New squatting test indices are useful for assessing baroreflex sensitivity in diabetes mellitus

AIMS The heart rate (HR) responses after performance of the squatting and standing manoeuvre are thought to be a useful tool to assess autonomic neuropathy in diabetics. Our aim was to develop new simple squatting test indices and to analyse their applicability to the assessment of baroreflex sensitivity (BRS) in patients with diabetes. METHODS Twenty healthy volunteers (mean age 23.2 +/- 3.8 years) and 51 patients with diabetes (mean age 55.9 +/- 10.6 years) were enrolled in study 1 and study 2, respectively. Each subject stood for 3 min (basal period), then squatted down for 1 min (Sq) and stood up again for 1 min (St). In study 1, the squatting test was performed before and after pharmacological autonomic blockade. In study 2, we measured HR in each period and calculated the difference between basal HR and HRSq (DeltaHRSq) and between HRSt and HRSq (DeltaHRSt). BRS was also measured using the phenylephrine method in diabetic patients. RESULTS In healthy individuals during autonomic blockade, HR changes were mainly controlled by the vagal tone during squatting and by the sympathetic tone during standing. In diabetic patients, DeltaHRSq and DeltaHRSt positively correlated (r = 0.86, P < 0.0001) and both DeltaHRSq and DeltaHRSt significantly correlated with BRS (r = 0.66, P < 0.0001 and r = 0.61, P < 0.0001, respectively). CONCLUSIONS The new squatting test indices provide useful information for assessing autonomic neuropathy and for identifying diabetic patients at high risk of cardiovascular events.