Issn Print: 1058-2916

Publication Date: 2001/03/01


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ESTIMATION OF CARDIAC FUNCTION IN RECIPIENTS OF A CONTINUOUS FLOW VENTRICULAR ASSIST DEVICE FOR BIOLOGICAL SIGNALS WITHOUT SENSORS

M. Oshikawa; Y. Taenaka; E. Tatsumi; T. Tsukiya; T. Nishinaka; Y. Takewa; H. Ohnishi; H. Takano

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Excerpt

In our previous report, we proposed an original control strategy for an implantable continuous flow pump (CFP) by analyzing motor current amplitude without specific sensors for biological signals and could detect the transition point from partial to total assist (t-point), and the starting point of sucking of the ventricle (s-point). The purpose of this experiment is to investigate the feasibility of estimating the cardiac function by monitoring the pump speed and current amplitude at the t-point and the s-point in an in-vitro mock circulation. In this study we devised a special mock circulation which consists of a pulsatile VAD simulating the left ventricle, two reservoirs, one was the left atrium and the other was the vascular bed, and a CFP as a left ventricular bypass. Motor current and pump speed was monitored and the index of current amplitude (ICA) was calculated as the difference of maximum and minimum value of current amplitude divided by simultaneous mean value. Pump speed was changed from 500 rpm to 2500 rpm and the changes of aortic pressure, left ventricular pressure, left atrial pressure, cardiac output, pump flow and ICA were monitored. This process was repeated in different conditions by changing preload, afterload and contractility of the left ventricle, and the results were summarized in the following table.
These data demonstrated that the observation of the behavior of the ICA value and the pump speed at the t-point and the s-point became a useful indicator to distinguish the altered condition of the preload, afterload and contractility, and to assess the current status of the cardiac function compared with the basal status. We conclude that it is feasible to estimate cardiac function of patients underwent circulatory assist with a CFP without specific sensors by monitoring changes of motor current amplitude and pump speed.
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