Vasovagal syncope is a common cause of syncope. In some cases, syncopal episode is recurrent, resulting in physical injury. Head-up tilt test with or without isoproterenol provocation has been a tool to diagnose vasovagal syncope. But the protocol of head-up tilt test has not been settled. In this study, we evaluate the usefulness of a head-up tilt test with isoproterenol provocation in patients with syncope or presyncope of unexplained origin.

Head-up tilt test was performed with patients in the fasting state in the morning. After supine heart rate and blood prewwure were obtained, each patient 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 1 µg/min and then increased by 1 µg/min every three minutes to a maximum of 5 µg/min while maintaining 70 degree upright position. The end points of test were positive response, intolerance of isoproterenol, heart rate>150 beats/min, and completion of the protocol. When an end point reached, the patient was rapidly returned to the horizontal position.

1) Of 122 patients with syncope or presyncope, 113 patients(93%) had prodromal symptoms.

2) 23 patients(19%) had physical injury during episode.

3) 93 patients(76%) experienced episodes while they were standing or sitting.

4) A total of 83 patients(68%) had a positve response during head-up tilt test ; 7 patients(8%) of these 83 patients had a positive response during the baseline tilt. But, 76 patients(92%) required isoproternol provocation to elicit this response.

5) The pattern of positive response showed vasodepressive pattern in 55 patients(67%), mixed pattern in 26 patients(31%), and cardioinhibitory pattern in 2 patients(2%).

6) No significant side effect of isoproterenol was noted.

7) There were no significant differences between positive response group and negative response group in terms of clinical characteristics and hemodynamic findings during head-up tilt test.

A head-up tilt test with isoproterenol provocation could be an useful tool for diagnosing vasovagal syncope or presyncope in adults.