Motor current waveforms as an index for evaluation of native cardiac function during left ventricular support with a centrifugal blood pump

Control of ventricular assist devices (VADs) for native heart preservation should be attempted, and it could be one strategy for dealing with the shor tage of donors in the future. In the application of a nonpulsatile blood pu mp for ventricular assistance from its apex to the aorta, the bypass flow a nd hence motor current of the pumps change in response to the ventricular p ressure change. Utilizing these intrinsic characteristics of the continuous flow pumps, this study investigated whether or not motor current could be used as an index for continuous monitoring of native cardiac function. In S tudy 1, a centrifugal blood pump (CFP) VAD was installed between the apex a nd descending aorta of a mock circulatory loop. In this model, a baseline w ith a preload of 10 mm Hg, afterload of 40 mm Hg, and left ventricular (LV) systolic pressure of 40 mm Hg was used. The pump rpm were fixed at 1,300, 1,500, and 1,700, and LV systolic pressure was increased up to 140 mm Hg by a step of 20 mm Hg while observing the changes in LV pressure, motor curre nt, pump flow, and aortic pressure. In Study 2, in vivo experiments were pe rformed using 5 sheep. A left heart bypass model was created using a centri fugal pump from the ventricular apex to the descending aorta. The LV pressu re was varied through administration of dopamine while observing the change s in LV pressure, pump flow, motor current, and aortic pressure at 1,500 an d 1,700 rpm. An excellent correlation was observed both in vitro and in viv o studies in the relationship between motor current and LV pressure. In Stu dy 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1,300, 1,5 00, and 1,700 rpm, respectively. In Study 2, they were 0.90 (Animal 1), 0.8 2 (Animal 2), 0.89 (Animal 3), 0.93 (Animal 4), and 0.70 (Animal 5) respect ively for 1,500 rpm, and 0.94 (Animal 2), 0.85 (Animal 3), 0.94 (Animal 4), and 0.89 (Animal 5) respectively, for 1,700 rpm. The relationship between motor current and pump flow and LV pressure showed an unstable correlation in an in vivo study. These results suggest that motor current amplitude mon itoring could be useful as an index for the control of VADs for native hear t preservation.