Usefulness of head-up tilt test in the evaluation and management of unexplained syncope or pre-syncope

This study included 87 consecutive patients with unexplained syncope or pre-syncope who had undergone the head-up tilt (HUT) test with concomitant isoproterenol infusion. A positive response was defined as development of syncope or pre-syncope in association with substantial hypotension (decline of systolic blood pressure greater than or equal to 20 mmHg). Coronary artery spasm was suggested from the clinical symptoms and electrocardiographic findings in 1 patient (1 / 87 = 1.1%). Intolerance to isoproterenol infusion was noted in 8 cases (8 / 87 = 9%). Of the 78 patients who completed the study, 73 showed positive responses (73 / 78 = 94%). (baseline systolic blood pressure = 125 +/- 23 mmHg vs endpoint systolic blood pressure = 76 +/- 11 mmHg, p < 0.05; baseline heart rate = 73 +/- 14 beats per minute vs endpoint HR = 80 +/- 24 beats per minute, p < 0.05). In 73 patients who showed positive responses, the systolic blood pressure (SBP) and heart rate (WR) returned to a safe level at 2 minutes when the patients were returned to a supine position (post-study 2 minutes SBP = 124 +/- 18 mmHg vs baseline SBP = 125 +/- 23 mmHg, p = NS; post-study 2 minutes HR = 82 +/- 18 beats per minute vs baseline HR = 73 +/- 14 brats per minute, p < 0.05). All 73 patients with a positive HUT test received Atenolol therapy (50 mg daily). Only 35 of these 73 patients took Atenolol regularly and had a repeat HUT test. After atenolol therapy, persistent positive responses were observed in 19 cases (19 / 35 = 54%) and negative responses were noted in 16 cases (16 / 35 = 46%). The mean dosage of isoproterenol needed to provoke a positive HUT test in 19 patients who had received Atenolol therapy and had a positive repeat HUT test was 2.3 +/- 1.2 g / min at baseline and 3.5 +/- 0.9 mug / min for post-Atenolol therapy (p < 0.001). Sixteen patients with a negative repeat T-TUT test were treated continuously with Atenolol and followed for a mean period of 13 +/- 11 months (range, 1-34 months). All 16 patients were free of syncope or pre-syncope during the period of follow up. In conclusion, the HUT test is mostly well tolerated and safe, even though the test has a low rate of adverse effects. Atenolol is effective for the prevention of provoked or spontaneous recurrent syncope or pre-syncope.