ABNORMAL CIRCADIAN VARIATION OF TOTAL VASCULAR TONE IN ELDERLY PATIENTS WITH ESSENTIAL-HYPERTENSION

Background: There is little information available on the circadian variation of total vascular tone in (TVT) elderly patients with essential hypertension. Therefore, the author studied the circadian variation of TVT in elderly subjects with essential hypertension as compared with normotensive subjects. Methods: The subjects consisted of four groups: a control group and patients with essential hypertension divided according to the three stages of the World Health Organization (WHO) classification. The patients with essential hypertension were diagnosed as such by ruling out secondary hypertension. To measure the blood pressure and the cardiac output concurrently and noninvasively, the author attached the subjects to an ambulatory blood pressure monitor and a cardiac output monitor, simultaneously, for a 24-hour period. The TVT, measured as total vascular resistance (TVR), was calculated as follows: [(mean blood pressure/cardiac index) x 1332 dyne/s/cm-5]. The TVR ratio was calculated as follows: [(each hourly value - the value at 2:00 AM)/the value at 2:00 AM] X 100. Results: The TVR ratio was significantly smaller during waking hours than during sleeping hours (P < 0.01). The TVR ratio during waking and sleeping hours was highest in the stage III subjects and decreased progressively in the stage II, stage I, and control subjects (P < 0.05, respectively). The value of the differences between the TVR ratio during sleeping hours and waking hours was highest in the control subjects and decreased progressively in the stage I, stage II, and stage III subjects (P<0.05, respectively). Conclusions: The TVT becomes larger and the circadian variation of the TVT becomes smaller according to the progression of the WHO stages of essential hypertension.