Syncope overview: Difference between revisions
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==Overview== | ==Overview== | ||
[[Syncope]] is defined as abrupt, transient complete loss of consciousness, inability to keep postural tone, rapid spontaneous recovery with the mechanism of [[cerebral hypoperfusion]]. [[Syncope]] is usually [[Classification|classified]] based on the underlying mechanisms leading to [[hypoperfusion]]. [[Syncope]] is [[Classification|classified]] to [[reflex-mediated]], [[orthostatic hypotension]], and [[cardiovascular]] and [[syncope]] of unknown origin subtypes. [[ Neurally mediated syncope]] (common faint) is the most common type of [[reflex syncope]] in younger patients occurs during upright position ( standing , sitting) with prodrome symptoms including [[diaphoresis]], [[warmth]], [[nausea]], and [[pallor]], usually after [[emotional stress]], [[pain]], medical setting. [[Orthostasis hypotension]] is defined as reduction in [[systolic blood pressure]] of ≥20 mmHg or [[diastolic blood pressure]] of ≥10 mm Hg within 3 minutes of standing position and is common in older patients. Carotid sinus syndrome is a type of reflex [[syncope]] due to carotid sinus hypersensitivity defined as [[pause]] ≥3 seconds and/or a reduction of [[systolic blood pressure]] ≥50 mm Hg during stimulation of the [[carotid sinus]] is more common in older patients. Taking [[history]] and [[physical examination] may helpful for the diagnosis. There are some [[conditions]] that are incorrectly [[Diagnose|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.There is limited information about the historical perspective of [[syncope]].There are several pathways to explain its [[pathophysiology]], depending on if it is either reflex syncope, [[orthostatic intolerance]], or [[cardiovascular]] [[syncope]]. [[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. [[Syncope]] should be differentiated from other [[conditions]] causing partial or complete [[loss of consciousness]]. These [[disorders]] may include, [[coma]], [[dizziness]], [[seizure]], and [[vertigo]]. There are [[conditions]] that may mistakenly be diagnosed as syncope. These [[conditions]] include [[epilepsy]], [[hypoglycemia]], [[intoxication]], [[cataplexy]], and [[transient ischemic attacks]]. | [[Syncope]] is defined as abrupt, transient complete loss of consciousness, inability to keep postural tone, rapid spontaneous recovery with the mechanism of [[cerebral hypoperfusion]]. [[Syncope]] is usually [[Classification|classified]] based on the underlying mechanisms leading to [[hypoperfusion]]. [[Syncope]] is [[Classification|classified]] to [[reflex-mediated]], [[orthostatic hypotension]], and [[cardiovascular]] and [[syncope]] of unknown origin subtypes. [[ Neurally mediated syncope]] (common faint) is the most common type of [[reflex syncope]] in younger patients occurs during upright position ( standing , sitting) with prodrome symptoms including [[diaphoresis]], [[warmth]], [[nausea]], and [[pallor]], usually after [[emotional stress]], [[pain]], medical setting. [[Orthostasis hypotension]] is defined as reduction in [[systolic blood pressure]] of ≥20 mmHg or [[diastolic blood pressure]] of ≥10 mm Hg within 3 minutes of standing position and is common in older patients. Carotid sinus syndrome is a type of reflex [[syncope]] due to carotid sinus hypersensitivity defined as [[pause]] ≥3 seconds and/or a reduction of [[systolic blood pressure]] ≥50 mm Hg during stimulation of the [[carotid sinus]] is more common in older patients. Taking [[history]] and [[physical examination] may helpful for the diagnosis. There are some [[conditions]] that are incorrectly [[Diagnose|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.There is limited information about the historical perspective of [[syncope]].There are several pathways to explain its [[pathophysiology]], depending on if it is either reflex syncope, [[orthostatic intolerance]], or [[cardiovascular]] [[syncope]]. [[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. [[Syncope]] should be differentiated from other [[conditions]] causing partial or complete [[loss of consciousness]]. These [[disorders]] may include, [[coma]], [[dizziness]], [[seizure]], and [[vertigo]]. There are [[conditions]] that may mistakenly be diagnosed as syncope. These [[conditions]] include [[epilepsy]], [[hypoglycemia]], [[intoxication]], [[cataplexy]], and [[transient ischemic attacks]]. The [[incidence]] of syncope ranges from 260 to 1950 cases per 100,000 individuals worldwide. It increases with age and especially after age 70 years old. [[Syncope]] affects men and women equally. [[Syncope]] is a [[Sign (medical)|sign]] of insufficient [[cerebral blood flow]] and it should be evaluated for the underlying [[Causes|cause]]. Possible underlying risk factors of cardiac [[syncope]] include Older age (>60 y), [[male]] sex, presence of known [[ischemic heart disease]], [[structural heart disease]], previous [[arrhythmias]], or reduced [[ventricular function]], brief prodromes such as [[palpitations]] or sudden [[loss of consciousness ]] without a prodrome, [[syncope]] during exertion, [[syncope]] in the supine position, low number of [[syncope]] episodes (1 or 2), abnormal [[cardiac]] examination, [[family history]] of inheritable conditions or [[premature sudden cardiac death]] ([[SCD]]) (<50 y of age), Presence of known [[congenital heart disease]]. Common risk factors associated with noncardiac causes of [[syncope]] include younger age, no known cardiac disease, [[syncope]] only in the standing position, positional change from supine or sitting to standing, presence of prodrome: [[nausea]], [[vomiting]], feeling warm, presence of specific triggers ||||( [[dehydration]], [[pain]], stressful stimulus, [[medical environment]]), situational triggers( [[cough]], [[laugh]], [[micturition]], [[defecation]], [[deglutition]]), history of [[syncope]] with similar characteristics and frequent recurrence.[[Patients]] with [[syncope]] are at risk of the development of [[complications]], such as trauma from frequent falls and [[Sudden cardiac death]]. The [[prognosis]] of [[syncope]] depends on underlying [[causes]]. [[Syncope]] caused by [[cardiovascular disease]]s may be life-threatening and is an important cause of [[sudden cardiac death]]. [[Prognosis]] of [[vasovagal syncope]] is favorable. [[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]].[[Patients]] with syncope usually appear normal. Physical examination of [[patients]] with [[syncope]] is usually remarkable for [[cardiac]] [[murmur]], [[orthostatic hypotension]], and altered level of consciousness. Generally, the [[ECG]] of individuals with [[syncope]] is normal. However, [[ECG]] may be remarkable for an [[arrhythmia]]. The [[arrhythmia]] may be seen on the [[EKG]] include [[sinus bradycardia]] <40 beats/min or repetitive sinoatrial blocks or [[Sinus pause|sinus pauses]] > 3s, [[Mobitz II]] 2nd or [[Third degree AV block|3rd-degree atrioventricular block]], alternating [[Left bundle branch block|left]] and [[right bundle branch block]], rapid [[paroxysmal supraventricular tachycardia]], [[ventricular tachycardia]], and [[pacemaker]] malfunction with cardiac pauses. [[Transthoracic echocardiography]] can be useful in the [[diagnostic]] workup of [[patients]] presenting with syncope. This evaluation is especially warranted in [[patients]] who are suspected to have structural heart disease. | ||
== Historical Perspective == | == Historical Perspective == | ||
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Syncope is usually [[Classification|classified]] based on the underlying mechanisms leading to [[hypoperfusion]]. According to '''European Society of Cardiology''' (ESC) guideline, syncope is [[Classification|classified]] to neurally-mediated, [[orthostatic hypotension]], and [[cardiovascular]] subtypes. There are some [[conditions]] that are incorrectly [[Diagnose|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. | Syncope is usually [[Classification|classified]] based on the underlying mechanisms leading to [[hypoperfusion]]. According to '''European Society of Cardiology''' (ESC) guideline, syncope is [[Classification|classified]] to neurally-mediated, [[orthostatic hypotension]], and [[cardiovascular]] subtypes. There are some [[conditions]] that are incorrectly [[Diagnose|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 == | == 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]]. | [[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 == | == 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. | [[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. | ||
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[[Syncope]] should be differentiated from other [[conditions]] causing partial or complete [[loss of consciousness]]. These [[disorders]] may include, [[coma]], [[dizziness]], [[seizure]], and [[vertigo]]. There are [[conditions]] that may mistakenly be diagnosed as syncope. These [[conditions]] include [[epilepsy]], [[hypoglycemia]], [[intoxication]], [[cataplexy]], and [[transient ischemic attacks]]. | [[Syncope]] should be differentiated from other [[conditions]] causing partial or complete [[loss of consciousness]]. These [[disorders]] may include, [[coma]], [[dizziness]], [[seizure]], and [[vertigo]]. There are [[conditions]] that may mistakenly be diagnosed as syncope. These [[conditions]] include [[epilepsy]], [[hypoglycemia]], [[intoxication]], [[cataplexy]], and [[transient ischemic attacks]]. | ||
== Epidemiology and Demographics == | == Epidemiology and Demographics == | ||
The [[incidence]] of syncope ranges from 260 to 1950 cases per 100,000 individuals worldwide. It increases with age and especially after age 70 years old. Syncope affects men and women equally. | The [[incidence]] of syncope ranges from 260 to 1950 cases per 100,000 individuals worldwide. It increases with age and especially after age 70 years old. [[Syncope]] affects men and women equally. | ||
== Risk Factors == | == Risk Factors == | ||
Syncope is a [[Sign (medical)|sign]] of insufficient [[cerebral blood flow]] and it should be evaluated for the underlying [[Causes|cause]]. Possible underlying [[ | [[Syncope]] is a [[Sign (medical)|sign]] of insufficient [[cerebral blood flow]] and it should be evaluated for the underlying [[Causes|cause]]. Possible underlying risk factors of cardiac [[syncope]] include Older age (>60 y), [[male]] sex, presence of known [[ischemic heart disease]], [[structural heart disease]], previous [[arrhythmias]], or reduced [[ventricular function]], brief prodromes such as [[palpitations]] or sudden [[loss of consciousness ]] without a prodrome, [[syncope]] during exertion, [[syncope]] in the supine position, low number of [[syncope]] episodes (1 or 2), abnormal [[cardiac]] examination, [[family history]] of inheritable conditions or [[premature sudden cardiac death]] ([[SCD]]) (<50 y of age), Presence of known [[congenital heart disease]]. Common risk factors associated with noncardiac causes of [[syncope]] include younger age, no known cardiac disease, [[syncope]] only in the standing position, positional change from supine or sitting to standing, presence of prodrome: [[nausea]], [[vomiting]], feeling warm, presence of specific triggers ||||( [[dehydration]], [[pain]], stressful stimulus, [[medical environment]]), situational triggers( [[cough]], [[laugh]], [[micturition]], [[defecation]], [[deglutition]]), history of [[syncope]] with similar characteristics and frequent recurrence. | ||
== Natural History, Complications, and Prognosis == | == Natural History, Complications, and Prognosis == | ||
[[Patients]] with syncope are at risk of the development of [[complications]], such as trauma from frequent falls and [[Sudden cardiac death]]. The [[prognosis]] of syncope depends on underlying [[causes]]. Syncope caused by [[cardiovascular disease]]s may be life-threatening and is an important cause of [[sudden cardiac death]]. [[Prognosis]] of [[vasovagal syncope]] is favorable. | [[Patients]] with syncope are at risk of the development of [[complications]], such as trauma from frequent falls and [[Sudden cardiac death]]. The [[prognosis]] of [[syncope]] depends on underlying [[causes]]. Syncope caused by [[cardiovascular disease]]s may be life-threatening and is an important cause of [[sudden cardiac death]]. [[Prognosis]] of [[vasovagal syncope]] is favorable. | ||
== Diagnosis == | == Diagnosis == | ||
=== History and Symptoms === | === 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. | [[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 === | === Physical Examination === | ||
[[Patients]] with syncope usually appear normal. Physical examination of [[patients]] with syncope is usually remarkable for [[cardiac]] [[murmur]], [[orthostatic hypotension]], and altered level of consciousness. | [[Patients]] with syncope usually appear normal. Physical examination of [[patients]] with [[syncope]] is usually remarkable for [[cardiac]] [[murmur]], [[orthostatic hypotension]], and altered level of consciousness. | ||
=== Laboratory Findings === | === Laboratory Findings === | ||
There are no [[diagnostic]] laboratory findings associated with syncope. Some [[patients]] with syncope may have [[acidosis]], which is usually suggestive of insufficient [[blood flow]]. Other possible laboratory findings may include [[hypoglycemia]], increased [[lactate]] level, [[hypoxia]], and [[hypercapnia]]. | There are no [[diagnostic]] laboratory findings associated with [[syncope]]. Some [[patients]] with [[syncope]] may have [[acidosis]], which is usually suggestive of insufficient [[blood flow]]. Other possible laboratory findings may include [[hypoglycemia]], increased [[lactate]] level, [[hypoxia]], and [[hypercapnia]]. | ||
===Electrocardiogram=== | ===Electrocardiogram=== | ||
Generally, the [[ECG]] of individuals with syncope is normal. However, [[ECG]] may be remarkable for an [[arrhythmia]]. The [[arrhythmia]] may be seen on the [[EKG]] include [[sinus bradycardia]] <40 beats/min or repetitive sinoatrial blocks or [[Sinus pause|sinus pauses]] > 3s, [[Mobitz II]] 2nd or [[Third degree AV block|3rd-degree atrioventricular block]], alternating [[Left bundle branch block|left]] and [[right bundle branch block]], rapid [[paroxysmal supraventricular tachycardia]], [[ventricular tachycardia]], and [[pacemaker]] malfunction with cardiac pauses. | Generally, the [[ECG]] of individuals with syncope is normal. However, [[ECG]] may be remarkable for an [[arrhythmia]]. The [[arrhythmia]] may be seen on the [[EKG]] include [[sinus bradycardia]] <40 beats/min or repetitive sinoatrial blocks or [[Sinus pause|sinus pauses]] > 3s, [[Mobitz II]] 2nd or [[Third degree AV block|3rd-degree atrioventricular block]], alternating [[Left bundle branch block|left]] and [[right bundle branch block]], rapid [[paroxysmal supraventricular tachycardia]], [[ventricular tachycardia]], and [[pacemaker]] malfunction with cardiac pauses. | ||
=== X-ray === | === X-ray === | ||
There are no [[x-ray]] findings associated with syncope. | There are no [[x-ray]] findings associated with [[syncope]]. | ||
===CT=== | ===CT=== | ||
There are no [[CT scan]] findings associated with syncope. | There are no [[CT scan]] findings associated with [[syncope]]. | ||
=== MRI === | === MRI === | ||
There are no [[MRI]] findings associated with syncope. | There are no [[MRI]] findings associated with syncope. | ||
===Echocardiography=== | ===Echocardiography=== | ||
[[Transthoracic echocardiography]] can be useful in the [[diagnostic]] workup of [[patients]] presenting with syncope. This evaluation is especially warranted in [[patients]] who are suspected to have | [[Transthoracic echocardiography]] can be useful in the [[diagnostic]] workup of [[patients]] presenting with syncope. This evaluation is especially warranted in [[patients]] who are suspected to have structural heart disease. | ||
===Other Diagnostic Studies=== | ===Other Diagnostic Studies=== | ||
There are no other [[imaging]] findings associated with syncope. | There are no other [[imaging]] findings associated with syncope. | ||
Revision as of 11:47, 23 November 2020
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Syncope overview On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2]
Overview
Syncope is defined as abrupt, transient complete loss of consciousness, inability to keep postural tone, rapid spontaneous recovery with the mechanism of cerebral hypoperfusion. Syncope is usually classified based on the underlying mechanisms leading to hypoperfusion. Syncope is classified to reflex-mediated, orthostatic hypotension, and cardiovascular and syncope of unknown origin subtypes. Neurally mediated syncope (common faint) is the most common type of reflex syncope in younger patients occurs during upright position ( standing , sitting) with prodrome symptoms including diaphoresis, warmth, nausea, and pallor, usually after emotional stress, pain, medical setting. Orthostasis hypotension is defined as reduction in systolic blood pressure of ≥20 mmHg or diastolic blood pressure of ≥10 mm Hg within 3 minutes of standing position and is common in older patients. Carotid sinus syndrome is a type of reflex syncope due to carotid sinus hypersensitivity defined as pause ≥3 seconds and/or a reduction of systolic blood pressure ≥50 mm Hg during stimulation of the carotid sinus is more common in older patients. Taking history and [[physical examination] may helpful for the diagnosis. 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.There is limited information about the historical perspective of syncope.There are several pathways to explain its pathophysiology, depending on if it is either reflex syncope, orthostatic intolerance, or cardiovascular syncope. 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. Syncope should be differentiated from other conditions causing partial or complete loss of consciousness. These disorders may include, coma, dizziness, seizure, and vertigo. There are conditions that may mistakenly be diagnosed as syncope. These conditions include epilepsy, hypoglycemia, intoxication, cataplexy, and transient ischemic attacks. The incidence of syncope ranges from 260 to 1950 cases per 100,000 individuals worldwide. It increases with age and especially after age 70 years old. Syncope affects men and women equally. Syncope is a sign of insufficient cerebral blood flow and it should be evaluated for the underlying cause. Possible underlying risk factors of cardiac syncope include Older age (>60 y), male sex, presence of known ischemic heart disease, structural heart disease, previous arrhythmias, or reduced ventricular function, brief prodromes such as palpitations or sudden loss of consciousness without a prodrome, syncope during exertion, syncope in the supine position, low number of syncope episodes (1 or 2), abnormal cardiac examination, family history of inheritable conditions or premature sudden cardiac death (SCD) (<50 y of age), Presence of known congenital heart disease. Common risk factors associated with noncardiac causes of syncope include younger age, no known cardiac disease, syncope only in the standing position, positional change from supine or sitting to standing, presence of prodrome: nausea, vomiting, feeling warm, presence of specific triggers ||||( dehydration, pain, stressful stimulus, medical environment), situational triggers( cough, laugh, micturition, defecation, deglutition), history of syncope with similar characteristics and frequent recurrence.Patients with syncope are at risk of the development of complications, such as trauma from frequent falls and Sudden cardiac death. The prognosis of syncope depends on underlying causes. Syncope caused by cardiovascular diseases may be life-threatening and is an important cause of sudden cardiac death. Prognosis of vasovagal syncope is favorable. 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.Patients with syncope usually appear normal. Physical examination of patients with syncope is usually remarkable for cardiac murmur, orthostatic hypotension, and altered level of consciousness. Generally, the ECG of individuals with syncope is normal. However, ECG may be remarkable for an arrhythmia. The arrhythmia may be seen on the EKG include sinus bradycardia <40 beats/min or repetitive sinoatrial blocks or sinus pauses > 3s, Mobitz II 2nd or 3rd-degree atrioventricular block, alternating left and right bundle branch block, rapid paroxysmal supraventricular tachycardia, ventricular tachycardia, and pacemaker malfunction with cardiac pauses. Transthoracic echocardiography can be useful in the diagnostic workup of patients presenting with syncope. This evaluation is especially warranted in patients who are suspected to have structural heart disease.
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
Syncope should be differentiated from other conditions causing partial or complete loss of consciousness. These disorders may include, coma, dizziness, seizure, and vertigo. There are conditions that may mistakenly be diagnosed as syncope. These conditions include epilepsy, hypoglycemia, intoxication, cataplexy, and transient ischemic attacks.
Epidemiology and Demographics
The incidence of syncope ranges from 260 to 1950 cases per 100,000 individuals worldwide. It increases with age and especially after age 70 years old. Syncope affects men and women equally.
Risk Factors
Syncope is a sign of insufficient cerebral blood flow and it should be evaluated for the underlying cause. Possible underlying risk factors of cardiac syncope include Older age (>60 y), male sex, presence of known ischemic heart disease, structural heart disease, previous arrhythmias, or reduced ventricular function, brief prodromes such as palpitations or sudden loss of consciousness without a prodrome, syncope during exertion, syncope in the supine position, low number of syncope episodes (1 or 2), abnormal cardiac examination, family history of inheritable conditions or premature sudden cardiac death (SCD) (<50 y of age), Presence of known congenital heart disease. Common risk factors associated with noncardiac causes of syncope include younger age, no known cardiac disease, syncope only in the standing position, positional change from supine or sitting to standing, presence of prodrome: nausea, vomiting, feeling warm, presence of specific triggers ||||( dehydration, pain, stressful stimulus, medical environment), situational triggers( cough, laugh, micturition, defecation, deglutition), history of syncope with similar characteristics and frequent recurrence.
Natural History, Complications, and Prognosis
Patients with syncope are at risk of the development of complications, such as trauma from frequent falls and Sudden cardiac death. The prognosis of syncope depends on underlying causes. Syncope caused by cardiovascular diseases may be life-threatening and is an important cause of sudden cardiac death. Prognosis of vasovagal syncope is favorable.
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
Patients with syncope usually appear normal. Physical examination of patients with syncope is usually remarkable for cardiac murmur, orthostatic hypotension, and altered level of consciousness.
Laboratory Findings
There are no diagnostic laboratory findings associated with syncope. Some patients with syncope may have acidosis, which is usually suggestive of insufficient blood flow. Other possible laboratory findings may include hypoglycemia, increased lactate level, hypoxia, and hypercapnia.
Electrocardiogram
Generally, the ECG of individuals with syncope is normal. However, ECG may be remarkable for an arrhythmia. The arrhythmia may be seen on the EKG include sinus bradycardia <40 beats/min or repetitive sinoatrial blocks or sinus pauses > 3s, Mobitz II 2nd or 3rd-degree atrioventricular block, alternating left and right bundle branch block, rapid paroxysmal supraventricular tachycardia, ventricular tachycardia, and pacemaker malfunction with cardiac pauses.
X-ray
There are no x-ray findings associated with syncope.
CT
There are no CT scan findings associated with syncope.
MRI
There are no MRI findings associated with syncope.
Echocardiography
Transthoracic echocardiography can be useful in the diagnostic workup of patients presenting with syncope. This evaluation is especially warranted in patients who are suspected to have structural heart disease.
Other Diagnostic Studies
There are no other imaging findings associated with syncope.
Other Diagnostic Studies
Other diagnostic studies for syncope include tilt table test. Tilt table test is especially useful in differentiating syncope from other possible causes of transient loss of consciousness, such as epilepsy and conversion disorder.
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.