Postural tachycardia syndrome (POTS) or paroxysmal sinus tachycardia (PST) due to the anxiety reaction? The supine variables were normal. The tilt test induced initial tachycardia associated with elevation of BP and CBFv (green ovals). This reaction is due to anxiety since BP and CBFv are elevated. In POTS, CBFv is usually unchanged or reduced. Similar reaction occurred at the end of the tilt (blue ovals). Note that patient was hyperventilating during the tilt (green tracing). The tilt test was done without any medication. Trial of beta blockers failed to improve orthostatic intolerance. Final diagnosis was PST. Mean supine HR was 91.5 ± 4.9 BPM; mean orthostatic HR during more steady HR (demarcated by a red box) was 109.3 ± 8.5 BPM. The mean HR during the whole tilting was 118.5 ± 13.8 BPM. Data from 25-year-old woman.