-
Journal of Applied Physiology... Mar 2003During standing, both the position of the cerebral circulation and the reductions in mean arterial pressure (MAP) and cardiac output challenge cerebral autoregulatory... (Review)
Review
During standing, both the position of the cerebral circulation and the reductions in mean arterial pressure (MAP) and cardiac output challenge cerebral autoregulatory (CA) mechanisms. Syncope is most often associated with the upright position and can be provoked by any condition that jeopardizes cerebral blood flow (CBF) and regional cerebral tissue oxygenation (cO(2)Hb). Reflex (vasovagal) responses, cardiac arrhythmias, and autonomic failure are common causes. An important defense against a critical reduction in the central blood volume is that of muscle activity ("the muscle pump"), and if it is not applied even normal humans faint. Continuous tracking of CBF by transcranial Doppler-determined cerebral blood velocity (V(mean)) and near-infrared spectroscopy-determined cO(2)Hb contribute to understanding the cerebrovascular adjustments to postural stress; e.g., MAP does not necessarily reflect the cerebrovascular phenomena associated with (pre)syncope. CA may be interpreted as a frequency-dependent phenomenon with attenuated transfer of oscillations in MAP to V(mean) at low frequencies. The clinical implication is that CA does not respond to rapid changes in MAP; e.g., there is a transient fall in V(mean) on standing up and therefore a feeling of lightheadedness that even healthy humans sometimes experience. In subjects with recurrent vasovagal syncope, dynamic CA seems not different from that of healthy controls even during the last minutes before the syncope. Redistribution of cardiac output may affect cerebral perfusion by increased cerebral vascular resistance, supporting the view that cerebral perfusion depends on arterial inflow pressure provided that there is a sufficient cardiac output.
Topics: Cerebrovascular Circulation; Gravitation; Hemodynamics; Humans; Hypotension, Orthostatic; Oxygen; Oxygen Consumption; Syncope
PubMed: 12571122
DOI: 10.1152/japplphysiol.00260.2002 -
Revista Portuguesa de Cardiologia :... Jan 2023
Topics: Humans; Syncope; Cardiovascular Diseases
PubMed: 36370989
DOI: 10.1016/j.repc.2022.01.010 -
Brazilian Journal of Cardiovascular... Feb 2021It is challenging to diagnose syncope in patients with pacemakers. Because these patients have increased morbidity and mortality risks, they require immediate attention...
INTRODUCTION
It is challenging to diagnose syncope in patients with pacemakers. Because these patients have increased morbidity and mortality risks, they require immediate attention to determine the causes in order to provide appropriate treatment. This study aimed to investigate the causes and predictive factors of syncope as well as the methods used to diagnose syncope in cardiac pacemaker patients.
METHODS
Patients with pacemakers implanted owing to sinus node disease or atrioventricular block were evaluated with standardized questionnaires, endocavitary electrograms, and other tests based on the suspected causes of syncope. Mann- Whitney U tests were used to analyze continuous variables and Chi-squared or Fisher's exact tests were used for categorical variables. Logistic regression was used for multivariate analyses. Statistical significance was P<0.05.
RESULTS
The study included 95 patients with pacemakers: 47 experienced syncope in the last 12 months and 48 did not. Of the 100 documented episodes of syncope, 48.9% were vasovagal syncopes, 17% had cardiac-related causes, 10.6% had unknown causes, and 8.5% had pacemaker failure. The multivariate analysis showed that a New York Heart Association (NYHA) Functional Class II was a significant factor for developing syncope (P<0.01).
CONCLUSION
While the most common type of syncope in pacemaker patients was neurally mediated, it is important to perform detailed evaluations in this population as the causes of syncope can be life-threatening. The best diagnostic methods were stored electrogram analysis and the tilt table test. NYHA Functional Class II patients were found to have a higher risk for syncope.
Topics: Atrioventricular Block; Humans; Pacemaker, Artificial; Syncope; Syncope, Vasovagal; Tilt-Table Test
PubMed: 33594860
DOI: 10.21470/1678-9741-2020-0076 -
Deutsches Arzteblatt International Mar 2015
Topics: Carbon Monoxide Poisoning; Critical Care; Emergency Medical Services; Female; Humans; Male; Smoking; Syncope
PubMed: 25869342
DOI: 10.3238/arztebl.2015.0221a -
The Israel Medical Association Journal... Jul 2021
Topics: Clinical Decision Rules; Clinical Decision-Making; Critical Pathways; Emergency Service, Hospital; Humans; Patient Admission; Patient Discharge; Patient Selection; Risk Assessment; Syncope
PubMed: 34251130
DOI: No ID Found -
Clinical Autonomic Research : Official... Jun 2022Orthostatic syncope (transient loss of conscious when standing-fainting) is common and negatively impacts quality of life. Many patients with syncope report experiencing... (Review)
Review
BACKGROUND
Orthostatic syncope (transient loss of conscious when standing-fainting) is common and negatively impacts quality of life. Many patients with syncope report experiencing fatigue, sometimes with "brain fog", which may further impact their quality of life, but the incidence and severity of fatigue in patients with syncope remain unclear. In this systematic review, we report evidence on the associations between fatigue and conditions of orthostatic syncope.
METHODS
We performed a comprehensive literature search of four academic databases to identify articles that evaluated the association between orthostatic syncope [postural orthostatic tachycardia syndrome (POTS), vasovagal syncope (VVS), orthostatic hypotension (OH)] and fatigue. Studies were independently screened using a multi-stage approach by two researchers to maintain consistency and limit bias.
RESULTS
Our initial search identified 2797 articles, of which 13 met our inclusion criteria (POTS n = 10; VVS n = 1; OH n = 1; VVS and POTS n = 1). Fatigue scores were significantly higher in patients with orthostatic syncope than healthy controls, and were particularly severe in those with POTS. Fatigue associated with orthostatic syncope disorders spanned multiple domains, with each dimension contributing equally to increased fatigue. "Brain fog" was an important symptom of POTS, negatively affecting productivity and cognition. Finally, fatigue was negatively associated with mental health in patients with POTS.
CONCLUSION
In conditions of orthostatic syncope, fatigue is prevalent and debilitating, especially in patients with POTS. The consideration of fatigue in patients with orthostatic disorders is essential to improve diagnosis and management of symptoms, thus improving quality of life for affected individuals.
Topics: Fatigue; Humans; Hypotension, Orthostatic; Postural Orthostatic Tachycardia Syndrome; Quality of Life; Syncope; Syncope, Vasovagal; Tilt-Table Test
PubMed: 35689118
DOI: 10.1007/s10286-022-00868-z -
Pediatrics Nov 2017Postvaccination syncope can cause injury. Drinking water prephlebotomy increases peripheral vascular tone, decreasing risk of blood-donation presyncope and syncope. This... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND AND OBJECTIVES
Postvaccination syncope can cause injury. Drinking water prephlebotomy increases peripheral vascular tone, decreasing risk of blood-donation presyncope and syncope. This study evaluated whether drinking water prevaccination reduces postvaccination presyncope, a potential syncope precursor.
METHODS
We conducted a randomized trial of subjects aged 11 to 21 years receiving ≥1 intramuscular vaccine in primary care clinics. Intervention subjects were encouraged to drink 500 mL of water, with vaccination recommended 10 to 60 minutes later. Control subjects received usual care. Presyncope symptoms were assessed with a 12-item survey during the 20-minutes postvaccination. Symptoms were classified with a primary cutoff sensitive for presyncope, and a secondary, more restrictive cutoff requiring greater symptoms. Results were adjusted for clustering by recruitment center.
RESULTS
There were 906 subjects randomly assigned to the control group and 901 subjects randomly assigned to the intervention group. None had syncope. Presyncope occurred in 36.2% of subjects by using the primary definition, and in 8.0% of subjects by using the restrictive definition. There were no significant differences in presyncope by intervention group for the primary (1-sided test, = .24) or restrictive outcome (1-sided test, = .17). Among intervention subjects vaccinated within 10 to 60 minutes after drinking all 500 mL of water ( = 519), no reduction in presyncope was observed for the primary or restrictive outcome (1-sided tests, = .13, = .17). In multivariable regression analysis, presyncope was associated with younger age, history of passing out or nearly passing out after a shot or blood draw, prevaccination anxiety, receiving >1 injected vaccine, and greater postvaccination pain.
CONCLUSIONS
Drinking water before vaccination did not prevent postvaccination presyncope. Predictors of postvaccination presyncope suggest opportunities for presyncope and syncope prevention interventions.
Topics: Adolescent; Child; Drinking; Drinking Water; Female; Humans; Male; Syncope; Vaccination
PubMed: 29061871
DOI: 10.1542/peds.2017-0508 -
British Medical Journal Oct 1958
Topics: Humans; Hypotension; Syncope
PubMed: 13572941
DOI: No ID Found -
American Family Physician Sep 2011Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of... (Review)
Review
Orthostatic hypotension is defined as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of standing when compared with blood pressure from the sitting or supine position. It results from an inadequate physiologic response to postural changes in blood pressure. Orthostatic hypotension may be acute or chronic, as well as symptomatic or asymptomatic. Common symptoms include dizziness, lightheadedness, blurred vision, weakness, fatigue, nausea, palpitations, and headache. Less common symptoms include syncope, dyspnea, chest pain, and neck and shoulder pain. Causes include dehydration or blood loss; disorders of the neurologic, cardiovascular, or endocrine systems; and several classes of medications. Evaluation of suspected orthostatic hypotension begins by identifying reversible causes and underlying associated medical conditions. Head-up tilt-table testing can aid in confirming a diagnosis of suspected orthostatic hypotension when standard orthostatic vital signs are nondiagnostic; it also can aid in assessing treatment response in patients with an autonomic disorder. Goals of treatment involve improving hypotension without excessive supine hypertension, relieving orthostatic symptoms, and improving standing time. Treatment includes correcting reversible causes and discontinuing responsible medications, when possible. Nonpharmacologic treatment should be offered to all patients. For patients who do not respond adequately to nonpharmacologic treatment, fludrocortisone, midodrine, and pyridostigmine are pharmacologic therapies proven to be beneficial.
Topics: Autonomic Nervous System Diseases; Blood Pressure; Exercise Therapy; Humans; Hypotension, Orthostatic; Syncope; Vasoconstrictor Agents
PubMed: 21888303
DOI: No ID Found -
Europace : European Pacing,... Mar 2024The term non-cardiac syncope includes all forms of syncope, in which primary intrinsic cardiac mechanism and non-syncopal transient loss of consciousness can be ruled...
The term non-cardiac syncope includes all forms of syncope, in which primary intrinsic cardiac mechanism and non-syncopal transient loss of consciousness can be ruled out. Reflex syncope and orthostatic hypotension are the most frequent aetiologies of non-cardiac syncope. As no specific therapy is effective for all types of non-cardiac syncope, identifying the underlying haemodynamic mechanism is the essential prerequisite for an effective personalized therapy and prevention of syncope recurrences. Indeed, choice of appropriate therapy and its efficacy are largely determined by the syncope mechanism rather than its aetiology and clinical presentation. The two main haemodynamic phenomena leading to non-cardiac syncope include either profound hypotension or extrinsic asystole/pronounced bradycardia, corresponding to two different haemodynamic syncope phenotypes, the hypotensive and bradycardic phenotypes. The choice of therapy-aimed at counteracting hypotension or bradycardia-depends on the given phenotype. Discontinuation of blood pressure-lowering drugs, elastic garments, and blood pressure-elevating agents such as fludrocortisone and midodrine are the most effective therapies in patients with hypotensive phenotype. Cardiac pacing, cardioneuroablation, and drugs preventing bradycardia such as theophylline are the most effective therapies in patients with bradycardic phenotype of extrinsic cause.
Topics: Humans; Bradycardia; Syncope; Syncope, Vasovagal; Hypotension; Hypotension, Orthostatic
PubMed: 38529800
DOI: 10.1093/europace/euae073