Mutual synchronization pattern as a complementary indicator of the short-term blood pressure – heart rate feedback regulation activity

We suggest a complementary indicator of the blood pressure – heart rate feedback regulation based on their synchronization pattern assessed by Hilbert transform. We determine the synchronization coefficient Sync as the fraction of time fragments where the standard deviation of the differences between instantaneous phases of blood pressure and pulse intervals are below a certain threshold. While BRS characterizes the intensity of the pulse intervals response to the blood pressure changes during observed feedback responses, the Sync likely indicates how often such responses are activated in the first place. Data from 95 tilt test records indicate that in both healthy subjects and patients with moderate autonomic dysfunction BRS and Sync are typically reciprocal suggesting that low intensity of the feedback responses characterized by low BRS is rather compensated by their more frequent activation indicated by higher Sync. In contrast, in diabetes patients with autonomic neuropathy BRS and Sync are positively correlated likely indicating the breakdown of this compensation in some of the diabetic patients. Therefore we suggest that Sync could be used as an additional indicator of the blood pressure – heart rate feedback regulation activity that is complementary to the widely used baroreflex sensitivity (BRS).