Nitrate‐Potentiated Head‐Up Tilt Testing (HUT) Has a Low Diagnostic Yield in Patients with Likely Vasovagal Syncope

BACKGROUND: Vasovagal syncope (VVS) is characterized by a wide spectrum of clinical presentations, but the relationship between clinical presentation and response to head-up tilt testing (HUT) has not yet been evaluated in detail. The aim of this study was to assess the relationship between the clinical presentation of VVS and HUT and clinical outcome at long-term follow-up. METHODS: Out of 671 consecutive subjects undergoing nitroglycerin-potentiated HUT for suspected VVS, 369 patients with normal electrocardiogram and no structural heart disease were included in our study. RESULTS: A history suggestive of typical or atypical VVS was obtained in 198 and 171 patients, respectively. The positivity rate of HUT was 65% and 36% in patients with established and likely VVS, respectively (P < 0.0001). In patients with established VVS, a time interval of ≤28 days between the last syncope and HUT was the only independent predictor of a positive test. In patients with likely VVS, no variable was predictive of a positive HUT. At a mean follow-up of 43 ± 27 months, the rate of adverse events (all-cause mortality, syncope recurrence, and major diagnostic and/or therapeutic procedures) was similar in patients of both groups, independent of HUT results. CONCLUSION: In patients with likely VVS, HUT has a low-diagnostic yield and may be inadequate to establish a reliable diagnosis. Similar long-term outcomes were observed in patients with positive or negative test results, suggesting that HUT is of limited value in the management of patients with suspected neurally mediated syncope.