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Updates in Mechanical Circulatory Support for Children

Iki Adachi, MD
Megan S del Corral, CCRN
David L S Morales, MD
Baylor College of Medicine, Houston, TX

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The number of children with heart failure has been increasing significantly. This large wave of end-stage pediatric heart failure patients cannot be fully addressed by heart transplantation alone because of limitation in donor organ availability that has been present for over a decade.

Unlike adult patients, where durable intracorporeal devices for mechanical circulatory support (MCS) are available, there have been no approved devices available for children that have gained widespread use even in developed countries, such as US and Japan, until recently. Therefore, extracorporeal membrane oxygenation (ECMO) has remained the most common form of pediatric MCS despite the fact that ECMO is not always an ideal solution. This frustrating situation, however, has been changing dramatically in the past 5 years.

US Food and Drug Administration approved the Berlin EXCOR®
In December 2011, Berlin EXCOR Pediatric VAD, which has been applied in Germany for over a decade, achieved an HDE approval by the US FDA, based on a clinical trial demonstrating that the EXCOR successfully bridged 90% of study patients to transplantation or recovery. Successful completion of the trial and subsequent FDA approval is a landmark event for pediatric heart failure treatment not only because this ushers in a new era for children with heart disease but this trial should serve as a model for future collaborative device investigations involving pediatric patients, industry, medicine, and the government. The Berlin Excor is the only true pediatric specific device to gain wide-spread use in the USA with over 300 implants and worldwide with over 1000 implants.

The Impact of Smaller Adult Devices for Pediatrics
The field of pediatric MCS is also greatly benefitting from the technological advancements of adult devices that offer a reduced morbidity profile and the ability to discharge patients home. We have been using these smaller intracorporeal devices such as the HeartMate II® and HeartWare® for patients with a BSA > 1.0 with our youngest being 9yo. We can now begin offering teenagers chronic VAD therapy as a destination or as period to see if they could become a transplant candidate. It is important to note that these devices are not approved for a certain age but by function with a recommended BSA. Besides supporting biventricular physiology, the field has begun to tackle univentricular circulations such as bidirectional Glenn patients with the Excor and the failing Fontan circulation with the HeartMateII®, this type of support we have termed "systemic VAD (SVAD)." [Although Fontan failure can be multifactorial, this experience should highlight that Fontan circulation can be supported with VAD therapy when the primary etiology of circulatory failure is due to ventricular dysfunction alone and when the systemic ventricular end-diastolic pressure is high. However, the majority of failing Fontan patients fail at multiple levels and will probably not benefit from VAD therapy alone. These patients could perhaps be best addressed with a Total Artificial Heart (TAH).]1

Total Artificial Heart for Pediatric Population
At this time, a TAH in adolescents could be helpful for certain conditions including chronic graft failure, failing Fontans, and certain types of end-stage congenital heart disease. A total replacement of an implanted graft eliminates the need of immunosuppression, which has a great advantage in the setting of an artificial device use. A VAD implantation late after congenital heart surgery can require multiple, concomitant procedures (i.e. aortic valve repair, conduit change, etc) depending on the anatomy and previous surgeries. These additional procedures require a prolonged pump-run and a cross-clamp time and thus change the morbidity profile of VAD implantation. In these circumstances, a TAH could be a better solution as demonstrated by a recent patient with congenitally corrected transposition of the great arteries and dextrocardia who required aortic valve and LV-PA conduit replacement through a 5th median sternotomy in order to place his BiVAD. Instead, he was implanted with a TAH that despite some technical challenges and modifications necessary for his anatomy (Fig), he tolerated well, was discharged home, and successfully transplanted 3months later.

Bridge to Recovery in Pediatric Population
ECMO, and short-term VADs in some institutions, have been routinely used as a short-term bridge to recovery in children with a temporary etiology of heart failure such as myocarditis or acute cardiac graft failure. However, availability of devices designed to provide support over a longer duration offers the opportunity to utilize these devices as a bridge to recovery in children with chronic heart failure. Pediatric myocardium may have higher potential to undergo reverse remodeling than that of an adult. At Texas Children's Hospital, a medical and rehabitation program has just been developed to evaluate all long-term VAD patients for the potential to undergo myocardial recovery. We have only experienced one successful application of an intracorporeal VAD for bridge-to-recovery in a 15yo boy with chronic heart failure. [Even though still an infrequent therapy for pediatric programs, the field of pediatric MCS has truly begun. This is underscored by the PUMPs for Kids Infants and Neonates (PUMPK.I.N.S.) program funded by the NHLBI to develop MCS for children. Presently, device and patients do exist to create an independent robust pediatric VAD program that supports children of all sizes and appropriately with the best type of short or long term devices for their specific type of heart failure.]2

References:

  1. Morales DL, Adachi I, Heinle JS, Fraser CD Jr. A new era: use of an intracorporeal systemic ventricular assist device to support a patient with a failing Fontan circulation. J Thorac Cardiovasc Surg. 2011;142:e138-40
  2. Lowry AW, Adachi I, Morales DL. The Potential to Avoid Heart Transplantation in Children: Outpatient Bridge to Recovery with an Intracorporeal Continuous-Flow Left Ventricular Assist Device in a 14-Year Old. Congenit Heart Dis. 2012 in press.

Figure at right:

Given the unusual orientation of l-malposed great arteries [aorta (in red) anterior and left to pulmonary trunk (blue)] in relation to l-looped ventricles (i.e. morphological right ventricle on the left), the right and left pumps were separated and implanted in a parallel orientation, instead of the normal criss-cross arrangement.

figure

Disclosure Statement: The authors have no conflicts of interest to disclose.