Blood trauma potential of the HeartWare Ventricular Assist Device in pediatric patients

Mechanical circulatory support has become a standard therapy for adult patients with end-stage heart failure. For pediatric patients, technologic development lags behind with no currently approved implantable rotary blood pump. As an alternative, the HeartWare Ventricular Assist Device (Medtronic, Minneapolis, Minn), originally designed for adults, is increasingly used in pediatric patients. The aim of this multicenter study was to assess in silico, in vitro, and in vivo the blood trauma potential of this pump in pediatric application.

Clinical outcome and indicators for in vivo blood trauma were investigated retrospectively in 14 pediatric patients with the HeartWare Ventricular Assist Device (age 11.3 ± 4.8 years). Blood trauma mechanisms of the HeartWare Ventricular Assist Device were examined in silico and in vitro at an adult and pediatric operating point (5 L/min and 2.5 L/min at 2800 rpm and 2200 rpm, respectively). The flow was simulated by computational fluid dynamics and analyzed regarding flow structures, shear stresses, and washout. Hemolysis was assessed with pumps circulating bovine blood in a temperate flow circuit.

In the retrospective in vivo analysis, lactate dehydrogenase and D-dimer values were 1.5- and 3-fold elevated, respectively, compared with adult patients with the HeartWare Ventricular Assist Device. Major bleedings were observed in 42.9%, and suspected pump thrombosis and neurologic dysfunction were observed in 14.3% of all patients. In the pediatric conditions, simulations predicted elevated mechanical stress profile below 50 Pa, more stagnant flow field, and longer washout times within the pump. In vitro measurements revealed an increased normalized index of hemolysis (17.5 vs 8.2 mg/100 L; P = .0021).

The HeartWare Ventricular Assist Device, operated at lower speeds and flows, induces elevated blood trauma. Further studies are required to assess the clinical implications of these findings.