Cardiac Transplantation and Mechanical Support for Functional Single Ventricle

Abstract

Cardiac transplantation has played a pivotal role in the therapeutic algorithm for anatomically uncorrectable congenital heart disease, particularly the failing single ventricle. The historical evolution from Kantrowitz to Bailey and beyond challenges the application of this scarce resource to complex cardiac malformations in the presence of physiologic and circulatory failure. While selection of cardiac transplantation as primary therapy for hypoplastic-left heart syndrome is currently rare, the failing single ventricle in various stages of the Fontan pathway is increasingly considered for this therapy. The results of transplantation in this complex situation have progressively improved and now approached the late outcomes for other conditions. Mechanical circulatory support for the failing single ventricle has recently carried infants and children to successful transplant. The development of miniaturized continuous flow pumps offers the hope of major new avenues of successful circulatory support for single ventricle patients.

The use of the Berlin Heart EXCOR in patients with functional single ventricle

“…The availability of pumps with stroke volumes as small as 10 mL, transparent chambers that allowed for direct inspection for thrombus, and the ability to replace pumps at the bedside have led to a considerable increase in the use of this device in the pediatric population since 2000. 6,11,15,17 The FDA approved the device in patients less than 21 years of age in December 2011, and at the time of writing, more than 1200 EXCOR Pediatric implants had taken place in more than 30 countries (personal communication from Berlin Heart, Woodlands, TX). Cardiac transplantation and mechanical support have always played a role in the treatment of CHD, but the small case numbers compared with adults has limited evaluation of the outcomes.…”

“…Pediatric transplantation represents only about 10% of total heart transplants performed worldwide, and, of those, only 5% to 10% are in patients with SV. 6,19 Children with SV treated with mechanical assistance represent an even smaller subset of patients, and the literature on this experience is largely limited to single-center case reports. 5,6,[20][21][22][23][24][25] Use of VAD support in a patient with a single ventricle was first reported in 2005 in an 25-yearold man after a Fontan operation.…”

“…27 Longer waiting times for patients listed, small size, and sensitization from previous operations with bioprosthetic tissue may lead to earlier consideration of mechanical assistance in this population, who often present with rapid circulatory collapse after compensated cardiac failure. 6,28 The small number of patients treated in this review precludes a detailed statistical analysis; however, certain practice patterns and outcomes can begin to be described. Although caution is recommended when considering the use of VAD support in a patient with SV, it is clear from this review that patients can be bridged successfully after a superior caval anastomosis or total cavopulmonary connection.…”

“…The frequency of complications such as bleeding and infection, as well as the inability to extubate or ambulate patients on ECMO makes it an inadequate therapy for patients needing more than a few days of support. [6][7][8] Mortality in children treated with ECMO as a bridge to cardiac transplantation is more than 50%, [8][9][10] and the subset of patients with single ventricular anatomy or physiology (SV) fare the worst. In a multiinstitutional review of more than 750 children supported on ECMO as a bridge to transplant, congenital heart disease (CHD) was the most common indication for listing (64%) and, of this group, 30% were SV (231 patients).…”

Changing Indications for Pediatric Heart Transplantation

“…32 Congenital heart disease itself has consistently been identified as a risk factor for early and midterm mortality after transplantation compared with patients with cardiomyopathy. 19,29,32,35,39,40,42,[92][93][94][95][96][97][98][99] The increased mortality occurs soon after transplantation and is likely the result of a combination of factors, including the debilitated state of the recipient, longer donor ischemic times, baseline renal insufficiency, a higher incidence of HLA-sensitized patients, and immune system dysfunction. In the Fontan patient, chronic hepatic congestion has been found to lead to fibrosis and ultimately cirrhosis.…”