The EXCOR Pediatric VAD can provide a bridge to transplant for children with SV anatomy or physiology, albeit less successfully than in children with BV. In this small series, results are better in patients with SCPC and TCPC. VAD support for patients with shunted sources of pulmonary blood flow should be applied with caution.

The anti-Factor Xa assay correlated better with heparin dosing than activated clotting time or activated partial thromboplastin time. Activated clotting time has a poor correlation to heparin doses commonly associated with extracorporeal membrane oxygenation. In pediatric extracorporeal membrane oxygenation, anti-Factor Xa assay may be a more valuable monitor of heparin administration.

Although definitive source identification remains elusive, we believe that the majority of bleeding arises in the small bowel, possibly due to angiodysplasias, similar to the pathophysiology encountered in patients with aortic stenosis and GI bleeding. As we move toward wider use of the HMII and other axial continuous-flow devices in both bridge-to-transplant patients and for destination therapy, more studies will be necessary to understand the mechanisms of this obscure GI bleeding and develop treatment strategies to minimize its development.

In our small patient sample with normal aortic valves, we showed the LVOT shape is usually not round and frequently, elliptical. Incorrectly assuming a round LVOT underestimated the ALVOT-3Dplan and consequently the AVA by 15%. Investigating the LVOT in aortic stenosis is warranted to evaluate whether RT3DE may improve measurement of AVA.