CIRCADIAN PUMP FLOW VARIATION IN ROTARY BLOOD PUMP RECIPIENTS

Aim: Overstimulation of the sympathetic system is typical for end-stage heart failure patients. For this reason the physiological circadian hemodynamic variability is diminished. Aim of this study was to investigate the circadian variability and long-term trends of the pump flow in the first 22 weeks after rotary blood pump (RBP) implantation. Methods: In 20 RBP patients, estimated pump flow and speed signals, sampled every 15 minutes, were collected. The circadian variation in the pump flow signal was quantified by fitting a sine wave to each day's pump flow signal and by determination of its amplitude. For the long-term trends, mean pump flow was calculated for each day. Results: Mean hospital stay after implantation was 36 + or - 10 days. Circadian variation in pump flow increased significantly during this first 5 weeks from a daily variation of 0.42 + or - 0.16 L/min to 0.63 + or - 0.25 L/min. After hospital discharge the mean circadian variation did not change significantly and was between 0.49 to 0.62 L/min. Mean pump speed did not change substantially throughout the whole observation period (range: 2760 to 2810 rpm), mean pump flow was between 5.2 and 5.5 L/min. Conclusions: Circadian pump flow variability increased in the first 5 weeks after RBP implantation. This could indicate post-operative improvement of the cardiovascular function, which remains quite stable afterwards. However, it must be noted that the circadian rhythm could also be influenced by the daily physical activity which increases especially around the initial hospital discharge.