Abstract 4118410: The Effect of Positive Tilt Table Tests on Long QT Syndrome Diagnosis: A Cross-Sectional Perspective

Background: The tilt table test (TTT) serves as a widely adopted diagnostic tool for evaluating syncope of undetermined etiology, with a positive result often indicative of parasympathetic overstimulation. This excessive activation of the parasympathetic system holds the potential to influence QTc measurement not only through rate modulation but also by impacting potassium ionic channels, given that muscarinic activation inwardly rectifies the K+ current. Methods: In this cross-sectional study, 478 patients experiencing syncope of unknown origin underwent evaluation with TTT and 24-hour Holter electrocardiogram monitoring. The Schwartz Score, utilized for diagnosing Long QT syndrome, was computed for all participants. Those with secondary causes of long QT were excluded from the analysis. The association between positive TTT results and Schwartz Score was then examined. Results: A total of 478 patients were enrolled in the study, comprising 208 (43.4%) males and 270 (56.4%) females. The mean age of the patients was 42.43±17.979 years. TTT results were positive in 289 (60.46%) patients and negative in 189 (39.54%) patients. Patients with positive TTT results exhibited a significantly higher mean Schwartz Score compared to those with negative results (2.77±0.08 vs. 1.99±0.12) (P<0.001) (Figure 1). The odds ratio for higher Schwartz scores in the presence of positive TTT results was 4.547. Conclusion: Caution is warranted when diagnosing long QT syndrome as a potential cause of syncope solely based on the Schwartz Score. This study underscores the necessity for potential modifications to the scoring system, acknowledging the impact of tilt table test outcomes on its predictive accuracy. These findings contribute to the ongoing discourse on refining diagnostic approaches for Long QT syndrome in the context of syncope, promoting more accurate and nuanced clinical decision-making.