Cardiovascular response during head-up tilt in chronic fatigue syndrome

This study examined the cardiovascular response to orthostatic challenge, a nd incidence and mechanisms of neurally mediated hypotension in chronic fat igue syndrome (CFS) during a head-up tilt test. Stoke volume was obtained b y a thoracic impedance cardiograph, and continuous heart rate and blood pre ssure were recorded during a 45-min 70 degrees head-up tilt test. Thirty-ni ne CFS patients and 31 healthy physically inactive control subjects were st udied. A positive tilt, i.e. a drop in systolic blood pressure of >25 mmHg, no concurrent increase in heart rate and/or development of presyncopal sym ptoms, was seen in 11 CFS patients and 12 control subjects (P>0.05). During baseline and the first 5 min of head-up tilt, CFS patients had higher hear t rate and smaller pulsatile-systolic area ban control subjects (P<0.05). A mong subjects who completed the test, those with CFS had higher heart rate and smaller stroke volume (P<0.05) than corresponding control subjects. Whe n comparing those who had a positive test outcome in each group, CFS patien ts had higher heart rates and lower pulse pressure and pulsatile-systolic a reas during the last 4 min before being returned to supine (P<0.05). These data show that there are baseline differences in the cardiovascular profile s of CFS patients when compared with control subjects and that this profile is maintained during head-up tilt. However, the frequency of positive tilt s and the haemodynamic adjustments made to this orthostatic challenge are n ot different between groups.