Duration of head-up tilt test for patients with suspected vasovagal syncope

Aims To investigate the appropriate duration of head-up tilt test (HUTT) needed to induce a positive reaction in patients with suspected vasovagal syncope. Methods and results Consecutive patients referred to the syncope unit of our centre for recurrent unexplained syncope were studied. The HUTT included a 30 min passive basic phase and a 20 min sublingual nitroglycerin provocation phase if syncope did not develop during the passive phase. We studied 773 consecutive patients, and 427 (55.2%) patients had a positive HUTT, including 46 patients (10.8%) during the passive basic phase and 381 patients (89.2%) during the nitroglycerin provocation phase. During the basic phase, positive reaction appeared at 7.5 min, and the percentage of positive cases increased with the duration of the test, reaching a peak (20.9%) at 22.5 min, and then decreasing gradually. Most positive reactions (96.1%) occurred between 10 and 25 min during the basic phase. During the nitroglycerin provocation phase, however, the percentage of positive reactions increased rapidly after sublingual nitroglycerin, peaking (35.7%) at 10 min, followed by a sharp decline. Most positive reactions (96.1%) occurred in the first 15 min of the provocation phase. Conclusion The HUTT was a useful diagnostic test in patients with suspected vasovagal syncope, and sublingual nitroglycerin increased the rate of positive reactions. The appropriate duration for HUTT required at least 25 min during the passive basic phase and 15 min during the nitroglycerin provocation phase.