Abstract 18026: Viscous Impeller Pump (VIP™) for Fontan Cavopulmonary Assist: Performance at Neonate and Infant scale
Background: The anatomic and physiologic constraints for mechanical cavopulmonary assist may differ in neonates and infants than compared to adults with failing Fontan circulations. Among these are small vessel size and risk of elevated pulmonary resistance. This goal of this study is to assess performance capability of a viscous impeller pump (VIP) at a scale and pressure (0-30 mmHg) necessary to power a Fontan circulation in infants and neonates.
Methods: A computational model of a total cavopulmonary connection (TCPC) was constructed at neonate/infant dimensions: SVC/IVC dia 11 mm; branch PA dia 9.5 mm. A biconical disk-shape impeller was designed: 9.9 mm diameter, 1,6 mm hub (∼ 5French), and 6 surface vanes (1.5 mm max height). Computational fluid dynamics was used to estimate hydraulic performance and shear stress across a range of conditions. For correlation, univentricular Fontan mock circulatory loop hydraulic studies and hemolysis assessment (bovine blood) were performed using an identical impeller and conduit.
Results: A simple, single impeller, VIP augments flow simultaneously in all 4 limbs of the TCPC at neonatal scale. The pump is not obstructive to flow at any speed, including when non-rotating. Pressure rise of 6, 16, and 38 mmHg (above Fontan venous pressure) is generated at a flow of 1 L/min at 3, 5, and 11K RPM respectively. At highest speed (12.5K RPM), maximal shear rate is only 160 Pascal (clinical threshold < 300 Pascal), predicting low hemolysis. Observed hemolysis is excellent (plasma free hemoglobin mean 11.4 mg/dl/hr, peak 20 mg/dl/hr over 6 hours at 9K RPM) with a Normalized Index of Hemolysis of 0.07 g/100L.
Conclusions: A VIP can augment Fontan cavopulmonary flow at neonate and infant scale in the proper pressure/flow range and with low risk of hemolysis. Surface vane structure is necessary for performance against increased pressure head. Percutaneous transvenous cavopulmonary assist holds promise to stabilize infants and children with elevated systemic venous pressure and low cardiac output after stage-2 or -3 Fontan repair. It may also serve as a bridge-to-Fontan by temporarily biventricularizing the circulation, compressing surgical staging, and resolving serious problems inherent in the existing staged palliative approach.
- © 2010 by American Heart Association, Inc.