HTX in a single ventricle cyanotic patient with a VAD can be challenging. Besides the presence of vascularized chest-wall-based adhesion from the chronic cyanotic state, adhesions induced by an intracorporeal VAD, platelet dysfunction from a chronic continuous flow VAD and renal insufficiency, and coagulation abnormalities from chronic cyanosis can predispose the patient for a post-operative hemorrhage [6, 7]. The bleeding susceptibility is further increased when the operation needs to be performed on bivalirudin as there is no reversal agent for it.

Bivalirudin is a direct thrombin inhibitor. It does not activate platelets and is used in type II HIT where there is an immune-based activation of platelets by heparin leading to arterio-venous thrombosis [4]. Thus, it is used as a systemic anticoagulant for the conduct of CPB in patients with HIT [1, 3]. Unlike heparin, there is no reversal agent for it, and it is predominantly cleared by plasma proteases (80%), with renal clearance (20%) having a smaller contribution [1]. The half-life of bivalirudin is 25–30 min. However, this can be substantially prolonged to 60 to 180 min with diminishing renal function [4]. After the conduct of CPB, bivalirudin is expected to clear in two-half lives, about 1 h after stopping the infusion with a normal renal function [1]. An alternative to bivalirudin is argatroban, another direct thrombin inhibitor. It is less preferred in HTX due to a less predictable dose response, its dependence on hepatic clearance which may be impaired due to congestion from right ventricular dysfunction after an HTX, longer half-life, and no option for hemofiltration for clearance [2].

Compared to unfractionated heparin, where its anticoagulant effect can be immediately reversed with protamine, bivalirudin has no reversal agent. When used for CPB, its effect ceases by proteolytic metabolism in the plasma and renal excretion when the infusion is stopped. Hence, it is recommended to discontinue the bivalirudin infusion about 15 min before weaning off CPB to allow for the proteolytic metabolism and renal excretion to be enhanced by modified ultrafiltration after termination of CPB to achieve hemostasis [1]. In our case, with extensive vascularized raw surface area causing signification bleeding, the possibility of deficient plasma proteases, impairment of the coagulation system from the chronic cyanosis, platelet dysfunction from chronic renal insufficiency and a continuous flow VAD, and the inability to perform modified ultrafiltration due to significant volumes changes from the bleeding, the bivalirudin effect persisted causing a serious feedback cycle of ongoing coagulopathy. If the rate of bleeding is slow, time can be given for the bivalirudin effect to wear off by enzymatic degradation and can be further enhanced by ultrafiltration. This strategy was followed after HTX in a cyanotic pediatric patient without an intracorporeal VAD and it took 12 h to achieve satisfactory hemostasis [2]. In our patient, the profuse non-surgical bleeding was controlled by tightly packing the pericardial space with a kaolin-impregnated, factor XII activating locally hemostatic gauze (QuickClot Z-fold), and the patient was transitioned to central VA ECMO with a hemofiltration device spliced in for removal of the bivalirudin. Given the coagulopathy, the ECMO was run without any anticoagulant, and with this, the bleeding rate was manageable, and the patient could be safely transported to the pediatric cardiovascular intensive care unit and kept normothermic, and satisfactory hemostasis was achieved in 8 h. The allograft and the lungs were protected from damage secondary to transfusion of large volumes of blood products and are known to be deleterious after an HTX [8]. There is always some degree of right ventricular dysfunction after an HTX which can exacerbate bleeding by central venous pressure elevation, and this was negated by VA ECMO support. In addition, there was renal protection due to stable hemodynamics with VA ECMO use.

In the published literature, five heart transplants on bivalirudin have been reported with two being pediatric transplants [3]. None of the transplants was done in a cyanotic patient with an intracorporeal chronic VAD. In most, the bleeding was manageable and was supported with blood product transfusion, and hemofiltration until the bivalirudin effect wore off.