Syncope (medicine)
Encyclopedia
Syncope the medical term for fainting, is precisely defined as a transient loss of consciousness
and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension
.
Many forms of syncope are preceded by a prodromal state that often includes dizziness
and loss of vision ("blackout
") (temporary), loss of hearing (temporary), loss of pain and feeling (temporary), nausea
and abdominal discomfort, weakness
, sweating
, a feeling of heat, palpitations and other phenomena, which, if they do not progress to loss of consciousness and postural tone are often denoted "presyncope". Abdominal discomfort prior to loss of consciousness may be indicative of seizure
which should be considered different than syncope.
There are two broad categories of syncope, cardiogenic or reflex
syncope underlie most forms of syncope. Cardiogenic forms are more likely to produce serious morbidity or mortality
and require prompt or even immediate treatment. Although cardiogenic syncope is much more common in older patients, an effort to rule out arrhythmic, obstructive, ischemic, or cardiomyopathic causes of syncope and circulatory inadequacy is mandatory in each patient.
Variants of reflex syncope often have characteristic histories, including precipitants and time course which are made evident by skilled history taking. Thus, the clinical history is the foremost tool used in the differential diagnosis of syncope. Physical examination, and electrocardiogram are part of the initial evaluation of syncope and other more specific tools such as loop recorders may be necessary in clinically uncertain cases.
Syncope does not occur with hypoxia
which can lead to death by suffocation
and does not fulfill the definition of syncope above. Syncope needs to be distinguished from coma
or cerebrovascular accident which can include persistent states of loss of consciousness.
Although syncope may cause physical injury such as head trauma, it is specifically not directly caused by head trauma (concussion) or by a seizure
disorder which may also produce short-lived unconsciousness unless these are also associated with globally reduced brain blood flow
. Syncope is extraordinarily common occurring for the most part in two age ranges: the teen age years, and during older age. Estimates of lifetime incidence of at least one syncopal episode include 40-50% of the general populace.
The respiratory system may contribute to oxygen levels through hyperventilation
, though a sudden ischaemic episode may also proceed faster than the respiratory system can respond. These processes cause the typical symptoms of fainting: pale skin, rapid breathing, nausea and weakness of the limbs, particularly of the legs. If the ischaemia is intense or prolonged, limb weakness progresses to collapse. An individual with very little skin pigmentation may appear to have all color drained from his or her face at the onset of an episode. This effect combined with the following collapse can make a strong and dramatic impression on bystanders.
The weakness of the legs causes most sufferers to sit or lie down if there is time to do so. This may avert a complete collapse, but whether the sufferer sits down or falls down the result of an ischaemic episode is a posture in which less blood pressure is required to achieve adequate blood flow. It is unclear whether this is a mechanism evolved in response to the circulatory difficulties of human bipedalism or merely a serendipitous result of a pre-existing circulatory response.
The vasovagal type can be considered in two forms:
A pattern of background factors contributes to the attacks. There is typically an unsuspected relatively low blood volume, for instance, from taking a low-salt diet in the absence of any salt-retaining tendency. Heat causes vaso-dilatation and worsens the effect of the relatively insufficient blood volume. That sets the scene, but the next stage is the adrenergic response. If there is underlying fear or anxiety (e.g., social circumstances), or acute fear (e.g., acute threat, needle phobia
), the vaso-motor centre demands an increased pumping action by the heart (flight or fight response). This is set in motion via the adrenergic (sympathetic) outflow from the brain, but the heart is unable to meet requirement because of the low blood volume, or decreased return. The high (ineffective) sympathetic activity is always modulated by vagal outflow, in these cases leading to excessive slowing of heart rate. The abnormality lies in this excessive vagal response. The tilt-table test typically evokes the attack.
Much of this pathway was discovered in animal experiments by Bezold (Vienna) in the 1860s. In animals, it may represent a defence mechanism when confronted by danger ("playing possum"). This reflex occurs in only some people and may be similar to that described in other animals.
The mechanism described here suggests that a practical way to prevent attacks would be, what might seem to be counterintuitive, to block the adrenergic signal with a beta-blocker. A simpler plan might be to explain the mechanism, discuss causes of fear, and optimise salt as well as water intake.
Psychological factors also have been found to mediate syncope. It is important for general practitioners and the psychologist in their primary care team to liaise closely and to help patients identify how they might be avoiding activities of daily living due to anticipatory anxiety in relation to a possible faint and the feared physical damage it may cause. Fainting in response to a blood stimulus, needle or a dead body are common and patients can quickly develop safety behaviours to avoid any recurrences of a fainting response. See link for a good description of psychological interventions and theories http://www.lenus.ie/hse/handle/10147/135366.
An evolutionary psychology
view is that some forms of fainting are non-verbal signals that developed in response to increased inter-group aggression during the paleolithic
. A non-combatant who has fainted signals that she or he is not a threat. This would explain the association between fainting and stimuli such as bloodletting and injuries seen in blood-injection-injury type phobia
s such as trypanophobia
as well as the gender differences.
and tachycardia
.
Bradycardia can be caused by heart blocks. Tachycardias include SVT (supraventricular tachycardia
) and VT (ventricular tachycardia
). SVT does not cause syncope except in Wolff-Parkinson-White syndrome
. Ventricular tachycardia
originate in the ventricles. VT causes syncope and can result in sudden death. Ventricular tachycardia, which describes a heart rate of over 100 beats per minute with at least three irregular heartbeats as a sequence of consecutive premature beats, can degenerate into ventricular fibrillation
, which requires DC cardioversion
.
Typically, tachycardic generated syncope is caused by a cessation of beats following a tachycardic episode. This condition, called tachycardia-bradycardia syndrome, is usually caused by sinoatrial node dysfunction or block or atrioventricular block
.
are the most common examples. Aortic stenosis presents with repeated episodes of syncope. Pulmonary embolism
can cause obstructed blood vessels. High blood pressure in the arteries supplying the lungs (pulmonary artery hypertension) can occur during pulmonary embolism
. Rarely, cardiac tumors such as atrial myxomas can also lead to syncope.
, acute aortic dissection, pericardial tamponade, pulmonary embolism, aortic stenosis, and pulmonary hypertension.
, a sinus node dysfunction, causing alternating bradycardia and tachycardia. Often there is a long pause asystole between heartbeat.
Adams-Stokes syndrome is a cardiac syncope which may occur with seizures caused by complete or incomplete heart block. Symptoms include deep and fast respiration, weak and slow pulse and respiratory pauses that may last for 60 seconds.
Aortic dissection
(a tear in the aorta) and cardiomyopathy
can also result in syncope.
Various medications, such as β-blockers, may cause bradycardia induced syncope.
Apparently healthy individuals may experience minor symptoms ("lightheadedness", "greying-out") as they stand up if blood pressure is slow to respond to the stress of upright posture. If the blood pressure is not adequately maintained during standing, faints may develop. However, the resulting "transient orthostatic hypotension" does not necessarily signal any serious underlying disease.
The most susceptible individuals are elderly frail individuals, or persons who are dehydrated from hot environments or inadequate fluid intake. More serious orthostatic hypotension is often the result of certain commonly prescribed medications such as diuretics, β-adrenergic blockers, other anti-hypertensives (including vasodilators), and nitroglycerin. In a small percentage of cases, the cause of orthostatic hypotensive faints is structural damage to the autonomic nervous system
due to systemic diseases (e.g., amyloidosis or diabetes) or in neurological diseases (e.g., Parkinson's disease).
, hypoglycemia
, growth spurts
, physical exercise in excess of the energy reserve of the body, emotional distress, and lack of sleep. Orthostatic hypotension
caused by standing up too quickly or being in a very hot room can also cause fainting.
More serious causes of fainting include cardiac (heart
-related) conditions such as an abnormal heart rhythm (an arrhythmia), wherein 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.
A hemoglobin
count may indicate anemia or blood loss. However, this has been shown to be useful in only about 5% of patients being evaluated for fainting.
An electrocardiogram
(ECG) records the electrical activity of the heart. It is estimated that from 20%-50% of patients will have an abnormal ECG. However, while an ECG may identify conditions such as atrial fibrillation, heart block, or a new or old heart attack, it typically does not provide a definite diagnosis for the underlying cause for fainting.
Sometimes, a Holter monitor
may be used. This is a portable ECG device that can record the wearer's heart rhythms during daily activities over an extended period of time. Since fainting usually does not occur upon command, a Holter monitor can provide a better understanding of the heart's activity during fainting episodes.
The Tilt table test
is performed to elicit orthostatic syncope secondary to autonomic dysfunction (neurogenic).
For patients with more than two episodes of syncope and no diagnosis on “routine testing”, an insertable cardiac monitor might be used. It lasts 14 to 18 months. Smaller than a pack of gum, it is inserted just beneath the skin in the upper chest area. The procedure typically takes 15 to 20 minutes. Once inserted, the device continuously monitors the rate and rhythm of the heart. Upon waking from a “fainting” spell, the patient places a hand held pager size device called an Activator over the implanted device and simply presses a button. This information is stored and retrieved by their physician.
was developed to isolate patients who have higher risk for a serious cause of syncope. Anyone with high risk criteria needs to be further investigated. They are summed up by the CHESS mnemonic: congestive heart failure, hematocrit <30%, electrocardiogram abnormality, shortness of breath, or systolic blood pressure <90 mm Hg.
in the form of phosphene
s, sudden sore throat, nausea, and general shakiness. For individuals who have problems with chronic fainting spells, therapy should focus on recognizing the triggers and learning techniques to keep from fainting. At the appearance of warning signs such as lightheadedness, nausea, or cold and clammy skin, counter-pressure maneuvers that involve gripping fingers into a fist, tensing the arms, and crossing the legs or squeezing the thighs together can be used to ward off a fainting spell. After the symptoms have passed, sleep
is recommended. If fainting spells occur often without a triggering event, syncope may be a sign of an underlying heart disease.
s are frequently cited), but it was fashionable for women to affect an aristocratic frailty and create a scene by fainting at a dramatic moment.
Some individuals occasionally or frequently play "the 'fainting game' " (also referred to in the US as "the 'choking game' "), which involves the deliberate induction of syncope via voluntary restriction of blood flow to the brain, an action that can result in acute or cumulative brain damage and even death.
Consciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
.
Many forms of syncope are preceded by a prodromal state that often includes dizziness
Dizziness
Dizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....
and loss of vision ("blackout
Blackout
-Loss of lighting or communication:* Power outage, an accidental loss of electric power* Rolling blackout, an intentional loss of electric power* Blackout , the practice of minimizing outdoor lighting for protection from attack...
") (temporary), loss of hearing (temporary), loss of pain and feeling (temporary), nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
and abdominal discomfort, weakness
Weakness
Weakness is a symptom represented, medically, by a number of different conditions, including: lack of muscle strength, malaise, dizziness, or fatigue. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a...
, sweating
Sweating
Perspiration is the production of a fluid consisting primarily of water as well as various dissolved solids , that is excreted by the sweat glands in the skin of mammals...
, a feeling of heat, palpitations and other phenomena, which, if they do not progress to loss of consciousness and postural tone are often denoted "presyncope". Abdominal discomfort prior to loss of consciousness may be indicative of seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
which should be considered different than syncope.
There are two broad categories of syncope, cardiogenic or reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
syncope underlie most forms of syncope. Cardiogenic forms are more likely to produce serious morbidity or mortality
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
and require prompt or even immediate treatment. Although cardiogenic syncope is much more common in older patients, an effort to rule out arrhythmic, obstructive, ischemic, or cardiomyopathic causes of syncope and circulatory inadequacy is mandatory in each patient.
Variants of reflex syncope often have characteristic histories, including precipitants and time course which are made evident by skilled history taking. Thus, the clinical history is the foremost tool used in the differential diagnosis of syncope. Physical examination, and electrocardiogram are part of the initial evaluation of syncope and other more specific tools such as loop recorders may be necessary in clinically uncertain cases.
Syncope does not occur with hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
which can lead to death by suffocation
Suffocation
Suffocation is the process of Asphyxia.Suffocation may also refer to:* Suffocation , an American death metal band* "Suffocation", a song on Morbid Angel's debut album, Altars of Madness...
and does not fulfill the definition of syncope above. Syncope needs to be distinguished from coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
or cerebrovascular accident which can include persistent states of loss of consciousness.
Although syncope may cause physical injury such as head trauma, it is specifically not directly caused by head trauma (concussion) or by a seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
disorder which may also produce short-lived unconsciousness unless these are also associated with globally reduced brain blood flow
Blood flow
Blood flow is the continuous running of blood in the cardiovascular system.The human body is made up of several processes all carrying out various functions. We have the gastrointestinal system which aids the digestion and the absorption of food...
. Syncope is extraordinarily common occurring for the most part in two age ranges: the teen age years, and during older age. Estimates of lifetime incidence of at least one syncopal episode include 40-50% of the general populace.
Central nervous system ischaemia
The central ischaemic response is triggered by an inadequate oxygenated blood in the brain.The respiratory system may contribute to oxygen levels through hyperventilation
Hyperventilation
Hyperventilation or overbreathing is the state of breathing faster or deeper than normal, causing excessive expulsion of circulating carbon dioxide. It can result from a psychological state such as a panic attack, from a physiological condition such as metabolic acidosis, can be brought about by...
, though a sudden ischaemic episode may also proceed faster than the respiratory system can respond. These processes cause the typical symptoms of fainting: pale skin, rapid breathing, nausea and weakness of the limbs, particularly of the legs. If the ischaemia is intense or prolonged, limb weakness progresses to collapse. An individual with very little skin pigmentation may appear to have all color drained from his or her face at the onset of an episode. This effect combined with the following collapse can make a strong and dramatic impression on bystanders.
The weakness of the legs causes most sufferers to sit or lie down if there is time to do so. This may avert a complete collapse, but whether the sufferer sits down or falls down the result of an ischaemic episode is a posture in which less blood pressure is required to achieve adequate blood flow. It is unclear whether this is a mechanism evolved in response to the circulatory difficulties of human bipedalism or merely a serendipitous result of a pre-existing circulatory response.
Vertebro-basilar arterial disease
Arterial disease in the upper spinal cord, or lower brain, causes syncope if there is a reduction in blood supply, which may occur with extending the neck or after drugs to lower blood pressure.Vasovagal
Vasovagal (situational) syncope—one of the most common types—may occur in scary, embarrassing or uneasy situations, or during blood drawing, coughing, urination or defecation. Other types include postural syncope (caused by a changing in body posture), cardiac syncope (due to heart-related conditions), and neurological syncope (due to neurological conditions). There are many other causes of syncope, including low blood-sugar levels and lung disease such as emphysema and a pulmonary embolus. The cause of the fainting can be determined by a doctor using a complete history, physical, and various diagnostic tests.The vasovagal type can be considered in two forms:
- Isolated episodes of loss of consciousness, unheralded by any warning symptoms for more than a few moments. These tend to occur in the adolescent age group, and may be associated with fasting, exercise, abdominal straining, or circumstances promoting vaso-dilation (e.g., heat, alcohol). The subject is invariably upright. The tilt-table test, if performed, is generally negative.
- Recurrent syncope with complex associated symptoms. This is so-called Neurally Mediated Syncope (NMS). It is associated with any of the following: preceding or succeeding sleepiness, preceding visual disturbance ("spots before the eyes"), sweating, light-headedness. The subject is usually but not always upright. The tilt-table test, if performed, is generally positive.
A pattern of background factors contributes to the attacks. There is typically an unsuspected relatively low blood volume, for instance, from taking a low-salt diet in the absence of any salt-retaining tendency. Heat causes vaso-dilatation and worsens the effect of the relatively insufficient blood volume. That sets the scene, but the next stage is the adrenergic response. If there is underlying fear or anxiety (e.g., social circumstances), or acute fear (e.g., acute threat, needle phobia
Trypanophobia
Trypanophobia is the extreme fear of medical procedures involving injections or hypodermic needles. It is occasionally referred to as aichmophobia, belonephobia,...
), the vaso-motor centre demands an increased pumping action by the heart (flight or fight response). This is set in motion via the adrenergic (sympathetic) outflow from the brain, but the heart is unable to meet requirement because of the low blood volume, or decreased return. The high (ineffective) sympathetic activity is always modulated by vagal outflow, in these cases leading to excessive slowing of heart rate. The abnormality lies in this excessive vagal response. The tilt-table test typically evokes the attack.
Much of this pathway was discovered in animal experiments by Bezold (Vienna) in the 1860s. In animals, it may represent a defence mechanism when confronted by danger ("playing possum"). This reflex occurs in only some people and may be similar to that described in other animals.
The mechanism described here suggests that a practical way to prevent attacks would be, what might seem to be counterintuitive, to block the adrenergic signal with a beta-blocker. A simpler plan might be to explain the mechanism, discuss causes of fear, and optimise salt as well as water intake.
Psychological factors also have been found to mediate syncope. It is important for general practitioners and the psychologist in their primary care team to liaise closely and to help patients identify how they might be avoiding activities of daily living due to anticipatory anxiety in relation to a possible faint and the feared physical damage it may cause. Fainting in response to a blood stimulus, needle or a dead body are common and patients can quickly develop safety behaviours to avoid any recurrences of a fainting response. See link for a good description of psychological interventions and theories http://www.lenus.ie/hse/handle/10147/135366.
An evolutionary psychology
Evolutionary psychology
Evolutionary psychology is an approach in the social and natural sciences that examines psychological traits such as memory, perception, and language from a modern evolutionary perspective. It seeks to identify which human psychological traits are evolved adaptations, that is, the functional...
view is that some forms of fainting are non-verbal signals that developed in response to increased inter-group aggression during the paleolithic
Paleolithic
The Paleolithic Age, Era or Period, is a prehistoric period of human history distinguished by the development of the most primitive stone tools discovered , and covers roughly 99% of human technological prehistory...
. A non-combatant who has fainted signals that she or he is not a threat. This would explain the association between fainting and stimuli such as bloodletting and injuries seen in blood-injection-injury type phobia
Blood-injection-injury type phobia
According to the DSM-IV classification of mental disorders blood-injection-injury type phobias constitute a subtype of specific phobias. It includes fear of blood , injury phobia and fear of receiving an injection or other invasive medical procedures.A distinctive feature of phobias of this type...
s such as trypanophobia
Trypanophobia
Trypanophobia is the extreme fear of medical procedures involving injections or hypodermic needles. It is occasionally referred to as aichmophobia, belonephobia,...
as well as the gender differences.
Deglutition syncope
Syncope may occur during deglutition. Manisty et al. note: "Deglutition syncope is characterised by loss of consciousness on swallowing; it has been associated not only with ingestion of solid food, but also with carbonated and ice-cold beverages, and even belching."Cardiac arrhythmias
Most common cause of cardiac syncope. Two major groups of arrhythmias are bradycardiaBradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
and tachycardia
Tachycardia
Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
.
Bradycardia can be caused by heart blocks. Tachycardias include SVT (supraventricular tachycardia
Supraventricular tachycardia
Supraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
) and VT (ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
). SVT does not cause syncope except in Wolff-Parkinson-White syndrome
Wolff-Parkinson-White syndrome
Wolff–Parkinson–White syndrome is a disorder of the heart in which the ventricles of the heart contract prematurely due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles...
. Ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
originate in the ventricles. VT causes syncope and can result in sudden death. Ventricular tachycardia, which describes a heart rate of over 100 beats per minute with at least three irregular heartbeats as a sequence of consecutive premature beats, can degenerate into ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
, which requires DC cardioversion
Cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...
.
Typically, tachycardic generated syncope is caused by a cessation of beats following a tachycardic episode. This condition, called tachycardia-bradycardia syndrome, is usually caused by sinoatrial node dysfunction or block or atrioventricular block
Atrioventricular block
An atrioventricular block involves the impairment of the conduction between the atria and ventricles of the heart.The causes of pathological AV block are varied and include ischaemia, infarction, fibrosis or drugs. Certain AV blocks can also be found as normal variants, such as in athletes or...
.
Obstructive cardiac lesion
Aortic stenosis and mitral stenosisMitral stenosis
Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
are the most common examples. Aortic stenosis presents with repeated episodes of syncope. Pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
can cause obstructed blood vessels. High blood pressure in the arteries supplying the lungs (pulmonary artery hypertension) can occur during pulmonary embolism
Pulmonary embolism
Pulmonary embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream . Usually this is due to embolism of a thrombus from the deep veins in the legs, a process termed venous thromboembolism...
. Rarely, cardiac tumors such as atrial myxomas can also lead to syncope.
Structural cardiopulmonary disease
These are relatively infrequent causes of faints. The most common cause in this category is fainting associated with an acute myocardial infarction or ischemic event. The faint in this case is primarily caused by an abnormal nervous system reaction similar to the reflex faints. In general, faints caused by structural disease of the heart or blood vessels are particularly important to recognize, as they are warning of potentially life-threatening conditions. Among other conditions prone to trigger syncope (by either hemodynamic compromise or by a neural reflex mechanism, or both), some of the most important are hypertrophic cardiomyopathyHypertrophic cardiomyopathy
Hypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...
, acute aortic dissection, pericardial tamponade, pulmonary embolism, aortic stenosis, and pulmonary hypertension.
Other cardiac causes
Sick sinus syndromeSick sinus syndrome
Sick sinus syndrome, also called sinus node dysfunction, is a group of abnormal heart rhythms presumably caused by a malfunction of the sinus node, the heart's primary pacemaker...
, a sinus node dysfunction, causing alternating bradycardia and tachycardia. Often there is a long pause asystole between heartbeat.
Adams-Stokes syndrome is a cardiac syncope which may occur with seizures caused by complete or incomplete heart block. Symptoms include deep and fast respiration, weak and slow pulse and respiratory pauses that may last for 60 seconds.
Aortic dissection
Aortic dissection
Aortic dissection occurs when a tear in the inner wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. The dissection typically extends anterograde, but can extend retrograde from the site of the intimal tear. Aortic dissection is a medical...
(a tear in the aorta) and cardiomyopathy
Cardiomyopathy
Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...
can also result in syncope.
Various medications, such as β-blockers, may cause bradycardia induced syncope.
Blood pressure
Orthostatic (postural) hypotensive faints are as common or perhaps even more common than vasovagal syncope. Orthostatic faints are most often associated with movement from lying or sitting to a standing position.Apparently healthy individuals may experience minor symptoms ("lightheadedness", "greying-out") as they stand up if blood pressure is slow to respond to the stress of upright posture. If the blood pressure is not adequately maintained during standing, faints may develop. However, the resulting "transient orthostatic hypotension" does not necessarily signal any serious underlying disease.
The most susceptible individuals are elderly frail individuals, or persons who are dehydrated from hot environments or inadequate fluid intake. More serious orthostatic hypotension is often the result of certain commonly prescribed medications such as diuretics, β-adrenergic blockers, other anti-hypertensives (including vasodilators), and nitroglycerin. In a small percentage of cases, the cause of orthostatic hypotensive faints is structural damage to the autonomic nervous system
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
due to systemic diseases (e.g., amyloidosis or diabetes) or in neurological diseases (e.g., Parkinson's disease).
Other causes
Factors that influence fainting are fasting long hours, taking in too little food and fluids, low blood pressureBlood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
, hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
, growth spurts
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
, physical exercise in excess of the energy reserve of the body, emotional distress, and lack of sleep. Orthostatic hypotension
Orthostatic hypotension
Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...
caused by standing up too quickly or being in a very hot room can also cause fainting.
More serious causes of fainting include cardiac (heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
-related) conditions such as an abnormal heart rhythm (an arrhythmia), wherein 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
Subclavian steal syndrome
In medicine, subclavian steal syndrome , also called subclavian steal phenomenon or subclavian steal steno-occlusive disease, is a constellation of signs and symptoms that arise from retrograde flow of blood in the vertebral artery or the internal thoracic artery, due to a proximal stenosis ...
and aortic stenosis.
Clinical tests
If one is suffering from syncope, there are many underlying causes that may be contributing to the episodes. It is important to understand that there is no master list of tests that are currently being used to diagnose the underlying cause(s). However, there are some common diagnostic tests for fainting.A hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
count may indicate anemia or blood loss. However, this has been shown to be useful in only about 5% of patients being evaluated for fainting.
An electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG) records the electrical activity of the heart. It is estimated that from 20%-50% of patients will have an abnormal ECG. However, while an ECG may identify conditions such as atrial fibrillation, heart block, or a new or old heart attack, it typically does not provide a definite diagnosis for the underlying cause for fainting.
Sometimes, a Holter monitor
Holter monitor
In medicine, a Holter monitor is a portable device for continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours...
may be used. This is a portable ECG device that can record the wearer's heart rhythms during daily activities over an extended period of time. Since fainting usually does not occur upon command, a Holter monitor can provide a better understanding of the heart's activity during fainting episodes.
The Tilt table test
Tilt table test
A tilt table test, occasionally called upright tilt testing, is a medical procedure often used to diagnose dysautonomia or syncope. Patients with symptoms of dizziness or lightheadedness, with or without a loss of consciousness , suspected to be associated with a drop in blood pressure or...
is performed to elicit orthostatic syncope secondary to autonomic dysfunction (neurogenic).
For patients with more than two episodes of syncope and no diagnosis on “routine testing”, an insertable cardiac monitor might be used. It lasts 14 to 18 months. Smaller than a pack of gum, it is inserted just beneath the skin in the upper chest area. The procedure typically takes 15 to 20 minutes. Once inserted, the device continuously monitors the rate and rhythm of the heart. Upon waking from a “fainting” spell, the patient places a hand held pager size device called an Activator over the implanted device and simply presses a button. This information is stored and retrieved by their physician.
San Francisco syncope rule
The San Francisco syncope ruleSan Francisco Syncope Rule
The San Francisco Syncope Rule is a simple rule for evaluating the risk of adverse outcomes in patient who present with fainting or syncope.The mnemonic for features of the rule is CHESS:• C - History of congestive heart failure...
was developed to isolate patients who have higher risk for a serious cause of syncope. Anyone with high risk criteria needs to be further investigated. They are summed up by the CHESS mnemonic: congestive heart failure, hematocrit <30%, electrocardiogram abnormality, shortness of breath, or systolic blood pressure <90 mm Hg.
Management
Recommended treatment involves returning blood to the brain by positioning the person on the ground, with legs slightly elevated or leaning forward and the head between the knees for at least 10-15 minutes, preferably in a cool and quiet place. As the dizziness and the momentary blindness passes, the person may experience a brief period of visual disturbancesEntoptic phenomenon
Entoptic phenomena are visual effects whose source is within the eye itself. In Helmholtz's words:...
in the form of phosphene
Phosphene
A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos and phainein...
s, sudden sore throat, nausea, and general shakiness. For individuals who have problems with chronic fainting spells, therapy should focus on recognizing the triggers and learning techniques to keep from fainting. At the appearance of warning signs such as lightheadedness, nausea, or cold and clammy skin, counter-pressure maneuvers that involve gripping fingers into a fist, tensing the arms, and crossing the legs or squeezing the thighs together can be used to ward off a fainting spell. After the symptoms have passed, sleep
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
is recommended. If fainting spells occur often without a triggering event, syncope may be a sign of an underlying heart disease.
Society and culture
Fainting in women was a commonplace trope or stereotype in Victorian England and in contemporary and modern depictions of the period. This may have been partly due to genuine ill-health (the respiratory effects of corsetCorset
A corset is a garment worn to hold and shape the torso into a desired shape for aesthetic or medical purposes...
s are frequently cited), but it was fashionable for women to affect an aristocratic frailty and create a scene by fainting at a dramatic moment.
Some individuals occasionally or frequently play "the 'fainting game' " (also referred to in the US as "the 'choking game' "), which involves the deliberate induction of syncope via voluntary restriction of blood flow to the brain, an action that can result in acute or cumulative brain damage and even death.
Further reading
- Grubb, Blair P. The Fainting Phenomenon; Understanding Why People Faint and What to Do About It. 2001. 2nd ed. New York: Blackwell Publishing, 2007