Worldwide Experience with the Syncardia Total Artificial Heart in the Pediatric Population

Abstract

Individual centers have documented the use of the Syncardia Total Artificial Heart (TAH) in adolescents with heart failure; however, the number of patients at any given center is small. Herein, we describe the worldwide experience for all patients ≤21 years old supported with the TAH between May 2005 and May 2015 (n = 43). The number of patients experiencing a positive outcome at 60, 90, and 120 days were 30 (70%), 27 (63%), and 25 (58%), respectively. Successful bridge to transplantation varied by diagnosis, but outcomes reported are similar to adults supported with the TAH or biventricular assist devices.

The Syncardia Total Artificial Heart (TAH) can be used to support adults with biventricular heart failure. Case reports and case series have documented the use of the device in adolescents including patients with single ventricle physiology and systemic right ventricles.^1–4 The TAH experience in adolescents is increasingly relevant given the increasing lifetime prevalence of congenital heart disease, especially complex congenital heart disease,⁵ and the ongoing Syncardia 50 cc TAH clinical trial (NCT02459054).

All children ≤21 years of age who received the Syncardia TAH between May 2005 and May 2015 were identified via the Syncardia TAH database (Table 1). Forty-three patients received a TAH during the study time period. The devices were placed at 30 institutions in eight countries. The majority of devices were placed in the United States (67%) with 34 (80%) placed after May 2010. Patients were predominately male (65%) and had a median age of 19 years of age with the youngest patient being 9 years of age. The most common diagnosis was dilated cardiomyopathy (DCM; 42%) followed by transplant rejection (19%) and congenital heart disease (16%). Limited data were available regarding the primary congenital heart diagnosis in six of the seven patients. The primary diagnoses for the congenital patients were as follows: s/p Fontan (2) (anatomic diagnosis unknown), Ebstein’s anomaly (1), atrioventricular canal defect (1), congenitally corrected transposition of the great arteries (2). The lesions associated with the primary diagnosis and surgical history were not contained within the database. Two patients (5%) were converted to a TAH after previous left ventricular assist device (LVAD) placement. The timing and reason for conversion relative to the LVAD were not contained within the database.

Table 1.: Characteristics of all Patients ≤21 Years (n = 43) Implanted with a Syncardia Total Artificial Heart Between May 2005 and May 2015

The patients were supported for a total of 5,757 days with a median patient support time of 63 days. The majority of patients were supported with a TAH for ≥90 days with the longest patient supported for a total of 979 days. Competing outcomes are shown in Figure 1. The number of patients experiencing a positive outcome (transplant or alive on device) at 60, 90, and 120 days were 30 (70%), 27 (63%), and 25 (58%), respectively. The majority of the mortality was experienced early after implant as 90 day conditional survival was 89% (16/18). Successful bridge to transplantation varied by diagnosis. Seventy five percent of patients with DCM were bridged to transplant whereas only 25% of patients with heart transplant rejection were transplanted (Fisher’s exact test, DCM versus transplant rejection; p = 0.03). Of the six transplant rejection patients who received a TAH and experienced mortality, early attrition was high as two died within a week and another two died at postoperative day 32 and 36. Of the two Fontan patients, one was supported to transplant after 61 days and the other died on postoperative day 110.

Figure 1.: Competing outcomes analysis for pediatric patients supported with a TAH. Outcomes at 60 days (dashed black line) are listed. TAH total artificial heart.

Thirteen patients (30%) were supported with the portable Syncardia Freedom driver for a total of 2,494 days. The median support duration on the Freedom driver was 146 days with a range of 1–939 days. Hospital discharge information was available for the nine patients supported with the Freedom driver in the United States. Six (66%) of the nine patients were discharged home and all nine patients supported with the Freedom driver in the United States were transplanted. Three of four (75%) patients supported with the Freedom driver outside of the United States were transplanted.

The current study demonstrates children and adolescents supported with the TAH have survival rates that are similar to adults supported with the TAH or biventricular assist devices.^1,6–7 Furthermore, a number of children were discharged home and successfully transplanted while supported on the portable Freedom driver. The early patient attrition with excellent late device survival and diagnosis-specific mortality suggests patient selection may be further optimized to improve clinical outcome. This analysis was limited by the lack of patient-specific data (clinical status at implant, baseline end organ function, congenital heart disease diagnosis/severity, etc) within the Syncardia patient database and we suspect many of these characteristics may be as important as diagnosis in predicting patient outcome. A majority of these adolescent and young adult cases were successfully supported by the TAH 70 cc device but the pediatric patient population that can benefit from this technology has been limited due to the large footprint of the device. The development of the 50 cc TAH has increased the number of children who may benefit from TAH support. Future collaboration among pediatric and adult TAH centers will enhance perioperative expertise and help to optimize patient selection and clinical outcomes.