Mechanical circulatory support: devices, outcomes and complications. Heart Fail Rev. 2013;18:35-53. [PMID: 22395673 DOI: 10.1007/s10741-012-9303-5]

Hemolysis Testing In Vitro: A Review of Challenges and Potential Improvements

Many medical devices such as cardiopulmonary bypass systems, mechanical heart valves, or ventricular assist devices are intended to come into contact with blood flow during use. In vitro hemolysis testing can provide valuable information about the hemocompatibility of prototypes and thus help reduce the number of animal experiments required. Such tests play an important role as research and development tools for objective comparisons of prototypes and devices as well as for the extrapolation of their results to clinical outcomes. Therefore, it is important to explore and provide new ways to improve current practices. In this article, the main challenges of hemolysis testing are described, namely the difficult blood sourcing, the high experimental workload, and the low reproducibility of test results. Several approaches to address the challenges identified are proposed and the respective literature is reviewed. These include the replacement of blood as the "shear-sensitive fluid" by alternative test fluids, the replacement of sparse, manual sampling and blood damage assessment by a continuous and automated monitoring, as well as an analysis of categories and causes of variability in hemolysis test results that may serve as a structural template for future studies.

Point-of-care testing of plasma free hemoglobin and hematocrit for mechanical circulatory support

Hematological analysis is essential for patients who are supported by a mechanical circulatory support (MCS). The laboratory methods used to analyze blood components are conventional and accurate, but they require a mandatory turn-around-time for laboratory results, and because of toxic substances, can also be hazardous to analysis workers. Here, a simple and rapid point-of-care device is developed for the measurement of plasma free hemoglobin (PFHb) and hematocrit (Hct), based on colorimetry. The device consists of camera module, minimized centrifuge system, and the custom software that includes the motor control algorithm for the centrifuge system, and the image processing algorithm for measuring the color components of blood from the images. We show that our device measured PFHb with a detection limit of 0.75 mg/dL in the range of (0–100) mg/dL, and Hct with a detection limit of 2.14% in the range of (20–50)%. Our device had a high correlation with the measurement method generally used in clinical laboratories (PFHb R = 0.999, Hct R = 0.739), and the quantitative analysis resulted in precision of 1.44 mg/dL for PFHb value of 14.5 mg/dL, 1.36 mg/dL for PFHb value of 53 mg/dL, and 1.24% for Hct 30%. Also, the device can be measured without any pre-processing when compared to the clinical laboratory method, so results can be obtained within 5 min (about an 1 h for the clinical laboratory method). Therefore, we conclude that the device can be used for point-of-care measurement of PFHb and Hct for MCS.

The Total Artificial Heart: Where Are We?

The total artificial heart (TAH) is a device that replaces the failing ventricles. There have been numerous TAHs designed over the last few decades, but the one with the largest patient experience is the SynCardia temporary TAH. The 50-mL and 70-mL sizes have been approved in the United States, Europe, and Canada as a bridge to transplantation. It is indicated in patients with severe biventricular failure or structural heart issues that preclude the use of a left ventricular assist device. The majority of the patients implanted are Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2. The 1-year survival in experienced centers that have implanted over 10 TAHs is 73%. The risk factors for death include older age, need for preimplantation dialysis, and malnutrition. The most common causes of death are multiple organ failure, usually the result of physiologic deterioration before implantation, and neurologic dysfunction. The device allows the patient to be discharged home and managed as an outpatient. Proper patient selection, the timing of intervention, patient care, and device management are essential for a suitable outcome. In addition, the CARMAT TAH is another device that will soon be studied in a clinical trial in the United States. The BiVACOR TAH is a revolutionary design utilizing electromagnetic levitation that is expected to enter a clinical trial in the next few years.

Mechanical circulatory support in the new era: an overview

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Biventricular mechanical support devices--clinical perspectives

Cardiac transplantation remains the optimal treatment for end stage heart failure in selected patients. However, the shortage of donor hearts, rigorous eligibility criteria and long waiting lists have increased the demand for alternative treatment strategies such as mechanical circulatory support. While many patients are adequately supported with left ventricular assist devices, frequently there is right heart failure or involvement of the right ventricle, requiring biventricular support. Pulsatile flow biventricular devices and total artificial hearts approved for temporary biventricular support have limitations including size, high rates of adverse events and restricted mobility which makes them unsuitable for long term support. A number of centres have reported dual continuous flow left ventricular assist devices as a means of supporting the left and right heart. This review will summarise the literature on the outcomes and complications from current biventricular support devices and assess the role of dual continuous flow VAD therapy, and the new continuous flow total heart replacement devices.

[Rehabilitation standards for follow-up treatment and rehabilitation of patients with ventricular assist device (VAD)]

The increasing use of ventricular assist devices (VADs) in terminal heart failure patients provides new challenges to cardiac rehabilitation physicians. Structured cardiac rehabilitation strategies are still poorly implemented for this special patient group. Clear guidance and more evidence for optimal modalities are needed. Thereby, attention has to be paid to specific aspects, such as psychological and social support and education (e.g., device management, INR self-management, drive-line care, and medication).In Germany, the post-implant treatment and rehabilitation of VAD Patients working group was founded in 2012. This working group has developed clear recommendations for the rehabilitation of VAD patients according to the available literature. All facets of VAD patients' rehabilitation are covered. The present paper is unique in Europe and represents a milestone to overcome the heterogeneity of VAD patient rehabilitation.

Developing a Kit and Video to Standardize Changes of Left Ventricular Assist Device Dressings

Context—

Driveline infection is a major cause of morbidity and mortality in the patients with a left ventricular assist device (LVAD). Our center developed 2 LVAD dressing change kits and instructional videos for the purpose of standardizing a protocol for the dressing changes.

Objective—

To develop 2 different types of driveline dressing kits and videos to help in standardizing the education of our patients, caregivers, and staff.

Design—

A survey to evaluate patient, caregiver, and staff satisfaction and ease of use relating to the newly implemented dressing kits and videos. A comparison of driveline infection rates before and after the quality improvement project also was conducted.

Patients/Participants, Settings—

LVAD patients, their caregivers, and staff from Spectrum Health in Grand Rapids, Michigan.

Results—

Surveys were sent to 80 patient/caregiver pairs and 330 staff members. A total of 5 patients, 10 caregivers, and 48 staff members completed the surveys. All participants agreed that patients' driveline sites looked about the same, if not better than, they did before the kits were made available. They also overwhelmingly agreed that the kits were convenient (98%) and easy to use (99%). Patients and their caregivers gave favorable responses to the videos. The project experienced a slight increase in driveline infection rates, but the difference was not statistically significant.

Conclusion—

Standardizing and producing a driveline kit facilitates the delivery of care in an LVAD program.

An autoregulation unit for enabling adaptive control of sensorized left ventricular assist device

This paper describes an integrated system for facing heart failures (HF) in an innovative way. Existing left ventricular assist devices (LVAD or VAD) are usually devoted to blood pumping without the possibility to adapt the speed to patient conditions during everyday activities. This is essentially due to the lack of sensorization, bulkiness, and the need of relying on device-specific controllers with reduced computing ability for the existing ventricular assist systems. In this work, an innovative integrated and portable device, the ARU, is presented for enhancing VADs applicability as a long-term solution to HF. The ARU is an universal device able to fulfill with the needs of sensorized VADs in terms of data storing, continuous monitoring, autoregulation and adaptation to patient condition changes during daily activities. The ARU is able to wirelessly interface wearable devices for offering additional monitoring features from remote. The ARU functionalities on bench have been tested by the interfacing with a sensorized VAD platform in order to prove the feasibility of the approach. Experiments of local and remote VAD speed changes and autoregulation algorithms have been successfully tested showing response time of 1 s.

An innovative adaptive control strategy for sensorized left ventricular assist devices

Nowadays advanced heart failure is mainly treated through heart transplantation. However, the low availability of donors makes the research of alternative therapies urgent. Continuous-flow left ventricular assist devices (LVADs) are going to assume a more significant role in assisting the failing heart. A recent challenge in clinical practice is the possibility to use LVAD as long-term therapy rather than as a bridge to transplantation. For this reason, more comfortable devices, able to dynamically adapt to the physiological cardiac demand in relation to the patient activity level, are needed in order to improve the life quality of patients with implants. Nevertheless, no control system has been developed yet for this purpose. This work proposes an innovative control strategy for a novel sensorized LVAD, based on the continuous collection of physical and functional parameters coming from implantable sensors and from the LVAD itself. Thanks to the proposed system, both the patient and the LVAD conditions are continuously monitored and the LVAD activity regulated accordingly. Specifically, a Proportional Integrative (PI) and a threshold control algorithms have been implemented, respectively based on flow and pressure feedbacks collected from the embedded sensors. To investigate the feasibility and applicability of this control strategy, an on-bench platform for LVADs sensing and monitoring has been developed and tested.

Machines versus medication for biventricular heart failure: focus on the total artificial heart

ABSTRACT 

The medical/surgical management of advanced heart failure has evolved rapidly over the last few decades. With better understanding of heart failure pathophysiology, new pharmacological agents have been introduced that have resulted in improvements in survival. For those patients that fail to improve, mechanical circulatory support with left ventricular assist devices and total artificial hearts (TAHs) have served as a beneficial bridge to transplantation. The TAH has continued to play a significant role as a bridge to transplantation in patients with biventricular failure and more selected indications that could not be completely helped with left ventricular assist devices. Improved survival with the TAH has resulted in more patients benefiting from this technology. Improvements will eventually lead to a totally implantable device that will permanently replace the failing human heart.

Outcomes of continuous flow ventricular assist devices

Heart transplantation is commonplace, the supply is limited. Many exciting changes in the field of mechanical circulatory support have occurred in the past few years, including the axial flow pump. Left ventricular assist device (LVAD) therapy is ever evolving. As the use of LVAD therapy increases it is important to understand the indications, surgical considerations and outcomes.

Ventricular Assist Devices - Evolution of Surgical Heart Failure Treatment

End-stage heart failure represents a substantial worldwide problem for the healthcare system. Despite significant improvements (medical heart failure treatment, implantable cardioverters, cardiac resyschronisation devices), long-term survival and quality of life of these patients remains poor. Heart transplantation has been an effective therapy for terminal heart failure, but it remains limited by an increasing shortage of available donor organs along with strict criteria defining acceptable recipients. For the last 50 years, mechanical alternatives to support the circulation have been investigated; however, during the early years device development has been marked in general by slow progress. However, in the past two decades, the technology has evolved dramatically. The purpose of this review is to give a short summary on the evolution of ventricular assist device (VAD) therapy and to give perspectives for future treatment of heart failure.

Destination therapy: the new gold standard treatment for heart failure patients with left ventricular assist devices

Heart failure continues to be a growing health problem, eluding large-scale improvement and treatment. Cardiac transplantation has been the gold standard treatment with high post-transplant survival rates and relatively good quality of life. However, there has been an extreme shortage of organ donations, limiting transplants to only a very small portion of patients with the condition. This led to a growing interest in alternative options for the increasing population of patients who are waitlisted or ineligible for transplantation. In recent years, ventricular assist device (VAD) technologies have advanced from pulsatile blood pumps to continuous-flow pumps that have demonstrated unprecedented post-implantation survival rates. The HeartMate II, the only commercially available, continuous flow left ventricular assist device (LVAD) in the United States and Europe, has been implanted in over 10,000 patients worldwide, setting a benchmark for biomedical modalities of advanced heart failure treatment. Thanks to the successes of contemporary LVADs, patients are able to enjoy a better lifestyle, with a significantly prolonged life span and the ability to regularly partake in physical activities. In this new biomedical generation, the usage of LVADs has begun to expand towards the treatment for a wider range of heart conditions, including earlier stages of heart failure. In fact, LVAD implantations have surpassed the number of transplants taken place annually. An increasing number of patients are considering the permanent, circulatory support with an LVAD, namely destination therapy, as a promising option for treating heart failure.