Dear Editor, we read with great interest the metanalysis by Guida et al. [1] about the diagnostic held of head up tilt test (HUTT) in patients with suspected vasovagal (VVS) syncope. The authors confirmed that HUTT positivity rate was higher with the nitroglycerin (NTG) potentiated HUTT, about 60 %, than drug-free or isoproterenol potentiated protocols, regardless the HUTT duration, population age and tilt table angle. Moreover, a similar specificity between different protocols, about 85 %, has been showed.
