Patients With a Body Surface Area Less Than 1.7 m2 Have a Good Outcome With the CardioWest Total Artificial Heart

Fluid Dynamic Study of the Penn State Pediatric Total Artificial Heart

Penn State University is developing a pediatric total artificial heart (TAH) as a bridge-to-transplant device that supports infants and small children with single ventricle anomalies or biventricular heart failure to address high waitlist mortality rates for pediatric patients with severe congenital heart disease (CHD). Two issues with mechanical circulatory support devices are thrombus formation and thromboembolic events. This in vitro study characterizes flow within Penn State's pediatric total artificial heart under physiological operating conditions. Particle image velocimetry (PIV) is used to quantify flow within the pump and to calculate wall shear rates (WSRs) along the internal pump surface to identify potential thrombogenic regions. Results show that the diastolic inflow jets produce sufficient wall shear rates to reduce thrombus deposition potential along the inlet side of the left and right pumps. The inlet jet transitions to rotational flow, which promotes wall washing along the apex of the pumps, prevents flow stasis, and aligns flow with the outlet valve prior to systolic ejection. However, inconsistent high wall shear rates near the pump apex cause increased thrombogenic potential. Strong systolic outflow jets produce high wall shear rates near the outlet valve to reduce thrombus deposition risk. The right pump, which has a modified outlet port angle to improve anatomical fit, produces lower wall shear rates and higher thrombus susceptibility potential (TSP) compared to the left pump. In summary, this study provides a fluid dynamic understanding of a new pediatric total artificial heart and indicates thrombus susceptibility is primarily confined to the apex, consistent with similar pulsatile heart pumps.

"It Works." Every heart transplant program should have one

The total artificial heart (TAH) provides full biventricular cardiac replacement, pulsatile perfusion at flows of 7-9 L/min at low filling pressures. This allows organs that are failing to recover and for the potential cardiac recipient to become a better transplant candidate. Postimplant patients are mobile and able to go through physical rehabilitation in a hospital or at home. The risks are acceptable as shown by the authors. TAH use in more transplant centers could save lives in many transplant candidates.

The Total Artificial Heart in End-Stage Congenital Heart Disease

The development of durable ventricular assist devices (VADs) has improved mortality rates and quality of life in patients with end stage heart failure. While the use of VADs has increased dramatically in recent years, there is limited experience with VAD implantation in patients with complex congenital heart disease (CHD), despite the fact that the number of patients with end stage CHD has grown due to improvements in surgical and medical care. VAD use has been limited in patients with CHD and end stage heart failure due to anatomic (systemic right ventricle, single ventricle, surgically altered anatomy, valve dysfunction, etc.) and physiologic constraints (diastolic dysfunction). The total artificial heart (TAH), which has right and left sided pumps that can be arranged in a variety of orientations, can accommodate the anatomic variation present in CHD patients. This review provides an overview of the potential use of the TAH in patients with CHD.

Physiological characterization of the SynCardia total artificial heart in a mock circulation system

The SynCardia total artificial heart (TAH) has emerged as an effective, life-saving biventricular replacement system for a wide variety of patients with end-stage heart failure. Although the clinical performance of the TAH is established, modern physiological characterization, in terms of elastance behavior and pressure-volume (PV) characterization has not been defined. Herein, we examine the TAH in terms of elastance using a nonejecting left ventricle, and then characterize the PV relation of the TAH by varying preload and afterload parameters using a Donovan Mock Circulatory System. We demonstrate that the TAH does not operate with time-varying elastance, differing from the human heart. Furthermore, we show that the TAH has a PV relation behavior that also differs from that of the human heart. The TAH does exhibit Starling-like behavior, with output increasing via preload-dependent mechanisms, without reliance on an alteration of inotropic state within the operating window of the TAH. Within our testing range, the TAH is insensitive to variations in afterload; however, this insensitivity has a limit, the limit being the maximum driving pressure of the pneumatic driver. Understanding the physiology of the TAH affords insight into the functional parameters that govern artificial heart behavior providing perspective on differences compared with the human heart.

Clinical Issues and Controversies in Heart Failure and Transplantation

Heart failure is a common problem among children admitted in the intensive care unit and is associated with significant morbidity and mortality. As such, the 2014 meeting of the Pediatric Cardiac Intensive Care Society included a session on Clinical Controversies in Heart Failure and Transplantation. This review contains the summaries of the podium presentations of this session and will cover some of the challenging aspects of caring for these patients including medical and mechanical support, fluid overload states, high-risk populations including those after heart transplantation, and end-of-life considerations.

Results with SynCardia total artificial heart beyond 1 year

Mechanical circulatory support devices have been increasingly used for long-term support. We reviewed outcomes in all patients supported with a SynCardia total artificial heart (TAH) for more than 1 year to assess its safety in long-term support. As of December 2011, all 47 patients who received the TAH from 10 centers worldwide were included in this retrospective study. Clinical data were collected on survival, infections, thromboembolic and hemorrhagic events, device failures, and antithrombotic therapy. The mean age of patients was 50 ± 1.57 years, the median support time was 554 days (range 365-1373 days). The primary diagnosis was dilated cardiomiopathy in 23 patients, ischemic in 15, and "other" in 9. After a minimum of 1 year of support, 34 patients (72%) were successfully transplanted, 12 patients (24%) died while on device support, and 1 patient (2%) is still supported. Five patients (10%) had a device failure reported. Major complications were as follows: systemic infections in 25 patients (53%), driveline infections in 13 patients (27%), thromboembolic events in 9 patients (19%), and hemorrhagic events in 7 patients (14%). SynCardia TAH has proven to be a reliable and effective device in replacing the entire heart. In patients who reached a minimum of 1 year of support, device failure rate is acceptable and only in two cases was the leading cause of death. Infections and hemorrhagic events were the major causes of death. Patients who remain supported beyond 1 year are still likely to survive to transplantation.

The evolving role of the total artificial heart in the management of end-stage congenital heart disease and adolescents

Advances in medical therapies have yielded improvement in morbidity and a decrease in mortality for patients with congenital heart disease, both surgically palliated and uncorrected. An unintended consequence is a cohort of adolescent and adult patients with heart failure who require alternative therapies. One intriguing option is placement of a total artificial heart (TAH) either as a bridge to transplant or as a destination therapy. Of the 1091 Jarvik-7 type TAH (Symbion, CardioWest and SynCardia) placed between 1985 and 2012, only 24 have been performed in patients with congenital heart disease, and a total of 51 were placed in patients younger than 21. At our institution, the SynCardia TAH was implanted in a 19-year-old patient with cardiac allograft failure because of chronic rejection and related multisystem organ failure including need for hemodialysis. Over the next year, she was nutritionally and physically rehabilitated, as were her end organs, allowing her to come off dialysis, achieve normal renal function and eventually be successfully transplanted. Given the continued growth of adolescent and adult congenital heart disease populations with end-stage heart failure, the TAH may offer therapeutic options where previously there were few. In addition, smaller devices such as the SynCardia 50/50 will open the door for applications in smaller children. The Freedom Driver offers the chance for patients to leave the hospital with a TAH, as does the AbioCor, which is a fully implantable TAH option. In this report, we review the history of the TAH and potential applications in adolescent patients and congenital heart disease.

Hemodynamic deterioration during extracorporeal membrane oxygenation weaning in a patient with a total artificial heart

OBJECTIVES

The Total Artificial Heart (Syncardia, Tucson, AZ) is approved for use as a bridge-to-transplant or destination therapy in patients who have irreversible end-stage biventricular heart failure. We present a unique case, in which the inferior vena cava compression by a total artificial heart was initially masked for days by the concurrent placement of an extracorporeal membrane oxygenation cannula.

PATIENT

This is the case of a 33-year-old man admitted to our institution with recurrent episodes of ventricular tachycardia requiring emergent total artificial heart and venovenous extracorporeal membrane oxygenation placement.

CONCLUSION

This interesting scenario highlights the importance for critical care physicians to have an understanding of exact anatomical localization of a total artificial heart, extracorporeal membrane oxygenation, and their potential interactions. In total artificial heart patients with hemodynamic compromise or reduced device filling, consideration should always be given to venous inflow compression, particularly in those with smaller body surface area. Transesophageal echocardiogram is a readily available diagnostic tool that must be considered standard of care, not only in the operating room but also in the ICU, when dealing with this complex subpopulation of cardiac patients.

Current approaches to device implantation in pediatric and congenital heart disease patients

The pediatric ventricular assist device (VAD) has recently shown substantial improvements in survival as a bridge to heart transplant for patients with end-stage heart failure. Since that time, its use has become much more frequent. With increasing utilization, additional questions have arisen including patient selection, timing of VAD implantation and device selection. These challenges are amplified by the uniqueness of each patient, the recent abundance of literature surrounding VAD use as well as the technological advancements in the devices themselves. Ideal strategies for device placement must be sought, for not only improved patient care, but also for optimal resource utilization. Here, we review the most relevant literature to highlight some of the challenges facing the heart failure specialist, and any physician, who will care for a child with a VAD.

SynCardia: the total artificial heart

The SynCardia total artificial heart (TAH) currently provides the most definitive option for patients with biventricular failure who are not candidates for isolated left ventricular (LV) assist device placement. The techniques for implantation are adaptable to almost all patients with advanced heart failure, including those with severe biventricular cardiomyopathy, complex congenital heart disease, failed LV assist devices, failed transplantations, and acquired structural heart defects that have failed or are not amenable to conventional surgical treatment. Over the years, the implantation technique has evolved in order to minimize the surgical invasiveness of the procedure, in anticipation of additional future surgery. Meticulous hemostasis with double layer sutures, use of Gore-Tex sheets around the TAH and the pericardial cavity, and use of tissue expanders to avoid contraction of pericardial cavity around the device are discussed in detail in the following report. Additionally, we will provide our experience with implantation of TAH in various challenging scenarios, such as patients with a small chest cavity, congenital heart defects, and simultaneous use of extracorporeal membrane oxygenation (ECMO).

Total artificial heart in the pediatric patient with biventricular heart failure

Mechanical circulatory support emerged for the pediatric population in the late 1980s as a bridge to cardiac transplantation. The Total Artificial Heart (TAH-t) (SynCardia Systems Inc., Tuscon, AZ) has been approved for compassionate use by the Food and Drug Administration for patients with end-stage biventricular heart failure as a bridge to heart transplantation since 1985 and has had FDA approval since 2004. However, of the 1,061 patients placed on the TAH-t, only 21 (2%) were under the age 18. SynCardia Systems, Inc. recommends a minimum patient body surface area (BSA) of 1.7 m(2), thus, limiting pediatric application of this device. This unique case report shares this pediatric institution's first experience with the TAH-t. A 14-year-old male was admitted with dilated cardiomyopathy and severe biventricular heart failure. The patient rapidly decompensated, requiring extracorporeal life support. An echocardiogram revealed severe biventricular dysfunction and diffuse clot formation in the left ventricle and outflow tract. The decision was made to transition to biventricular assist device. The biventricular failure and clot formation helped guide the team to the TAH-t, in spite of a BSA (1.5 m(2)) below the recommendation of 1.7 m(2). A computed tomography (CT) scan of the thorax, in conjunction with a novel three-dimensional (3D) modeling system and team, assisted in determining appropriate fit. Chest CT and 3D modeling following implantation were utilized to determine all major vascular structures were unobstructed and the bronchi were open. The virtual 3D model confirmed appropriate device fit with no evidence of compression to the left pulmonary veins. The postoperative course was complicated by a left lung opacification. The left lung anomalies proved to be atelectasis and improved with aggressive recruitment maneuvers. The patient was supported for 11 days prior to transplantation. Chest CT and 3D modeling were crucial in assessing whether the device would fit, as well as postoperative complications in this smaller pediatric patient.

Update on ventricular assist devices

PURPOSE OF REVIEW

Over the past two decades, medicine has seen a robust increase in the use of ventricular assist devices. The purpose of this review is to update the information concerning these devices, their advantages and disadvantages as well as their complications. This is essential, as the demand for these devices is increasing due to the increasing number of patients with end-stage heart failure and limited number of donor hearts available for transplantation.

RECENT FINDINGS

First-generation devices consisted of large, cumbersome consoles requiring patient immobilization and often times hospitalization in an ICU setting. Second-generation models focused on patient mobility and discharge from hospital with an improvement in infection rates as well as 1 and 2-year survival rates. Designs for newer devices are focusing on full implantation without percutaneous lines, axial flow mechanisms and patient comfort. Additionally, total artificial hearts are being designed for the treatment of biventricular failure. The indications for ventricular assist devices are also being expanded to include destination therapy and alternatives to cardiac transplantation, as the supply of organs continues to be limiting.

SUMMARY

This paper reviews the characteristics, outcomes and design of ventricular assist devices.

CardioWest temporary total artificial heart

BACKGROUND

The CardioWest temporary total artificial heart (TAH-t) replaces both native ventricles of the heart and is more beneficial for a select group of patients than most other typical ventricular assist devices (VADs). This review will expand on the current literature and highlight the chronology of this device. The CardioWest TAH-t has been implanted in over 715 patients at 30 multiple institutional centers worldwide as a bridge-to-transplant (BTT) since 1993. The mechanical flow dynamics of the device are manufactured and designed differently from other traditional VADs, allowing increased outputs and normal filling pressures, allowing for sufficient organ and tissue perfusion and dramatic recoveries, allowing patients to return to an almost normal quality of life.

RESULTS

There was a 79% survival to transplant achievement in the protocol group who received the TAH-t versus a 46% in the control group (P < 0.001). Furthermore, there was a 70% survival rate at one year in the protocol group versus 31% in the control group (P < 0.001). The one- and five-year survival rates after transplantation were 69% and 34%, respectively, in the control group and 86% and 64%, respectively, in the protocol group.

CONCLUSION

It is evident that the advancement of modern engineering and medicine has made way for a reliable and durable device that provides a promising future in the field of end-stage heart failure.

[Assisted circulation: an overview from a clinical perspective]

A higher grade cardiac failure is associated with poor prognosis. In addition to medical conservative treatment and traditional cardiac surgery, in the past years different forms of an assisted circulation evolved. Short-term devices serve to bridge an acute life-threatening situation. The chosen system is dependent on the anticipated clinical course. It is possible to fall back on slightly assisting techniques up to a complete takeover of the cardiac pump function. In the case of severe cardiac failure, the question for transplantation has to be addressed because transplantation is the treatment of choice to date. For an assisted circulation in cases of chronic congestive failure, devices of different generations are available. First generation pulsatile systems are used for assistance of the left ventricle and results have been shown to be superior to medical therapy (REMATCH). With second generation continuous-flow systems, results regarding infections, thromboembolism and also quality of life appear to be further improved. Contact-free centrifugal pumps as third generation systems are in clinical evaluation. So-called "total artificial hearts" are successfully used for bridge-to-transplantation. Taken together, a graded safe treatment of cardiac failure is available today. In the near future, it could be possible to reach results similar to those of cardiac transplantation.