Development of an interprofessional pediatric ventricular assist device support team

Caring for pediatric patients with a ventricular assist device (VAD) requires a collaborative approach from an interprofessional team to ensure maximum patient safety and optimal outcomes. Initiating a VAD program is challenging, due to the complex medical and technical nature of this device and associated learning needs. At our institution, the development of the interprofessional VAD support team was established in four phases. Initial Education, Core Team Formation, Expansion, and Evaluation. A "core VAD team" was created after the initial education at an established VAD center. In a third step, all efforts were directed toward increasing the number of health care professionals caring for the VAD patients in the Cardiac Critical Care setting and on the Cardiac ward. The last phase consists of ongoing evaluation. Several key areas imperative to the care of a patient on a VAD were identified and further elaborated. The complex care of a patient on a VAD needs a specialized team approach to cover all patient care needs. Ongoing interprofessional education continues to improve competency of care. Continuity of care was assured on all levels of service to ensure the best possible outcomes.     

Hurricane Katrina: emergent interstate transport of an evacuee on biventricular assist device support

In many U.S. hospitals, mechanical circulatory support has become routine. However, catastrophes such as Hurricane Katrina test the abilities of a hospital system to sustain patients on such support and transport them in emergent situations. A 15-year-old boy with dilated cardiomyopathy who was receiving biventricular mechanical circulatory support at a New Orleans hospital was successfully transported by Angel One Transport from Arkansas Children's Hospital across state lines to Texas Children's Hospital, where he was stabilized and received an orthotopic heart transplant.     

Prolonged biventricular assist device support as a bridge to heart transplantation

We report a case in which long-term biventricular assist device (BiVAD) support enabled successful heart transplantation. The patient was diagnosed with dilated cardiomyopathy at age 11. She underwent implantation of a Toyobo LVAD, tricuspid valvuloplasty and annuloplasty at age 15. Right heart bypass (RHB) was established using a centrifugal pump. Right ventricular function showed no improvement during a ten-day period, and RHB was switched to a Toyobo RVAD on postoperative day (POD) 11. Because of poor oxygenation, veno-venous extracorporeal membrane oxygenation (V–V ECMO) was instituted. She was weaned from V–V ECMO on POD 14. She was brought to the United States on POD 189 under BiVAD support, and underwent heart transplantation on POD 199. She was discharged 4 months later. Two years after heart transplantation, she remained in New York Heart Association class one without rejection.     

Development of an implantable small right ventricular assist device

Currently, at least two permanent implantable left ventricular assist devices (LVADs) are used clinically. Unfortunately, there is no small implantable right ventricular assist device (RVAD) available, even though at least 25-30% of this patient population has right ventricular failure. If a small implantable RVAD were available, biventricular assist could support patients with right ventricular failure. A small atraumatic and antithrombogenic RVAD is being developed to meet this clinical need. This small centrifugal blood pump, the Gyro PI pump, is 6.5 cm in diameter and 4.6 cm in height and has three unique characteristics to prevent thrombus formation: (1) the double pivot bearing and magnetic coupling system enable this pump to be completely sealless; (2) the secondary vanes at the bottom of the impeller accelerate the blood flow and prevent blood stagnation; and (3) the eccentric inlet port enables the top female bearing to be embedded into the top housing and decrease blood cell trauma. The inflow conduit consists of a wire reinforced tube and a hat-shaped tip that is biolized with gelatin to create a thrombus resistant material. This conduit is directly implanted into the right ventricle, and the outflow conduit is anastomosed to the PA. The pump can be implanted inside the abdominal wall or in the thoracic cavity. Biocompatibility of this pump was proved in two calves by thrombus free implantation as an LVAD for 284 days and 200 days. Two RVAD implantations were conducted, aiming for 1-month system feasibility studies. During the month, the RVADs operated satisfactorily without any thromboembolic incident. No blood clots or abnormal findings were seen inside the pump, nor were there abnormal findings in the explanted lungs except for small areas of atelectasis. The pump flow was 3.02 +/- 0.38 L/min in calf 1 and 3.75 +/- 1.18 L/min in calf 2. The power requirement was 7.28 +/- 0.43W for calf 1 and 14.52 +/- 3.93W for calf 2. The PaO2 was 72.0 +/- 3.60 mm Hg (calf 1) and 72.0 +/- 7.63 mm Hg (calf 2); PaCO2 was 38.3 +/- 2.17 mm Hg (calf 1) and 34.1 +/- 1.95 mm Hg (calf 2); and SaO2 was 94.1 +/- 1.37% (calf1) and 95.0 +/- 1.95% (calf 2). Gas exchange via the lungs was maintained. These studies indicate that the Gyro PI pump is suitable as a single implantable RVAD, and is a feasible RVAD as a part of a BiVAD system in terms of pump performance and thrombus resistance.     

A novel miniature ventricular assist device for hemodynamic support

The HemoDynamics Systems enabler is a new cardiac assist pump that can expel blood from the left ventricle and provide pulsatile flow in the aorta. We evaluated the efficacy of the 18 Fr enabler. The enabler was inserted from the left ventricular apex into the ascending aorta in eight sheep. Heart failure (mild, moderate, and severe) was induced by microsphere injection into the coronary arteries to reduce cardiac output by 10-30%, 31-50%, and more than 50% from baseline, respectively. The enabler was activated, and its flow was increased to approximately 2.0 L/min. Hemodynamic variables were recorded before and after activation. In moderate heart failure, cardiac output and mean aortic pressure increased from 2.3 +/- 0.6 L/min and 59 +/- 12 mm Hg before assist to 2.8 +/- 0.6 L/min and 70 +/- 8 mm Hg at 30 minutes after activation, respectively (p < 0.01). Left atrial pressure decreased from 17 +/- 3 to 13 +/- 4 mm Hg (p < 0.05). Similar findings were observed in mild and severe heart failure. Despite its small diameter, the enabler significantly improved the hemodynamics of failing hearts and may potentially serve as a means of peripheral left ventricular support. Further study is warranted.     

Post-CABG sternum sparing biventricular assist device implantation technique using the right pulmonary artery for right ventricular assist device outflow cannulation

Journal of Artificial Organs -     

Emergency implantation of a left ventricular assist device in adolescents with biventricular failure

Adolescents with congestive cardiomyopathy who present with intractable arrhythmia or progressive ventricular failure have a very poor prognosis and often die awaiting cardiac transplantation (CTx). We present our recent experience with a pneumatically powered left ventricular assist device (LVAD) implanted emergently to salvage adolescents with severe biventricular failure. Four patients, aged 15-17 years, body surface areas of 1.5-1.7 m2, with dilated cardiomyopathy (LV diastolic dimension, 7.1-8.3 cm); two presented with cardiovascular collapse, one with refractory ventricular tachycardia, and one with cardiac arrest. Hemodynamic and biochemical data before and 1 week after LVAD placement are expressed as mean and range values. None of the patients required right ventricular assist, and all patients achieved functional recovery while on LVAD support (8-71 days). Currently, all four patients are alive (11-22 months) after successful CTx. We conclude that emergency implantation of an LVAD in adolescents with biventricular heart failure can be life saving. As has been shown in the adult population, such a ventricular assist system restores normal circulatory hemodynamics, reverses multi-organ dysfunction, and provides a "safe" bridge to transplantation.     

Successful use of temporary right ventricular support to avoid implantation of biventricular long-term assist device: a transcutaneous approach

Severe right ventricular (RV) failure after left ventricular assist device (LVAD) implantation is a serious complication with a poor prognosis. The most effective therapy for these patients is an upgrade to biventricular mechanical support. However, it is well recognized that primary and secondary biventricular ventricular assist device implantation is associated with higher mortality rates. We report on three patients with cardiogenic shock, who were provided on an emergency basis with a percutaneous extracorporeal life support (ECLS) system by the femoral vessels. After stabilization, a LVAD was implanted. To avoid secondary RV failure, the ECLS was switched to a transcutaneous RV assist device (RVAD) as a temporary RV support. The arterial cannula was removed from the femoral artery, and a prosthesis-supported cannula was sutured to the pulmonary artery and passed through a subxiphoid exit. The femoral vein cannula was left in situ. Both cannulae were connected to a centrifugal pump. Two patients could be weaned from the RVAD; the system was explanted under local anesthesia. One patient died due to internal bleeding. In conclusion, the ease of device implantation, weaning, and explantation justifies a liberal use of temporary RV support to avoid implantation of the problematic long-term biventricular assist devices.     

Development of implantable right ventricular assist device

Implantable ventricular assist devices (VADs) are indicated for long waiting periods before transplantation and also as a destination therapy. Meanwhile, right ventricular failure (RVF) is one of the four major complications observed in patients after left VAD (LVAD) implantation, with an incidence of approximately 20%. Preoperative prediction of the complication remains difficult, and the mortality is very high. To date, no implantable right VAD (RVAD) is available for the clinical situation. The possibility of realizing an implantable RVAD with Gyro centrifugal pump (PI-710 pump) was investigated. Eleven chronic animal experiments with LVAD and RVAD implantation were performed. Right heart bypass was established between right outflow and pulmonary trunk, and the pump was implanted in the preperitoneal space. The anatomic fit was good. The mean term of the experiments was 59 days, with excellent pump performance. Stable pulmonary hemodynamics and respiratory function were maintained during all of the experimental terms. No specific abnormal histologic findings of the lung were confirmed; however, tunica media hypertrophy was recognized in some cases. The PI-710 pump is feasible as a clinically implantable RVAD, but further study of histologic and pulmonary vascular changes after RVAD implantation is needed.     

Development of compact ventricular assist device for chronic use

A compact and reliable mechanical ventricular assist device is expected for chronic use. A magnetically suspended centrifugal pump (MSCP) is a seal-less, bearingless pump that can be operated for a long time with-out fear of leak or thrombus formation around the shaft. This paper reports recent progress with the MSCP, including pulse-pressure generation: In three sheep with acute heart failure induced by injection of beta-blockers, left ventricular assist was instituted with an inflow cannula into the left atrium (LA) and left ventricle (LV), and the outflow cannula to the descending aorta. The timing of the pulsation was synchronized with the electrocardiogram. Cardiac performance was evaluated by a conductance catheter and a tipped manometer in the LV. As pump speed increased, the pump flow became almost continuous. After application of pulsation, the pulse pressure increased from 5 to 25 mmHg, irrespective of the inflow cannulation site and the timing of pulsation. With LA cannulation, LV pressure at copulsation was slightly higher than at counterpulsation. Chronic animal trial: The MSCP was implanted in three sheep. The inflow cannula was inserted into the LV. The native heart was kept intact. The inner surface was coated with heparin. Continuous hemodynamic monitoring as well as periodic blood sampling was performed. The duration of running of the pump was 60, 140, and 248 days. The causes of termination were infection and failure of magnetic suspension due to electrical short. No thrombus or embolic findings were observed in the whole body after sacrifice. Renal and hepatic functions were within normal range throughout the experiment. It is concluded that the MSCP can produce pulsation irrespective of the inflow cannulation site and timing of synchronization. It is a promising device for chronic ventricular support.     

Total percutaneous biventricular assist device implantation for fulminant myocarditis

Journal of Artificial Organs - We report an effective therapeutic approach of mechanical circulatory support for a patient with cardiogenic shock and respiratory insufficiency due to fulminant...     

Direct percutaneous endoscopic jejunostomy placement in a patient with intracorporeal left ventricular assist device

We present a case involving a patient who required enteral feeding after implantation of an abdominally positioned left ventricular assist device. The position of the device occupied most of the abdomen, precluding percutaneous endoscopic gastrostomy tube placement. However, in the case presented, direct percutaneous endoscopic jejunostomy (DPEJ) tube placement was achieved without interfering with the intracorporeal device. To our knowledge, there are no previous reports in the literature of successful DPEJ placement in a patient with an abdominally positioned heart assist device. DPEJ should be considered as a long-term enteral feeding route when structural barriers prevent percutaneous gastric access.     

Optimization of a miniature Maglev ventricular assist device for pediatric circulatory support

A miniature Maglev blood pump based on magnetically levitated bearingless technology is being developed and optimized for pediatric patients. We performed impeller optimization by characterizing the hemodynamic and hemocompatibility performances using a combined computational and experimental approach. Both three-dimensional flow features and hemolytic characteristics were analyzed using computational fluid dynamics (CFD) modeling. Hydraulic pump performances and hemolysis levels of three different impeller designs were quantified and compared numerically. Two pump prototypes were constructed from the two impeller designs and experimentally tested. Comparison of CFD predictions with experimental results showed good agreement. The optimized impeller remarkably increased overall pump hydraulic output by more than 50% over the initial design. The CFD simulation demonstrated a clean and streamlined flow field in the main flow path. The numerical results by hemolysis model indicated no significant high shear stress regions. Through the use of CFD analysis and bench-top testing, the small pediatric pump was optimized to achieve a low level of blood damage and improved hydraulic performance and efficiency. The Maglev pediatric blood pump is innovative due to its small size, very low priming volume, excellent hemodynamic and hematologic performance, and elimination of seal-related and bearing-related failures due to adoption of magnetically levitated bearingless motor technology, making it ideal for pediatric applications.     

Left ventricular outflow tract obstruction associated with chronic ventricular assist device support

Favorable long-term patient outcome after insertion of a left ventricular assist device (LVAD) as a bridge to recovery or destination therapy for the treatment of end-stage cardiomyopathy is adversely affected by pathophysiologic changes affecting the heart. Alterations in the native aortic valve apparatus, specifically aortic valve cusp fusion, is an example of such a phenomenon and may especially affect patients in cases of bridge to recovery, a rare but reported event. A retrospective review of the last 33 LVAD placements at our institution was conducted, including reviews of operative reports and pathologic examinations of the native hearts. Seven hearts were found to have varying degrees of aortic valve cusp fusion after chronic LVAD support (63-1, 339 days). Five of these patients had native aortic valves, and two had bioprosthetic valves. The left ventricular outflow tracts in two patients were surgically occluded at the time of LVAD insertion. Aortic valve cusp fusion occurs in roughly 25% of patients on chronic LVAD support. This phenomenon may prove to be clinically significant by creating a potential source of emboli and infection. In addition, in the case of myocardial recovery, left ventricular outflow tract obstruction could limit parallel flow and produce suprasystemic ventricular pressures that in turn would elevate left ventricular end diastolic pressures. The latter may contribute to further myocardial injury, ultimately limiting the ability of an otherwise recovered heart to be weaned from LVAD support.     

Development of a percutaneous pediatric ventricular assist device

Remarkable progress has been made on ventricular assist devices for adult patients. Unfortunately, similar devices are not yet available in the United States for pediatric heart patients. The goal of this project is to demonstrate the feasibility of a percutaneous ventricular assist device for pediatric patients above 2 kg. The proposed system consists of an extracorporeal centrifugal blood pump, a transseptal venous cannula that takes blood from the left atrium to the pump, an arterial cannula that returns the blood to the arterial system, and a controller to adjust pump speed/flow. Using an ad hoc pediatric pump prototype and a spectrum of specially designed cannulae of various sizes, benchtop studies showed that the proposed system could deliver blood flow in a range of 0.3 to 3.0 l/min. For smaller patients (2-35 kg), the transseptal cannula was designed to be placed in the internal jugular vein and the arterial cannula in the internal carotid artery. For larger patients (> 35 kg), the femoral vein and artery would be used. Further development effort will be focused on reducing the hemolysis of the pump design, refining the cannula design, and demonstrating the safety and functionality in animal studies.     

Ethical considerations for ventricular assist device support: a 10-point model

The potential for long-term support on a ventricular assist device (VAD) in the bridge-to-transplant (BTT) and destination therapy (DT) settings has created unprecedented ethical challenges for patients and caregivers. Concerns include the patient's adaptation to life on a device and the ethical, clinical, and practical issues associated with living on mechanical support. On the basis of our experience treating 175 consecutive VAD patients, we have developed a model to address the ethical and psychosocial needs of patients undergoing VAD implantation. Patient preparation for VAD implantation encompasses three phases: 1) initial information regarding the physical events involved in implantation, risks and benefits of current device technology, and the use of VAD as a rescue device; 2) preimplant preparation including completion of advance directives specific to BTT/DT, competency determination, and identifying a patient spokesperson, multidisciplinary consultants, and cultural preferences regarding device withdrawal; and 3) VAD-specific end-of-life issues including plans for device replacement and palliative care with hospice or device withdrawal. This three-phase 10-point model addresses the ethical and psychosocial issues that should be discussed with patients undergoing VAD support.     

Quantification of interventricular dyssynchrony during continuous-flow left ventricular assist device support

Journal of Artificial Organs - Under continuous-flow left ventricular assist device (CF-LVAD) support, the ventricular volume change and cardiac cycle between the left ventricle (LV) and right...