Development of a new method for assessing the cardiac baroreflex: response to downward tilting in patients with diabetes mellitus.
OBJECTIVE
To investigate the clinical value of a new non-invasive method for assessing baroreflex sensitivity using downward tilting.


METHODS
34 patients with diabetes mellitus, mean (SD) age, 53.6 (11.8) years.


METHODS
Arterial blood pressure and ECG were recorded simultaneously while the 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 degrees /s (downward tilting baroreflex sensitivity test, DT-BRS). A beat to beat systolic blood pressure increase associated with a corresponding lengthening of the RR interval was noted during downward tilting. Baroreflex sensitivity 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 interval during downward tilting was highly correlated with Phe-BRS (r = 0.83, p < 0.0001). Both DT-BRS and Phe-BRS were correlated with the high frequency (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) during upright tilting (p < 0.005). DT-BRS and Phe-BRS were also correlated with 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 determining baroreflex sensitivity and may be a useful index of reflex cardiac vagal and sympathetic function in patients with diabetes mellitus.
Nakagawa
M
M
Department of Laboratory Medicine Oita Medical University, 1-1 Idaigaoka, Hasama, Oita 879-5593, Japan. mikinak@oita-med.ac.jp
Takahashi
N
N
Ooie
T
T
Yufu
K
K
Hara
M
M
Watanabe
M
M
Nobe
S
S
Yonemochi
H
H
Katsuragi
I
I
Okeda
T
T
Sakata
T
T
Saikawa
T
T
D000328:Adult; D000368:Aged; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002316:Cardiotonic Agents; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D005260:Female; D006334:Heart Function Tests / Q000379:methods / Q000592:standards; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010656:Phenylephrine; D012680:Sensitivity and Specificity; D018667:Tilt-Table Test / Q000379:methods* / Q000592:standards
D002316:Cardiotonic Agents; D010656:Phenylephrine