Head-up tilt test is increasingly being used to diagnosis neurocardiogenic syncope. But the protocol of head-up tilt test has not been settled. The purpose of this study was to evaluate the effect of isoproterenol provocation during head-up tilt test in normal volunteers with no prior history of syncope or presyncope.

Head-up tilt test was performed with 53 volunteers (age 309, male 27, female 26) in the fasting state. After supine heart rate and blood pressure were obtained, each volunteer was tilted to the 70 degree upright position for 30 minutes using a motorized tilt table with a footboard. If the test was negative in the baseline tilt, intravenous isoproterenol was started at 1g/min and then increased by 1g/min every three minutes to a maximum of 5g/min while maintaining 70 degree upright position. The end points of test were positive response, intolerance to isoproterenol, heart rate >150beat/min and completion of the protocol. When an end point was reached, the volunteer was rapidly returned to the supine position.

Positive response to head-up tilt test was noted in 14 cases (26%). The pattern of positive response was vasodepressive in all cases. There was no significant side effect of isoproterenol. There was no significant difference between positive and negative response group in terms of age, sex, peak infusion rate of isoproterenol and hemodynamic response. The positive response rate at 2 g/min , 3 g/min, 4 g/min and 5 g/min of isoproterenol infusion was 1.9%, 9.7%, 23.7% and 32.5%, respectively.

Head-up tilt test at 70 degree angle with isoproterenol infusion provided an adequate specificity.