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Syncope

Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome. The condition is caused by transient interruption of cerebral blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure that may be benign Benign Fibroadenoma or related to a underlying life-threatening condition. Syncope is not a distinct disease entity; rather, it is a symptom of another pathologic process, whether it be transient or a more established disease process. Syncope may be accompanied by other symptoms, such as light-headedness, sweating, palpitations Palpitations Ebstein’s Anomaly, nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, feeling warm or cold, and visual blurring. Workup includes a detailed history and physical examination, electrocardiography Electrocardiography Recording of the moment-to-moment electromotive forces of the heart as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a cathode ray tube display. Electrocardiogram (ECG), echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA), provocative testing (tilt-table test), or imaging of the suspected culprit vasculature. In many cases, a definite etiology is not found. Management is based on the underlying cause and can include physical countermaneuvers, stopping offending drugs, volume resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome, blood transfusion, and/or cardiac or vascular interventions.

Last updated: Oct 27, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Definition and Epidemiology

Definition

Syncope is a self-limiting Self-Limiting Meningitis in Children, transient loss of consciousness caused by inadequate cerebral blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure that results in inadequate cerebral perfusion. 

  • There is associated loss of postural integrity. 
  • A spontaneous return to baseline levels of neurologic function without the need for resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome or intervention is typical.

Presyncope (also known as near-syncope) is part of the syncope spectrum.

  • Like syncope, it may present with prodromal symptoms. 
  • However, there is no loss of consciousness.

Epidemiology

  • Accounts for: 
    • > 2% of all ED encounters
    • > 5% of all hospital admissions
  • Lifetime prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency in general population: approximately 10%–20%
  • Occurrence has a bimodal age distribution:
    • A peak in late adolescence to early adulthood (mostly vasovagal origin)
    • Second peak in older age, with a sharp rise thereafter

Etiology

Regardless of the underlying cause, syncope is a manifestation of hypoperfusion to either the cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex: Anatomy (bilateral) or the reticular activating system ( RAS RAS Renal artery stenosis (RAS) is the narrowing of one or both renal arteries, usually caused by atherosclerotic disease or by fibromuscular dysplasia. If the stenosis is severe enough, the stenosis causes decreased renal blood flow, which activates the renin-angiotensin-aldosterone system (RAAS) and leads to renovascular hypertension (RVH). Renal Artery Stenosis).

Neurocardiogenic syncope

  • Also known as vasovagal syncope
  • Neurocardiogenic symptoms most common cause of syncope
  • Usually a benign Benign Fibroadenoma, self-limited episode of systemic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension caused by a reflex that increases vagal tone and/or decreases sympathetic tone (i.e., excessive autonomic reflex activity)
  • Manifestations affecting perfusion include:
    • Vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs
    • Reduced cardiac filling 
    • Bradycardia Bradycardia Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias
  • These dynamics result in: 
    • Cerebral hypoperfusion 
    • Loss of consciousness
    • Loss of cortical stimulation of postural tone
  • Situational causes (as a group, referred to as “situational syncope”) include:
    • Emotional stress:
      • Witnessing trauma
      • Sight of needles or blood
      • Extreme anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder or panic attack Panic attack A panic attack is not a mental disorder. Rather, this disorder is a sudden, spontaneous, time-limited period (minutes to an hour) of heightened anxiety or intense fear, often with physical symptoms. Panic Disorder
      • Extreme pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways 
    • Prolonged standing
    • Micturition
    • Defecation Defecation The normal process of elimination of fecal material from the rectum. Gastrointestinal Motility
    • Swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility
    • Coughing/ sneezing Sneezing The sudden, forceful, involuntary expulsion of air from the nose and mouth caused by irritation to the mucous membranes of the upper respiratory tract. Rhinovirus
    • Carotid hypersensitivity:
      • Syncope (or presyncope) resulting from excessive reflex response to carotid sinus Carotid sinus The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure. Carotid Arterial System: Anatomy stimulation
      • Stimuli include head turning, tight neckwear, shaving.

Orthostatic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension

Orthostatic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension is defined by a drop in systolic blood pressure ≥ 20 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg  or reflex tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children > 20 beats per minute with positional change (i.e., failure or inadequacy of the autonomic reflex response).

Volume depletion Volume depletion Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Volume depletion can be caused by GI losses, renal losses, bleeding, poor oral Na intake, or third spacing of fluids. Volume Depletion and Dehydration:

  • Hemorrhage:
    • Traumatic hemorrhage
    • Retroperitoneal Retroperitoneal Peritoneum: Anatomy hemorrhage
    • GI blood loss
    • Splenic rupture Splenic rupture Splenic rupture is a medical emergency that carries a significant risk of hypovolemic shock and death. Injury to the spleen accounts for nearly half of all injuries to intra-abdominal organs. The most common reason for a rupture of the spleen is blunt abdominal trauma, specifically, motor vehicle accidents. Rupture of the Spleen
    • Obstetric/gynecologic blood loss
  • GI losses:
    • Vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
    • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea
  • Diminished thirst drive (primarily in older individuals)
  • Water deprivation
  • Diuretic use
  • Immobility/ deconditioning Deconditioning Psychotherapy

Autonomic dysfunction Autonomic Dysfunction Anterior Cord Syndrome:

  • Primary: 
    • Pure autonomic failure Pure autonomic failure A degenerative disease of the autonomic nervous system that is characterized by idiopathic orthostatic hypotension and a greatly reduced level of catecholamines. No other neurological deficits are present. Hypotension
    • Parkinson disease Parkinson disease Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson’s Disease
    • Multiple system atrophy Multiple System Atrophy A syndrome complex composed of three conditions which represent clinical variants of the same disease process: striatonigral degeneration; shy-drager syndrome; and the sporadic form of olivopontocerebellar atrophies. Clinical features include autonomic, cerebellar, and basal ganglia dysfunction. Pathologic examination reveals atrophy of the basal ganglia, cerebellum, pons, and medulla, with prominent loss of autonomic neurons in the brain stem and spinal cord. Atypical Parkinsonian Syndromes
    • Lewy body dementia Dementia Major neurocognitive disorders (NCD), also known as dementia, are a group of diseases characterized by decline in a person’s memory and executive function. These disorders are progressive and persistent diseases that are the leading cause of disability among elderly people worldwide. Major Neurocognitive Disorders
  • Secondary: 
    • Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
    • Amyloidosis Amyloidosis Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). Amyloidosis
    • Spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy injury 
    • Autoimmune neuropathy Neuropathy Leprosy
    • Paraneoplastic neuropathy Neuropathy Leprosy

Cardiac syncope

  • Heart rhythm disturbances:
    • Tachyarrhythmias:
      • Supraventricular tachycardias
      • Ventricular tachycardias
    • Bradyarrhythmias Bradyarrhythmias Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias (with inadequate ventricular compensation Compensation Respiratory Acidosis): 
      • Sinus node dysfunction Sinus node dysfunction A condition caused by dysfunctions related to the sinoatrial node including impulse generation (cardiac sinus arrest) and impulse conduction (sinoatrial exit block). It is characterized by persistent bradycardia, chronic atrial fibrillation, and failure to resume sinus rhythm following cardioversion. This syndrome can be congenital or acquired, particularly after surgical correction for heart defects. Bradyarrhythmias
      • Atrioventricular block Atrioventricular block Atrioventricular (AV) block is a bradyarrhythmia caused by delay, or interruption, in the electrical conduction between the atria and the ventricles. Atrioventricular block occurs due to either anatomic or functional impairment, and is classified into 3 types. Atrioventricular block (AV block)
    • Other:
      • Long QT syndrome Long QT syndrome Long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization that produces QT prolongation on electrocardiogram (ECG). Long QT syndrome is associated with an increased risk of developing life-threatening cardiac arrhythmias, specifically torsades de pointes. Long QT Syndrome
      • Brugada syndrome Brugada syndrome An autosomal dominant defect of cardiac conduction that is characterized by an abnormal st-segment in leads v1-v3 on the electrocardiogram resembling a right bundle-branch block; high risk of ventricular tachycardia; or ventricular fibrillation; syncopal episode; and possible sudden death. This syndrome is linked to mutations of gene encoding the cardiac sodium channel alpha subunit. Ventricular Tachycardia
      • Pacemaker Pacemaker A device designed to stimulate, by electric impulses, contraction of the heart muscles. It may be temporary (external) or permanent (internal or internal-external). Bradyarrhythmias failure
  • Myocardial ischemia Myocardial ischemia A disorder of cardiac function caused by insufficient blood flow to the muscle tissue of the heart. The decreased blood flow may be due to narrowing of the coronary arteries (coronary artery disease), to obstruction by a thrombus (coronary thrombosis), or less commonly, to diffuse narrowing of arterioles and other small vessels within the heart. Coronary Heart Disease:
    • MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
    • Ischemic cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Cardiomyopathy: Overview and Types
    • Left ventricular free wall rupture
  • Structural heart disease:
    • Hypertrophic cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Cardiomyopathy: Overview and Types
    • Cardiac tamponade Tamponade Pericardial effusion, usually of rapid onset, exceeding ventricular filling pressures and causing collapse of the heart with a markedly reduced cardiac output. Pericarditis
    • Severe native valve disease:
    • Prosthetic valve Prosthetic Valve Soft Tissue Abscess dysfunction
    • Congenital Congenital Chorioretinitis coronary anomalies
    • Cardiac masses and tumors (e.g., atrial myxoma Myxoma A benign neoplasm derived from connective tissue, consisting chiefly of polyhedral and stellate cells that are loosely embedded in a soft mucoid matrix, thereby resembling primitive mesenchymal tissue. It occurs frequently intramuscularly where it may be mistaken for a sarcoma. It appears also in the jaws and the skin. Cardiac Myxoma)

Syncope related to pathology of the great vessels

  • Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism (PE; saddle embolus Saddle embolus Emboli at the bifurcation of the main pulmonary artery. Pulmonary Embolism)
  • Severe pulmonary hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
  • Aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection

Cerebrovascular causes of syncope

  • Bilateral carotid artery disease
  • Subclavian steal syndrome Subclavian steal syndrome A clinically significant reduction in blood supply to the brain stem and cerebellum (i.e., vertebrobasilar insufficiency) resulting from reversal of blood flow through the vertebral artery from occlusion or stenosis of the proximal subclavian or brachiocephalic artery. Common symptoms include vertigo; syncope; and intermittent claudication of the involved upper extremity. Subclavian steal may also occur in asymptomatic individuals. Subclavian Steal Syndrome
  • Global cerebral hypoperfusion
  • Epidural hematoma Hematoma A collection of blood outside the blood vessels. Hematoma can be localized in an organ, space, or tissue. Intussusception (“ lucid interval Lucid Interval Epidural Hemorrhage”)
  • Subarachnoid hemorrhage Subarachnoid Hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most SAHs originate from a saccular aneurysm in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage
  • Transient ischemic attack Transient ischemic attack Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction caused by ischemia without infarction that resolves completely when blood supply is restored. Transient ischemic attack is a neurologic emergency that warrants urgent medical attention. Transient Ischemic Attack (TIA)

Medication-related syncope

Medication-related syncope is generally related to orthostasis or an effect on cardiovascular function.  

  • Diuretics Diuretics Agents that promote the excretion of urine through their effects on kidney function. Heart Failure and Angina Medication (e.g., thiazides or loop diuretics Loop diuretics Loop diuretics are a group of diuretic medications primarily used to treat fluid overload in edematous conditions such as heart failure and cirrhosis. Loop diuretics also treat hypertension, but not as a 1st-line agent. Loop Diuretics):
    • May induce volume depletion Volume depletion Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Volume depletion can be caused by GI losses, renal losses, bleeding, poor oral Na intake, or third spacing of fluids. Volume Depletion and Dehydration
    • May induce electrolyte disturbances
  • Vasoactive medications (e.g., calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes channel blockers, beta blockers, alpha blockers, nitrates Nitrates Nitrates are a class of medications that cause systemic vasodilation (veins > arteries) by smooth muscle relaxation. Nitrates are primarily indicated for the treatment of angina, where preferential venodilation causes pooling of blood, decreased preload, and ultimately decreased myocardial O2 demand. Nitrates, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).):
    • May induce vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs
    • May induce bradycardia Bradycardia Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias or suppress vascular autoregulation Autoregulation Systemic and Special Circulations
  • Antiarrhythmics:
  • Antidepressants (e.g., tricyclic drugs, selective serotonin reuptake inhibitors Serotonin Reuptake Inhibitors Antidepressants encompass several drug classes and are used to treat individuals with depression, anxiety, and psychiatric conditions, as well as those with chronic pain and symptoms of menopause. Antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and many other drugs in a class of their own. Serotonin Reuptake Inhibitors and Similar Antidepressants ( SSRIs SSRIs Serotonin Reuptake Inhibitors and Similar Antidepressants), etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).):

Toxic metabolic causes of syncope

  • Electrolyte disturbance
  • Hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage
  • Hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Intoxication:
    • Alcohol
    • Illicit drugs Illicit Drugs Drugs that are manufactured, obtained, or sold illegally. They include prescription drugs obtained or sold without prescription and non-prescription drugs. Illicit drugs are widely distributed, tend to be grossly impure and may cause unexpected toxicity. Delirium
    • Prescription medication abuse
Dynamics of neurocardiogenic syncope

Dynamics of neurocardiogenic (also known as vasovagal, reflex, or neurally mediated) syncope:
Normally, the heart and the CNS provide hemodynamic inputs to the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem, which then balances sympathetic and parasympathetic tone to maintain perfusion.
A failure of this mechanism, in the face of physiologic stress, results in a paradoxical withdrawal of sympathetic tone simultaneous to increased parasympathetic discharge.
Vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs and relative hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension combined with bradycardia Bradycardia Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias lead to poor cerebral perfusion and syncope.

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Mnemonic

Causes of syncope “SVNCOPE”

  • Situational
  • Vasovagal
  • Neurogenic
  • Cardiac
  • Orthostatic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
  • Psychiatric
  • Everything else

Clinical Presentation

Presenting symptoms

  • Witnessed or unwitnessed loss of consciousness
    • May or may not be preceded by prodromal symptoms
    • May or may not be associated with an identifiable trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation associated with situational syncope
    • May or may not be attributed to an underlying pathologic disturbance
  • Loss of postural tone (e.g., a fall if standing, a slump if seated)
    • May or may not be accompanied by brief convulsive activity
      • May be mistaken for seizure
      • Distinguished from seizure by brevity of convulsions Convulsions Seizures and absence of postictal Postictal Period after the seizure episode during which the individual is disoriented. Seizures state
    • Postural tone returns to normal after individual regains consciousness
  • Major or minor trauma associated with loss of postural tone
  • Spontaneous return of consciousness:
    • Individual may report fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia or tiredness.
    • Generally, return to neurologic baseline level of function, unless:
      • Cause of syncope is cerebrovascular in nature.
      • Neurologic trauma is sustained during postural loss.

Prodromal symptoms

The following symptoms are associated with imminent syncope or presyncope:

  • Light-headedness
  • A feeling of being warm or cold
  • Sweating
  • Palpitations Palpitations Ebstein’s Anomaly
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics or nonspecific abdominal discomfort
  • Visual blurring; can proceed to temporary darkening
  • Diminution of hearing and occurrence of unusual sounds
  • Pallor reported by onlookers

Red flags

Certain presentations suggest more serious causes of syncope:

  • Syncope during exertion
  • Syncope while supine
  • Multiple recurrences within a short period of time
  • Heart murmur or other findings suggesting structural abnormalities
  • Older age
  • Significant injury during syncope
  • Family history Family History Adult Health Maintenance of: 
    • Sudden unexplained death Unexplained Death Sudden Infant Death Syndrome (SIDS)
    • Exertional syncope
    • Unexplained recurrent syncope
    • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures

Diagnosis

The etiology of approximately ½ of syncope cases remains undetermined despite an exhaustive workup. It is imperative to rule out life-threatening etiologies, such as cardiac syncope, PE, subarachnoid hemorrhage Subarachnoid Hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most SAHs originate from a saccular aneurysm in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage, and blood loss.

History

  • Number, frequency, and duration of episodes
  • Onset
  • Position
  • Trauma sustained during loss of postural tone
  • Provocative factors:
    • During or immediately after exertion/exercise (red flag)
    • During or immediately after:
    • While in a warm and/or crowded place
    • During prolonged standing
    • During the postprandial period
    • In association with:
      • Emotional stress
      • Fear
      • Intense pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Immediately following carotid sinus Carotid sinus The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure. Carotid Arterial System: Anatomy stimulation
    • While supine (suggestive of a serious problem)
  • Associated symptoms preceding and/or following the event:
    • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics
    • Vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
    • Feeling cold or clammy
    • Visual auras or blurry vision Vision Ophthalmic Exam
    • Palpitations Palpitations Ebstein’s Anomaly
    • Shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
    • Chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Additional symptoms following the syncopal event:
    • Confusion
    • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
    • Injury
    • Bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess or bowel incontinence
    • Recurrent syncope 
  • Witnessed signs:
    • Manner in which collapse happened
    • External appearance of individual
    • Estimated duration of loss of consciousness
    • Physical movements noted
    • Any breathing changes seen
    • Associated trauma
  • Preexisting medical conditions:
    • Structural heart disease:
      • Ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
      • Valvular heart disease
      • Congenital Congenital Chorioretinitis heart disease
      • Cardiomyopathies Cardiomyopathies A group of diseases in which the dominant feature is the involvement of the cardiac muscle itself. Cardiomyopathies are classified according to their predominant pathophysiological features (dilated cardiomyopathy; hypertrophic cardiomyopathy; restrictive cardiomyopathy) or their etiological/pathological factors (cardiomyopathy, alcoholic; endocardial fibroelastosis). Cardiomyopathy: Overview and Types
      • Prior cardiac surgery Cardiac surgery Cardiac surgery is the surgical management of cardiac abnormalities and of the great vessels of the thorax. In general terms, surgical intervention of the heart is performed to directly restore adequate pump function, correct inherent structural issues, and reestablish proper blood supply via the coronary circulation. Cardiac Surgery
    • Neurologic conditions:
      • Seizure disorders
      • Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache headaches
      • Parkinson disease Parkinson disease Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson’s Disease
      • Stroke
    • Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus:
      • Predisposition to cardiovascular/cerebrovascular disease
      • Prone to development of autonomic neuropathy Neuropathy Leprosy
    • Intoxication:
      • Alcohol
      • Illicit drugs Illicit Drugs Drugs that are manufactured, obtained, or sold illegally. They include prescription drugs obtained or sold without prescription and non-prescription drugs. Illicit drugs are widely distributed, tend to be grossly impure and may cause unexpected toxicity. Delirium
      • Prescription narcotics (e.g., opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics, benzodiazepines Benzodiazepines Benzodiazepines work on the gamma-aminobutyric acid type A (GABAA) receptor to produce inhibitory effects on the CNS. Benzodiazepines do not mimic GABA, the main inhibitory neurotransmitter in humans, but instead potentiate GABA activity. Benzodiazepines, amphetamines Amphetamines Analogs or derivatives of amphetamine. Many are sympathomimetics and central nervous system stimulators causing excitation, vasopressin, bronchodilation, and to varying degrees, anorexia, analepsis, nasal decongestion, and some smooth muscle relaxation. Stimulants)
  • Medications:
  • Family history Family History Adult Health Maintenance:
    • Sudden death (< 40 years of age)
    • Familial cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Cardiomyopathy: Overview and Types
    • Seizure disorders or migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache headaches
    • Familial predisposition to syncope

Physical examination

  • Vital signs:
    • Pulse and blood pressure taken with individual supine, seated, and standing (orthostatic vital signs)
      • Drop of systolic BP > 20 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg diagnostic of orthostatic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
      • Drop of systolic BP > 30 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg in hypertensive individuals
    • Note speed and regularity of pulse.
    • Note rate, regularity, and intensity of breathing effort.
  • Cardiac examination:
    • Note presence of heart murmur, especially if new or worsened.
    • Comparative pulse timing and blood pressure: 
      • Incongruence between upper limbs indicative of proximal aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
      • Incongruence between upper and lower limbs indicative of distal aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
    • Note presence of jugular venous distention ( JVD JVD Cardiovascular Examination), pulmonary rales Rales Respiratory Syncytial Virus, peripheral edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema.
    • Note presence of bruits, especially if new or worsened.
  • Neurologic examination:

ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)

ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) is indicated for all individuals presenting with syncope, regardless of suspected etiology. ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) monitoring should be continued throughout the ED or hospital stay. Notable findings may include:

  • Arrhythmias
  • ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) changes suggestive of cardiac ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
  • PR segment, QRS duration, QT interval QT interval Electrocardiogram (ECG) prolongation (especially if new or worsened)
  • Right heart strain pattern ( S1 S1 Heart Sounds, Q3, T3 T3 A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5′ position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly t3. Thyroid Hormones) suggestive of PE
  • Conduction blocks
  • Specific signs of congenital Congenital Chorioretinitis or acquired structural heart disease

Echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA)

  • Used to screen for structural heart disease in known or suspected cases
  • May detect:
    • Valvular abnormalities
    • Wall-motion abnormalities
    • Left ventricular dysfunction
    • Elevated pulmonary pressures (suggestive of PE)
    • Pericardial effusion Pericardial effusion Fluid accumulation within the pericardium. Serous effusions are associated with pericardial diseases. Hemopericardium is associated with trauma. Lipid-containing effusion (chylopericardium) results from leakage of thoracic duct. Severe cases can lead to cardiac tamponade. Pericardial Effusion and Cardiac Tamponade
    • Masses
    • Vegetations

Laboratory evaluation

  • CBC:
    • RBC indices for: 
      • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
      • Blood loss
      • Erythrocytosis
    • WBC indices for: 
      • Evidence of infection
      • Lymphoproliferation
    • Platelet count for: 
      • Bleeding
      • Thrombotic tendencies
  • CMP to evaluate for:
    • Renal or hepatic dysfunction
    • Electrolyte disturbance
    • Acid–base imbalance
    • Hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Coagulation studies Coagulation studies Coagulation studies are a group of hematologic laboratory studies that reflect the function of blood vessels, platelets, and coagulation factors, which all interact with one another to achieve hemostasis. Coagulation studies are usually ordered to evaluate patients with bleeding or hypercoagulation disorders. Coagulation Studies:
    • PT/PTT to evaluate for coagulopathy
    • Especially in suspected intracerebral/cerebrovascular or GI hemorrhage
  • Cardiac biomarkers:
    • Includes:
      • MB isoenzyme of creatine Creatine An amino acid that occurs in vertebrate tissues and in urine. In muscle tissue, creatine generally occurs as phosphocreatine. Creatine is excreted as creatinine in the urine. Acute Kidney Injury kinase (CKMB)
      • Cardiac troponins
      • Beta-natriuretic peptide
    • Evaluate for the presence of ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease and/or heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
  • Urine toxicology screen
  • Urine hCG for women of childbearing age

Imaging

  • Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (CT, MRI of head/ brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification) for: 
    • Suspected intracranial mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
    • Intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage
    • Cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke
    • Traumatic brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification injury
  • CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests of the chest or ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing/perfusion (VQ) scan for suspected PE
  • Carotid Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography) scan for suspected carotid vascular disease
  • Abdominal CT or ultrasonography to evaluate for: 
    • Splenic rupture Splenic rupture Splenic rupture is a medical emergency that carries a significant risk of hypovolemic shock and death. Injury to the spleen accounts for nearly half of all injuries to intra-abdominal organs. The most common reason for a rupture of the spleen is blunt abdominal trauma, specifically, motor vehicle accidents. Rupture of the Spleen
    • Aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms
    • Intraabdominal and retroperitoneal Retroperitoneal Peritoneum: Anatomy bleeding
  • Abdominoplevic ultrasonography to evaluate for ectopic pregnancy Ectopic pregnancy Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Ectopic Pregnancy or gynecologic sources of hemorrhage 
  • Lower-extremity ultrasonography to evaluate for deep vein thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus ( DVT DVT Deep vein thrombosis (DVT) usually occurs in the deep veins of the lower extremities. The affected veins include the femoral, popliteal, iliofemoral, and pelvic veins. Proximal DVT is more likely to cause a pulmonary embolism (PE) and is generally considered more serious. Deep Vein Thrombosis)
  • Specific imaging indicated for evaluation of other suspected etiologies

Other tests

  • Tilt-table test: changes in posture from lying to standing to evaluate cause of syncope
  • Electroencephalography Electroencephalography Seizures to evaluate for possible seizure
  • Holter monitoring or loop recording for cardiac rhythm disturbances that manifest during the initial ED visit or hospital stay
  • Other specific testing indicated for evaluation of other suspected etiologies

Management

Much of the management of syncope will be specific to the confirmed or suspected etiology. Because the specific etiology of syncope often goes undiagnosed, general measures are discussed here.

Treatment of prodromal symptoms

This includes physical countermaneuvers, such as: 

  • Leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy crossing: simultaneous tensing of leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy, abdominal, and buttock muscles
  • Handgrip: consists of maximum grip on a rubber ball or similar object
  • Arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy tensing: involves gripping one hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy with the other while simultaneously abducting both hands

Immediate treatment

  • Assist the individual to the ground, chair, or stretcher to avoid traumatic injury.
  • Lay individual supine with legs elevated to help with venous return to the heart and to eventually restore cerebral perfusion.
  • Assess vital signs (blood pressure, pulse, respiratory rate Respiratory rate The number of times an organism breathes with the lungs (respiration) per unit time, usually per minute. Pulmonary Examination).
  • Observe other signs (pallor, diaphoresis, seizure activity).
  • Get additional assistance:
    • Call 911.
    • “Is there a doctor in the house?”
  • Attempt to arouse the individual.
  • If high-risk factors are present, admit to the most appropriate unit in the hospital (e.g., telemetry Telemetry Transmission of the readings of instruments to a remote location by means of wires, radio waves, or other means. Crush Syndrome, ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus).

Risk assessment Risk assessment The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. Preoperative Care

  • Low risk for poor outcomes if no evidence of heart disease is identified
  • High-risk features associated with poor outcomes:
    • Evidence of structural or ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
    • History of structural or ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
    • Older age
    • Syncope while supine
    • Syncope during exertion
    • Palpitations Palpitations Ebstein’s Anomaly at time of syncope
    • Chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways at time of syncope
    • Dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea at time of syncope
    • Syncope without prodrome Prodrome Symptoms that appear 24–48 hours prior to migraine onset. Migraine Headache
    • Family history Family History Adult Health Maintenance of sudden cardiac death Sudden cardiac death Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest
    • Association with thunderclap headache Thunderclap Headache Subarachnoid Hemorrhage
    • High-risk physical examination findings:
      • Abnormal vital signs
      • Abnormal cardiac exam
      • Abnormal pulmonary exam
      • Abnormal neurologic exam
    • Abnormal ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)
    • Persistently low blood pressure
    • Low hematocrit Hematocrit The volume of packed red blood cells in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, anemia shows a low value; polycythemia, a high value. Neonatal Polycythemia
  • Promptly rule out life-threatening causes of syncope or syncope mimics (seizure and cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke are not true causes of syncope):
    • MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
    • Nonperfusing cardiac arrhythmia
    • PE
    • Cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke
    • Intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage
    • Aortic rupture
    • Massive hemorrhage
    • Seizure

Therapies to prevent syncope recurrence

Reflex syncope: carotid sinus Carotid sinus The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure. Carotid Arterial System: Anatomy syncope:

Orthostatic hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension

  • Medication-induced:
    • Discontinue offending medication.
    • Substitute with an alternative agent.
    • Adjust dose.
    • Change timing of drug administration.
  • Volume depletion Volume depletion Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Volume depletion can be caused by GI losses, renal losses, bleeding, poor oral Na intake, or third spacing of fluids. Volume Depletion and Dehydration
    • Volume resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome
    • Discontinue/adjust dose of diuretics Diuretics Agents that promote the excretion of urine through their effects on kidney function. Heart Failure and Angina Medication.
    • Counsel about hydration and salt intake.
    • Treat underlying cause (e.g., gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis, hemorrhage).

Causes of syncope that warrant immediate admission/intervention

Cardiac emergencies:

  • Arrhythmias:
    • Documented, suspected, or induced ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia:
      • Advanced cardiac life support (ACLS) protocol if indicated
      • Antiarrhythmics
      • Catheter ablation
      • Implantable cardioverter– defibrillator Defibrillator Cardiac electrical stimulators that apply brief high-voltage electroshocks to the heart. These stimulators are used to restore normal rhythm and contractile function in hearts of patients who are experiencing ventricular fibrillation or ventricular tachycardia that is not accompanied by a palpable pulse. Some defibrillators may also be used to correct certain noncritical dysrhythmias (called synchronized defibrillation or cardioversion), using relatively low-level discharges synchronized to the patient’s ECG waveform. Cardiac Arrest
    • Supraventricular arrhythmias: 
      • ACLS protocol if indicated
      • Antiarrhythmics
      • Catheter ablation
    • Bradyarrhythmias Bradyarrhythmias Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias: permanent pacemakers
  • Ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease ( IHD IHD Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease) or acute coronary syndrome (ACS):
    • Activate ACS protocol if indicated.
    • Coronary intervention or cardiac surgery Cardiac surgery Cardiac surgery is the surgical management of cardiac abnormalities and of the great vessels of the thorax. In general terms, surgical intervention of the heart is performed to directly restore adequate pump function, correct inherent structural issues, and reestablish proper blood supply via the coronary circulation. Cardiac Surgery if indicated 
  • Obstruction to left ventricular outflow caused by aortic stenosis Aortic stenosis Aortic stenosis (AS), or the narrowing of the aortic valve aperture, is the most common valvular heart disease. Aortic stenosis gradually progresses to heart failure, producing exertional dyspnea, angina, and/or syncope. A crescendo-decrescendo systolic murmur is audible in the right upper sternal border. Aortic Stenosis
    • Balloon valvuloplasty
    • Aortic valve Aortic valve The valve between the left ventricle and the ascending aorta which prevents backflow into the left ventricle. Heart: Anatomy replacement

Cerebrovascular emergencies:

  • Immediate noncontrast CT of head if cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke (hemorrhagic or ischemic) or intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage is suspected
  • Appropriate admission/transfer/consultation depending on findings:
    • Neurology
    • Neurosurgery Neurosurgery Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Neurosurgery
    • Interventional vascular team:
      • Interventional radiology Interventional radiology Subspecialty of radiology that combines organ system radiography, catheter techniques and sectional imaging. Penetrating Abdominal Injury
      • Interventional vascular surgery Vascular surgery Vascular surgery is the specialized field of medicine that focuses on the surgical management of the pathologies of the peripheral circulation. The main goal of most vascular procedures is to restore circulatory function to the affected vessels by relieving occlusions or by redirecting blood flow (e.g., bypass). Vascular Surgery/ neurosurgery Neurosurgery Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Neurosurgery
    • Neurologic ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus monitoring

Hemorrhagic emergencies:

Differential Diagnosis

  • Seizure: abnormal electrical activity of the neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology in the cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex: Anatomy that can manifest in numerous ways depending on the region of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification affected. There are numerous etiologies, and investigation of the root cause should be part of the initial evaluation. Diagnosis is made by a clinical evaluation, lab testing, neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant, electroencephalography Electroencephalography Seizures, and antiseizure drug levels. Treatment is by elimination Elimination The initial damage and destruction of tumor cells by innate and adaptive immunity. Completion of the phase means no cancer growth. Cancer Immunotherapy of the cause, if possible, antiseizure drugs, and surgery when drugs are ineffective. 
  • Traumatic brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification injury: physical injury to brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification tissue that temporarily or permanently impairs brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification function. Traumatic brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification injury can be caused by falls, motor vehicle accidents Motor Vehicle Accidents Spinal Cord Injuries, assaults, and sports activities. Individuals may present with loss of consciousness, confusion, amnesia, seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures, and focal neurologic deficits Neurologic Deficits High-Risk Headaches. Diagnosis is by initial rapid trauma assessment, neurologic examination, and CT scan. Initial treatment is optimizing brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification perfusion and supportive care. Severe injuries may require timely surgical intervention.  
  • Intoxication: reversible syndrome associated with substance use, which may cause physical and mental changes (varies depending on the substance that was ingested). Intoxication may lead to accidental death via overdose, and various substances may carry significant complications that increase morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status and mortality Mortality All deaths reported in a given population. Measures of Health Status. Management is usually supportive, although some substances have reversible pharmacologic agents. 
  • Conversion disorders: also called functional neurologic symptom disorder. Conversion disorders are psychiatric disorders with prominent motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology or sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology impairment that is not compatible with any known neurologic medical condition. The deficits are not consciously produced. Individuals are typically impaired in their social and professional life, but can also be inappropriately unconcerned with their symptoms. Treatment centers around education and psychotherapy Psychotherapy Psychotherapy is interpersonal treatment based on the understanding of psychological principles and mechanisms of mental disease. The treatment approach is often individualized, depending on the psychiatric condition(s) or circumstance. Psychotherapy.

References

  1. McDermott, D. (2020). Approach to the adult patient with syncope in the emergency department. Retrieved September 25, 2021, from https://www.uptodate.com/contents/approach-to-the-adult-patient-with-syncope-in-the-emergency-department
  2. Chen-Scarabelli, C., Scarabelli, T. M. (2004). Neurocardiogenic syncope. BMJ 329:336–341. https://doi.org/10.1136/bmj.329.7461.336
  3. Kharsa A, Wadhwa R. Carotid sinus hypersensitivity. StatPearls. Retrieved September 25, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK559059/
  4. Benditt D. (2021). Syncope in adults: epidemiology, pathogenesis, and etiologies. UpToDate. Retrieved September 1, 2021, from https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies
  5. Benditt D. (2021). Syncope in adults: clinical manifestations and initial diagnostic evaluation. UpToDate. Retrieved September 1, 2021, from https://www.uptodate.com/contents/syncope-in-adults-clinical-manifestations-and-initial-diagnostic-evaluation
  6. Benditt D. (2019). Syncope in adults: management. UpToDate. Retrieved September 2, 2021, from https://www.uptodate.com/contents/syncope-in-adults-management
  7. Thompson A.D., Shea M.J. (2020). Syncope.  MSD Manual Professional Version. Retrieved September 2, 2021, from https://www.msdmanuals.com/professional/cardiovascular-disorders/symptoms-of-cardiovascular-disorders/syncope
  8. Kenaan M., Eagle K. (2018). Syncope. Oxford Medicine Online. Retrieved September 2, 2021, from  https://oxfordmedicine.com/view/10.1093/med/9780190862800.001.0001/med-9780190862800-chapter-6
  9. Morag R. (2017). Syncope. Medscape. Retrieved September 2, 2021, from https://emedicine.medscape.com/article/811669

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