1. Cardiac output, lower-limb blood flow, hepatic and renal blood flows were studied in 16 patients with borderline and 16 patients with sustained essential hypertension and compared with 16 age-matched control subjects.
2. In borderline hypertension cardiac output and lower-limb blood flow were significantly elevated, while hepatic and renal blood flows were within the normal range. Cardiac output and lower-limb blood flow were positively correlated.
3. In sustained hypertension cardiac output, lower-limb blood flow and hepatic blood flow were within the normal range. Renal blood flow was significantly reduced. Lower-limb blood flow was negatively correlated with mean arterial pressure.
4. If borderline hypertension is an early stage of fixed hypertension, the present study suggests that the changes in cardiac output observed in hypertension are mainly related to lower-limb (and muscle) blood flow.