Percutaneous lead dysfunction in the HeartMate II left ventricular assist device.

Background: The incidence of percutaneous lead failure among patients supported with a HeartMate II left ventricular assist device is unknown.

Methods: All HeartMate II left ventricular assist device driveline dysfunctions reported to Thoratec Corporation were retrospectively reviewed. The location and severity of driveline failures and their association with adverse clinical outcomes were examined.

Cardiac autonomic nerve stimulation in the treatment of heart failure.

Research on the therapeutic modulation of cardiac autonomic tone by electrical stimulation has yielded encouraging early clinical results. Vagus nerve stimulation has reduced the rates of morbidity and sudden death from heart failure, but therapeutic vagus nerve stimulation is limited by side effects of hypotension and bradycardia. Sympathetic nerve stimulation that has been implemented in the experiment may exacerbate the sympathetic-dominated autonomic imbalance.

Periarteritis in lung from a continuous-flow right ventricular assist device: role of the local Renin-Angiotensin system.

Background: We previously reported renal arterial periarteritis after implantation of a continuous-flow left ventricular assist device in calves. The purpose of the present study was to investigate whether the same periarteritis changes occur in the intrapulmonary arteries after implantation of a continuous-flow right ventricular assist device (CFRVAD) in calves and to determine the mechanism of those histologic changes.

Methods: Ten calves were implanted with a CFRVAD for 29 ± 7 days, and we compared pulmonary artery samples and hemodynamic data before and after CFRVAD implantation prospectively.

Overview of current sutureless and transcatheter mitral valve replacement technology.

Mitral valve (MV) regurgitation is the most prevalent form of heart valve disease. As it comes to surgical repair or replacement of the diseased valves, the procedure has been established as safe and effective; however, its invasiveness still carries considerable risk of significant morbidity and mortality. With aging comes increased MV dysfunction, and thus minimally invasive technology is rapidly evolving to meet the challenges of older patients' preoperative comorbidities and risks associated with surgery.

Mechanical circulatory support for heart failure: past, present and a look at the future.

Heart transplantation remains the gold standard for long-term cardiac replacement, but a shortage of donor organs will always limit this option. For both transplant-eligible and noneligible patients, advances in mechanical circulatory support have revolutionized the options for the management of end-stage heart failure, and this technology continues to bring us closer to a true alternative to heart transplantation. This review provides a perspective on the past, present and future of mechanical circulatory support and addresses the changes in technology, patient selection and management strategies needed to have this therapy fully embraced by the heart failure community, and perhaps replace heart transplantation either as the therapy of choice or as a strategy by which to delay transplantation in younger patients.

Preload sensitivity in cardiac assist devices.

With implantable cardiac assist devices increasingly proving their effectiveness as therapeutic options for end-stage heart failure, it is important for clinicians to understand the unique physiology of device-assisted circulation. Preload sensitivity as it relates to cardiac assist devices is derived from the Frank-Starling relationship between human ventricular filling pressures and ventricular stroke volume. In this review, we stratify the preload sensitivity of 17 implantable cardiac assist devices relative to the native heart and discuss the effect of preload sensitivity on left ventricular volume unloading, levels of cardiac support, and the future development of continuous-flow total artificial heart technology.

Axial and centrifugal continuous-flow rotary pumps: a translation from pump mechanics to clinical practice.

The recent success of continuous-flow circulatory support devices has led to the growing acceptance of these devices as a viable therapeutic option for end-stage heart failure patients who are not responsive to current pharmacologic and electrophysiologic therapies. This article defines and clarifies the major classification of these pumps as axial or centrifugal continuous-flow devices by discussing the difference in their inherent mechanics and describing how these features translate clinically to pump selection and patient management issues. Axial vs centrifugal pump and bearing design, theory of operation, hydrodynamic performance, and current vs flow relationships are discussed.

Effects of percutaneous stimulation of both sympathetic and parasympathetic cardiac autonomic nerves on cardiac function in dogs.

Objective: Augmentation of left ventricular (LV) contractility and heart rate (HR) by sympathetic nerve stimulation and amelioration of heart failure by vagal nerve stimulation has been reported. However, the effects of concomitant electrical stimulation of both sympathetic and parasympathetic cardiac nerves in tissues such as those of the cardiac plexus remain unclear. This study sought to assess acute changes in cardiac function and hemodynamics in response to endovascular cardiac plexus stimulation (CPS).

Effect of epivascular cardiac autonomic nerve stimulation on cardiac function.

Background: The cardiac plexus contains sympathetic and parasympathetic cardiac nerves. Our goal was to assess the hemodynamic and functional effects of stimulating the cardiac autonomic nervous system (CANS) at the epivascular surfaces of the cardiac plexus. Although CANS therapy to modulate cardiovascular function has drawn widespread interest, research has focused only on stimulating parasympathetic or sympathetic nerves, not both at once.

Implantable continuous-flow right ventricular assist device: lessons learned in the development of a cleveland clinic device.

Although the need for right ventricular assist device (RVAD) support for right ventricular failure after the implantation of a continuous-flow left ventricular assist device has decreased, right ventricular failure still occurs in as many as 44% of patients after continuous-flow left ventricular assist device insertion. Cleveland Clinic's DexAide continuous-flow RVAD was implanted in 34 calves during the course of its development. This review discusses lessons learned in the design and development of an implantable continuous-flow RVAD that are drawn from the results of these in vivo studies, our clinical experience with RVAD support, and a review of previously published reports on clinical RVAD use.

Hemodynamic differences between the awake and anesthetized conditions in normal calves.

There is insufficient information in the literature about baseline circulatory parameters in normal calves in the anesthetized versus postoperative awake conditions under which a large volume of medical research is conducted. Eleven calves (mean body weight, 78.1 ± 14.

Transcatheter heart valve with variable geometric configuration: in vitro evaluation.

Clinically, the current transcatheter aortic valve (TAV) technology has shown a propensity for paravalvular leakage; studies have correlated this flaw to increased calcification at the implantation site and with nonideal geometry of the stented valve. The present study evaluated the hydrodynamics of different geometric configurations, in particular the intravalvular considerations. Three TAV devices were made to create a representative, size 26 mm TAV.

Performance of bioprosthetic valves after glycerol dehydration, ethylene oxide sterilization, and rehydration.

Objective: : Most commercially available bioprosthetic valves are stored in an aldehyde solution. We report a new alternative method: Self-expanding valves composed of dehydrated tissues with a high glycerin:water ratio can be collapsed into specially designed sheaths prior to sterilization for ease of delivery and storage.

Materials And Methods: : Changes in tissue dimension of five samples of bovine pericardium were evaluated from baseline after glycerol treatment, air-drying, ethylene oxide (EtO) sterilization, and rehydration with water.

Performance of extracorporeally adjustable ventricular assist device inflow cannula.

Purpose: This study evaluated the feasibility and efficacy of a newly developed adjustable left ventricular assist device inflow cannula in a short-term calf model.

Description: In this inflow cannula, the angle between the cannula body and the inflow cannula tip can be altered extracorporeally by manipulating 2 externalized cables connected to the cannula. The cannula tip is adjustable in any plane to a maximum of ±15 degrees.

Speed modulation of the continuous-flow total artificial heart to simulate a physiologic arterial pressure waveform.

This study demonstrated the concept of using speed modulation in a continuous-flow total artificial heart (CFTAH) to shape arterial pressure waveforms and to adjust pressure pulsatility. A programmable function generator was used to determine the optimum pulsatile speed profile. Three speed profiles [sinusoidal, rectangular, and optimized (a profile optimized for generation of a physiologic arterial pressure waveform)] were evaluated using the CFTAH mock circulatory loop.

In vivo biocompatibility evaluation of a new resilient, hard-carbon, thin-film coating for ventricular assist devices.

The purpose of this study was to evaluate in vivo the biocompatibility of BioMedFlex (BMF), a new resilient, hard-carbon, thin-film coating, as a blood journal bearing material in Cleveland Heart's (Charlotte, NC, USA) continuous-flow right and left ventricular assist devices (RVADs and LVADs). BMF was applied to RVAD rotating assemblies or both rotating and stator assemblies in three chronic bovine studies. In one case, an LVAD with a BMF-coated stator was also implanted.

In vivo evaluation of zirconia ceramic in the DexAide right ventricular assist device journal bearing.

Zirconia is a ceramic with material properties ideal for journal bearing applications. The purpose of this study was to evaluate the use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. Zirconia ceramic was used instead of titanium to manufacture the DexAide stator housing without changing the stator geometry or the remaining pump hardware components.

A pilot study for inducing chronic heart failure in calves by means of oral monensin.

Introduction: Heart failure remains a major cause of mortality in the United States, despite advancing technologies, newer methods of treatment, and novel devices. To evaluate such novel devices, a large-animal model of chronic heart failure is critical in carrying out preclinical animal studies.

Methods: We evaluated the efficacy of oral monensin in inducing stable heart failure in five Jersey calves.

Introduction of fixed-flow mode in the DexAide right ventricular assist device.

Background: Although some continuous-flow left ventricular assist device algorithms have been created to respond to varying patient physiology, very little research has been conducted on control of right ventricular support in uni- or biventricular application. The purpose of this study was to develop and evaluate a simple and reliable fixed-flow algorithm for the DexAide right ventricular assist device (RVAD). This algorithm automatically adjusts speed to maintain a target flow while preventing ventricular suction when a requested target flow exceeds available tricuspid flow.

Use of zirconia ceramic in the DexAide right ventricular assist device journal bearing.

Our aim was to evaluate the potential use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. The DexAide titanium stator was replaced by a zirconia stator in several blood pump builds, without changing the remaining pump hardware components. In vitro pump performance and efficiency were evaluated at a predetermined pump speed and flow.

An innovative, sensorless, pulsatile, continuous-flow total artificial heart: device design and initial in vitro study.

Background: We are developing a very small, innovative, continuous-flow total artificial heart (CFTAH) that passively self-balances left and right pump flows and atrial pressures without sensors. This report details the CFTAH design concept and our initial in vitro data.

Methods: System performance of the CFTAH was evaluated using a mock circulatory loop to determine the range of systemic and pulmonary vascular resistance (SVR and PVR) levels over which the design goal of a maximum absolute atrial pressure difference of 10 mm Hg is achieved for a steady-state flow condition.

In vivo acute performance of the Cleveland Clinic self-regulating, continuous-flow total artificial heart.

Background: The purpose of this study was to evaluate the acute in vivo pump performance of a unique valveless, sensorless, pulsatile, continuous-flow total artificial heart (CFTAH) that passively self-balances left and right circulations without electronic intervention.

Methods: The CFTAH was implanted in two calves, with pump and hemodynamic data recorded at baseline over the full range of pump operational speeds (2,000 to 3,000 rpm) in 200-rpm increments, with pulsatility variance, and under a series of induced hemodynamic states created by varying circulating blood volume and systemic and pulmonary vascular resistance (SVR and PVR).

Results: Sixty of the 63 induced hemodynamic states in Case 1 and 73 of 78 states in Case 2 met our design goal of a balanced flow and maximum atrial pressure difference of 10 mm Hg.

Human clinical fitting study of the DexAide right ventricular assist device.

The DexAide right ventricular assist device (RVAD) has been developed as an implantable RVAD. The purpose of this study was to determine the final design and optimal anatomical placement of the DexAide RVAD when implanted simultaneously with either of two commercially available left ventricular assist devices (LVADs) in patients. A mock-up DexAide RVAD was used to assess configuration with each of two types of commercially available LVADs at the time of LVAD implantation in three human clinical cases.

Development of DexAide right ventricular assist device: update II.

The DexAide right ventricular assist device (RVAD) is a magnetically and hydrodynamically levitated implantable centrifugal pump. Recent progress includes 1) redesign of the inflow/outflow conduits, which yielded two successful 3-month experiments, 2) development of alternative journal bearing materials, and 3) completion of an 18-month duration of in vitro endurance testing. Verification testing of the RVAD electronics has been completed, and a prototype biventricular assist device (BVAD) system has been tested.

A novel device for left atrial appendage exclusion: the third-generation atrial exclusion device.

Objective: Occlusion of the left atrial appendage is proposed to reduce the risk of stroke in patients with atrial fibrillation. The third-generation atrial exclusion device, modified to provide uniform distribution of pressure at appendage exclusion, was assessed for safety and effectiveness in a canine model and compared with a surgical stapler.

Methods: The atrial exclusion device consists of 2 parallel, straight, rigid titanium tubes and 2 nitinol springs with a knit-braided polyester fabric.