Author + information
- aDivision of Pediatric Cardiology, Department of Pediatrics, Stollery Children’s Hospital, University of Alberta, Edmonton, Canada
- bDivision of Cardiac Surgery, Department of Surgery, University of Alberta, Edmonton, Canada
- ↵∗Address for correspondence:
Dr. Jennifer Conway, Department of Pediatrics, Stollery Children’s Hospital, University of Alberta, 8440-112 Street Northwest, 4C2, Edmonton, Alberta T6G 2B7, Canada.
The use of ventricular assist devices (VADs) in the pediatric population continues to gain interest among clinicians as an alternative to extracorporeal membrane oxygenation (ECMO) for temporary circulatory support (TCS). In the pediatric population, extracorporeal membrane oxygenation (ECMO) has been the traditional method of TCS whereas durable VADs have been reserved for longer-term support. The interest in the use of temporary VAD support in pediatrics has grown likely from the ability to evaluate for recovery, assess the neurologic status and potential for decreased complications, and determine treatment options without the time constraints of ECMO. Despite the potential advantages, the use of TCS with VAD has lagged behind the use of long-term VADs, likely a reflection of the limited published experience of single case reports or small case series (1–3) and the need for central cannulation for most of the devices in pediatrics. For these reasons, further studies reporting the outcomes of TCS with VAD compared with ECMO are important to determine the optimal treatment strategy.
In this issue of the Journal, Yarlagadda et al. (4) reported a retrospective propensity score (PS)–matched study using data from the Organ Procurement and Transplantation Network that compares outcomes in children undergoing bridge to heart transplantation (HT) with a TCS device or ECMO. Supporting the increased interest in this field, the authors found that the number of TCS devices increased dramatically during the study period, from <3 per year before 2011 to 50 in 2015. Overall, 164 patients underwent PS matching with 82 patients in the ECMO and TCS cohorts, respectively. The study found that the support duration was longer and survival to transplant better in the TCS cohort compared with the ECMO cohort, translating into a 2-fold higher waitlist survival, and a modest 90-day reduction in pre-transplant mortality (45% ECMO, 39% TCS) with no significant difference in post-HT survival. Importantly, this study is the largest to date and first to suggest that patient survival is superior with TCS devices compared with ECMO.
The survival benefit to TCS with VAD over ECMO seen in this study may be due to a variety of mechanisms. Several different VAD pumps exist including the CentriMag and PediMag (Thoratec, Pleasanton, California), Maquet Rotaflow (DataScope/Maquet, Rastatt, Germany), Impella (Abiomed, Danvers, Massachusetts), and TandemHeart (CardiacAssist, Pittsburgh, Pennsylvania). Each of these devices varies in terms of mechanical composition and potential configuration during implantation with unique advantages and disadvantages. Namely, the CentriMag and PediMag are magnetically levitated with no bearing or seals with the added benefit of potentially less thrombus formation (5). Another potential source of complication seen with ECMO can arise from the oxygenator required to provide respiratory support. In contrast, VAD circuits can be utilized with or without an oxygenator, thus in cases where an oxygenator is not required, a benefit may be seen with VAD support over ECMO.
Support duration was significantly longer for TCS devices compared with ECMO (median 19 days vs. 6 days; p < 0.001) in this study. Despite the significantly longer bridge duration, a similar number of patients remained on support at the time of transplant (ECMO 54% vs. TCS 68%; p = 0.25) with no significant difference in post-HT survival. This observation implies that early identification of patients who may benefit from TCS coupled with early initiation of support may lead to increased survival to transplant and ultimately improved outcomes for children faced with end-stage heart failure awaiting heart transplantation. Although the field has traditionally categorized many of these pumps as short term the reality is that a number of them are being used for longer-term support, as highlighted by the 25th to 75th interquartile range of support for the CentriMag-PediMag patients of 12 to 62 days.
Although the results of the current report are encouraging, there are several points that warrant further discussion. First, the survival rate post-HT after bridging with ECMO support in this study is higher than previously reported and in fact is no different than those on TCS (6). This is likely related to the PS-matching algorithm, where very ill ECMO patients were less likely to be PS matched to a similarly ill TCS patient. Therefore, the general conclusion that there is no difference in post-transplant outcomes on patients supported with a temporary VAD compared with ECMO would be incorrect and needs to be taken into the context of the patients included in this study. Furthermore, the indication for TCS with VAD or ECMO in this study was isolated to bridge to HT. TCS with VAD has been used for a variety of indications in the pediatric patient, however, given the narrow inclusion criteria we are limited in making generalizations about these devices for broader application (7). Finally, although the present study provides support to the feasibility of TCS as a bridge to HT with superior survival compared with ECMO, very little is known about the morbidity encountered by these patients. There has been no comparison to date between ECMO and TCS with respect to the adverse events encountered and the impact they have on outcomes. Thus, our enthusiasm for a broader application of TCS support as a bridge to HT must be tempered pending further analysis of safety outcomes.
The use of TCS with VAD has already gained wide adoption with adults, yet remains a relatively novel approach in the pediatric population (8). As with any emerging therapy, defining criteria for optimal patient selection poses a significant challenge. The lack of clear safety outcomes remains the largest barrier to expansion of the use of short-term VAD support in the pediatric population. The PEDIMACS (Pediatric Interagency Registry for Mechanical Circulatory Support) registry collects data on short-term VADs including survival and adverse events. Emerging analysis from the PEDIMACS registry will help to better elucidate factors that may influence survival along with incidence of adverse events during short-term VAD support to develop optimal patient selection criteria.
The current report provides the first demonstrable survival advantage to TCS devices over ECMO for children as a bridge to HT. The results of the present report increase our confidence surrounding the use of TCS devices as a bridge to HT in the pediatric population and suggest that temporary VAD support is now emerging as a tool for managing end-stage heart failure refractory to medical therapy. Although this study lends support to the use of temporary VAD for bridge to HT, emerging analysis of registry data will provide the comparative safety profiles of VAD and ECMO. Although this study included only children undergoing bridge to HT, further study is required to evaluate the use of TCS devices in a broad category of indications. Use of short-term VAD support has expanded dramatically in the pediatric population and enthusiasm for this technique will likely continue to grow. Ongoing refinement of TCS devices will continue to promote their increased utilization, expanding the therapeutic options for children with end-stage heart failure, and ultimately leading to improved outcomes and reduced mortality.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Contrafouris C.A.,
- Chatzis A.C.,
- Kanakis M.A.,
- Azariadis P.A.,
- Mitropoulos F.A.
- Kumar T.K.S.,
- Ballweg J.,
- Knott-Craig C.J.
- Yarlagadda V.V.,
- Maeda K.,
- Zhang Y.,
- et al.
- Dipchand A.I.,
- Mahle W.T.,
- Tresler M.,
- et al.
- Conway J.,
- Al-Aklabi M.,
- Granoski D.,
- et al.
- Stretch R.,
- Sauer C.M.,
- Yuh D.D.,
- Bonde P.