Hemodynamic study of 85 patients with borderline hypertension

Abstract

Hemodynamic changes in supine and upright position (50 ° head-up tilt) and during exercise were studied in 40 normal subjects and 85 patients with borderline hypertension. The latter were classified in 2 groups, according to the level of cardiac index. In group I, with patients in the supine position, cardiac index, stroke index, heart rate and plasma volume were normal, but total peripheral resistance was increased ( P < 0.01). During upright tilt, orthostatic decrease of mean arterial pressure ( P < 0.05) was observed, and the increase in total peripheral resistance was not greater than in normal subjects. The hemodynamic response to exercise was similar to that of normal subjects. In patients in group II, cardiac index, stroke index and heart rate were increased ( P < 0.001), but plasma volume was decreased ( P < 0.01) and total peripheral resistance was below normal ( P < 0.001). With patients in the upright position, diastolic orthostatic hypertension was observed ( P < 0.001) and total peripheral resistance was greater than normal ( P < 0.01) despite an abnormal fall of cardiac index ( P < 0.05). The hemodynamic response to exercise indicated that total peripheral resistance did not decrease as in normal subjects and in patients of group I ( P < 0.001). This study provides evidence that (1) total peripheral resistance is abnormal in patients with borderline hypertension, but only during upright tilt and exercise in patients with high cardiac index, and (2) 2 main disorders seem to be important in the early stage of hypertension: abnormality of blood volume (or blood volume distribution, or both) and impaired neurogenic activity.