The clinical story began long before the emergency that defined it. The boy was born at full term with a normal birth weight of 2608 grams, but by two months of age he was hospitalized for poor weight gain and declining cardiac function. Oral medications stabilized him enough for discharge after a two-month stay. Genetic testing eventually revealed a nonsense mutation, designated c.153C > G, in the TAZ gene, the molecular signature of Barth syndrome. This X-linked recessive condition arises from defects in an enzyme that remodels cardiolipin, a phospholipid essential to the structure and function of mitochondria, the energy-producing structures inside cells. The result is a constellation of problems: dilated cardiomyopathy in which the heart muscle stretches and weakens, generalized muscular hypotonia, and cyclical neutropenia that leaves patients vulnerable to infection. When the child was readmitted at one year of age with severe cardiac dysfunction and a brain natriuretic peptide level of 2096 pg/mL, a marker of profound heart strain, inotropic drugs failed to rescue him and he was transferred to Osaka for transplant registration and placement of a Berlin Heart EXCOR, the only durable ventricular assist device approved for small children in Japan.

His condition deteriorated faster than the transplant system could move. On admission he weighed just 6.1 kilograms and measured 67.5 centimeters. Echocardiography showed a left ventricle dilated to 38 millimeters, a z-score of +5.7 relative to normal body size, an ejection fraction of only 15 percent, and severe mitral regurgitation; his BNP had surged to 7667 pg/mL. Soon after arrival he developed runs of non-sustained ventricular tachycardia, a dangerous rhythm disturbance, and amiodarone therapy dropped his blood pressure. The team established venoarterial extracorporeal membrane oxygenation through neck vessels as an emergency salvage measure, but acute pulmonary congestion followed, forcing the decision to implant a biventricular assist device using centrifugal pumps. For the left side, surgeons used a 6-mm apical inflow cannula and a 6-mm arterial outflow cannula; for the right side, they placed a 14-Fr inflow cannula into the inferior vena cava via the right atrium and an 8-Fr outflow cannula into the distal pulmonary artery trunk, all secured with purse-string sutures.

What happened next is the technical heart of the report. The right ventricular assist device pumped roughly 900 mL/min, yet the left-sided pump could not function efficiently. The culprits were severe pulmonary hypertension and pulmonary regurgitation, which together prevented blood pushed into the pulmonary circulation from returning effectively to the left heart. In a decisive maneuver, the surgeons relocated the right-sided outflow cannula from the pulmonary artery into the left atrium, temporarily routing oxygenated blood directly to the left side of the heart and bypassing the obstructed pulmonary circuit. Left ventricular assist device flow stabilized at approximately 600 mL/min. The strategy bought time, but it carried trade-offs: left atrial cannulation raises the risk of systemic thromboembolism, and the circuit could not be disconnected from the artificial lung that oxygenates blood outside the body. The team therefore treated the configuration as a bridge within a bridge, to be dismantled as soon as the pulmonary vasculature could tolerate normal routing.

That evaluation came quickly. Cardiac catheterization on postoperative day 5, performed during temporary interruption of right-sided pumping, recorded a pulmonary artery pressure of 21/15 mmHg with a mean of 18 mmHg and a pulmonary vascular resistance index of 3.5 Wood units times meters squared, values indicating acceptable pulmonary vascular physiology. On postoperative day 13 the outflow cannula was moved back to the pulmonary artery trunk and the artificial lung was removed from the circuit. Bedside echocardiography then showed improving right ventricular contraction, but chest X-rays revealed progressing pulmonary congestion, which the surgeons attributed to excessive pulmonary blood flow generated by full right-sided support. Their response was a careful titration: right pump flow was gradually reduced to low-flow assistance. Throughout this period the left pump maintained a stable 900 mL/min flow and central venous pressure held near 12 mmHg even when right-sided support fell to 400 mL/min or was interrupted entirely, evidence that the native right ventricle and pulmonary circulation had recovered enough to fill the left pump on their own. Concerned about circuit thrombosis during prolonged low flow, the team removed the right ventricular assist device on postoperative day 20.

The recovery of other organs lagged behind the heart but eventually followed. Acute kidney and liver failure complicated the early postoperative course, requiring continuous hemodiafiltration from postoperative day 7. Bilirubin climbed as high as 15.1 mg/dL and renal dysfunction persisted for more than a month, but hemofiltration was discontinued on day 44, total bilirubin normalized on day 61, and the child was extubated on day 55. Only after these markers of end-organ recovery did the team secure in-house approval for heart transplant registration, the prerequisite under Japanese rules for implanting the Berlin Heart EXCOR, which was converted from the temporary centrifugal left ventricular assist device 76 days after the original biventricular implantation. The boy then remained stable on the pulsatile device for 374 days before undergoing successful heart transplantation, a total mechanical support journey of roughly 450 days from the first emergency pump to the donor heart.

The Osaka team frames the case within a strategy known as bridge to candidacy, an approach better documented in adults. In Japan, pediatric candidates face an average wait of 686 days for a donor heart, even though ten-year survival after pediatric transplantation reaches 96.2 percent, and by 2022 only 68 patients under 18 had ever been transplanted in the country. The Berlin Heart EXCOR has been approved there only since 2015 and only for patients already registered for transplantation, which creates a chicken-and-egg problem for infants whose comorbidities disqualify them from listing. Adult data show the workaround can succeed: large series report that short-term mechanical support can reverse refractory cardiogenic shock long enough for conversion to durable devices, with survival comparable to direct bridge-to-transplant pathways, though right ventricular support during the conversion emerges as a mortality risk factor. Pediatric evidence is thinner, but a Berlin group’s ten-year experience with 56 children and a multicenter United States study both suggest that prior extracorporeal support does not necessarily doom Berlin Heart outcomes, while low body weight, kidney and liver dysfunction, and biventricular support do worsen survival.

The case also contributes to a re-evaluation of Barth syndrome itself as a transplant indication. Because the condition combines heart failure with skeletal myopathy and immune compromise, patients were once considered unsuitable candidates, but after the first successful transplant in 1997, London investigators reported four successful cases, and a registry analysis of 43 transplanted Barth patients found outcomes for survival, infection, malignancy, and graft vasculopathy essentially equivalent to those of other recipients. The Osaka authors add an important caveat drawn from recent metabolic studies: transplantation does not fully normalize exercise tolerance, muscle mass, or substrate metabolism, because the underlying cardiolipin defect persists in skeletal muscle and other tissues. Their patient was not systematically assessed for these parameters after transplantation, a limitation the team acknowledges, and long-term multidisciplinary follow-up of neurodevelopment and metabolic status continues.

Beyond the individual rescue, the report is a detailed argument for staged, physiology-driven management of the failing right heart in small children. When pulmonary hypertension and valve regurgitation sabotage the left-sided pump, temporarily diverting right-sided outflow to the left atrium can stabilize the circulation; once catheterization confirms that pulmonary vascular resistance has fallen, rerouting to the pulmonary artery removes the thrombotic risk of left atrial cannulation and permits artificial lung removal, and stepwise flow reduction then tests whether the native right ventricle can carry the load. In this case that sequence converted a child in refractory cardiogenic shock with failing kidneys and liver into a registered transplant candidate with a durable device. The authors suggest the approach may extend the bridge-to-candidacy strategy to other high-risk pediatric patients with biventricular failure complicated by pulmonary hypertension, a population for whom waiting lists are long and options have historically been few.

Subject of Research: Bridge-to-candidacy mechanical circulatory support and heart transplantation in a pediatric patient with Barth syndrome-associated biventricular heart failure

Article Title: Successful bridge to heart transplantation in a pediatric patient with biventricular heart failure associated with Barth syndrome: a case report

Article References: Arita, K., Kido, T., Taira, M., Watanabe, T., Narita, J., Ishida, H., Ishii, R., Ueno, T., & Miyagawa, S. (2026). Successful bridge to heart transplantation in a pediatric patient with biventricular heart failure associated with Barth syndrome: a case report. Journal of Artificial Organs, 29(4), Article 60. https://doi.org/10.1007/s10047-026-01587-2

Image Credits: AI Generated

DOI: 10.1007/s10047-026-01587-2

Keywords: Barth syndrome, heart transplantation, ventricular assist device, Berlin Heart EXCOR, biventricular heart failure, pediatric cardiology, pulmonary hypertension, cardiogenic shock, mechanical circulatory support, TAZ gene, dilated cardiomyopathy, bridge to candidacy