Advances in mechanical assist devices and artificial hearts for children

Human fitting of pediatric and infant continuous-flow total artificial heart: visual and virtual assessment

Background

This study aimed to determine the fit of two small-sized (pediatric and infant) continuous-flow total artificial heart pumps (CFTAHs) in congenital heart surgery patients.

Methods

This study was approved by Cleveland Clinic Institutional Review Board. Pediatric cardiac surgery patients (n = 40) were evaluated for anatomical and virtual device fitting (3D-printed models of pediatric [P-CFTAH] and infant [I-CFTAH] models). The virtual sub-study consisted of analysis of preoperative thoracic radiographs and computed tomography (n = 3; 4.2, 5.3, and 10.2 kg) imaging data.

Results

P-CFTAH pump fit in 21 out of 40 patients (fit group, 52.5%) but did not fit in 19 patients (non-fit group, 47.5%). I-CFTAH pump fit all of the 33 patients evaluated. There were critical differences due to dimensional variation (p < 0.0001) for the P-CFTAH, such as body weight (BW), height (Ht), and body surface area (BSA). The cutoff values were: BW: 5.71 kg, Ht: 59.0 cm, BSA: 0.31 m². These cutoff values were additionally confirmed to be optimal by CT imaging.

Conclusions

This study demonstrated the range of proper fit for the P-CFTAH and I-CFTAH in congenital heart disease patients. These data suggest the feasibility of both devices for fit in the small-patient population.

HeartWare Explant After Recovery 6 Years After Implant in a 3-Year-Old Child: Has the Game Changed?

The use of continuous-flow mechanical circulatory support in preschool children remains anecdotal. This case report describes the sequel to the implantation with a HeartWare HVAD system (Medtronic, Minneapolis, MN) in a 3-year old child. A 3-year-old boy with myocarditis-related cardiomyopathy underwent implantation with a HeartWare device. After an uncomplicated postoperative course, the patient was discharged home. Serial echocardiography showed progressive left ventricular recovery. After 6 months, the device was decommissioned, and the outflow graft was tied off. Six years after insertion, the device was explanted uneventfully. The HeartWare ventricular assist device offers viable long-term mechanical circulatory support in selected children that results in sustainable care and good quality of life.

Challenges and Future Directions in Left Ventricular Assist Device Therapy

The clinical use of left ventricular assist devices (LVADs) in the growing epidemic of heart failure has improved quality of life and long-term survival for this otherwise devastating disease. The current generation of commercially available devices offers a smaller profile that simplifies surgical implantation, a design that optimizes blood flow characteristics, with less adverse events and improved durability than their predecessors. Despite this, the risk for adverse events remains significant, as do burdens for patients and their caregivers. Appropriate patient selection remains key to optimal LVAD outcomes.

Paracorporeal Connection to Heart-Lung Machine in Transplant Surgery With the Berlin Heart Ventricular Assist Device

This report describes a simple way to deal with time-consuming adhesions and cannula handling in patients with a paracorporeal assist device who are undergoing heart transplantation. By connecting the extrathoracic lines to the heart-lung machine, chest reentry becomes a straightforward issue.

Initial in vitro testing of a paediatric continuous-flow total artificial heart

OBJECTIVES

Mechanical circulatory support has become standard therapy for adult patients with end-stage heart failure; however, in paediatric patients with congenital heart disease, the options for chronic mechanical circulatory support are limited to paracorporeal devices or off-label use of devices intended for implantation in adults. Congenital heart disease and cardiomyopathy often involve both the left and right ventricles; in such cases, heart transplantation, a biventricular assist device or a total artificial heart is needed to adequately sustain both pulmonary and systemic circulations. We aimed to evaluate the in vitro performance of the initial prototype of our paediatric continuous-flow total artificial heart.

METHODS

The paediatric continuous-flow total artificial heart pump was downsized from the adult continuous-flow total artificial heart configuration by a scale factor of 0.70 (1/3 of total volume) to enable implantation in infants. System performance of this prototype was evaluated using the continuous-flow total artificial heart mock loop set to mimic paediatric circulation. We generated maps of pump performance and atrial pressure differences over a wide range of systemic vascular resistance/pulmonary vascular resistance and pump speeds.

RESULTS

Performance data indicated left pump flow range of 0.4-4.7 l/min at 100 mmHg delta pressure. The left/right atrial pressure difference was maintained within ±5 mmHg with systemic vascular resistance/pulmonary vascular resistance ratios between 1.4 and 35, with/without pump speed modulation, verifying expected passive self-regulation of atrial pressure balance.

CONCLUSIONS

The paediatric continuous-flow total artificial heart prototype met design requirements for self-regulation and performance; in vivo pump performance studies are ongoing.

Early in vivo experience with the pediatric continuous-flow total artificial heart

BACKGROUND

Heart transplantation in infants and children is an accepted therapy for end-stage heart failure, but donor organ availability is low and always uncertain. Mechanical circulatory support is another standard option, but there is a lack of intracorporeal devices due to size and functional range. The purpose of this study was to evaluate the in vivo performance of our initial prototype of a pediatric continuous-flow total artificial heart (P-CFTAH), comprising a dual pump with one motor and one rotating assembly, supported by a hydrodynamic bearing.

METHODS

In acute studies, the P-CFTAH was implanted in 4 lambs (average weight: 28.7 ± 2.3 kg) via a median sternotomy under cardiopulmonary bypass. Pulmonary and systemic pump performance parameters were recorded.

RESULTS

The experiments showed good anatomical fit and easy implantation, with an average aortic cross-clamp time of 98 ± 18 minutes. Baseline hemodynamics were stable in all 4 animals (pump speed: 3.4 ± 0.2 krpm; pump flow: 2.1 ± 0.9 liters/min; power: 3.0 ± 0.8 W; arterial pressure: 68 ± 10 mm Hg; left and right atrial pressures: 6 ± 1 mm Hg, for both). Any differences between left and right atrial pressures were maintained within the intended limit of ±5 mm Hg over a wide range of ratios of systemic-to-pulmonary vascular resistance (0.7 to 12), with and without pump-speed modulation. Pump-speed modulation was successfully performed to create arterial pulsation.

CONCLUSION

This initial P-CFTAH prototype met the proposed requirements for self-regulation, performance, and pulse modulation.

Systemic Atrioventricular Valve Excision and Ventricular Assist Devices in Pediatric Patients

BACKGROUND

Continuous-flow ventricular assist devices (CF VADs) designed for adults are increasingly used in pediatric patients. However, there is greater risk of device inflow obstruction as a result of size and anatomy.

METHODS

We reviewed all cases of systemic atrioventricular valve (AVV) excision with HeartWare HVAD (HeartWare, Framingham, MA) implantation in the systemic ventricle performed at our institution from November 2015 to May 2016.

RESULTS

AVV excision with CF VAD implantation was undertaken in 3 patients. Patient 1 was palliated in infancy, resulting in biventricular physiology with a systemic right ventricle, and presented at age 15 years with worsening ventricular dysfunction. After CF VAD implantation in the systemic ventricle and discharge to home, tricuspid valve obstruction to VAD inflow developed, and the patient and underwent tricuspid valve excision on postoperative day 52. Patients 2 and 3 were aged younger than 4 years, with a body surface area of 0.62 m² and 0.58 m², respectively, and had undergone Fontan palliation, with subsequent systemic ventricular dysfunction and AVV regurgitation. In both Fontan patients, the CF VAD was implanted in the right atrium with simultaneous excision of the AVV. None have had evidence of elevated atrial pressures or recalcitrant pulmonary edema. At a mean follow-up of 359 days (range, 304 to 422 days), there have been no concerns for inflow obstruction or low flow.

CONCLUSIONS

CF VAD implantation with AVV excision can successfully support complex pediatric patients in a wide range of size and anatomy (small chambers, systemic right ventricles). This technique may allow for CF VAD implantation in patients previously deemed too small for such support.

The Use of Berlin Heart EXCOR VAD in Children Less than 10 kg: A Single Center Experience

Objective: Despite the improvement in ventricular assist device (VAD) therapy in adults and in adolescents, in infant population only Berlin Heart EXCOR (BHE) is licensed as long term VAD to bridge children to Heart Transplantation (HTx). Particularly demanding in terms of morbidity and mortality are smallest patients namely the ones implanted in the first year of life or with a lower body surface area. This work aims at retrospective reviewing a single center experience in using BHE in children with a body weight under 10 kg.

Methods: Data of all pediatric patients under 10 kg undergoing BHE implantation in our institution from March 2002 to March 2016 were retrospectively reviewed.

Results: Of the 30 patients enrolled in the study, 53% were male, 87% were affected by a dilated cardiomyopathy with an average weight and age at the implantation of 6.75 ± 2.16 Kg and 11.57 ± 10.12 months, respectively. Three patients (10%) required a BIVAD implantation. After the implantation, 7 patients (23%) required re-intervention for bleeding and 9 patients (30%) experienced BHE cannulas infection. A total of 56 BHE pump were changed for thrombus formation (1.86 BHE pump for patient). The average duration of VAD support was 132.8 ± 94.4 days. Twenty patients (67%) were successfully transplanted and 10 patients (33%) died: 7 for major neurological complication and 3 for sepsis.

Conclusion: Mechanical support in smaller children with end stage heart failure is an effective strategy for bridging patients to HTx. The need for BIVAD was relegated, in the last years, only to restrictive cardiomiopathy. Further efforts are required in small infants to improve anticoagulation strategy to reduce neurological events and BHE pump changes.