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

Background: There is little information available on the circadian var iation of total vascular tone in (TVT) elderly patients with essential hypertension. Therefore, the author studied the circadian variation o f 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 acc ording to the three stages of the World Health Organization (WHO) clas sification. The patients with essential hypertension were diagnosed as such by ruling out secondary hypertension. To measure the blood press ure and the cardiac output concurrently and noninvasively, the author attached the subjects to an ambulatory blood pressure monitor and a ca rdiac output monitor, simultaneously, for a 24-hour period. The TVT, m easured as total vascular resistance (TVR), was calculated as follows: [(mean blood pressure/cardiac index) x 1332 dyne/s/cm-5]. The TVR rat io 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 significan tly smaller during waking hours than during sleeping hours (P < 0.01). The TVR ratio during waking and sleeping hours was highest in the sta ge III subjects and decreased progressively in the stage II, stage I, and control subjects (P < 0.05, respectively). The value of the differ ences between the TVR ratio during sleeping hours and waking hours was highest in the control subjects and decreased progressively in the st age I, stage II, and stage III subjects (P<0.05, respectively). Conclu sions: The TVT becomes larger and the circadian variation of the TVT b ecomes smaller according to the progression of the WHO stages of essen tial hypertension.