1. In 31 consecutively referred patients (20 females, 11 males) with overt or suspected orthostatic disorders, the changes in blood pressure and heart rate that occur in the first 2 min of standing were analysed.
2. Blood pressure was measured continuously by Finapres. The blood pressure and heart rate responses after 1–2 min of standing (early steady-state response) were used to classify the patients as follows: group I (n = 17, age 42 ± 17 years), normal early steady-state blood pressure and heart rate responses; group II (n = 5, age 40 ± 14 years), combination of normal early steady-state blood pressure and postural tachycardia; group III (n = 9, age 51 ± 14 years), hypotensive orthostatic response with (4/9) or without (5/9) postural tachycardia. We examined whether additional information could be obtained by beat-to-beat analysis of the initial circulatory response (first 30 s). It was quantified by identifying the blood pressure trough and overshoot and the maximum heart rate and relative bradycardia.
3. The initial drop in systolic and diastolic blood pressures did not differ between the three groups. A recovery of blood pressure with a systolic and/or diastolic blood pressure overshoot was present in all group I and II patients, but was absent in all except two patients in group III. The initial maximum heart rate increase did not differ between the three groups. The relative bradycardia was less in groups II and III than in group I.
4. We conclude that analysis of the beat-to-beat blood pressure changes in the first 30 s after the onset of standing provides almost all the information that is necessary to determine abnormalities in orthostatic circulatory control.