenuate or reverse pathologic remodeling cascades. CorMatrix Cardiovascular, Inc.

Cavopulmonary assist for the failing Fontan circulation: impact of ventricular function on mechanical support strategy.

Mechanical circulatory support--either ventricular assist device (VAD, left-sided systemic support) or cavopulmonary assist device (CPAD, right-sided support)--has been suggested as treatment for Fontan failure. The selection of left- versus right-sided support for failing Fontan has not been previously defined. Computer simulation and mock circulation models of pediatric Fontan patients (15-25 kg) with diastolic, systolic, and combined systolic and diastolic dysfunction were developed.

Extended extra-aortic counterpulsation with the C-Pulse device does not alter aortic wall structure.

The C-Pulse System is an implantable, extra-aortic, non-blood-contacting counterpulsation device, investigational in the United States and intended for use as a heart assist device for heart failure (NYHA class III-ambulatory IV) patients. As long-term effects of this implantable extra-aortic counterpulsation device on the aortic wall structure are not well established, we examined the histological and clinical data of a patient supported on the device for 21 months. A 58-year-old woman diagnosed with nonischemic cardiomyopathy (NYHA III) remained symptomatic despite optimal medical therapy and dual chamber pacemaker.

Early feasibility testing and engineering development of the transapical approach for the HeartWare MVAD ventricular assist system.

Implantation of ventricular assist devices (VADs) for the treatment of end-stage heart failure (HF) falls decidedly short of clinical demand, which exceeds 100,000 HF patients per year. Ventricular assist device implantation often requires major surgical intervention with associated risk of adverse events and long recovery periods. To address these limitations, HeartWare, Inc.

Large animal models for left ventricular assist device research and development.

In vivo preclinical testing of left ventricular assist devices (LVADs) warrants a large animal model that faithfully simulates human etiology. Although LVAD recipients are in end-stage heart failure (HF), healthy, young animals have served as the experimental platform for most LVAD research and development (R&D) to demonstrate device safety, reliability, and biocompatibility. The rapidly growing HF epidemic, donor heart shortage, and clinical acceptance of LVAD for bridge-to-transplant therapy (BTT) has led to the expanded role of LVAD for destination therapy and bridge-to-recovery therapy.

Fault detection in rotary blood pumps using motor speed response.

Clinical acceptance of ventricular assist devices (VADs) as long-term heart failure therapy requires safe and effective circulatory support for a minimum of 5 years. Yet, VAD failure beyond 2 years of support is still a concern. Currently, device controllers cannot consistently predict VAD failure modes, and undetected VAD faults may lead to catastrophic device failure.

Novel thrombosis risk index as predictor of left ventricular assist device thrombosis.

Left ventricular assist devices (LVADs) are an effective therapy for patients with advanced heart failure, increasing patient survival and quality of life. Left ventricular assist devices are associated with the risks of bleeding and thrombosis. We used lactate dehydrogenase (LDH) and brain natriuretic peptide (BNP) as biomarkers for developing a thrombosis risk index.

Rotary pumps and diminished pulsatility: do we need a pulse?

Ventricular assist devices (VADs) have been successfully used as a bridge to heart transplant and destination therapy (DT) for congestive heart failure (HF) patients. Recently, continuous flow VAD (CVAD) has emerged as an attractive clinical option for long-term mechanical support of HF patients, with bridge-to-transplant outcomes comparable with pulsatile flow VAD (PVAD). Continuous flow VADs are smaller, more reliable, and less complex than the first-generation PVAD.

Flow modulation algorithms for intra-aortic rotary blood pumps to minimize coronary steal.

Intra-aortic rotary blood pumps (IARBPs) have been used for partial cardiac support during cardiogenic shock, myocardial infarction, percutaneous coronary intervention, and potentially viable for long-term circulatory support. Intra-aortic rotary blood pump support continuously removes volume from the aortic root, which lowers left ventricular preload, external work (LVEW), and improves end-organ perfusion. However, IARBP support diminishes aortic root pressure and coronary artery.