title: Utility of corrected QT interval in orthostatic intolerance.
abstract: We performed this study to determine whether electrocardiographic corrected QT (QTc) interval predicts alterations in sympathovagal balance during orthostatic intolerance (OI). We reviewed 1,368 patients presenting with symptoms suggestive of OI who underwent electrocardiography and composite autonomic function tests (AFTs). Patients with a positive response to the head-up tilt test were classified into orthostatic hypotension (OH), neurocardiogenic syncope (NCS), or postural orthostatic tachycardia syndrome (POTS) groups. A total of 275 patients (159 OH, 54 NCS, and 62 POTS) were included in the final analysis. Between-group comparisons of OI symptom grade, QTc interval, QTc dispersion, and each AFT measure were performed. QTc interval and dispersion were correlated with AFT measures. OH Patients had the most severe OI symptom grade and NCS patients the mildest. Patients with OH showed the longest QTc interval (448.8±33.6 msec), QTc dispersion (59.5±30.3 msec) and the lowest values in heart rate response to deep breathing (HRDB) (10.3±6.0 beats/min) and Valsalva ratio (1.3±0.2). Patients with POTS showed the shortest QTc interval (421.7±28.6 msec), the highest HRDB values (24.5±9.2 beats/min), Valsalva ratio (1.8±0.3), and proximal and distal leg sweat volumes in the quantitative sudomotor axon reflex test. QTc interval correlated negatively with HRDB (r = -0.443, p<0.001) and Valsalva ratio (r = -0.425, p<0.001). We found negative correlations between QTc interval and AFT values representing cardiovagal function in patients with OI. Our findings suggest that prolonged QTc interval may be considered to be a biomarker for detecting alterations in sympathovagal balance, especially cardiovagal dysfunction in OH.
authors.affiliation: Department of Neurology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jung Bin
authors.initials: JB
authors.lastname: Kim
authors.affiliation: Department of Neurology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Soonwoong
authors.initials: S
authors.lastname: Hong
authors.affiliation: Department of Neurology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jin-Woo
authors.initials: JW
authors.lastname: Park
authors.affiliation: Department of Cardiology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Dong-Hyuk
authors.initials: DH
authors.lastname: Cho
authors.affiliation: Department of Neurology, Institute of Health Science, Gyeongsang National University, School of Medicine, Jinju, Korea.
authors.forename: Ki-Jong
authors.initials: KJ
authors.lastname: Park
authors.affiliation: Department of Neurology, Korea University Medical Center, Korea University College of Medicine, Seoul, Korea.
authors.forename: Byung-Jo
authors.initials: BJ
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D001369:Axons / Q000502:physiology; D003710:Demography; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007024:Hypotension, Orthostatic / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D054971:Orthostatic Intolerance / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012018:Reflex; D012119:Respiration; D014463:Ultrasonography