Use of systolic time intervals in studying hypertension.

Systolic time intervals were measured in 54 hypertensive patients divided into three groups according to severity of hypertension, variability of blood pressure levels and presence or absence of a hyperkinetic heart. The three groups were: borderline hypertension (BLH), fixed essential hypertension (FEH) and hyperkinetic essential hypertension (HEH). Systolic time intervals (STI) provided information indicating an increased cardioadrenergic drive in BLH and HEH. This was supported by finding that propranolol abolished the increased contractility found at rest in BLH and HEH.