'Front-loaded' head-up tilt table testing: validation of a rapid first line nitrate-provoked tilt protocol for the diagnosis of vasovagal syncope.Age Ageing. 2008 Jul; 37(4):411-5.AA
Head-up tilt testing is the investigation of choice in the diagnosis of vasovagal syncope. The test is time consuming and labour intensive, with conventional tilt testing taking up to 45 min. We compared a shortened 'front-loaded' 20-min glyceryl trinitrate-provoked head-up tilt (FLGTN-HUT) with the standard 40-min passive tilt (HUT) as first line investigations in patients with unexplained syncope and asymptomatic controls. In the study, 149 consecutive patients with unexplained syncope and 83 asymptomatic controls were enrolled. Subjects were randomly assigned to FLGTN-HUT (800 mcg, metred spray) or HUT, then the opposite tilt-test 1 week later. Seventeen (11.4%) patients had diagnostic haemodynamic changes and symptom reproduction during HUT and 54 (36.2%) during FLGTN-HUT. A total of 24.8% more patients had a positive test with FLGTN-HUT than with passive HUT (95% CI: 16.3%, 33.4%). Nine (10.8%) controls had significant haemodynamic changes during HUT and 23 (27.7%) during GTN provocation. Seven controls had haemodynamic changes on both HUT and FLGTN-HUT testing. The controls group had 16.8% more significant haemodynamic changes with FLGTN-HUT than with HUT (95% CI: 0.06, 27.4). The front-loaded GTN protocol provided a higher diagnostic rate than passive tilt testing, and provides a rapid alternative to conventional methods, though false positivity rates are higher.