Evaluation of real‐time thrombus detection method in a magnetically levitated centrifugal blood pump using a porcine left ventricular assist circulation model

Abstract

Pump thrombosis induces significant complications and requires timely detection. We proposed real‐time monitoring of pump thrombus in a magnetically levitated centrifugal blood pump (mag‐lev pump) without using additional sensors, by focusing on the changes in the displacement of the pump impeller. The phase difference between the current and displacement of the impeller increases with pump thrombus. This thrombus detection method was previously evaluated through simulated circuit experiments using porcine blood. Evaluation of real‐time thrombus detection in a mag‐lev blood pump was performed using a porcine left ventricular assist circulation model in this study. Acute animal experiments were performed five times using five Japanese domestic pigs. To create thrombogenic conditions, fibrinogen coating that induces thrombus formation in a short time was applied to the inner surfaces of the pump. An inflow and an outflow cannula were inserted into the apex of the left ventricle and the carotid artery, respectively, by a minimally invasive surgical procedure that allowed minimal bleeding and hypothermia. Pump flow was maintained at 1 L/min without anticoagulation. The vibrational frequency of the impeller (70 Hz) and its vibrational amplitude (30 μm) were kept constant. The thrombus was detected based on the fact that the phase difference between the impeller displacement and input current to the magnetic bearing increases when a thrombus is formed inside a pump. The experiment was terminated when the phase difference increased by over 1° from the lowest value or when the phase difference was at the lowest value 12 hours after commencing measurements. The phase difference increased by over 1° in three cases. The pump was stopped after 12 hours in two cases. Pump thrombi were found in the pump in three cases in which the phase difference increased by over 1°. No pump thrombus was found in the other two cases in which the phase difference did not increase. We succeeded in real‐time thrombus monitoring of a mag‐lev pump in acute animal experiments.

Innovative experimental animal models for real‐time comparison of antithrombogenicity between two oxygenators using dual extracorporeal circulation circuits and indocyanine green fluorescence imaging

“…The antithrombotic evaluation of pumps or oxygenators without anticoagulants has been reported previously 9,28,29 . In this study, no anticoagulant was used, except when inserting the cannula.…”

“…Furthermore, this model can reduce the cost, effort, and number of animals sacrificed based on the 3R approach for animal welfare 27 . In most animal experiments, a single ECMO circuit is attached to one animal, and the antithrombogenicity of the oxygenator is evaluated after the ECMO circuit is removed from the animal at the end of the experiment 6,17,28,29 . Therefore, the superiority or inferiority of the antithrombogenicity of the oxygenators is not determined until the two experiments are completed.…”

“…30 The antithrombotic evaluation of pumps or oxygenators without anticoagulants has been reported previously. 9,28,29 In this study, no anticoagulant was used, except when inserting the cannula. ACT was maintained for 80-100 s throughout the experiment to facilitate comparisons between devices.…”

Impact of volute design features on hemodynamic performance and hemocompatibility of centrifugal blood pumps used in ECMO

“…Flow losses and blood damage events in the volute of centrifugal blood pumps have been demonstrated and reported 52‐55 . Traditional volute design theory has also formally failed to effectively guide the design of centrifugal blood pumps 56 .…”

“…Researchers have observed, either by numerical simulations or experiments, flow losses and inverse pressure gradients within the volute 52,53 seriously affected hydraulic performance and blood compatibility of the blood pump. In clinical practice, researchers have observed thrombosis inside the volute 52,54,55 . Up to now, there are limited studies on the effect of blood pump volute design factors on blood pump hemocompatibility.…”