Purpose: In order to identify neurally mediated syncope, head-up tilt testing was performed in patients with recurrent unexplained syncope.
Methods: The tests were performed in 125 patients in the fasting state, between 8:30 and 11:30 a.m. The blood pressure and heart rate were continuously monitored during 20 minutes in the resting state, and then, positioned at 60 degrees angle, for up to 40 minutes. A group of 20 patients with first negative test was submitted to intravenous isoproterenol in bolus of 2 micrograms every 2 minutes until symptoms occur or at a total dose of 8 micrograms. The test was considered positive when systolic blood pressure decreased at least 30 mmHg and the patient experimented syncope or pre-syncope.
Results: In 52 patients the test was positive (41.6%), 63.5% of which had hypotension exclusively; 7.7% asystole; and 28.8% had hypotension and bradycardia. Nine of the 20 patients submitted to isoproterenol test were positive (45%). All patients recovered spontaneously after returning to supine position.
Conclusion: Head-up tilt testing is a safe and effective method for the identification of neurally mediated syncope.