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The Boy in the Bubble and the Baby With the Berlin Heart: The Dangers of “Bridge to Decision” in Pediatric Mechanical Circulatory Support

Hollander, Seth A.*; Hollander, Ethan J.

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doi: 10.1097/MAT.0000000000000729
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Abstract

On September 21, 1971, David Phillip Vetter was born to unusual circumstances.1 With his mother a known carrier of Severe Combined Immunodeficiency Syndrome (SCID, an x-linked disease), baby David had a 50% chance of having it himself. If he did, his only hope would be a bone marrow transplant from his sister, who had only a 1 in 4 chance of being a suitable donor. Otherwise, he would likely die upon his first exposure to virus or bacteria. To be safe, the plan was to deliver David in a sterile environment via cesarean section and then temporarily place him into a sterile protective isolator where he would be tested for SCID and, if necessary and possible, get a bone marrow transplant from his histocompatible sister.

The remainder of the story is well known. David tested positive for SCID. His sister was not a match, and the isolator became his permanent home. David, “The Boy in the Bubble”, was now stuck.

No plans had been made for this contingency. The isolator, intended as a bridge to bone marrow transplantation, had instead become a bridge to nowhere. Ultimately, after enduring 12 years in isolation waiting for a technological advancement that never came, David received a bone marrow transplant from his unmatched sister. He died 4 months later from a posttransplant malignancy.

David’s predicament could have been anticipated. But for his professional caregivers, optimism prevailed. As Dr. John Montgomery, one of his treating physicians, remarked reflectively in the 2006 PBS American Experience documentary, “The Boy in the Bubble”:

I have to be honest that we never sat down and outlined “This is what we will do ‘if’.” It was an unspoken understanding that he would match [his sister] Katherine, we would transplant him, it would work, and six weeks to three months later, he would be reconstituted and come out, and we would all be joyful, and maybe famous.2

For me, a pediatric cardiologist specializing in mechanical circulatory support, David’s case is a cautionary tale. Like SCID, pediatric heart failure is a rare and life-threatening condition for which transplantation (in this case, of the heart) is often the only option for prolonged survival. Unfortunately, the likelihood of death while waiting for a suitable organ remains high, particularly for infants.3 Nearly 15 year ago, the pulsatile, paracorporeal Berlin Heart EXCOR ventricular assist device was developed, as the isolator was for David, to be a “bridge to transplantation” for infants and small children for whom death is otherwise imminent.4 This “bridge” can sustain circulation until a suitable donor can be found and has been used in more than 1500 children for this purpose.5

This “miraculous” machine, however, offers both freedoms and restrictions. Once implanted, patients are tethered to a large pneumatic driver weighing more than 200 pounds and must remain hospitalized until the device is removed, either at the time of transplantation or, in rare cases, myocardial recovery. Despite this, after the postoperative recovery period, children supported with the EXCOR device feel little discomfort, do not require intensive care, and can be expected to be nearly fully functional for months, or even years, while on support.6 Infants can be held by their parents, and older children can attend hospital school, allowing for the cultivation of family bonding and other social relationships, while the often lengthy search for a suitable donor organ continues. (Figure 1).

Figure 1.
Figure 1.:
A: An infant supported by the EXCOR participates in age-appropriate rehabilitation. B: David Vetter in his isolator (photo courtesy of Texas Children's Hospital).

A donor organ, however, is a precious commodity, and listing for transplantation is reserved for those with acceptable survival potential. The identification of medical or social barriers to transplantation is a critical task of any pediatric heart transplant team during the evaluation process. Yet for many patients, heart failure symptoms progress quickly, faster than the patient’s suitability for transplant can be evaluated. In such situations, the EXCOR device, like David’s isolator, may be implanted as a bridge-to-decision, stabilizing the patient while a transplant evaluation is completed. If the patient turns out to be a suitable transplant candidate, the EXCOR serves its intended purpose as a temporary support device. However, if contraindications to transplant become evident, clinicians could find themselves faced with an impossible choice between the inappropriate use of a donor organ, indefinite internment in the hospital, or compassionate deactivation of a life-sustaining therapy in a child who is awake, interactive, and comfortable.

Therein lies the potential for history to repeat itself. It is generally accepted that children with severe pulmonary vascular disease or other conditions likely to cause premature death should not be transplanted nor should children with inadequate social supports to ensure medication adherence. Nevertheless, our center, like others, has used the EXCOR to save the lives of patients before satisfying all the requirements for transplant listing. Although it has yet to occur, these situations could easily result in a child with end-stage heart failure facing an indefinite period of support, just like David Vetter.

So what will become of today’s bridge-to-decision children? Some will proceed to transplant and others will succumb to their disease. But some carry the risk of ending up like the Boy in the Bubble, not actively dying and in no acute distress, but with no clear plan for liberation from the technology that binds them to a hospitalized existence.

As biomedical science carries us ever forward in our ability to sustain life in the face of terminal illness, we must always bear in mind the unintended consequences of life dependent on technology. In an industry where technological advancements will always outpace regulations and where the ethics that guide us often evolve in real time, we as healthcare providers must always be mindful to govern ourselves, recognizing that our desire to save patients sometimes comes with the power to entrap them. We must couple hope with objectivity and clearly see the true purpose of our interventions. When necessary, we must find the bravery not to proceed.

David Vetter’s isolator was a medical miracle that gave him life but at the expense of his freedom. Much in the same way, the miraculous EXCOR must not be a machine that simply sustains the circulation. It must be, and always remain, a bridge to somewhere.

References

1. Rennie D. Bubble boy. JAMA 1985.253: 7880.
2. Goodman B, Maggio J. The Boy in the Bubble. American Experience [Television] PBS, 2006.
3. Morrow WR, Naftel D, Chinnock R, et al. Outcome of listing for heart transplantation in infants younger than six months: predictors of death and interval to transplantation. The Pediatric Heart Transplantation Study Group. J Heart Lung Transplant 1997.16: 12551266.
4. Fraser CD Jr, Jaquiss RD, Rosenthal DN, et al.; Berlin Heart Study Investigators: Prospective trial of a pediatric ventricular assist device. N Engl J Med 2012.367: 532541.
5. Almond CS, Morales DL, Blackstone EH, et al. Berlin Heart EXCOR pediatric ventricular assist device for bridge to heart transplantation in US children. Circulation 2013.127: 17021711.
6. Hollander SA, Hollander AJ, Rizzuto S, Reinhartz O, Maeda K, Rosenthal DN. An inpatient rehabilitation program utilizing standardized care pathways after paracorporeal ventricular assist device placement in children. J Heart Lung Transplant 2014.33: 587592.
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