Heart Rate Information Flow Specifically Assesses Complex Cardiovascular Communication Alterations due to Multiple Organ Dysfunction Syndrome

Background: The multiple organ dysfunction syndrome (MODS) as a consecutive failure of several organs has still an unexpected high mortality of more than 50%. Autonomic dysfunction as a feature of an impaired interorgan communication might facilitate the development of MODS („uncoupling“ of organs in MODS) and has prognostic implications. This complex interorgan communication is reflected by the information flow of heart rate fluctuations. The present study is aimed at the identification of specific communication deficits based on the time scale of information flow. Methods and Results: 36 MODS patients (28 days lethality: 26 survivors and 10 non-survivors) and 50 controls were assigned to this study and a 24-h ECG was recorded. 24-h, as well as 6-h sequences of the recordings during awakeness and sleep were analyzed and measures of short-term and long-term information flow of the heart rate fluctuations (HRF) according to the heart rate variability (HRV) task force were assessed. Due to MODS we found reduced information flow over the heart beat period, but increased information flow over all longer time scales up to 1000s. In the HF band filtered heart rate series the information flow was increased during awakeness, but reduced during sleep. The 28 day prognosis based on the information flow parameters of HRF was significantly better than that based of the task force HRV. Conclusions: These results indicate: 1) uncoupling of the sinus node from any modulations, 2) distinguished relevance of the vagally mediated communication, and 3) restricted long-time complex communication, reflecting the complete system of autonomic and humoral mechanisms. Consequently, the information flow of the heart beat series over different time scales specifically reflects the altered complex communication and might specify the analysis of „uncoupling“ of organs due to MODS. The better prognosis of the patients supports our hypothesis that specific communication measures such as information flow better assesses the complex physiological systems than standard measures in the time and frequency domain.