Neurally mediated hypotension and autonomic dysfunction measured by heart rate variability during head-up tilt testing in children with chronic fatigue syndrome

Abstract

Recent investigations suggest a role for neurally mediated hypotension (NMH) in the symptomatology of chronic fatigue syndrome (CFS) in adults. Our previous observations in children with NMH and syncope (S) unrelated to CFS indicate that the modulation of sympathetic and parasympathetic tone measured by indices of heart rate variability (HRV) is abnormal in children who faint during head-up tilt (HUT). In order to determine the effects of autonomic tone on HUT in children with CFS we performed measurements of HRV during HUT in 16 patients aged 11-19 with CFS. Data were compared to 26 patients evaluated for syncope and with 13 normal control subjects. After 30 minutes supine, patients were tilted to 80 degrees for 40 minutes or until syncope occurred. Time domain indices included RR interval, SDNN, RMSSD, and pNN50. An autoregressive model was used to calculate power spectra. LFP (.04-.15 Hz), HFP (.15-.40Hz), and TP (.01-.40Hz). Data were obtained supine (baseline) and after HUT. Thirteen CFS patients fainted (CFS+, 5/13 pure vasodepressor syncope) and three patients did not (CFS-). Sixteen syncope patients fainted (S+, all mixed vasodepressor-cardioinhibitory) and 10 did not (S-). Four control patients fainted (Control+, all mixed vasodepressor-cardioinhibitory) and nine did not (Control-). Baseline indices of HRV were not different between Control+ and S+, and between Control- and S-, but were depressed in S+ compared to S-. HRV indices were strikingly decreased in CFS patients compared to all other groups. With tilt, SDNN, RMSSD, and pNN50 and spectral indices decreased in all groups, remaining much depressed in CFS compared to S or control subjects. With HUT, sympathovagal indices (LFP/HFP, nLFP, and nHFP) were relatively unchanged in CFS, which contrasts with the increase in nLFP with HUT in all other groups. With syncope RMSSD, SDNN, LFP, TP, and HFP increased in S+ (and Control+), suggesting enhanced vagal heart rate regulation. These increases were not observed in CFS+ patients. CFS is associated with NMH during HUT in children. All indices of HRV are markedly depressed in CFS patients, even when compared with already low HRV in S+ or Control+ patients. Sympathovagal balance does not shift toward enhanced sympathetic modulation of heart rate with HUT and there is blunting in the overall HRV response with syncope during HUT. Taken together these data may indicate autonomic impairment in patients with CFS.

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

“…Twenty-two children with a diagnosis of POTS ranged in age from 12 to 17 y (median, 15.2 y). Fourteen patients fulfilled the CDC criteria for CFS (8), as we have previously discussed (5,6,9). There were 28 girls and eight boys.…”

“…All testing was performed in the laboratory during a single day. The methods have been previously described (5,6,9). After overnight fast, tests began between 0900 and 1000.…”

“…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 adolescent patients with CFS often have findings of POTS during HUT (3)(4)(5)(6). Conversely, patients with POTS often have fatigue as a prominent clinical feature (2,7).…”

Postural Orthostatic Tachycardia Syndrome (POTS) and Vitamin B12 Deficiency in Adolescents

“…Previous studies have demonstrated that adolescent patients with CFS often exhibit POTS findings during the HUTT. 9,10 Neurally mediated hypotension has been shown to be the most common cause of unexplained recurrent syncope, and overlapping findings have been found in CFS and neurally mediated hypotension. 9 When defining hyperadrenergic orthostatic hypotension with increased plasma levels of epinephrine and norepinephrine, Streeten 11 found that orthostatic hypotension developed due to the accumulation of blood resulting from anatomic or functional postganglionic denervation in the lower-limb veins.…”

Chronic fatigue syndrome in 57-year-old woman

“…CFS has sometimes been referred to as the "chronic fatigue immune dysfunction syndrome", because a number of studies have found irregularities of the immune system. Recently, the role of abnormal autonomic function in the pathogenesis of chronic fa-tigue syndrome has been investigated, suggesting potential significance in the diagnostic pro-cess of this condition in the future [24][25][26][27][28][29].…”