Variability of arterial blood pressure and classification of essential hypertension by multivariate statistical analysis.

The subjects included in the present study were 141 hospitalized patients with essential hypertension (EH) and 45 patients with EH complicated with apoplexy and myocardial infarction. Of the former 15 underwent a 24-hour measurement of direct arterial pressure under unrestricted conditions, and 45 were examined for functioning of the carotid sinus reflex. (1) Even among the hospitalized patients with EH, blood pressure (BP) showed large diurnal variations. Falls and spontaneous fluctuations in BP were observed at a time during nocturnal sleep. The lowest BP (the "dale" pressure) observed at that time remained almost unchanged throughout the night (S.D. less than or equal to 6 mmHg) for each patient. Since casual BP varies considerably during a day, other laboratory findings should also be taken into account for evaluation prior to initiating antihypertensive treatment. (2) The 186 patients with EH were classified by multivariate statistical analyses of laboratory findings into 4 clusters (types). Then, a new severity index was made in order to evaluate atherosclerotic and hypertensive changes in each patient. (3) A newly devised carotid sinus stimulator was used to enhance the distensibility of the carotid sinus. A decrease in systolic blood pressure (delta SBP) was observed after stimulation although differences in delta SBP were found between the 4 clusters. There was a positive correlation between delta SBP and the elastic modulus of the common carotid artery (r = 0.55, P less than 0.01). (4) Each cluster was characterized by differences in plasma renin activity and cardiovascular abnormalities. This classification is considered to be useful for the antihypertensive treatment.