Dysregulation of peripheral and central chemoreflex responses in Chagas' heart disease patients without heart failure.
(65/693)
BACKGROUND: The peripheral and central chemoreflexes are important autonomic mechanisms for regulating breathing and cardiovascular function. Although pathological inflammatory infiltration of the peripheral chemoreceptors and central nervous system has been reported in Chagas' disease, functional evaluation of chemoreflexes has not yet been performed. METHODS AND RESULTS: The hypothesis that chemoreflex function is altered in patients with Chagas' heart disease (CH) but normal left ventricle function was tested in 12 CH patients and 13 matched control subjects. The ventilatory rate, minute ventilation, heart rate, mean arterial pressure, forearm blood flow, forearm vascular resistance, and venous norepi-nephrine responses to hypoxia and hypercapnia were determined. During hypoxia, the decrease in oxygen saturation was smaller in CH patients, despite a similar ventilatory response between groups. Both groups showed an increase in heart rate during hypoxia, but this response was blunted in CH patients. Although the mean arterial pressure response to hypoxia was similar in both groups, forearm vascular resistance significantly decreased in control subjects while remaining unchanged in CH patients. Moreover, a significant increase in plasma norepinephrine levels elicited by stimulation of peripheral chemoreceptors was observed only in the CH group. During hypercapnia, the increase in minute ventilation was smaller in CH patients, who did not exhibit the increase in norepinephrine observed in control subjects. CONCLUSIONS: These data suggest that CH potentiates respiratory, cardiovascular, and autonomic responses to peripheral chemoreceptor activation by hypoxia in patients with normal left ventricular function. The ventilatory and sympathetic responses to central chemoreceptor activation by hypercapnia, however, are significantly blunted. (+info)
Evaluation of cardiac beta-adrenergic receptor function in children by dobutamine stress echocardiography.
(66/693)
OBJECTIVE: To investigate the role of dobutamine stress echocardiography in evaluating cardiac beta-adrenergic receptor (beta-AR) function and responsiveness in children. METHODS: Left ventricular ejection fraction (EF), fractional shortening (FS), left ventricular end systolic volume index (ESVI), the ratio of systolic blood pressure and ESVI (SP/ESVI) were measured by dobutamine stress echocardiography (DSE) in 30 children with beta-AR hypersensitivity, 15 children with dilated cardiomyopathy and 30 normal children respectively. RESULTS: Before pharmacological stress, EF and FS were 0.72 and 0.39 respectively in beta-AR hypersensitivity group versus 0.70 and 0.35 respectively in control group. There was no difference of the indices between the two groups (P > 0.05). SP/ESVI was 0.76, higher than the value of 0.66 in control group (P < 0.05); EF, FS and SP/ESVI were 0.41, 0.15 and 0.10 respectively, which were significantly lower than those in control group. After dobutamine stress of 5 micrograms.kg-1.min-1 and 10 micrograms.kg-1.min-1, EF, FS and SP/ESVI were significantly increased in patients with beta-AR hypersensitivity and there were no changes in children with dilated cardiomyopathy compared with values of baseline. CONCLUSION: Cardiac beta-AR function and responsiveness can be evaluated by dobutamine stress echocardiography. (+info)
Autonomic nervous system derangement in fibromyalgia syndrome and related disorders.
(67/693)
Fibromyalgia syndrome is a chronic, painful musculoskeletal disorder of unknown etiology and/or pathophysiology. During the last decade many studies have suggested autonomic nervous system involvement in this syndrome, although contradictory results have been reported. This review focuses on studies of the autonomic nervous system in fibromyalgia syndrome and related disorders, such as chronic fatigue syndrome and irritable bowel syndrome on the one hand and anxiety disorder on the other, and highlights techniques of dynamic assessment of heart rate variability. It raises the potentially important prognostic implications of protracted autonomic dysfunction in patient populations with fibromyalgia and related disorders, especially for cardiovascular morbidity and mortality. (+info)
Hypoglycemia-associated autonomic failure in diabetes.
(68/693)
Hypoglycemia is the limiting factor in the glycemic management of diabetes. The concept of hypoglycemia-associated autonomic failure (HAAF) in diabetes posits that recent antecedent iatrogenic hypoglycemia causes both defective glucose counterregulation (by reducing the epinephrine response to falling glucose levels in the setting of an absent glucagon response) and hypoglycemia unawareness (by reducing the autonomic and the resulting neurogenic symptom responses) and thus a vicious cycle of recurrent hypoglycemia. Perhaps the most compelling support for HAAF is the finding that as little as 2-3 wk of scrupulous avoidance of hypoglycemia reverses hypoglycemia unawareness and improves the reduced epinephrine component of defective glucose counterregulation in most affected individuals. Insight into this pathophysiology has led to a broader view of the clinical risk factors for hypoglycemia to include indexes of compromised glucose counterregulation and provided a framework for the study of the mechanisms of iatrogenic hypoglycemia and, ultimately, its elimination from the lives of people with diabetes. (+info)
Recognizing and treating diabetic autonomic neuropathy.
(69/693)
Diabetic autonomic neuropathy can cause heart disease, gastrointestinal symptoms, genitourinary disorders, and metabolic disease. Strict glycemic control can slow the onset of diabetic autonomic neuropathy and sometimes reverse it. Pharmacologic and nonpharmacologic therapies are available to treat symptoms. (+info)
Basilar artery aneurysm with autonomic features: an interesting pathophysiological problem.
(70/693)
Unruptured cerebral aneurysms often present with neuro-ophthalmological symptoms but ocular autonomic involvement from an aneurysm of the posterior circulation has not previously been reported. A patient is described with a basilar artery aneurysm presenting with headache and unilateral autonomic symptoms. After angiographic coiling of the aneurysm there was a near complete resolution of these features. The relevant anatomy and proposed mechanism of autonomic involvement of what may be considered--from a pathophysiological perspective as a secondary trigeminal-autonomic cephalgia--is discussed (+info)
Mechanisms underlying the impairment in orthostatic tolerance after nocturnal recumbency in patients with autonomic failure.
(71/693)
In the present study, we have assessed in patients with neurogenic orthostatic hypotension the haemodynamics underlying the reduced tolerance to standing after prolonged recumbency at night. In 10 patients with neurogenic orthostatic hypotension (age 33-68 years), of which seven were being treated with fludrocortisone and/or sleeping in the 12 degrees head-up tilt position, 24 h continuous non-invasive finger blood pressure was recorded by a Portapres device. Beat-to-beat blood pressure, heart rate, stroke volume, cardiac output and total peripheral vascular resistance obtained by pulse contour analysis were assessed during 5 min of standing in the evening (at 22.30 hours) and in the morning (at 06.30 hours). On average, the inverse of the normal 24 h blood pressure profile was found, with a large diversity in blood pressure profiles among patients. Supine blood pressure values were similar, but standing blood pressure values were lower in the morning than in the evening (P<0.01). This resulted from larger falls in stroke volume and cardiac output upon standing in the morning compared with the evening, while total peripheral resistance did not change. There was no relationship between the decrease in body weight during the night (mean 0.9 kg; range 0.2-1.6 kg) and the evening-morning difference in standing blood pressure. We conclude that, in patients with neurogenic orthostatic hypotension, the impaired tolerance to standing in the morning is due to larger falls in stroke volume and cardiac output. Not only nocturnal polyuria, but also a redistribution of body fluid, are likely mechanisms underlying the pronounced decreases in stroke volume and cardiac output after prolonged recumbency at night. (+info)
Adrenergic nervous activity in patients after surgical correction of tetralogy of Fallot.
(72/693)
OBJECTIVES: The study was done to define the role of the autonomic nervous system in postoperative tetralogy of Fallot. BACKGROUND: Subsequent to surgical correction of tetralogy of Fallot, patients are at long-term risk of sudden death owing to ventricular electrical instability. The status of the sympathetic nervous system in these patients, known to play an important role in other patients at risk, remains unknown. METHODS: We used (123)I metaiodobenzylguanidine (MIBG) with tomographic imaging, combined with assessment of heart rate variability (HRV), to evaluate the activity of the sympathetic nervous system. We analyzed 22 patients who had undergone total correction of tetralogy of Fallot: 13 with either no or minor ventricular arrhythmias, and 9 with sustained ventricular tachycardia or ventricular fibrillation. RESULTS: Analysis of HRV revealed a reduction in vagal control and sympathetic dominance in all patients compared with a healthy control group of 20 subjects. A significant difference was found in the standard deviation of all the adjacent intervals between normal beats (SDNN) in patients with or without severe ventricular arrhythmias. A significant reduction in uptake of (123)I MIBG was demonstrated 30 min after IV injection, and a trend toward reduction after 5 h, associated with reduced washout indices. These data reflect a decrease in the number of nerve endings in the right and left ventricular walls, and an inhomogeneous distribution of the adrenergic nervous system. The uptake of MIBG was significantly reduced in the patients at risk of ventricular tachycardia or fibrillation. CONCLUSIONS: Subsequent to surgical correction of tetralogy of Fallot, the positive correlation between myocardial uptake of MIBG, SDNN and the QRS dispersion confirmed the usefulness of analysis of the adrenergic nervous system to stratify patients at risk of life-threatening arrhythmias. (+info)