Syncope overview
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American Roentgen Ray Society Images of Syncope overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2]
Overview
Syncope (IPA: Template:IPA and Template:IPA), is a sudden, and generally momentary, loss of consciousness, or blacking out caused by the Central Ischaemic Response, because of a lack of sufficient blood and oxygen in the brain. The first symptoms a person feels before fainting are dizziness; a dimming of vision, or brownout; tinnitus; and feeling hot. Moments later, the person's vision turns black, and he or she drops to the floor (or slumps if seated in a chair). If the person is unable to slump from the position to a near-horizontal position, he or she risks dying of the Suspension trauma effect. More serious causes of fainting include cardiac (heart-related) causes such as an abnormal heart rhythm (an arrhythmia), where the heart beats too slowly, too rapidly, or too irregularly to pump enough blood to the brain. Some arrhythmias can be life-threatening. Other important cardio-vascular conditions that can be manifested by syncope include subclavian steal syndrome and aortic stenosis.
Historical Perspective
There is limited information about the historical perspective of syncope.
Classification
Syncope is usually classified based on the underlying mechanisms leading to hypoperfusion. According to European Society of Cardiology (ESC) guideline, syncope is classified to neurally-mediated, orthostatic hypotension, and cardiovascular subtypes. There are some conditions that are incorrectly diagnosed as syncope. These conditions are usually associated with partial or complete loss of consciousness such as epilepsy, metabolic disorders, transient ischemic attack or conditions with loss of posture and without loss of consciousness like cataplexy, drop attacks, falls and pseudo-syncope.
Pathophysiology
Syncope is an entity in which loss of conscience due to cerebral hypoperfusion presents. There are several pathways to explain its pathophysiology, depending on if it is either reflex syncope, orthostatic intolerance, or cardiovascular syncope.
Causes
Peripheral vascular resistance and cardiac output are the two main determinants for the presentation of syncope. autonomic nervous system impairment due to drugs or an autonomic failure, can lead to a decrease in peripheral vascular resistance. Reflex activity impairment may also cause a decrease of peripheral vascular resistance, as the body normal compensation reflexes fail. Decrease in cardiac output may be due to venous pooling, cardioinhibitory reflexes, arrhythmia, hypertension, pulmonary embolism, and volume depletion leading to diminished venous return, among others.
Differentiating Syncope from other Diseases
Screening
Epidemiology and Demographics
Risk Factors
Natural History, Complications, and Prognosis
Diagnosis
History and Symptoms
Syncope itself is a symptom. Patients with syncope may feel balcking out, dizziness, lightheadedness, and temporary loss of consciousness. Patients may experience other symptoms based on the underlying causes of the syncope.
Physical Examination
Laboratory Findings
Electrocardiogram
Electrocardiogram and Holter monitoring can help to analyze the electrical activities of the heart. They can supply information about the heart rhythm and indirectly, the heart size. It may help a doctor determine the relationship between syncope and any possible arrhythmias. Compared to a Holter monitor, electrophysiologic studies have a higher diagnostic yield, and it should be ordered for any patient with suspected arrhythmia.
X-ray
There are no x-ray findings associated with syncope.
CT
Head images such as CT and MRI, may be useful to check for brain diseases that can cause syncope. A CT scan can show brain structure and locate lesions and its surrounding tissues. An MRI uses magnetic fields to produce detailed images of the body, but it is a different type of image than what is produced by computed tomography (CT).
MRI
Echocardiography
In patients with known heart disease, echocardiography is needed to check the heart structure and assess left ventricular function. It uses sound waves to produce an image of the valves, ventricles, and atrium. The image shows the structure of the mitral valve and its movement during the beating of the heart.
Other Diagnostic Studies
A tilt table test can help to reveal abnormal cardiovascular reflexes that produce syncope. During the test, you stand and your initial blood pressure and heart rate are recorded as the baseline. Then the table is tilted at 70 degrees for 45 minutes. Your blood pressure and heart rate are recorded again. At the same time, the nurse observes whether symptoms such as nausea or vomiting appear. A positive result suggests the possibility of vasovagal syncope.
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Surgical intervention is not recommended for the management of syncope.
Primary Prevention
There are no established measures for the primary prevention of syncope.
Secondary Prevention
There are no established measures for the secondary prevention of syncope.