Investigation of Hemocompatibility of Rotary Blood Pumps: The Case of the Sputnik Ventricular Assist Device

The hemocompatibility of Sputnik rotary blood pumps of the first and second generation (Sputnik-1 and Sputnik-2) was studied using numerical simulation. The influence of the flow geometry on scalar shear stresses (SSS), the residence time, and the volume of recirculation zones was determined. Volume fractions of SSS were obtained for the threshold stress levels of 9, 50, and 150 Pa at a fixed pump speed of 8000 rpm (mean flow rate, 4.5 L/min; pressure, 80 mm Hg). At all selected threshold stress levels, the elevated SSS volumes for the first-generation rotor pump were found to exceed those for the second-generation pump. Thus, the latter has a lesser effect on blood cells. The average residence time was found to be 39 and 29 ms for the Sputnik-1 and Sputnik-2 pumps, respectively; the respective recirculation zone volumes were 4.36 and 1.72 mL. The lesser volume of recirculation zones for the second-generation rotor pump reduces the probability of formation of stagnation zones and, therefore, the probability of clotting. The simulation results showed that upgrading the design of the Sputnik rotor pump had a positive effect on its hemocompatibility.