STATISTICAL BASE VALUE OF 24-HOUR BLOOD-PRESSURE DISTRIBUTION IN PATIENTS WITH ESSENTIAL-HYPERTENSION

The purpose of this study was to calculate statistically the minimum ( base) blood pressure (BP) of nighttime (sleep-time) BP values obtained by ambulatory BP monitoring (ABPM) and to investigate its clinical si gnificance. Twenty-four-hour recording of ECG with ABPM was performed directly (n=89) or indirectly (n=117) in 206 patients with essential h ypertension. A telemeter was used for the direct method and a multi-bi omedical recorder (TM2425) was used for indirect measurement. First. m inimum heart rate (HR0=60/RR0) was determined from sleep-time ECG. The mean product of sleep-time diastolic BP (DBP) and pulse interval (RR) was divided by RR, to obtain DBP, [DBP0=(DBPXRR)s/RR0]. The correlati on between systolic BP (SBP) and DBP was used to determine SBP0 corres ponding to DBP0. Statistical base mean BP (MBP0) was calculated from t hese values, and its reproducibility and relation to hypertension seve rity were investigated. MBP0 values were similar to true base values o f sleep-time MBP obtained by the direct method (mean+/-SD difference, 2.0+/-4.2 mm Hg). Direct MBP0 criteria predicted hypertension severity (mild, moderate, or severe target organ damage) more accurately (pred ictive accuracy, 89%) than daytime MBP criteria (53%, P<0101). Almost the same results were obtained using indirect MBP0 criteria. Day-to-da y indirect MBP0 variation (mean absolute difference) was smaller (2.4/-1.8 mm Hg) than day-to-day daytime and nighttime MBP variation (6.3/-5.3 and 5.4+/-3.4 mm Hg, respectively; n=61, P<0.01), and the correl ation coefficient between day-to-day variations of daytime MBP and phy sical activity (measured by an acceleration sensor) was 0.38 (P<0.05). In conclusion, statistical base BP was almost equal to true base (min imum) BP of sleep-time BP distribution. It was closely related to the severity of hypertensive organ damage, was highly reproducible, and is considered likely to serve stochastically and physiologically as a re presentative BP value in an individual subject.