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Autonomic Imbalance (autonomic + imbalance)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

The autonomic control of accommodation and implications for human myopia development: a review

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2003
Jennifer C. Chen
Abstract Prolonged nearwork has long been associated with myopia development, however, there is no well described linking mechanism. One theory suggests that if accommodation accuracy during nearwork is not maintained, the defocused retinal image leads to myopia development. Here we review the findings of research aimed at determining whether the autonomic inputs to the ciliary smooth muscle are involved in this type of environmental myopia. We examine whether an autonomic imbalance could be a precursor to axial elongation and the resulting myopia. Accommodation responses, such as tonic accommodation and nearwork-induced accommodative adaptation, as a function of refractive error, are described in relation to an autonomic imbalance model. The collective results of this research point to anomalous accommodation responses, possibly as a result of underlying anomalous autonomic input to the ciliary muscle, being involved in myopia development and progression. [source]

Influence of Age on Linear and Nonlinear Measures of Autonomic Cardiovascular Modulation

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Michael K. Boettger M.D.
Background: Age has been identified as an independent risk factor for cardiovascular diseases. In addition, autonomic imbalance toward sympathetic preponderance has been shown to facilitate the occurrence of heart disease. Here, we aimed to assess autonomic modulation of cardiovascular parameters during normal ageing applying well-established linear and novel nonlinear parameters. Methods: Linear and nonlinear measures of heart rate variability and complexity as well as measures of QT interval variability and baroreflex sensitivity were obtained from a total of 131 healthy, medication-free participants from a continuous age range between 20 and 90 years, who were allocated to three different age groups. Results: Heart rate variability and complexity significantly decreased with age, while regularity of heart rate time series increased. In addition, QT interval variability linearly increased with age, while baroreflex sensitivity showed a pronounced decrease. Overall, concerning effects of ageing, linear and nonlinear parameters showed equal differentiation between groups. Conclusion: These data indicate a shift of autonomic balance toward sympathetic predominance in higher age groups, limiting the reactiveness of the cardiovascular system to adjust to different demands and increasing the risk for developing tachyarrhythmias. Ann Noninvasive Electrocardiol 2010;15(2):165,174 [source]

Annual Scientific Meeting of ASCEPT, 1999 Careful Screening To Target Interventions To Prevent Sudden Cardiac Death

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2001
Allan D Struthers
SUMMARY 1. Cardiac death is due not only to coronary artery disease, but also to left ventricular (LV) abnormalities (fibrosis, dysfunction) and arrhythmogenic triggers, such as autonomic imbalance. 2. Nitric oxide deficiency could be a key mediator leading not only to coronary atherosclerosis, but also to LV abnormalities and autonomic imbalance. 3. It may be possible to screen for the above abnormalities (e.g. echocardiography and brain natriuretic peptide levels for LV abnormalities, 24 h tapes for autonomic imbalance and QT interval analysis). 4. Once individuals are identified as being at high risk, a range of interventions is possible (e.g. intensive statin therapy or angiotensin-converting enzyme inhibitors if LV abnormalities or autonomic imbalance are found). [source]

Paroxysmal atrial fibrillation and insidious neck pain

CLINICAL CARDIOLOGY, Issue 3 2000
Marcio V. Nastri M.D.
Abstract Paroxysmal atrial fibrillation (AF) is an arrhythmia usually secondary to autonomic imbalance, and it may occur in the absence of any structural heart disease. The case of a patient with paroxysmal AF, in whom the arrhythmia may have been a presenting symptom of a later diagnosed cervical schwannoma, is reported. [source]

Cardiac baroreflex control in humans during and immediately after brief exposure to simulated high altitude

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2002
Frédéric Roche
Summary To examine the baroreflex response in humans during and immediately after acute hypoxia exposure, the cardiac baroreflex sensitivity (BRS) was studied using adaptation of RR intervals in response to spontaneous systolic blood pressure fluctuations (sequences methodology) in 11 unacclimatized subjects. All measurements were made under fixed breathing rate, and realized consecutively at baseline level (20 min), at an inspired oxygen concentration of 11% (15 min) and again under normoxic conditions (20 min; recovery period). The spontaneous baroreflex response decreases progressively during hypoxic exposure, causing a tachycardic response at this FiO2 without any significant alteration of the systolic or diastolic blood pressure. The magnitude of decrease for this variable at the end of exposure averaged 42·9 ± 15·6%. The simultaneous spectral analysis of heart rate (HR) variability in hypoxic condition confirmed an alteration in the parasympathetic activity (HFnu: ,17·8 ± 30·9% versus basal conditions, P<0·01) counterbalanced by an exaggerated sympathetic activity (LFnu: +33 ± 42·4%, P<0·05) at the sinus node. Interestingly, we could observe an enhanced cardiac baroreflex response during the period following the inhalation of the hypoxic mixture (+130·6 ± 15·6% of basal conditions, P<0·001). There is a relationship with a significant and abrupt increase in the parasympathetic control of HR (mean HR reached 111 ± 8·1% of the mean basal HR, P<0·01). These results suggest that brief exposure to hypoxia under rate-controlled ventilation is associated with a significant alteration in the spontaneous cardiac baroreflex. This important cardiac autonomic imbalance is followed by a significant increase in the cardiac parasympathetic drive even after the disappearance of the hypoxic stimulus. [source]