Objective-To investigate the clinical value of a new non-invasive method fo
r assessing baroreflex sensitivity using downward tilting.
Patients-34 patients with diabetes mellitus, mean (SD) age, 53.6 (11.8) yea
Design-Arterial blood pressure and ECG were recorded simultaneously while t
he patients were on a tilt table. After 20 minutes at a 70 degrees upright
tilt, the patients were returned to the supine position at a speed of 3.2 d
egrees /s (downward tilting baroreflex sensitivity test, DT-BRS). A beat to
beat systolic blood pressure increase associated with a corresponding leng
thening of the RR interval was noted during downward tilting. Baroreflex se
nsitivity was also assessed using the conventional method of an intravenous
injection of phenylephrine (Phe-BRS). Heart rate variability was analysed
during rest and tilting.
Results-The slope of the regression line for systolic blood pressure v RR i
nterval during downward tilting was highly correlated with Phe-BRS (r = 0.8
3, p < 0.0001). Both DT-BRS and Phe-BRS were correlated with the high frequ
ency (HF) component of resting heart rate variability (p < 0.005) and with
the ratio of the low frequency to the high frequency component (LF/HF) duri
ng upright tilting (p < 0.005). DT-BRS and Phe-BRS were also correlated wit
h the difference between rest and tilting values of HF and LF/HF (p < 0.005
Conclusions-DT-BRS provides a physiological, non-invasive method for determ
ining baroreflex sensitivity and may be a useful index of reflex cardiac va
gal and sympathetic function in patients with diabetes mellitus.