Head-up Tilt Table Testing: a state-of-the-art review.

Vasovagal syncope (VVS) is the commonest cause of syncope accounting for up to 60% of all cases. The head-up tilt-table test (HUTT) was first described as a diagnostic test for VVS in 1986 and is now in widespread use as a research and diagnostic tool. Vasovagal syncope was previously thought to be confined to younger patients but with the introduction of HUTT, it is now being diagnosed with greater frequency in the elderly. Research into the physiological changes in susceptible individuals during HUTT has greatly increased our understanding of the pathophysiological processes underlying VVS; in particular, the hypotensive response during VVS is associated with sympathetic withdrawal rather than bradycardia alone. Various provocation agents, including nitrates, isoprotenerol and lower body negative pressure have been described to improve the diagnostic yield of the HUTT. Glyceryl trinitrate is now routinely administered during HUTTs. Individuals with typical presentations and infrequent episodes do not require investigation with HUTT as history alone is often diagnostic. The head-up tilt-table test is, however, required with atypical features, seizure activity, occupational issues, and is more likely to be required in older patients. The practicalities of conducting the HUTT and limitations of HUTTs are also discussed.