Impact of Inflow Ratio on a Double-Inflow Cavopulmonary Assist Device

The Fontan circulation is a palliative treatment for univentricular heart disease but is prone to progressive hemodynamic failure. To address this, a novel cavopulmonary assist device (CPAD) with dual inlets from the superior and inferior caval veins was developed. This study examines how varying inflow ratios (IRs) affect the CPAD's hydraulic performance, hemocompatibility, and flow estimation accuracy. Hydraulic performance, represented by the pressure head-flow (H-Q) characteristics, was experimentally and numerically assessed at different IRs. Hemolysis was evaluated experimentally at the nominal operating point (4 L/min, 2,500 RPM) for IRs of 1:1 and 1:3 (n = 5). Additionally, hemocompatibility-related metrics were determined numerically. Furthermore, the robustness of conventional flow estimation methods, based on motor current, pump speed, and viscosity, under varying IRs was examined. In vitro and in silico results indicated low variations in both hydraulic performance (ΔH < 2.2 mm Hg) and hemolysis(22.4% in measured Normalized Index of Hemolysis [NIH]; 4.9% in predicted damage index [DI]) across all investigated IRs. The flow estimation model based on motor current, rotational speed, and fluid viscosity showed high accuracy regardless of the IR, with root mean square error (RMSE) less than 0.148 L/min and R ² greater than 0.99. The analyzed double-inflow CPAD performed reliably across the investigated IRs, supporting its suitability for a broad patient population and enabling precise flow monitoring.