Detection and Avoiding Ventricular Suction of Ventricular Assist Devices

Abstract

Continuous flow blood pumps, such as axial flow and centrifugal pumps, have been gaining interest as circulatory devices for total artificial hearts (TAHs) and a biventricular assist device (BVAD) because of their smaller size and simpler structure compared to pulsatile pumps. However, continuous flow pumps are more prone to suction of the left ventricle than pulsatile pumps are. Sudden increases in flow rate to meet changes in physiological demand, especially in the left pump, often cause ventricle suction. In this study, a control algorithm to prevent suction from occurring in the left ventricle by controlling the rotational speed of the right pump, instead of reducing the cardiac output of the left pump, was developed and investigated. The method was tested in acute animal experiments with calves. The results indicate that this proposed method is capable of preventing suction and could simultaneously maintain circulatory control. A key advantage of this control system is that flow rates can be maximized while avoiding ventricle suction conditions particularly when the circulatory system is unstable such as in a the first few days after operation.

Classification of Physiologically Significant Pumping States in an Implantable Rotary Blood Pump: Effects of Cardiac Rhythm Disturbances

“…This coefficient would be found by examining pump behavior in response to changes in the cardiovascular system during a postoperative calibration phase-an undesirable requirement. Tanaka et al (8) propose a suction detection mechanism based on a single index (I s = LPF{(I mean − I min )/(I max − I min )}; LPF = low-pass filter) similar to the N profile parameter employed here. However, no discussion is made with regard to interanimal variation in the index.…”

“…The flat H-Q characteristic means that pump flow is particularly sensitive to differential pressure variation, and is the result of high impeller radial off-flow and relatively low impeller to housing clearances (<50 µm), which reduces flow leakage. Therefore, as evidenced by comparison with other studies (4,8,12), the shape of the speed waveform is inherently different and more informative than that obtained from other pumps. These waveform characteristics were exploited to detect a range of pumping states with a level of accuracy surpassing that of most previous work in this area.…”

“…For example, Yuhki et al (5) considered a waveform deformation index (WDI) based on a spectral analysis of the speed signal; Endo et al (6,7) investigated the symmetry in the current amplitude; and Voigt et al (12) used the amplified, differentiated current signal as a suction indicator. Most groups, however, fall short of developing algorithms to automate the detection of these abnormal pumping states, and thus do not provide a statistical assessment of the success of their methods (5)(6)(7)(8). The studies that have presented numerical results (4,11,12), however, provide a valuable platform against which a comparison with the current study can be made.…”

“…Experimentation in the transition of pumping states has previously been investigated by a number of groups (4)(5)(6)(7)(8)(9)(10)(11)(12). Various groups (9) employ invasive sensors to aid in this process (e.g., to measure the pump flow signal).…”

“…However, it is desirable to avoid their use due to a considerable reduction in system reliability and increased cost. Research efforts have thus predominantly involved waveform analysis of the noninvasive pump motor feedback signals (current or speed), from which a number of useful indices have been derived by various authors (5)(6)(7)(8)(10)(11)(12) as indicators of either over-or underpumping of the heart. For example, Yuhki et al (5) considered a waveform deformation index (WDI) based on a spectral analysis of the speed signal; Endo et al (6,7) investigated the symmetry in the current amplitude; and Voigt et al (12) used the amplified, differentiated current signal as a suction indicator.…”