Analysis of LVAD log files for the early detection of pump thrombosis

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Abstract
Nowadays, one standard therapy for advanced heart failure is the implantation of left ventricular assist devices (LVAD). The LVAD is a mechanical pump, which supports the heart to pump blood to the rest of the body. However, there are serious complications including pump thrombosis. Pump thrombosis is a formation of blood clot inside the LVAD pump, which can result in pump stop and worst case leads to death. To increase the probability of success in thrombosis treatment, an early diagnosis of pump thrombosis is important. An often mentioned indication for pump thrombosis is an increase in pump current. For this reason, this paper analyzes the log files of LVAD patients. Four algorithms were developed and applied to the measured pump current with the aim to detect an increase in pump current earlier as it is actually done by the physician. The first algorithm incorporated different absolute thresholds. In addition, the second algorithm considered the circadian fluctuation to estimate suitable thresholds. The third and fourth algorithms applied a relative threshold based on the standard deviation of the pump current. The third algorithm applied a standard deviation, which is calculated for each patient and each hours of the day individually. The fourth algorithm used for each patient an individual average standard deviation. This paper shows the results of 5 pump thromboses curves analyzed with the different algorithms each. Using the fourth algorithm, a pump current increase was detected approximately 4 days earlier compared to the “High Watt” alarm caused by the LVAD controller.

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