Textbook of Urgent Care Medicine, Chapter 20, Syncope

Published on October 26, 2026

Original Author: Kenneth V. Iserson, MD

Originally published in 2014. Substantially updated and clinically reviewed in 2026 to reflect current evidence, guidelines, and urgent care practice.

Introduction

Syncope occurs in all age groups, but the likelihood of cardiac and other serious causes increases with age and with the prevalence of structural heart disease, arrhythmia, autonomic dysfunction, and polypharmacy.

Noncardiac causes tend to be more common in children and young adults. Though a benign cause is usually found for syncope in children, care must be taken not to miss serious causes.

The goals in the urgent care setting include the following:

Assessing whether the patient experienced true syncope, presyncope, or another form of transient loss of consciousness
Determining whether the event could have a life-threatening etiology
Stabilizing the patient, as required
Transferring patients who need emergency monitoring, imaging, specialty evaluation, or therapeutic intervention

Presentation

Syncope

Syncope is an abrupt, transient, complete loss of consciousness with loss of postural tone caused by transient global cerebral hypoperfusion and followed by rapid, spontaneous recovery. The term does not include seizure, coma, intoxication, head trauma, or other causes of prolonged altered consciousness.

Presyncope

Presyncope (near-syncope) is the sensation of impending loss of consciousness without complete loss of consciousness. It may include graying or tunneling of vision, weakness, diaphoresis, nausea, or light-headedness. Presyncope and syncope share many causes; concerning presyncope should not be dismissed simply because complete loss of consciousness did not occur.

Triage Pearls

Immediate assessment should focus on airway, breathing, circulation, persistent abnormal vital signs, mental status, and evidence of a high-risk cause. Arrange EMS transfer to an emergency department when any of the following are present:

Persistent hypotension, significant bradycardia or tachycardia, hypoxemia, or incomplete recovery
Chest pain, significant dyspnea, new palpitations immediately before syncope, or suspected acute coronary syndrome, pulmonary embolism, or aortic catastrophe
Syncope during exertion or while supine, especially with known structural heart disease or a family history of premature sudden cardiac death
New focal neurologic deficit, severe sudden headache, or concern for intracranial hemorrhage
Active or suspected significant bleeding, including gastrointestinal bleeding, ruptured ectopic pregnancy, or internal hemorrhage
Major injury resulting from the event
A clearly abnormal ECG suggesting ischemia, high-grade conduction disease, pre-excitation, Brugada pattern, marked QT abnormality, or significant arrhythmia

Witnesses to the syncopal event can often describe its character and time course better than the patient. Ask about setting, prodrome, abruptness, position, movement during the event, duration, and rate of recovery.

Table 1. Common Presyncope Symptoms

Symptom	Clinical note
Pallor	Often accompanies reflex/vasovagal episodes
Diaphoresis	Common vasovagal prodrome
Palpitations	Raises concern for arrhythmia when immediately preceding the event
Weakness or light-headedness	Nonspecific but common
Nausea or epigastric discomfort	Common vasovagal prodrome
Blurred, grayed, or tunnel vision	Typical cerebral hypoperfusion symptom
Paresthesias	May occur, especially with hyperventilation

History Pearls

Patient history remains the most effective method to begin assessment of the cause and seriousness of a syncopal event. Combine the patient and bystander history with age, cardiac history, family history, medications, substance use, and the limited information gained from physical examination and testing.

Prior syncope or presyncope and whether the current episode is similar
Known coronary artery disease, cardiomyopathy, heart failure, valvular disease, congenital heart disease, arrhythmia, or implanted cardiac device
Family history of unexplained sudden death, inherited arrhythmia syndrome, or cardiomyopathy, especially at a young age
Syncope during exertion, while supine, or without warning
Palpitations, chest pain, dyspnea, or reduced exercise tolerance
Volume loss or bleeding: vomiting, diarrhea, poor intake, melena, hematemesis, heavy vaginal bleeding, recent surgery, or trauma
Pregnancy possibility with abdominal or pelvic pain or bleeding
Medications that lower blood pressure, slow cardiac conduction, prolong the QT interval, or contribute to dehydration; ask specifically about recent dose changes or new drugs
Diabetes and use of insulin or other glucose-lowering medication
Heat exposure, dehydration, alcohol, or recreational drug use
Situational triggers such as urination, defecation, coughing, pain, fear, or prolonged standing
Features suggesting seizure rather than syncope: prolonged post-event confusion, lateral tongue injury, sustained tonic-clonic activity, or a characteristic epileptic aura

Physical Exam Pearls

The physical exam supplements the patient and bystander history. It should be directed toward cardiovascular, volume, neurologic, bleeding, pregnancy-related, and traumatic causes.

Vital signs: pulse rate and rhythm, respiratory rate, oxygen saturation, temperature, and blood pressure
Orthostatic blood pressure and pulse when the patient can stand safely
General appearance: persistent pallor, diaphoresis, dehydration, or evidence of trauma
Cardiac exam: pathologic murmur, irregular rhythm, bradycardia or tachycardia, or signs of heart failure
Lung exam: focal abnormality, hypoxemia, or findings suggesting pulmonary edema
Abdominal exam when bleeding, aneurysm, or other intra-abdominal disease is suspected
Focused neurologic exam for new focal deficits or persistent altered mental status
Targeted examination for bleeding or pregnancy-related disease when suggested by the history; routine rectal or pelvic examination is not required for every patient

For orthostatic measurements, have the patient rest supine for approximately 5 minutes, then measure blood pressure and pulse after standing, including at about 1 and 3 minutes when feasible. A sustained fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg within 3 minutes supports orthostatic hypotension. Interpret the finding in clinical context.

Testing Pearls

Electrocardiography

A resting 12-lead ECG should be obtained in patients presenting with syncope. Review it for the following:

Acute ischemia or infarction
Significant bradycardia, sinus pauses, high-grade atrioventricular block, or bifascicular block
Ventricular or supraventricular tachyarrhythmia
Markedly prolonged or short QT interval
Brugada pattern
Pre-excitation or other evidence of an inherited arrhythmia syndrome
Pacemaker or implanted-device malfunction
Patterns suggesting structural heart disease or hypertrophic cardiomyopathy

Ancillary Testing

Routine comprehensive laboratory testing has a low yield. Order tests only when the history, examination, or ECG suggests a specific diagnosis or when the result will change disposition.

Point-of-care glucose when hypoglycemia is possible
CBC when anemia or bleeding is suspected
Electrolytes and renal function when dehydration, medication effect, or metabolic abnormality is suspected
Pregnancy testing when pregnancy is possible and the result affects the differential or imaging
Troponin when acute coronary syndrome or myocardial injury is suspected; it is not a routine urgent-care syncope test
Other targeted testing, including D-dimer or infectious studies, only when the corresponding diagnosis is clinically suspected

Routine head CT, brain MRI, carotid imaging, EEG, or chest imaging is not indicated for uncomplicated syncope without neurologic findings, head injury, or another specific clinical indication. Patients who need advanced imaging, echocardiography, prolonged rhythm monitoring, or other hospital-level testing should be referred or transferred according to urgency.

Diagnosis Pearls

Most episodes can be placed into one of three broad groups: reflex (vasovagal or situational) syncope, orthostatic syncope, or cardiac syncope. The urgent care task is often not to establish the final diagnosis, but to identify patients who are low risk enough for outpatient care and those who require emergency evaluation.

Reflex/Vasovagal Events

A typical vasovagal episode usually has a recognizable trigger or prolonged upright posture, a prodrome of warmth, nausea, diaphoresis, or visual dimming, and rapid recovery after lying down. A typical history in a young patient with a normal examination and ECG is reassuring, but the diagnosis should not be used to explain away high-risk features.

Table 2. Features That Influence Urgent Care Disposition

Category	Practical interpretation
Lower-risk features	Clear vasovagal or situational trigger; prodrome; prolonged standing; normal vital signs after recovery; normal cardiac exam; normal ECG; no known structural heart disease; no major injury.
Higher-risk features	Syncope during exertion or while supine; no prodrome; palpitations immediately before loss of consciousness; known heart disease; family history of premature sudden cardiac death; persistent abnormal vital signs; abnormal cardiac exam; abnormal ECG; chest pain or dyspnea; major bleeding; severe headache or focal neurologic deficit; incomplete recovery.
Risk scores	ED-derived tools such as the Canadian Syncope Risk Score or FAINT score may inform risk assessment in appropriate settings, but they require variables not always available in urgent care and should not replace clinical judgment or delay transfer when a serious cause is suspected.

Syncope Versus Seizure

Brief myoclonic or tonic movements can occur during syncope and do not by themselves establish seizure. Prolonged postictal confusion, sustained convulsive activity, lateral tongue biting, or a characteristic epileptic aura favor seizure. Rapid return to baseline favors syncope.

Other Important Causes

Orthostatic syncope may follow volume loss, autonomic dysfunction, or medication effects. A positive orthostatic measurement does not automatically exclude another serious cause.
Cardiac syncope is more likely with exertional or supine events, abrupt loss of consciousness without prodrome, structural heart disease, abnormal ECG, or palpitations immediately before the event.
Pulmonary embolism, significant hemorrhage, ectopic pregnancy, aortic catastrophe, and acute coronary syndrome should be considered when the history or examination points in those directions rather than screened for routinely in every patient.
Neurologic disease is an uncommon cause of true syncope. Focal neurologic findings, persistent altered mental status, or severe sudden headache suggest an alternative diagnosis and require emergency evaluation.
Psychogenic pseudosyncope is a recognized diagnosis, but a syncopal event should not be attributed to a psychiatric cause until dangerous medical causes have been reasonably excluded.

Table 3. Differential Diagnosis of Syncope and Syncope Mimics

Category	Examples
Reflex	Vasovagal; situational (micturition, defecation, cough, pain, fear, prolonged standing); carotid sinus syndrome
Orthostatic	Volume depletion or hemorrhage; medication-related hypotension; autonomic dysfunction; postprandial hypotension
Cardiac arrhythmic	Bradyarrhythmia; high-grade AV block; ventricular or supraventricular tachyarrhythmia; long-QT syndrome; Brugada syndrome; device malfunction
Cardiac structural / cardiopulmonary	Aortic stenosis; hypertrophic cardiomyopathy; heart failure; tamponade; pulmonary embolism; pulmonary hypertension; aortic catastrophe
Metabolic / toxic	Hypoglycemia; hypoxia; medication effect; alcohol or recreational drug effect; carbon monoxide exposure
Neurologic / other mimics	Seizure; subarachnoid hemorrhage or other acute neurologic event when suggested by symptoms; psychogenic pseudosyncope; prolonged intoxication or altered-consciousness states that are not true syncope

Treatment and Disposition Pearls

Disposition According to Risk

Patients with a clearly low-risk reflex or orthostatic cause, normal recovery, reassuring vital signs and examination, and a normal ECG may be managed without hospital admission when appropriate follow-up is available. Treat reversible contributors such as dehydration or medication-related hypotension when safe to do so.

Patients with high-risk features, suspected cardiac syncope, significant comorbidity with an unexplained event, abnormal ECG, exertional syncope, persistent abnormal vital signs, or concern for hemorrhage, pulmonary embolism, ectopic pregnancy, stroke/hemorrhage, or another serious diagnosis should be transferred to an emergency department for monitoring and further evaluation.

Athletes with exertional syncope should not return to competitive sports until they have undergone cardiovascular assessment by an experienced clinician.

For unexplained recurrent syncope, the definitive workup may include ambulatory rhythm monitoring, echocardiography, exercise testing, or autonomic/tilt testing depending on the suspected cause; these tests are generally outside the scope of urgent care.

Medicolegal Pearls

Document the event description, witness history when available, recovery, vital signs, orthostatic measurements when obtained, cardiac and neurologic examination, and ECG interpretation.
Do not discharge a patient with unexplained persistent abnormal vital signs or a high-risk clinical or ECG feature.
Document consideration of serious diagnoses that fit the presentation, including arrhythmia, acute coronary syndrome, pulmonary embolism, significant hemorrhage, ectopic pregnancy, aortic catastrophe, and intracranial disease when clinically relevant.
If outpatient management is chosen, document why the presentation is considered low risk, the follow-up plan, and appropriate activity/driving restrictions based on the suspected cause and local requirements.

References

Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope. Circulation. 2017;136(5):e60-e122.
Bayard M, Gerayli F, Holt J. Syncope: evaluation and differential diagnosis. Am Fam Physician. 2023;108(5):454-463.
Juraschek SP, Cortez MM, Flack JM, et al. Orthostatic hypotension in adults with hypertension: a scientific statement from the American Heart Association. Hypertension. 2024;81:e16-e30.
Thiruganasambandamoorthy V, Sivilotti MLA, Le Sage N, et al. Multicenter emergency department validation of the Canadian Syncope Risk Score. JAMA Intern Med. 2020;180(5):737-744.
Suh EH, Winskill C, Sacco DL, et al. Validation of 2 syncope risk scores and comparison with physician risk estimation. JAMA Netw Open. 2026;9(5):e2617362.
Kligerman SJ, Bykowski J, Schueller G, et al. ACR Appropriateness Criteria: Syncope. J Am Coll Radiol. 2021;18(5S):S229-S238.
Brignole M, Moya A, de Lange FJ, et al. 2018 ESC guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39(21):1883-1948.