‘Front-loaded’ head-up tilt table testing: validation of a rapid first line nitrate-provoked tilt protocol for the diagnosis of vasovagal syncope

Abstract

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.

The Newcastle protocols 2008: an update on head-up tilt table testing and the management of vasovagal syncope and related disorders

“…If the patient has had a previous adverse reaction to nitrates or has suspected psychogenic syncope (where nitrate-induced false positivity may serve only to further confuse the issue), passive (unprovoked) tilt testing for 40 minutes remains the first-line tilt. If the 20/15 tilt is negative, and there is still need for a tilt diagnosis, the 20-minute 800 μg GTN tilt14 – 16 (“front-loaded GTN head-up tilt”16) should be used, though with care regarding a higher propensity to false positivity 16. The test is short, and has far fewer contraindications with superior tolerability in all age groups to isoproterenol provocation, the previous protocols’ second-line tilt test 1 13 – 16.…”

“…If the 20/15 tilt is negative, and there is still need for a tilt diagnosis, the 20-minute 800 μg GTN tilt14 – 16 (“front-loaded GTN head-up tilt”16) should be used, though with care regarding a higher propensity to false positivity 16. The test is short, and has far fewer contraindications with superior tolerability in all age groups to isoproterenol provocation, the previous protocols’ second-line tilt test 1 13 – 16. While isoproterenol tilt testing has a far larger evidence base worldwide,2 17 the complications mentioned above, its poor tolerability (particularly in the elderly),15 side-effect profile and multiple absolute and relative contraindications (see original protocols1) make it a third-line choice in our practice.…”

Syncope in the Older Person

“…7,51,52 Both passive and GTN-provoked protocols have been used extensively, whereas a shorter front-loaded GTN-provoked test may be used in those with mobility issues who might have difficulty standing for long periods. 53 This elderly woman's diagnosis of VVS was made in the context of a normal surface ECG, no structural heart disease, and a diagnostic tilt table test, per European Society of Cardiology (ESC) guidelines. 5 Given her cardiovascular risk factors, it would be important to guide further investigations along the cardiac route should further syncope occur despite optimal therapy.…”

Update on syncope in the older person – a clinical review

“…It resulted in the front-loaded GTN protocol providing a higher diagnostic rate than passive tilt testing, and provides a rapid alternative to conventional methods, though false positivity rates are higher. 69 In an elderly population with syncope of unknown origin submitted to HUTT, the response to glyceryl trinitrate is not dose dependent, and no difference was found in the rate of exaggerated responses to nitrates with different GTN dosages. 70 Autonomic dysfunction, which can be found during tilt test, is probably an important cause of syncope in the elderly, regardless of the occurrence of symptoms during the tilt test.…”