Circulatory and catecholamine changes during head-up tilt testing in neurocardiogenic (vasovagal) syncope

Abstract

Changes in heart rate, arterial pressure, norepinephrine and epinephrine levels were compared in 19 consecutive patients (10 men and 9 women, mean age 46 ± 16 years) with neurocardiogenic syncope and 11 age- and sex-matched control subjects (5 men and 6 women, mean age 49 ± 15 years) during head-up tilt testing. Norepinephrine and epinephrine levels were measured at the baseline supine position, in the initial upright position, every 90 seconds during the 70° upright tilt, at the time of termination due to hypotension and syncope (or at 15 minutes in control subjects), and at 40 seconds and 1 minute and 40 seconds in the supine position after terminating the headmp tilt test. Baseline norepinephrine, epinephrine and heart rate were slightly higher in patients. Despite a significant decrease in mean arterial pressure during head-up tilt testing in patients (51 ± 20 mm Hg, p < 0.001), norepinephrine levels in patients and control subjects at the time of terminating the head-up tilt test were comparable (459 ± 204 vs 473 ± 172 pg/ml)- A fivefold increase in epinephrine levels (73 ± 53 to 345 ± 260 pg/ml; p < 0.01) were seen in patients, whereas control subjects had insignificant change (38 ± 16 to 65 ± 44 pg/ml). It is concluded that diminished neuronal sympathetic activity and enhanced adrenomedullary activity is demonstrated during head-up tilt testing in patients with neurocardiogenic syncope.