Usefulness of Head-up Tilt Test in the Evaluation and Management of Unexplained Syncope or Pre-syncope

Abstract

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 > 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 (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 mg / min at baseline and 3.5 ± 0.9 mg / 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.