ABSTRACT
There are several examinations to evaluate cardiac autonomic function. Autonomic neuropathy is a common complication of diabetes mellitus and is associated with increased mortality. Baroreflex sensitivity (BRS) is a marker for the ability to augment vagal activity. Several studies have shown that BRS is impaired in diabetes with autonomic neuropathy. The head-up tilt test is the most useful tool to diagnose the neurally mediated syncope. We have developed a new non-invasive method to evaluate the baroreflex using downward tilting (DT-BRS). In our previous study conducted in healthy volunteers and diabetic patients, we demonstrated a strong correlation between systolic blood pressure increase and corresponding RR interval lengthening during downward tilting, which yielded DT-BRS values that correlated well with the BRS value obtained by the phenylephrine method (Phe-BRS). Heart rate responses observed after both squatting and standing (squatting test) are assumed to be a simple and useful tool to assess autonomic activity. We reported that indices of the squatting test showed a significant correlation with BRS assessed by Phe-BRS in diabetes. DT-BRS and the squatting test may provide promising information for the assessment of reflex vagal activity in diabetes.
