Biomedical subjects
Publications and source records attributed to B P Grubb.
The disorders of autonomic control associated with orthostatic intolerance are a diverse group that can result in syncope and near-syncope. A basic understanding of these disorders is essential to diagnosis and proper treatment. Ongoing studies should help to define better the spectrum of these disorders and to elaborate better diagnostic and treatment modalities.
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This study investigated psychological and physiological factors in two groups of patients who had tilt table testing for autonomic dysfunction. The first group of 61 patients completed assessments of depression, anxiety, and symptom effects on lifestyle. The 25 patients identified as tilt positive were younger (30.5 years) and had higher mean depression scores (7.6) compared to the tilt-negative response group (n = 36); the latter averaged 40 years of age and had mean depression scores of 4.6. These differences were statistically significant. Women testing tilt positive were significantly more depressed than tilt-negative women (P = 0.02). More severe depressive symptoms were associated with lower blood pressure (BP) (P < 0.05). A second group of 52 patients was monitored during tilt for BP, heart rate (HR), skin temperature (TEMP), skin conductance level (SCL), and forehead muscle tension (EMG). Twenty-seven tested positive and 23 were negative. There were statistically significant group differences in systolic BP and diastolic BP (P < 0.05). There was a significant interaction between tilt status (positive or negative) and time (P = 0.03) in HR. TEMP increased 2 degrees over time in both groups (P < 0.05). The decrease in SCL from 13.7 to 10.4 mu omega in the tilt-positive response group compared to the slight increase in the tilt-negative group was significantly different (P < 0.05). Identification of psychological factors correlated with BP and physiological changes that accompany decreases in BP in tilt-positive response patients could guide management of patients with autonomic dysfunction.
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BACKGROUND: Since the renaissance of tilt table testing in clinical cardiology some 15 years ago, the syndromes of autonomic dysfunction with orthostatic intolerance underwent improved differentiation and classification. In the present review a variant of autonomic dysfunction with orthostatic intolerance--POTS (postural orthostatic tachycardia syndrome)--will be discussed. DIAGNOSIS AND TREATMENT: The affected patients present with orthostatic intolerance, postural tachycardia, exercise intolerance, fatigue, dizziness and in some cases with other dysautonomic symptoms such as gastrointestinal or sudomotor dysfunction. Together with the clinical history, tilt table testing is the cornerstone of diagnostic evaluation by which the syndrome can be distinguished from typical neurocardiogenic disorders. POTS is characterized by different subtypes; accordingly, therapy for relief of symptoms is variable and includes beta blockers for patients with the hyperadrenergic type and alphamimetics for those with partial dysautonomia. CONCLUSION: Although it is now possible to differ POTS from other forms of autonomic dysfunction, further research is warranted to clarify the pathophysiology of this syndrome and its subtypes and to improve therapeutic interventions.
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Stimulated by the wide-spread use of tilt table testing, disorders of autonomic function with orthostatic hypotension have recently gained attention by clinical cardiologists. At the same time, improved characterization of the underlying circulatory responses have led to a reclassification of these syndromes. In particular, three subgroups of chronic primary dysautonomia have been defined: pure autonomic dysfunction, multiple system atrophy, and the postural orthostatic tachycardia syndrome. On the other hand, acute dysautonomias represent a rare yet clinically sometimes dramatic form of autonomic disorders. Several diseases as well as enzymatic disorders, and pharmacological drugs may cause secondary dysautonomia. The clinical correlate of all these forms of dysautonomia is orthostatic hypotension and syncope. Thus, a careful history forms the basis of a successful diagnostic workup of the underlying cause of syncope. This review summarizes the current knowledge of autonomic disorders, their classification and diagnostic and therapeutic strategies.
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The evaluation of syncope occurring during exercise or occurring spontaneously in highly trained individuals presents a unique diagnostic challenge. It is of critical importance to exclude potential life-threatening disorders such as hypertrophic cardiomyopathy, long QT syndrome, right ventricular dysplasia, anomalous coronary artery distribution, valvular heart disease, myocarditis, or exercise-induced arrhythmia. This review is not directed towards identifying, treating, or determining athletic eligibility of individuals with such disorders. Rather, we endeavour to discuss the pathophysiology of exercise-induced neurocardiogenic syncope and to address the role of head upright tilt testing in evaluating syncope in athletic individuals in whom proper evaluation has excluded the presence of ischaemic heart disease or primary structural or electrical heart disease.
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Head upright tilt table testing has become an accepted method to measure an individual's predisposition to autonomically mediated periods of hypotension and bradycardia severe enough to cause frank syncope. At the same time it has become increasingly apparent that less profound falls in blood pressure, while not sufficient to result in loss of consciousness, may cause symptoms such as near syncope, vertigo, and dizziness. We describe a subgroup of adolescents that have a mild form of autonomic dysfunction that exhibit disabling symptoms such as postural tachycardia and palpitations, extreme fatigue, lightheadedness, exercise intolerance, and cognitive impairment. During baseline tilt table testing at a 70 degrees angle, these patients demonstrated a heart rate increase of > or = 30 beats/min (or a maximum heart rate of > or = 120 beats/min) within the first 10 minutes upright (not associated with profound hypotension), which reproduced their clinical symptom complex. Similar observations have been made in the adult population and has been termed the postural orthostatic tachycardia syndrome (POTS). We report that POTS may also occur in adolescents and represents a mild, potentially treatable form of autonomic dysfunction that can be readily identified during head upright tilt table testing.
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For nearly a century, physicians have been aware of a syndrome consisting of a relatively stereotyped presentation, usually in young patients, who complain of fatigue, malaise and effort intolerance, sometimes of trembling and weakness of the lower limbs. This is associated with an excessive tachycardia in the orthostatic position. This syndrome has recently been called idiopathic orthostatic tachycardia. The tilt test has enabled "quantification" of normal responses. Patients complaining of the symptoms described above and which, during the first minutes of orthostatism, increase their heart rates by more than 30 beats per minute or attain a rate of at least 110/min, are considered to be suffering from this syndrome. The physiopathology is not clear but, globally, there seems to be two sub-groups, the first considered to be a partial dysautonomic disorder and the second, the result of hypersensitivity of the beta-receptors. Besides the tilt test, the diagnosis can also be presumed after an excessive tachycardia response to an intravenous infusion of 1 microgram/min of isoprenaline. The treatment of these patients is uncertain as there is no single approach which is always effective. In addition to "simple" but essential advice, a number of drugs may be used although there is no means of predicting the efficacy of the result in a given patient. A major principle should be emphasised: ablation of the sinus node for inappropriate tachycardia may eliminate the only compensatory mechanism of autonomic dystonia and make the patients even more symptomatic than they were.