title: Differences in cardiac autonomic function contributes to heart rate abnormalities in POTS and IST.
abstract: Our objective was to examine the differences in cardiac autonomic function in Postural Tachycardia Syndrome (POTS) versus inappropriate sinus tachycardia (IST). Subjects (IST, n = 8; POTS, n = 12) were studied using standard measurements of the autonomic reflex screen, baroreflex function and spectral analysis. Data was compared to age/gender-matched controls (n = 20). The components of the autonomic reflex screen did not differ between groups. The exception was the significant but expected difference in postural heart rate increment on head-up tilt in POTS (47.9 ± 13.8; n = 12) compared to IST (30.9 ± 9.7; n = 8; p = 0.008). Accordingly the Orthostatic Intolerance Scale showed significantly greater orthostatic symptoms in POTS (2.6 ± 0.5; n = 12) versus IST patients (0.4 ± 0.5; n = 8; p < 0.001). Conversely, IST patients had a significantly higher resting heart rate (96 ± 12; n = 8) when compared to POTS patients (73 ± 12; n = 12; p = 0.001). There was a significant difference in vagal baroreflex sensitivity (BRSv) in POTS (8.21 ± 2.3, n = 12) compared to IST patients (5.30 ± 2.94, n = 8, p = 0.036) during the Valsalva maneuver. Only POTS subjects showed a significant increase in sympathovagal balance (LF/HF) with tilt (FFT, 8.29 ± 6.38; AR, 7.84 ± 5.24) compared to the supine position (FFT, 2.25 ± 1.75; AR, 1.99 ± 1.38; p < 0.05) for both frequency domains. Differences in cardiac autonomic function contribute to changes in positional and non-positional heart rate in postural tachycardia syndrome versus inappropriate sinus tachycardia. These findings shed further light on the autonomic dysfunction underlying POTS and IST.
authors.affiliation: Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, London, Ontario, Canada.
authors.forename: James C
authors.initials: JC
authors.lastname: Corkal
authors.affiliation: Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, London, Ontario, Canada; Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada.
authors.forename: Iryna
authors.initials: I
authors.lastname: Palamarchuk
authors.affiliation: Department of Clinical Neurological Sciences, University Hospital, London Health Sciences Centre, London, Ontario, Canada; Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada. Electronic address: kkimpin@uwo.ca.
authors.forename: Kurt
authors.initials: K
authors.lastname: Kimpinski
mesh_terms: D000293:Adolescent; D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D054972:Postural Orthostatic Tachycardia Syndrome / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D012720:Severity of Illness Index; D013616:Tachycardia, Sinus / Q000503:physiopathology*; D055815:Young Adult
keywords: Autonomic nervous system; Autonomic reflex screen; Inappropriate sinus tachycardia; Orthostatic intolerance; Postural tachycardia syndrome