Autonomic Nervous System Dysfunction in Adolescents with Postural Orthostatic Tachycardia Syndrome and Chronic Fatigue Syndrome Is Characterized by Attenuated Vagal Baroreflex and Potentiated Sympathetic Vasomotion

Abstract

The objective was to determine the nature of autonomic and vasomotor changes in adolescent patients with orthostatic tachycardia associated with the chronic fatigue syndrome (CFS) and the postural orthostatic tachycardia syndrome (POTS). Continuous electrocardiography and arterial tonometry was used to investigate the heart rate and blood pressure responses before and 3-5 min after head-up tilt in 22 adolescents with POTS and 14 adolescents with CFS, compared with control subjects comprising 10 healthy adolescents and 20 patients with simple faint. Heart rate and blood pressure variability, determined baroreceptor function using transfer function analysis, and measured cardiac vagal and adrenergic autonomic responses were calculated using timed breathing and the quantitative Valsalva maneuver. Two of 10 healthy controls and 14 of 20 simple faint patients experienced vasovagal syncope during head-up tilt. By design, all CFS and POTS patients experienced orthostatic tachycardia, often associated with hypotension. R-R interval and heart rate variability were decreased in CFS and POTS patients compared with control subjects and remained decreased with head-up tilt. Low-frequency (0.05-0.15 Hz) blood pressure variability reflecting vasomotion was increased in CFS and POTS patients compared with control subjects and increased further with head-up tilt. This was associated with depressed baroreflex transfer indicating baroreceptor attenuation through defective vagal efferent response. Only the sympathetic response remained. Heart rate variability declined progressively from normal healthy control subjects through syncope to POTS to CFS patients. Timed breathing and Valsalva maneuver were most often normal in CFS and POTS patients, although abnormalities in select individuals were found. Heart rate and blood pressure regulation in POTS and CFS patients are similar and indicate attenuated efferent vagal baroreflex associated with increased vasomotor tone. Loss of beat-to-beat heart rate control may contribute to a destabilized blood pressure resulting in orthostatic intolerance. The dysautonomia of orthostatic intolerance in POTS and in chronic fatigue are similar. Abbreviations CFS, chronic fatigue syndrome POTS, postural orthostatic tachycardia syndrome HUT, head-up tilt CDC, Centers for Disease Control and Prevention BP, blood pressure LF, low frequency HF, high frequency VLF, very low frequency HRV, heart rate variability Orthostatic intolerance is defined by the inability to remain upright without severe signs and symptoms such as hypotension, tachycardia, lightheadedness, pallor, fatigue, weakness, and nausea. Orthostatic intolerance appears in many guises including overt dysautonomia, vasovagal syncope, and orthostatic tachycardia (1). POTS is operationally defined by the presence of symptoms of orthostatic intolerance associated with an increase in sinus heart rate of Ͼ30 beats/min or to a rate of Ͼ120 beats/min during the first 10 min of HUT table testing (2). Previous work, including our own, has suggested that...

Small Heart With Low Cardiac Output for Orthostatic Intolerance in Patients With Chronic Fatigue Syndrome

“…13 In their assessment of both sympathetic baroreflex sensitivity and cardiovagal baroreflex sensitivity, the function of the autonomic nervous system was intact in the patients, 13 although other researchers have postulated autonomic nervous dysfunction with exaggerated sympathetic nervous activation over compensatory levels while standing as a major mechanism behind the symptoms. 4,5,20,24,27 Elucidation of the pathophysiology of CFS and OI may lead to better therapeutic strategies. Recently, xenon-computed tomography blood-flow studies demonstrated that CFS patients have global cerebral hypoperfusion with reduced absolute cortical blood flow in broad areas, especially in bilateral middle cerebral artery territories, compared with healthy controls.…”

The Relationship between Vascular Function and the Autonomic Nervous System

“…The pathological mechanism of POTS is autonomic dysfunction, including vagal withdrawal with intact vasoactive barorefl exes and sympathoexcitation, which may contribute to vasomotor instability and orthostatic intolerance in these patients. 62) With regard to vascular function, Liao, et al demonstrated that abnormally augmented, fl ow-mediated dilation and abnormal function of the vascular endothelium may play important roles in POTS in children. 63) A study reporting that NOS3 alleles, which encode the predominant isoform of NOS in the vasculature, represent genetic factors associated with POTS also supports the contribution of the endothelium to the pathology of POTS.…”

Pooling in Chronic Orthostatic Intolerance

“…11 After a minimum 15-minute waiting period, at least 500 beats were acquired during baseline supine conditions and during incremental tilts. I used custom software to collect RR intervals and systolic, diastolic, and mean BPs as sequences of discrete point events for each heart beat.…”