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 > or = 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 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 (HR) 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 beats 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 microg/min at baseline and 3.5 +/- 0.9 microg/min for post-Atenolol therapy (p < 0.001). Sixteen patients with a negative repeat HUT 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.