Long QT syndrome diagnosis may be affected by positive tilt table test; a cross-sectional study

Background: Tilt Table Test (TTT) is usually used for assessment of syncope with undefined etiology. Positive test occurs in those with parasympathetic overstimulation. This overactivation of parasympathetic system may affect QTc measurement; not only through rate modulation, but also from through potassium ionic channels as muscarinic activated inward rectifying K + current. Methods: and Materials: in this cross-sectional study, 478 patients with syncopal attacks of unknown origin underwent evaluation with TTT as well as 24-hour Holter electrocardiogram monitoring. Schwartz score (for diagnosis of Long QT syndrome) was calculated for all of them. Those with secondary causes of long QT excluded from survey. Then the association of positive TTT and Schwartz score was assessed. Results: 478 patients entered the study 208 (43.4%) of whom were male and 270 (56.4%) were female. The mean age of the patients was 42.43 ± 17.979 years old. TTT was positive in 289 (60.46%) patients and was negative in 189 (39.54%) patients. the mean Schwartz score was significantly higher in patients with positive TTT (2.77 ± 0.08 vs. 1.99 ± 0.12) (P < 0.001). Conclusion: Diagnosis of long QT syndrome as a cause of syncope should not be made hesitantly by the use of Schwartz score as this scoring system might need to be modified based on the results of tilt table test.