Comparison of provocative tests for unexplained syncope: isoprenaline and glyceryl trinitrate for diagnosing vasovagal syncope

Aims To compare the sensitivity, specificity and adverse event profile of g lyceryl trinitrate head-up tilt with isoprenaline head-up tilt in the diagn osis of vasovagal syncope in patients with unexplained syncope and healthy controls Methods and Results Forty-eight patients with unexplained syncope and negat ive passive head-up tilt at 70 degrees for 40 min, and 14 healthy controls underwent glyceryl trinitrate head-up tilt and isoprenaline head-up tilt (m aximum dose 5 mug . min(-1)) one week apart in random order. Outcome measur es were production of symptoms (syncope, pre-syncope) with development of h ypotension. In those with negative passive head-up till, the sensitivity of glyceryl trinitrate for diagnosing vasovagal syncope was 48% and the speci ficity was 71%. Glyceryl trinitrate was well tolerated. Isoprenaline sensit ivity was 21% with specificity 64%. Side-effects prevented completion of th e test in 68%. Commonest adverse events were the development of hypertensio n or tachycardia and intolerable flushing or nausea. Conclusions Glyceryl trinitrate head-up tilt is as effective as isoprenalin e head-up tilt as a provocative agent for vasovagal syncope and has a lower incidence of adverse events (C) 2001 The European Society of Cardiology.