Clinical recognition of neurally mediated syncope

Background: Most cases of syncope are due to hypotension, with a vasovagal response the commonest single mechanism. Neurally mediated syncope (NMS) is a vasovagal response evoked by common physical or psychological stress factors in susceptible individuals. Although upright tilt table testing (TTT) has been developed to diagnose this condition, the clinical recognition of this common syndrome in the general community remains poor. Aims: To evaluate the clinical presentation of patients with NMS and pre-syncope, proven by TTT, and compare them to patients with syncope that have a low probability of having NMS (e.g. older patients with cardiac disease and negative TTT). Methods: Prospective evaluation by questionnaire at the time of TTT, including documentation of presenting symptoms and signs, and provoking factors in consecutive patients. Comparisons between patient groups analyzed using chi-squared tests and logistic regression. Results: Neurally mediated syncope patients were more likely to present with both syncope and pre-syncope, often with prolonged histories of pre-syncope. Certain provoking stress factors were more common in NMS, with multiple factors often present. Most NMS patients had a hypotensive prodrome before syncope, whereas control patients had a higher incidence of syncope without warning. Conclusion: Neurally mediated syncope patients present with situational syncope that is not only stereotypical for the individual, but shares common features with other similar patients. While none of the clinical observations is unique to NMS, a carefully detailed history can elicit a convincing diagnostic pattern that can often obviate the need for extensive and expensive investigation, and in younger patients a TTT may not be required to make the diagnosis.