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At least 379 records · Page 21Linked to original sources
PubMed1996

Transient autonomic dysfunction precedes ST-segment depression in patients with syndrome X.

Increased sympathetic drive has been suggested to play a role in the pathogenesis of syndrome X (angina pectoris, positive exercise testing, and angiographically normal coronary arteries). Heart rate variability (HRV) studies have shown that patients with syndrome X have an imbalance in autonomic nervous system activity (sympathetic predominance). However, it is not known if transient ST-segment depression which occurs in syndrome X during daily activities is related to this autonomic nervous system dysfunction. This study investigates the relation between the response of the autonomic nervous system, as assessed by HRV analysis, and the occurrence of transient ST-segment depression during 24-hour ambulatory electrocardiographic monitoring in 23 patients (4 men and 19 women, mean age 55 +/- 6 years) with syndrome X. The frequency-domain variables of HRV low-frequency (0.04 to 0.15 Hz) and high-frequency (0.15 to 0.40 Hz) power were measured at 6-minute intervals during the 30 minutes preceding the onset of transient ST-segment depression. Fourteen patients (61%) had > or = 1 episode of ST-segment depression in the 24 hours, whereas the remaining 9 patients (39%) had no significant ST-segment change. HRV measures differed according to whether or not ST-segment depression was associated with increased heart rate. Episodes of ST-segment depression associated with increased heart rate were preceded by a reduction of high-frequency power and an increase in the low-frequency--high-frequency ratio, whereas episodes of ST-segment depression not associated with increased heart rate showed no significant HRV changes. Low-frequency power remained unchanged irrespective of heart rate. Thus, in patients with syndrome X, a sympathovagal imbalance (sympathetic predominance due to vagal tone withdrawal) precedes episodes of ST-segment depression that are associated with an increased heart rate.

Autonomic Nervous System↗
PubMed1996

Cardiac autonomic dysfunction in relapsing-remitting multiple sclerosis during a stable phase.

The autonomic cardiovascular system was studied by means of autonomic tests and heart rate variability related to body movements during sleep, in 20 patients with relapsing-remitting multiple sclerosis in a stable phase and in 9 normal subjects. Responses to autonomic tests in multiple sclerosis and control subjects were similar. Heart rate variability, instead, showed a lower degree of adaptability in patients with multiple sclerosis than in controls during sleep, because of sympathetic system dysfunction. No significant correlation between magnetic resonance lesions and cardiovascular sleep indexes was found.

Adult↗
PubMed2001

Autonomic dysfunction in the ICU patient.

The sympathetic-parasympathetic balance may be altered in critically ill patients. Assessment of autonomic function provides information concerning prognosis, pathogenesis, and treatment strategies in ICU-relevant disorders. Proven tools are heart rate variability, baroreflex sensitivity, and, with limitations, cardiac chemoreflex sensitivity. New nonlinear methods are being evaluated that may predict risk more precisely in critically ill patients. This article summarizes application of these tools in the ICU. In addition, a model is introduced for investigating the impaired autonomic function in multiple organ dysfunction syndrome and sepsis, integrating extrinsic mechanisms and factors that are intrinsic to the cardiac tissue. By this combined approach, the authors hope to gain insight into the pathogenesis of multiple organ dysfunction syndrome. New pathophysiologic concepts are needed for the development of treatment strategies for this life-threatening disease.

Autonomic Nervous System↗
PubMed1994

Cardiovascular autonomic dysfunction in normotensive awake subjects with obstructive sleep apnoea syndrome.

Cardiovascular autonomic function in normotensive awake patients with obstructive sleep apnoea syndrome was studied in 21 normotensive (mean age 48 +/- 14 years), drug-free men with obstructive sleep apnoea syndrome. Cardiovascular reflex tests with continuous blood pressure monitoring and biochemical indices were performed the morning after a standard polygraphic sleep recording. A group of 20 age-matched (mean age 49 +/- 19 years) normal subjects was used as controls. The obstructive sleep apnoea syndrome patients showed higher heart rate and noradrenaline plasma levels (p < 0.05) at rest and a higher blood pressure response to head-up tilt (p < 0.01), suggesting sympathetic overactivity. Respiratory arrhythmia, baroreflex sensitivity index and Valsalva ratio were significantly lower in the obstructive sleep apnoea syndrome group (p < 0.01) whereas the decrease in heart rate induced by the cold face test was significantly higher (p < 0.05) showing a blunting of reflexes dependent on baroreceptor or pulmonary afferents with normal or increased cardiac vagal efferent activity. These abnormalities in autonomic regulation may predispose obstructive sleep apnoea syndrome patients to cardiovascular complications like hypertension and cardiac arrhythmias.

Adult↗
PubMed2003

[Pandysautonomia. Severe autonomic dysfunction accompanying polyneuropathy].

The case of a young woman with complete autonomic paralysis following an event of respiratory and gastrointestinal infections is described. The diagnosis was based upon clinical, neurophysiological, and laboratory findings. In view of the occurrence of identical--although less pronounced--autonomic disturbances in some cases of Guillain-Barré syndrome and the high incidence of minor degrees of weakness, paresthesias, reflex loss, and CSF protein elevation in dysautonomic polyneuropathy, it seems likely that the latter disorder is also an immune polyneuropathy affecting the autonomic fibers within the peripheral nerves.

Adult↗
PubMed1984

Modulation of presynaptic gamma aminobutyric acid release by prostaglandin E2: explanation for epileptogenic activity and dysfunction in autonomic cardiac neural discharge leading to arrhythmias?

Sudden unexplained death accounts for 5-17% of deaths in the epileptic population. It has no known etiology by definition but autonomic dysfunction has been mentioned as a possible progenitor. A review of the literature was begun to ascertain a possible mechanism by which epileptogenic activity and autonomic dysfunction may be induced in these patients. Prostaglandin E2 is implicated as a possible gamma aminobutyric acid neurotransmitter inhibiting agent responsible for epileptogenic activity and autonomic dysfunction leading to arrhythmias in epileptic patients who suddenly die from unexplainable causes.

Animals↗
PubMed2005

Bilateral stimulation of nucleus subthalamicus in advanced Parkinson's disease: no effects on, and of, autonomic dysfunction.

It is not known whether bilateral stimulation of the subthalamic nucleus, performed to improve skeletal motor control in advanced Parkinson's disease, also affects central autonomic regulation of cardiovascular motor function. Furthermore, reduced treatment with dopaminergic and other drugs after bilateral stimulation of the subthalamic nucleus could affect cardiovascular autonomic reflexes and/or other factors controlling blood pressure level. The primary aim of this study was to investigate putative effects of bilateral stimulation of the subthalamic nucleus on the autonomic nervous system, using respiratory heart rate variability and blood pressure responses to tilt as indices. Baseline autonomic tests were performed in 19 patients with Parkinson's disease and 10 matched healthy subjects. Patients were divided in two groups and re-investigated after 1 year of optimized pharmacological treatment (n = 8) or 1 year of bilateral subthalamic nucleus stimulation (n = 11). Both skeletal motor dysfunction and dopaminergic drug treatment were significantly reduced after 1 year of bilateral subthalamic nucleus stimulation. However, heart rate variability as well as blood pressure during tilt was reduced compared to baseline to a similar extent in both patient groups. The number of individual patients showing pathological autonomic test results at 1-year follow-up increased only in the subthalamic nucleus stimulation group. Despite reduced pharmacological treatment and reduced motor disability, bilateral subthalamic nucleus stimulation does not improve cardiovascular autonomic reflex function or protect against development of cardiovascular autonomic failure in Parkinson's disease. Preoperative cardiovascular autonomic reflex dysfunction, conversely, does not exclude an excellent stimulation effect.

Aged↗
PubMed1994

[Autonomic dysfunction in chronic hypotension associated with uremia].

BACKGROUND: Chronic hypotension is a not uncommon complication among hemodialyzed patients which is responsible of an important morbidity. The autonomic nervous system (ANS) dysfunction seems to play a key role in the pathogenesis of chronic hypotension. METHODS: In order to study whether ANS dysfunction is responsible for chronic hypotension in hemodialyzed patients, the authors evaluated the integrity of the whole baroreflex arc by the Valsalva's manoeuver, of parasympathetic efferent pathway by the deep-breathing test and of sympathetic efferent pathway by the hand-grip test in 16 hemodialyzed patients with chronic hypotension, 17 normotensive hemodialyzed patients and 17 normal control subjects. Plasma catecholamine levels were also measured in these patients. RESULTS: In normotensive patients, Valsalva's manoeuver response (p < 0.005) and deep-breathing test response (p < 0.05) were lowered, while hand-grip test response was preserved. In chronic hypotensive patients, in addition to an impaired deep-breathing test (p < 0.05), a further reduced Valsalva's manoeuver response and a lower pressor response to hand-grip test were observed (p < 0.001). Catecholamine levels were higher in both groups of patients (p < 0.01) with respect to control subjects, specially in chronic hypotensive patients. CONCLUSIONS: In hemodialyzed patients (both normotensive and hypotensive) the whole baroreflex function and parasympathetic response are impaired. The lower pressor response to hand-grip test observed in hypotensive patients, in spite of the higher catecholamine levels, suggest that in these patients the cardiovascular dysfunction cannot be ascribed to a reduced sympathetic "outflow" but to a resistance of the target organs (heart and vessels) to the sympathetic stimulation.

Adult↗
PubMed2002

Cardiovascular autonomic dysfunction in familial Mediterranean fever.

OBJECTIVE: To compare the hemodynamic responses to autonomic challenge evoked by upright tilt table testing in patients with familial Mediterranean fever (FMF). METHODS: Forty consecutive patients with FMF and 25 age and sex matched healthy controls were evaluated using the head-up tilt test (HUTT). The main outcome measures were the values of blood pressure (BP) and heart rate (HR) recorded during recumbence and tilt. The endpoints of vasodepressor and cardioinhibitory reactions, orthostatic tachycardia, and postural tachycardia syndrome were recorded. RESULTS: Patients with FMF exhibited significantly higher diastolic BP during supine and tilt measurements (p = 0.003 and 0.04, respectively). In response to tilt, patients showed significant increases in HR compared to healthy subjects (p = 0.02). Pathological endpoints on tilt were observed in the FMF group in 7 patients (17%) and in no controls. FMF severity, genotype, duration of illness, response to therapy, and associated amyloidosis did not correlate with pathological reactions on HUTT. CONCLUSION: FMF patients exhibit an abnormal cardiovascular reactivity, which is clinically occult, but can be detected on autonomic challenge. The abnormal autonomic activity in FMF is similar to dysautonomia described in a variety of rheumatic disorders.

Adolescent↗