Comparison of a Shortened Isosorbide Dinitrate‐Potentiated Head‐Up Tilt Testing with the Conventional Protocol: Tolerance and Diagnostic Accuracy

Abstract

The head-up tilt test (HUT) is widely used to investigate unexplained syncope; however, in clinical practice, it is long and sometimes not well tolerated. To compare the sensitivity, specificity, accuracy, and patients' tolerance of a conventional and shortened HUT. Patients with a history of vasovagal syndrome (VVS) were randomized to a conventional HUT (group I) consisting of 20-minute passive tilt followed by 25 minutes after administration of sublingual isosorbide dinitrate (ISDN), or a shortened HUT (group II) where ISDN was given immediately after tilt and observed for 25 minutes. The control group consisted of age- and gender-matched subjects without VVS symptoms. A specific questionnaire to evaluate tolerance was applied. Sixty patients (29 ± 10 years, 82% female) were included. In group I, 22/30 patients had a positive HUT compared to 21/30 in group II (73% vs 70%, P = 0.77). There was also no difference in the accuracy between the two protocols (63% vs 73%, P = 0.24). The time to positivity was shorter in group II (13.2 minutes vs 30 minutes, P < 0.001). Within the control group (n = 60), the frequency of false-positives was 47% and 23% for the conventional and shortened HUT, respectively (P = 0.058). After conventional HUT, 65.2% subjects reported that the test was too long compared to 25% subjects after the shortened HUT (P = 0.002). In this study, the HUT without passive phase was not inferior to the conventional HUT regarding sensitivity, specificity, and accuracy. Furthermore, the shortened ISDN-potentiated protocol allowed faster diagnosis and was better tolerated.