Peter C. Rowe, MD
Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Neurally Mediated Hypotension and CFS
Over the past half century, chronic fatigue has been described as a prominent symptom in a variety of syndromes of orthostatic intolerance. These overlapping syndromes have been variously termed neurally mediated (or vaso-vagal) hypotension, delayed orthostatic hypotension, postural orthostatic tachycardia syndrome, and idiopathic hypovolemia. Perhaps the first suggestion that these abnormalities were responsible for symptoms of what we now call chronic fatigue syndrome (CFS) was made in 1940 by MacLean and Allen. These authors described a syndrome of excessive elevation in heart rate with upright posture seemed identical to "effort syndrome, irritable heart or neurocirculatory asthenia" (JAMA 1940;115:2162-7). They recommended treatment with up to 14g of sodium per day and sleeping in a head-up position.
Recent work in our center and others has emphasized a high prevalence of neurally mediated hypotension (NMH), and less commonly postural orthostatic tachycardia syndrome, in those with an established diagnosis of CFS. In a 1995 study of 23 adolescents and adults with CFS, we identified hypotension in response to a three stage 70 degree upright tilt table test in 96% of patients, versus 29% of healthy controls. During the first 45 minutes of upright tilt, 16 patients (or 70%) with CFS developed hypotension, while all controls maintained a normal blood pressure.Perhaps more importantly, all 23 with CFS but none of the controls developed orthostatic symptoms during this first stage of tilt testing, suggesting that orthostatic intolerance may be a defining feature of the illness.
With open treatment of the NMH, 9 of 19 (47%) reported a substantial improvement in symptoms, defined carefully as a score or 7 or more on a 10 point wellness scale, along with similar degrees of improvement in activity and cognitive function. A further 7 reported being at least somewhat better (JAMA 1995;274:961-7).
To determine whether the subjective report of improvement in symptoms was associated with objective improvement in tolerance of upright tilt, 6 of the patients with an almost complete resolution of symptoms on therapy agreed to undergo repeat tilt testing. Five of 6 had normal tilt test responses while on therapy, and the sixth had a marked improvement. Three others with mild improvements in symptoms continued to have abnormal tilt tests (Pediatr Res 1995;37:33A).
These observations are being examined more systematically in a randomized trial of flurocortisone among those with CFS and NMH. In the first 50 subjects, we identified abnormal hemodynamic responses to an abbreviated, two-stage upright tilt test in 62%; the median time to hypotension for those with NMH was 39 minutes. In response to quiet upright posture, all 50 subjects developed at least four orthostatic symptoms within the first 45 minutes, including fatigue 82%, lightheadedness 78%, non-headache pain 70%, and nausea 62%.
Similar rates of hypotension and provocation of pain in response to upright tilt have been identified in 20 subjects with fibromyalgia. Of interest, those with fibromyalgia had provocation of characteristic pain after a median of 10 minutes after assumption of upright tilt testing. (Clin Exp Rheumatol 1997;15:239-46). Other work has suggested that abnormalities in autonomic tone, as measured by heart rate variability, may be abnormal in those with CFS during upright tilt (JM Stewart, Pediatr Res 1997;41:26A) but our studies have demonstrated no differences between those with CFS and controls (Clin Autonomic Res 1997;7:293-7). This talk will discuss selected issues in the clinical overlap of chronic fatigue syndrome and orthostatic intolerance.
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