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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]], and 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 during the episode of [[syncope]].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]]. 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.[[CXR]] is necessary for evaluation of patients presented with [[syncope]] and abnormal findings may be suggestive of adverse event. [[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. CT scan is useful when other modalities are inconclusive for evaluation of [[structural heart disease]] in the presence of [[syncope]].If [[syncope]] is suspected due to [[pulmonary thromboembolism]] CT scan is recommended. [[Cardiac MRI]] can be useful in the presence of [[syncope]] and suspected structural or infiltrative heart disease such as [[arrhythmogenic right ventricular dysplasia]] or cardiac [[sarcoidosis]]. Other [[diagnostic]] studies for [[syncope]] include [[tilt table test]] and [[Exercise Stress 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. A [[tilt table test]] can help to reveal [[Vasovagal syncope]] or hypotensive [[syncope]]. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced [[hypotension ]] with or without [[bradycardia]] or [[asystole]] suggestive of [[vasovagal syncope]]. If [[hypotension]] occurs within the first 3 minutes of test [[orthostasis hypotension ]] is concerned. In [[delay orthostasis hypotension]] fall in blood pressure occurs after 3 minutes. [[Exercise stress test]] ([[EST]]) is recommended in the presence of [[syncope]] during exercise or syncope during the occurrence of angina pectori suspected [[myocardial ischemia]]. Contraindications for [[EST]] in patients with [[syncope]] include: [[hypertrophic obstructive cardiomyopathy]], severe [[aortic stenosis]],[[Catecholaminegic polymorphic ventricular tachycardia]](CPVT), [[pulmonary artery hepertension]],[[Interarterial anomalous coronary artery ]],[[Long QT syndrome type 1]]. Medical therapy is the mainstay of the treatment based on the cause and mechanism of [[syncope]] for preventing [[syncope]] recurrences and traumatic injuries and prolong survival. All patients with cardiac [[syncope]] should be hospitalized. If the machanism of [[syncope]] is [[bifascicular block]], [[permanent pacemaker]] is recommended. In the setting of [[inferior myocardial infarction]] and [[complete heart block]], implantation of permanent pacemaker is not the first decision and the best approach is treatment of [[myocardial infarction]]. In [[syncope]] secondary to documented [[VT]], [[VF]] due to [[structural heart disease]] such as ischemic and non-ischemic [[cardiomyopathy]] and decreased [[left ventricular ejection fraction]] treatment of [[arrhythmia]] and [[ICD implantation]] is warranted. In [[VT]] secondary to sarcoidosis and frequent [[syncope]] due to reentry [[arrhythmia]] loop around the granulom formation in [[myocardium]], [[ICD implantation]] is necessary. In inherent causes of [[ventricular tachyarrhythmia]] such as [[Long QT syndrome]], [[Short QT syndrome]], [[Brugada]], [[Cathecolaminegic polymorphic ventricular tachycardia]] ([[CPVT]]), [[Arrhythmogenic right ventricular dysplasia]]([[ARVC]]) making decision for [[ICD implantation]] is associated with documented [[ventricular tachyarrhythmia]]. For other type of [[syncope]] increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with [[neurally mediated syncope]] should be educated about participate factors such as [[dehydration]],[[prolong standing]], [[alcohol]],[[diuretic]], [[vasodilators]] and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in [[neurally mediated syncope]] include [[betablocker]],[[midoderine]], [[SSRI]]. Ingestion of 500 cc water acutely prevents hypotensive [[syncope]]. Some of the measures that can be taken to prevent [[vasovagal syncopal]] episodes include avoidance of prolonged standing, hot environment, humid atmosphere. Secondary prevention strategies following [[syncope]] include [[ICD implantation]] in [[ventricular arrhythmia]] and avoidance of driving for a specific time based on the guideline. | [[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]], and 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 during the episode of [[syncope]].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]]. 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.[[CXR]] is necessary for evaluation of patients presented with [[syncope]] and abnormal findings may be suggestive of adverse event. [[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. CT scan is useful when other modalities are inconclusive for evaluation of [[structural heart disease]] in the presence of [[syncope]].If [[syncope]] is suspected due to [[pulmonary thromboembolism]] CT scan is recommended. [[Cardiac MRI]] can be useful in the presence of [[syncope]] and suspected structural or infiltrative heart disease such as [[arrhythmogenic right ventricular dysplasia]] or cardiac [[sarcoidosis]]. Other [[diagnostic]] studies for [[syncope]] include [[tilt table test]] and [[Exercise Stress 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. A [[tilt table test]] can help to reveal [[Vasovagal syncope]] or hypotensive [[syncope]]. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced [[hypotension ]] with or without [[bradycardia]] or [[asystole]] suggestive of [[vasovagal syncope]]. If [[hypotension]] occurs within the first 3 minutes of test [[orthostasis hypotension ]] is concerned. In [[delay orthostasis hypotension]] fall in blood pressure occurs after 3 minutes. [[Exercise stress test]] ([[EST]]) is recommended in the presence of [[syncope]] during exercise or syncope during the occurrence of angina pectori suspected [[myocardial ischemia]]. Contraindications for [[EST]] in patients with [[syncope]] include: [[hypertrophic obstructive cardiomyopathy]], severe [[aortic stenosis]],[[Catecholaminegic polymorphic ventricular tachycardia]](CPVT), [[pulmonary artery hepertension]],[[Interarterial anomalous coronary artery ]] ,[[Long QT syndrome type 1]]. Medical therapy is the mainstay of the treatment based on the cause and mechanism of [[syncope]] for preventing [[syncope]] recurrences and traumatic injuries and prolong survival. All patients with cardiac [[syncope]] should be hospitalized. If the machanism of [[syncope]] is [[bifascicular block]], [[permanent pacemaker]] is recommended. In the setting of [[inferior myocardial infarction]] and [[complete heart block]], implantation of permanent pacemaker is not the first decision and the best approach is treatment of [[myocardial infarction]]. In [[syncope]] secondary to documented [[VT]], [[VF]] due to [[structural heart disease]] such as ischemic and non-ischemic [[cardiomyopathy]] and decreased [[left ventricular ejection fraction]] treatment of [[arrhythmia]] and [[ICD implantation]] is warranted. In [[VT]] secondary to sarcoidosis and frequent [[syncope]] due to reentry [[arrhythmia]] loop around the granulom formation in [[myocardium]], [[ICD implantation]] is necessary. In inherent causes of [[ventricular tachyarrhythmia]] such as [[Long QT syndrome]], [[Short QT syndrome]], [[Brugada]], [[Cathecolaminegic polymorphic ventricular tachycardia]] ([[CPVT]]), [[Arrhythmogenic right ventricular dysplasia]]([[ARVC]]) making decision for [[ICD implantation]] is associated with documented [[ventricular tachyarrhythmia]]. For other type of [[syncope]] increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with [[neurally mediated syncope]] should be educated about participate factors such as [[dehydration]],[[prolong standing]], [[alcohol]],[[diuretic]], [[vasodilators]] and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in [[neurally mediated syncope]] include [[betablocker]],[[midoderine]], [[SSRI]]. Ingestion of 500 cc water acutely prevents hypotensive [[syncope]]. Some of the measures that can be taken to prevent [[vasovagal syncopal]] episodes include avoidance of prolonged standing, hot environment, humid atmosphere. Secondary prevention strategies following [[syncope]] include [[ICD implantation]] in [[ventricular arrhythmia]] and avoidance of driving for a specific time based on the guideline. | ||
== Historical Perspective == | ==Historical Perspective== | ||
There is limited information about the historical perspective of [[syncope]]. | There is limited information about the historical perspective of [[syncope]]. | ||
== Classification == | ==Classification== | ||
[[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]] 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. | [[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]] 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. | ||
== 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. | ||
== Differentiating Syncope from other Diseases == | ==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]]. | [[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 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. | [[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=== | ||
[[CXR]] is necessary for evaluation of patients presented with [[syncope]] and abnormal findings may be suggestive of adverse event. | [[CXR]] is necessary for evaluation of patients presented with [[syncope]] and abnormal findings may be suggestive of adverse event. | ||
| Line 45: | Line 45: | ||
If [[syncope]] is suspected due to [[pulmonary thromboembolism]] CT scan is recommended. | If [[syncope]] is suspected due to [[pulmonary thromboembolism]] CT scan is recommended. | ||
=== MRI === | ===MRI=== | ||
[[Cardiac MRI]] can be useful in the presence of [[syncope]] and suspected structural or infiltrative heart disease such as [[arrhythmogenic right ventricular dysplasia]] or cardiac [[sarcoidosis]]. | [[Cardiac MRI]] can be useful in the presence of [[syncope]] and suspected structural or infiltrative heart disease such as [[arrhythmogenic right ventricular dysplasia]] or cardiac [[sarcoidosis]]. | ||
| Line 53: | Line 53: | ||
There are no other [[imaging]] findings associated with syncope. | There are no other [[imaging]] findings associated with syncope. | ||
=== Other Diagnostic Studies === | ===Other Diagnostic Studies=== | ||
Other [[diagnostic]] studies for syncope include [[tilt table test]] and [[Exercise Stress 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. A [[tilt table test]] can help to reveal [[Vasovagal syncope]] or hypotensive [[syncope]]. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced [[hypotension ]] with or without [[bradycardia]] or [[asystoe]] suggestive of [[vasovagal syncope]]. If [[hypotension]] occurs within the first 3 minutes of test [[orthostasis hypotension ]] is concerned. In [[delay orthostasis hypotension]] fall in blood pressure occurs after 3 minutes. [[Exercise stress test]] ([[EST]]) is recommended in the presence of [[syncope]] during exercise or [[syncope]] during the occurrence of angina pectori suspected [[myocardial ischemia]]. Contraindications for [[EST]] in patients with [[syncope]] include: [[hypertrophic obstructive cardiomyopathy]], severe [[aortic stenosis]],[[Catecholaminegic polymorphic ventricular tachycardia]](CPVT), [[pulmonary artery hepertension]],[[Interarterial anomalous coronary artery ]],[[Long QT syndrome type 1]]. | Other [[diagnostic]] studies for syncope include [[tilt table test]] and [[Exercise Stress 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. A [[tilt table test]] can help to reveal [[Vasovagal syncope]] or hypotensive [[syncope]]. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced [[hypotension ]] with or without [[bradycardia]] or [[asystoe]] suggestive of [[vasovagal syncope]]. If [[hypotension]] occurs within the first 3 minutes of test [[orthostasis hypotension ]] is concerned. In [[delay orthostasis hypotension]] fall in blood pressure occurs after 3 minutes. [[Exercise stress test]] ([[EST]]) is recommended in the presence of [[syncope]] during exercise or [[syncope]] during the occurrence of angina pectori suspected [[myocardial ischemia]]. Contraindications for [[EST]] in patients with [[syncope]] include: [[hypertrophic obstructive cardiomyopathy]], severe [[aortic stenosis]],[[Catecholaminegic polymorphic ventricular tachycardia]](CPVT), [[pulmonary artery hepertension]],[[Interarterial anomalous coronary artery ]] ,[[Long QT syndrome type 1]]. | ||
== Treatment == | ==Treatment== | ||
=== Medical Therapy === | ===Medical Therapy=== | ||
Medical therapy is the mainstay of the treatment based on the cause and mechanism of [[syncope]] for preventing [[syncope]] recurrences and traumatic injuries and prolong survival. All patients with cardiac [[syncope]] should be hospitalized. If the machanism of [[syncope]] is bifascicular block, [[permanent pacemaker]] is recommended. In the setting of [[inferior myocardial infarction]] and [[complete heart block]], implantation of permanent pacemaker is not the first decision and the best approach is treatment of [[myocardial infarction]]. In [[syncope]] secondary to documented [[VT]], [[VF]] due to [[structural heart disease]] such as ischemic and non-ischemic [[cardiomyopathy]] and decreased [[left ventricular ejection fraction]] treatment of [[arrhythmia]] and [[ICD implantation]] is warranted. In [[VT]] secondary to sarcoidosis and frequent [[syncope]] due to reentry [[arrhythmia]] loop around the granulom formation in [[myocardium]], [[ICD implantation]] is necessary. In inherent causes of [[ventricular tachyarrhythmia]] such as [[Long QT syndrome]], [[Short QT syndrome]], [[Brugada]], [[Cathecolaminegic polymorphic ventricular tachycardia]] ([[CPVT]]), [[Arrhythmogenic right ventricular dysplasia]]([[ARVC]]) making decision for [[ICD implantation]] is associated with documented [[ventricular tachyarrhythmia]]. For other type of [[syncope]] increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with [[neurally mediated syncope]] should be educated about participate factors such as [[dehydration]],[[prolong standing]], [[alcohol]],[[diuretic]], [[vasodilators]] and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in [[neurally mediated syncope]] include [[betablocker]],[[midoderine]], [[SSRI]]. | Medical therapy is the mainstay of the treatment based on the cause and mechanism of [[syncope]] for preventing [[syncope]] recurrences and traumatic injuries and prolong survival. All patients with cardiac [[syncope]] should be hospitalized. If the machanism of [[syncope]] is bifascicular block, [[permanent pacemaker]] is recommended. In the setting of [[inferior myocardial infarction]] and [[complete heart block]], implantation of permanent pacemaker is not the first decision and the best approach is treatment of [[myocardial infarction]]. In [[syncope]] secondary to documented [[VT]], [[VF]] due to [[structural heart disease]] such as ischemic and non-ischemic [[cardiomyopathy]] and decreased [[left ventricular ejection fraction]] treatment of [[arrhythmia]] and [[ICD implantation]] is warranted. In [[VT]] secondary to sarcoidosis and frequent [[syncope]] due to reentry [[arrhythmia]] loop around the granulom formation in [[myocardium]], [[ICD implantation]] is necessary. In inherent causes of [[ventricular tachyarrhythmia]] such as [[Long QT syndrome]], [[Short QT syndrome]], [[Brugada]], [[Cathecolaminegic polymorphic ventricular tachycardia]] ([[CPVT]]), [[Arrhythmogenic right ventricular dysplasia]]([[ARVC]]) making decision for [[ICD implantation]] is associated with documented [[ventricular tachyarrhythmia]]. For other type of [[syncope]] increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with [[neurally mediated syncope]] should be educated about participate factors such as [[dehydration]],[[prolong standing]], [[alcohol]],[[diuretic]], [[vasodilators]] and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in [[neurally mediated syncope]] include [[betablocker]],[[midoderine]], [[SSRI]]. | ||
=== Surgery === | ===Surgery=== | ||
[[Surgical]] [[Intervention (counseling)|intervention]] is not recommended for the management of syncope. | [[Surgical]] [[Intervention (counseling)|intervention]] is not recommended for the management of syncope. | ||
=== Primary Prevention === | ===Primary Prevention=== | ||
Some of the measures that can be taken to prevent [[vasovagal syncopal]] episodes include avoidance of prolonged standing, hot environment, humid atmosphere. | Some of the measures that can be taken to prevent [[vasovagal syncopal]] episodes include avoidance of prolonged standing, hot environment, humid atmosphere. | ||
=== Secondary Prevention === | ===Secondary Prevention=== | ||
Secondary prevention strategies following [[syncope]] include [[ICD implantation]] in [[ventricular arrhythmia]] and avoidance of driving for a specific time based on the guideline. | Secondary prevention strategies following [[syncope]] include [[ICD implantation]] in [[ventricular arrhythmia]] and avoidance of driving for a specific time based on the guideline. | ||
[[Category:Emergency medicine]] | [[Category:Emergency medicine]] | ||
Latest revision as of 17:29, 15 July 2021
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Syncope Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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Syncope overview On the Web |
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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: Sara Zand, M.D.[2] Sahar Memar Montazerin, M.D.[3]
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, and 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 during the episode of syncope.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. 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.CXR is necessary for evaluation of patients presented with syncope and abnormal findings may be suggestive of adverse event. 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. CT scan is useful when other modalities are inconclusive for evaluation of structural heart disease in the presence of syncope.If syncope is suspected due to pulmonary thromboembolism CT scan is recommended. Cardiac MRI can be useful in the presence of syncope and suspected structural or infiltrative heart disease such as arrhythmogenic right ventricular dysplasia or cardiac sarcoidosis. Other diagnostic studies for syncope include tilt table test and Exercise Stress 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. A tilt table test can help to reveal Vasovagal syncope or hypotensive syncope. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced hypotension with or without bradycardia or asystole suggestive of vasovagal syncope. If hypotension occurs within the first 3 minutes of test orthostasis hypotension is concerned. In delay orthostasis hypotension fall in blood pressure occurs after 3 minutes. Exercise stress test (EST) is recommended in the presence of syncope during exercise or syncope during the occurrence of angina pectori suspected myocardial ischemia. Contraindications for EST in patients with syncope include: hypertrophic obstructive cardiomyopathy, severe aortic stenosis,Catecholaminegic polymorphic ventricular tachycardia(CPVT), pulmonary artery hepertension,Interarterial anomalous coronary artery ,Long QT syndrome type 1. Medical therapy is the mainstay of the treatment based on the cause and mechanism of syncope for preventing syncope recurrences and traumatic injuries and prolong survival. All patients with cardiac syncope should be hospitalized. If the machanism of syncope is bifascicular block, permanent pacemaker is recommended. In the setting of inferior myocardial infarction and complete heart block, implantation of permanent pacemaker is not the first decision and the best approach is treatment of myocardial infarction. In syncope secondary to documented VT, VF due to structural heart disease such as ischemic and non-ischemic cardiomyopathy and decreased left ventricular ejection fraction treatment of arrhythmia and ICD implantation is warranted. In VT secondary to sarcoidosis and frequent syncope due to reentry arrhythmia loop around the granulom formation in myocardium, ICD implantation is necessary. In inherent causes of ventricular tachyarrhythmia such as Long QT syndrome, Short QT syndrome, Brugada, Cathecolaminegic polymorphic ventricular tachycardia (CPVT), Arrhythmogenic right ventricular dysplasia(ARVC) making decision for ICD implantation is associated with documented ventricular tachyarrhythmia. For other type of syncope increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with neurally mediated syncope should be educated about participate factors such as dehydration,prolong standing, alcohol,diuretic, vasodilators and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in neurally mediated syncope include betablocker,midoderine, SSRI. Ingestion of 500 cc water acutely prevents hypotensive syncope. Some of the measures that can be taken to prevent vasovagal syncopal episodes include avoidance of prolonged standing, hot environment, humid atmosphere. Secondary prevention strategies following syncope include ICD implantation in ventricular arrhythmia and avoidance of driving for a specific time based on the guideline.
Historical Perspective
There is limited information about the historical perspective of syncope.
Classification
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 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.
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
CXR is necessary for evaluation of patients presented with syncope and abnormal findings may be suggestive of adverse event.
CT
CT scan is useful when other modalities are inconclusive for evaluation of structural heart disease in the presence of syncope.(Class2b, 2017AHA/ACC/HRS guideline). If syncope is suspected due to pulmonary thromboembolism CT scan is recommended.
MRI
Cardiac MRI can be useful in the presence of syncope and suspected structural or infiltrative heart disease such as arrhythmogenic right ventricular dysplasia or cardiac sarcoidosis.
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 and Exercise Stress 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. A tilt table test can help to reveal Vasovagal syncope or hypotensive syncope. The patient is on the table is tilted at 70 degrees for 45 minutes. A positive test is defined induced hypotension with or without bradycardia or asystoe suggestive of vasovagal syncope. If hypotension occurs within the first 3 minutes of test orthostasis hypotension is concerned. In delay orthostasis hypotension fall in blood pressure occurs after 3 minutes. Exercise stress test (EST) is recommended in the presence of syncope during exercise or syncope during the occurrence of angina pectori suspected myocardial ischemia. Contraindications for EST in patients with syncope include: hypertrophic obstructive cardiomyopathy, severe aortic stenosis,Catecholaminegic polymorphic ventricular tachycardia(CPVT), pulmonary artery hepertension,Interarterial anomalous coronary artery ,Long QT syndrome type 1.
Treatment
Medical Therapy
Medical therapy is the mainstay of the treatment based on the cause and mechanism of syncope for preventing syncope recurrences and traumatic injuries and prolong survival. All patients with cardiac syncope should be hospitalized. If the machanism of syncope is bifascicular block, permanent pacemaker is recommended. In the setting of inferior myocardial infarction and complete heart block, implantation of permanent pacemaker is not the first decision and the best approach is treatment of myocardial infarction. In syncope secondary to documented VT, VF due to structural heart disease such as ischemic and non-ischemic cardiomyopathy and decreased left ventricular ejection fraction treatment of arrhythmia and ICD implantation is warranted. In VT secondary to sarcoidosis and frequent syncope due to reentry arrhythmia loop around the granulom formation in myocardium, ICD implantation is necessary. In inherent causes of ventricular tachyarrhythmia such as Long QT syndrome, Short QT syndrome, Brugada, Cathecolaminegic polymorphic ventricular tachycardia (CPVT), Arrhythmogenic right ventricular dysplasia(ARVC) making decision for ICD implantation is associated with documented ventricular tachyarrhythmia. For other type of syncope increasing salt and discontinuation of causing medications and education of the patient is recommended. Patients with neurally mediated syncope should be educated about participate factors such as dehydration,prolong standing, alcohol,diuretic, vasodilators and sitting down or lie-down at the onset of symptoms and doing counterpressure maneuvers( hand gripping, leg crossing, arm tensing). Medications may be helpful in neurally mediated syncope include betablocker,midoderine, SSRI.
Surgery
Surgical intervention is not recommended for the management of syncope.
Primary Prevention
Some of the measures that can be taken to prevent vasovagal syncopal episodes include avoidance of prolonged standing, hot environment, humid atmosphere.
Secondary Prevention
Secondary prevention strategies following syncope include ICD implantation in ventricular arrhythmia and avoidance of driving for a specific time based on the guideline.