Partial Vs. Full Support of the Heart with a Continuous-flow Left Ventricular Assist Device

Partial Vs. Full Support of the Heart with a Continuous-flow Left Ventricular Assist Device
Author: Carlo Renato G. Bartoli
Publisher:
Total Pages: 220
Release: 2011
Genre: Heart, Mechanical
ISBN:

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INTRODUCTION: Heart failure is a major and growing public health concern. Although heart failure has been considered an inexorable and progressive disorder, emerging evidence suggests that some patients may have reversible left ventricular dysfunction. Indeed, recent reports have documented the potential for myocardial recovery in humans in response to prolonged mechanical circulatory support with a left ventricular assist device (LVAD). However, myocardial recovery remains uncommon, and a strategy of unloading the failing left ventricle with a continuous-flow (non-pulsatile) LVAD has not been specifically developed to promote favorable myocardial remodeling. As a preliminary investigation, we developed a bovine model of chronic, ischemic heart failure and quantified the effects of different levels of support with a continuous-flow LVAD on myocardial mechanoenergetics. METHODS: Normal cows (n=8) and cows with chronic, ischemic heart failure (n=9) were studied. To induce heart failure, 90 um micro spheres were percutaneously injected into the left main coronary artery. Heart failure developed over 60 days. In an acute surgery, a continuous-flow LVAD was implanted and operated at Low Partial Support (~1.5 L/min support, aortic valve opening every beat), High Partial Support (~3 L/min support, aortic valve opening every beat) and Full Support (~5 L/min, aortic valve maintained closed, left ventricle maximally unloaded). Cardiac and systemic arterial hemodynamics were measured with flow probes and pressure catheters. Myocardial blood flow was mapped with 15 um fluorescent-labeled microspheres. After termination, molecular and histological markers of heart failure were quantified. RESULTS: In normal animals, increasing levels of non-pulsatile support deranged the profile of cardiac and arterial hemodynamics. As cardiac workload decreased, myocardial vascular resistance increased, and myocardial blood flow decreased. The ratio between blood supply and demand did not change and indicated appropriate coronary autoregulation and the presence of an intact coronary reserve. Animals with chronic, ischemic heart failure exhibited hallmark signs of severe left ventricular systolic dysfunction that included a 50% reduction in ejection fraction, left ventricular dilatation, decreased cardiac output and arterial pressures, decreased end-organ blood flow, severe myocardial fibrosis, myocyte hypertrophy, and increased myocardial apoptosis. In animals with chronic heart failure, increasing levels of non-pulsatile support similarly deranged the profile of cardiac and arterial hemodynamics. As cardiac workload decreased, myocardial vascular resistance increased. However myocardial blood flow did not change and indicated a lack of a coronary reserve. Importantly, during full but not partial support, the ratio between blood supply and demand improved significantly to levels observed in normal control animals. CONCLUSIONS: After the implantation of an LVAD, full but not partial support of the failing left ventricle with an LVAD normalizes the myocardial blood supply/demand relationship. In the immediate postoperative period, the left ventricle should be completely unloaded. Chronic studies are necessary to determine whether a transition to partial support may prevent myocardial atrophy and fibrosis that is seen with prolonged full support. Our bovine model of chronic, ischemic heart failure is appropriate for such a study.

Ventricular Assist Devices in Advanced-Stage Heart Failure

Ventricular Assist Devices in Advanced-Stage Heart Failure
Author: Shunei Kyo
Publisher: Springer Science & Business Media
Total Pages: 154
Release: 2013-11-25
Genre: Medical
ISBN: 4431544666

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This book focuses on how ventricular assist devices (VADs) can help provide destination therapy for patients with terminal heart failure, one of the most serious diseases in the world today because of the tremendous number of patients, the high mortality rate, and the cost of care. One means of providing cardiological support for patients suffering from heart failure is with VADs, and more than 10,000 patients worldwide have now been implanted with these devices. Half of them already have lived more than one year, and 2,000 patients more than two years, after surgery. This improved survival means that we have reached a point where VADs can be used for destination therapy, not just for bridge-to-recovery or bridge-to-transplant. In view of the increasing number of patients with advanced-stage heart failure and the availability and longevity of transplanted hearts, VADs can solve many problems. In addition to providing information about the devices themselves, this book includes vital guidelines on long-term management and support of VAD-implanted patients’ everyday lives.

Left Ventricular Assist Devices, An Issue of Cardiology Clinics

Left Ventricular Assist Devices, An Issue of Cardiology Clinics
Author: John A. Elefteriades
Publisher: Elsevier Health Sciences
Total Pages: 188
Release: 2011-11-28
Genre: Medical
ISBN: 1455712043

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A left ventricular assist device (LVAD) is a surgically implanted pump that helps the left ventricle pump blood to the rest of the body. The purpose of this issue is to let cardiologists know about the latest devices, their complications, and the clinical situations in which they are most beneficial.

Core Topics in Cardiothoracic Critical Care

Core Topics in Cardiothoracic Critical Care
Author: Kamen Valchanov
Publisher: Cambridge University Press
Total Pages: 541
Release: 2018-07-05
Genre: Medical
ISBN: 1108665675

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Most patients with critical cardiac or thoracic conditions will at some stage pass through the cardiothoracic critical care unit. Critical care presents more complex clinical data than any other area of medicine. The new edition of Core Topics in Cardiothoracic Critical Care focuses on the latest practise in the management of patients in cardiothoracic intensive care. The practice of cardiothoracic critical care medicine is constantly evolving, and this new edition reflects the modernized learning styles for trainees. Each chapter includes key learning points as well as sample multiple choice questions and answers to assist in exam preparation. This edition also features updated chapters on ECMO, perioperative management of patients undergoing emergency cardiothoracic surgery, and advanced modes of organ support for patients. This text provides key knowledge in a concise and accessible manner for trainees, clinicians and consultants from specialities and disciplines such as cardiology and anaesthesia, and nursing and physiotherapy.

Use of Left Ventricular Assist Devices As Destination Therapy in End-Stage Congestive Heart Failure: a Systematic Review

Use of Left Ventricular Assist Devices As Destination Therapy in End-Stage Congestive Heart Failure: a Systematic Review
Author: U. S. Department of Veterans Affairs
Publisher: Createspace Independent Pub
Total Pages: 48
Release: 2013-05-22
Genre: Medical
ISBN: 9781489539755

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Several common chronic conditions such as atherosclerotic heart disease and hypertension as well as other diseases can result in heart failure, a reduced ability of the heart to pump blood and maintain normal bodily functions. More than 100,000 people in the U.S. with progressive heart failure are refractory to available treatments and have high rates of hospitalization and mortality and a poor quality of life due to limited physical and social activities and psychological stress. Heart transplantation is currently the preferred treatment for end-stage heart failure. Unfortunately, the supply of donor hearts is far less than needed and many patients do not meet the criteria for heart transplantation primarily due to old age and comorbidities such as diabetes with damage to vital organs, pulmonary hypertension, renal insufficiency, malignancies and morbid obesity. Implantable mechanical pumps that assist the circulation of blood by one or both ventricles of the heart have evolved over several decades. Typically blood flows from the native left ventricle of the heart into the surgically implanted assist device and is pumped out into the aorta via an implanted conduit. Currently, long-term implantable left ventricular assist devices require an external source of power and control module. Surgical placement of a left ventricular assist device is increasingly done as a last resort for patients with refractory heart failure who are not eligible for heart transplantation, so called destination therapy. Some patients may improve after they receive a ventricular assist device as destination therapy and become eligible for heart transplantation even though this was not the initial therapeutic goal. A limited number may recover enough heart function to not need a heart transplant or mechanical assist device. Although survival with a newer generation continuous flow ventricular assist device is approaching that of a heart transplant, long-term use of the device by patients who are eligible for a heart transplant is not currently accepted practice. Conversely, many patients that receive a ventricular assist device as a bridge to transplant use the device for increasingly prolonged periods while waiting for a donated heart and some may become ineligible for a heart transplant. The purpose of this report is to review the scientific evidence for use of ventricular assist devices as destination therapy for patients with severe, refractory heart failure who are not eligible for heart transplantation at the time the device is implanted. Although many patients receive the same types of ventricular assist devices as a bridge to heart transplantation or recovery, the characteristics, hence risk profiles, of patients receiving bridge therapy are different from patients selected to receive a device as permanent destination therapy. Furthermore many bridged patients do receive a heart transplant that alters patient outcomes. This review focused on evidence about patient outcomes, patient selection and cost effectiveness of ventricular assist devices specifically intended as destination therapy. The primary goals of destination therapy are to: prolong survival, improve daily function and health-related quality of life, minimize harms including infection, major bleeding episodes, thromboembolic events including strokes and device malfunction or failure especially those that require hospital care. The key questions were: #1. How does use of an FDA-approved, current generation LVAD as destination therapy (i.e., the HeartMate II left ventricular assist device) effect patient outcomes? #2. What patient or site characteristics have been associated with patient benefits or harms when the FDA-approved, current generation LVAD is used as destination therapy? #3. What is the range of cost-effectiveness estimates of using the FDA-approved, current generation LVAD as destination therapy in end-stage heart failure and what explains variation in these estimates?

RPM and Flow Modulation for a Continuous Flow Left Ventricular Assist Device to Increase Vascular Pulsatility

RPM and Flow Modulation for a Continuous Flow Left Ventricular Assist Device to Increase Vascular Pulsatility
Author: Mickey S. Ising
Publisher:
Total Pages: 97
Release: 2011
Genre: Heart
ISBN:

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Purpose: Continuous flow (CF) left ventricular assist devices (LVAD) support diminishes vascular pressure pulsatility. Despite its recent clinical success and reliability, CF LVAD support has been associated with adverse events including gastrointestinal bleeding, aortic valve insufficiency, and hemorrhagic strokes. To overcome these limitations, we have developed flow/RPM modulation algorithms to provide vascular pulsatility using a CF LVAD. Methods: The effects of timing and synchronizing the CF LVAD flow/RPM modulation to the native ventricle, modulation amplitude, and modulation widths were studied on the native ventricle and vasculature using computer simulation, mock loop, and animal model studies. A total of over 100 combinations of flow modulation algorithms to modulate CF LVAD flow/RPM were tested for partial and full LVAD support modes. Results: Modulation of CF LVAD flow/RPM resulted in an increased arterial pressure pulsatility of up to 50 mmHg during asynchronous modulation and 20 mmHg during synchronous modulation. Synchronous CF LVAD RPM modulation allowed for a range of reduced left ventricular external work (LVEW) as compared to un-modulated CF LVAD support conditions. Full support co-pulsation (high RPM during systole, low RPM during diastole) created greater pulse pressures as compared to counter pulsation (high RPM during diastole, low RPM during systole). However, all full support modulation timings yielded higher pulse pressure than normal full support CF LVAD flow at low ventricular contractilities. Importantly, reduction in LVEW and increase in pulsatility may be adjusted to user-defined values while maintaining the same average CF LVAD flow rate. Conclusions: These LVAD flow/RPM modulations may reduce the incidence of adverse events associated with the CF LVAD therapy by increasing vascular pulsatility and reducing vascular impedance. Further, these methods of CF LVAD flow/RPM modulation may enable tailored unloading of the native ventricle to provide rest and rehabilitation (maximal unloading to rest followed by gradual reloading to wean), which may promote sustainable myocardial recovery.

Recent Advances in the Field of Ventricular Assist Devices

Recent Advances in the Field of Ventricular Assist Devices
Author: Kazuo Komamura
Publisher: BoD – Books on Demand
Total Pages: 106
Release: 2013-05-08
Genre: Medical
ISBN: 9535111116

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Recent Advances in the Field of Ventricular Assist Devices covers recent various advances and developments relating to ventricular assist devices and their diverse complications. Firstly, we overview recent technical advances as well as current indications, clinical outcomes, and countermeasures against complications, and furthermore, the latest techniques to identify clinical effectiveness at the patient’s bedside. Secondly, we elucidate the current status of countermeasures against gastrointestinal bleeding, and current research on allosensitization during the usage of continuous flow pump. Finally, we explore the possibility of a new adjunct therapy in combination with ventricular assist devices. We hope that this book will provide valuable and up-to-date information on research and clinical use of ventricular assist devices.

New Aspects of Ventricular Assist Devices

New Aspects of Ventricular Assist Devices
Author: Guillermo Reyes
Publisher: BoD – Books on Demand
Total Pages: 146
Release: 2011-08-29
Genre: Medical
ISBN: 9533076763

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Ventricular assist device has become one of the standard therapies for the support and the management of the failing heart. Updating our knowledge about these devices is mandatory in order to improve patient outcomes. In this book we can read the efforts made by many physicians concerned with the treatment of heart failure with mechanical devices. We all hope that the information compiled by experts in ventricle assist devices in this book will help us all to do better our main task - heal patients.

Mechanical Circulatory Support: Principles and Applications

Mechanical Circulatory Support: Principles and Applications
Author: David L. Joyce
Publisher: McGraw Hill Professional
Total Pages: 270
Release: 2011-10-07
Genre: Medical
ISBN: 0071785078

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An all-in-one guide to mechanical assist devices for the treatment of heart failure This complete guide addresses all of the clinical scenarios encountered by the health care team during the pre-operative, intra-operative, and post-operative periods following device implantation. In addition, it outlines the specific attributes of various technologies that are currently utilized by clinicians, giving you a practical view of how the latest devices work. You’ll also find a mini-catalog of the spectrum of current devices, complete with their technical and clinical specifications. Drawing on the latest published data and the combined global expertise of a renowned author team, Mechanical Circulatory Support puts the field’s most essential perspectives right at your fingertips. FEATURES: The unmatched mechanical circulatory device sourcebook, covering the physiological, technical, regulatory, and clinical aspects of ventricular assist devices Full-color presentation features a wide range of photographs, radiographs, tables, and clearly labeled clinical and schematic illustrations Essential insights into the physiology of heart failure, which provides a basic foundation of knowledge for understanding the role of mechanical circulatory assistance in the management of heart failure Logical two-part organization consisting of: Clinical Considerations in mechanical circulatory support, including device history/development and indications for device therapy; perioperative management; complications; and special considerations (use in infants/children, pulmonary hypertension during LVAD support, and more) Device-Specific Considerations, which provides a mini-catalog of manufacturer’s devices—-from short-term devices to long-term continuous flow devices—-and highlights technical and clinical specifications for each product Guide to appropriate device selection using a simplified framework in an industry that produces an increasing array of short- and long-term therapies Helpful chapter introductions provide essential background information that places each chapter topic in its proper clinical and technical context Conclusions at the end of each chapter offer a concise summary of chapter material Full chapter-ending references provide opportunities for further research

The Artificial Heart

The Artificial Heart
Author: Institute of Medicine
Publisher: National Academies Press
Total Pages: 313
Release: 1991-02-01
Genre: Medical
ISBN: 0309045320

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A significant medical event is expected in 1992: the first human use of a fully implantable, long-term cardiac assist device. This timely volume reviews the artificial heart program-and in particular, the National Institutes of Health's major investment-raising important questions. The volume includes: Consideration of the artificial heart versus heart transplantation and other approaches to treating end-stage heart disease, keeping in mind the different outcomes and costs of these treatments. A look at human issues, including the number of people who may require the artificial heart, patient quality of life, and other ethical and societal questions. Examination of how this technology's use can be targeted most appropriately. Attention to achieving access to this technology for all those who can benefit from it. The committee also offers three mechanisms to aid in allocating research and development funds.