Presyncope and Syncope: Workup and Emergency Management

Syncope and its precursor, presyncope, are among the most common presenting complaints in emergency departments. The clinical challenge lies less in the acute management itself – most patients are already conscious again at the time of presentation – but in risk stratification. Behind a seemingly harmless "fainting spell" may lurk a life-threatening cardiac cause. At the same time, an indiscriminate workup leads to unnecessary hospital admissions and resource consumption. A structured approach with clear decision points is therefore essential.

Definitions and Differentiation

Syncope is defined as a transient, self-limiting loss of consciousness caused by transient global cerebral hypoperfusion. Its characteristics include rapid onset, short duration (usually under 20 seconds, rarely more than a few minutes), and spontaneous, complete recovery without neurological deficit.

Presyncope describes the prodromal stage with symptoms such as dizziness, nausea, sweating, tunnel vision, and the sensation of impending loss of consciousness – without actually progressing to complete loss of consciousness. Clinically, it must be taken just as seriously as complete syncope with regard to the underlying etiology.

Critical is the differentiation from conditions that can mimic syncope but are not syncope:

• Epileptic seizure: prolonged loss of consciousness, postictal confusion, lateral tongue bite, tonic-clonic movements (not just myoclonus)
• Hypoglycemia: prolonged impairment of consciousness, no self-limiting course
• Psychogenic pseudosyncope: often longer duration, eyes closed, no signs of injury, situational context
• TIA/Stroke: focal neurological deficits; loss of consciousness is possible with vertebrobasilar ischemia but rarely occurs in isolation
• Intoxication: often identifiable from the history

Pathophysiology and Classification

The common final pathway of every syncope is transient cerebral hypoperfusion. Classification is based on the underlying mechanism:

Reflex Syncope (Neurocardiogenic)

The most common form, which includes vasovagal syncope, situational syncope, and carotid sinus syncope. The pathomechanism is based on an inappropriate reflex response with vasodilation (vasodepressor type), bradycardia (cardioinhibitory type), or a combination of both (mixed type).

Typical triggers:

• Prolonged standing, heat, crowds
• Pain, blood draws, emotional stress
• Micturition, defecation, coughing, swallowing (situational)
• Head turning, shaving, tight collar (carotid sinus)

Orthostatic Syncope

Caused by an inadequate compensatory mechanism during position change from lying/sitting to standing. By definition, orthostatic hypotension is present when:

• Systolic blood pressure drop ≥ 20 mmHg or
• Diastolic drop ≥ 10 mmHg or
• Systolic blood pressure < 90 mmHg

within 3 minutes of standing up.

Common causes:

• Volume depletion (dehydration, hemorrhage)
• Medication-related (antihypertensives, diuretics, tricyclic antidepressants, alpha-blockers, nitrates)
• Autonomic dysfunction (diabetes mellitus, Parkinson's disease, multiple system atrophy)
• Age-related baroreflex impairment

Cardiac Syncope

The most dangerous category with the highest mortality. It is subdivided into:

Arrhythmogenic:

• Bradycardia: sinus node dysfunction, second-degree AV block Mobitz type II or third-degree AV block
• Tachycardia: ventricular tachycardia (VT), Torsades de Pointes, supraventricular tachycardia with high ventricular rate
• Channelopathies: Long QT syndrome, Brugada syndrome, CPVT
• Pacemaker/ICD dysfunction

Structural:

• Aortic stenosis (most common structural cause)
• Hypertrophic obstructive cardiomyopathy (HOCM)
• Pulmonary embolism
• Aortic dissection
• Cardiac tamponade
• Atrial myxoma

Red Flags: When Does Syncope Become Dangerous?

Identifying warning signs is the key to correct risk stratification. The following red flags suggest a potentially life-threatening cause and require further workup, usually on an inpatient basis:

Historical Red Flags:

• Syncope during physical exertion (not after – that would be more suggestive of vasovagal)
• Syncope while supine or from sleep
• Palpitations immediately before the event
• Sudden loss of consciousness without prodromal symptoms
• Positive family history of sudden cardiac death (especially in those under 40)
• Known structural heart disease or reduced left ventricular function
• First episode in patients > 60 years without a clear trigger
• Chest pain or dyspnea before syncope

Clinical and Diagnostic Red Flags:

• Abnormal ECG (see below)
• Systolic heart murmur (aortic stenosis, HOCM)
• Persistent bradycardia < 40/min or tachycardia in the emergency department
• Hypotension unresponsive to position change
• Signs of gastrointestinal bleeding (rectal examination!)
• Elevated troponin or significant BNP elevation

ECG Findings You Must Not Miss

The 12-lead ECG is the single most important investigation in syncope. The following findings should be classified as high-risk:

• QTc prolongation > 500 ms (or > 460 ms with symptoms)
• QTc shortening < 340 ms
• Brugada pattern (coved-type ST elevation in V1–V3)
• Epsilon wave or T-wave inversions in right precordial leads (suggestive of ARVC)
• Second-degree AV block Mobitz type II or third-degree AV block
• Alternating bundle branch block
• Sinus bradycardia < 40/min or sinoatrial pauses > 3 seconds
• Ventricular tachycardia or non-sustained VT
• Signs of preexcitation (delta wave, short PR interval)
• Pathological Q waves (suggestive of old infarction as an arrhythmogenic substrate)
• ST-segment changes (acute ischemia)

Risk Scores: Structured Decision Aids

Several validated scores assist with risk stratification. None replaces clinical judgment, but they provide a systematic basis for the decision between discharge and hospital admission.

Canadian Syncope Risk Score (CSRS)

This score was specifically developed for the emergency department and stratifies the risk of a serious adverse event within 30 days.

Variables and point allocation:

• Predisposition for vasovagal syncope: −1
• Heart disease in medical history: +1
• Systolic blood pressure < 90 mmHg or > 180 mmHg: +2
• Elevated troponin (above the 99th percentile): +2
• Abnormal QRS axis: +1
• QRS duration > 130 ms: +1
• QTc > 480 ms: +2
• ED diagnosis: vasovagal syncope: −2
• ED diagnosis: cardiac syncope: +2

Interpretation: A score ≤ −1 indicates very low risk (< 1%) and supports outpatient follow-up. Scores ≥ 3 are associated with significantly increased risk and justify inpatient monitoring.

San Francisco Syncope Rule (SFSR)

The SFSR uses the acronym CHESS:

• Congestive heart failure (history of heart failure)
• Hematocrit < 30%
• ECG abnormal
• Shortness of breath (dyspnea)
• Systolic blood pressure < 90 mmHg

If one or more criteria are present, inpatient workup is recommended. Sensitivity is good, but specificity is limited, leading to a relatively high rate of hospital admissions.

EGSYS Score

Particularly useful for differentiating between cardiac and non-cardiac syncope:

• Palpitations before syncope: +4
• Abnormal ECG and/or heart disease: +3
• Syncope during exertion: +3
• Syncope while supine: +2
• Autonomic prodromes (nausea, sensation of warmth): −1
• Predisposing factors (crowds, standing, heat): −1

A score ≥ 3 is highly suggestive of a cardiac etiology.

Structured Emergency Management

Initial Stabilization

Initial management follows the ABCDE approach:

1. Airway/Breathing: Airway management and supplemental oxygen as needed in unconscious patients
2. Circulation: Monitoring (ECG, blood pressure, SpO₂), large-bore intravenous access
3. For persistent bradycardia: Atropine 0.5 mg IV (repeatable up to a maximum of 3 mg); if refractory, transcutaneous pacing
4. For hemodynamically unstable tachycardia: Synchronized cardioversion
5. For hypotension/volume depletion: Fluid bolus with crystalloid solution (e.g., 500 mL Ringer's lactate); if hemorrhage is suspected, consider blood products

Baseline Workup in the Emergency Department

The following diagnostics should be performed for every syncope:

• 12-lead ECG (mandatory for every syncope)
• Orthostatic test: Blood pressure measurement supine and after 1, 3, and if applicable 5 minutes of standing
• Blood glucose (point-of-care)
• Detailed history (the single most important diagnostic measure!): Prodromes, triggers, body position, witness observations (duration, myoclonus, skin color), medication history, family history

Laboratory diagnostics (targeted, not as routine screening):

• Troponin: if cardiac cause is suspected or in unclear syncope in at-risk patients
• Complete blood count: if anemia/hemorrhage is suspected
• Electrolytes: if taking diuretics, or with vomiting, diarrhea
• BNP/NT-proBNP: as a marker for structural heart disease
• D-dimer: only if there is clinical suspicion of pulmonary embolism (Wells score)
• β-hCG: in women of childbearing age (ectopic pregnancy as a cause of hemorrhage)

Advanced Diagnostics

Depending on the clinical scenario:

• Echocardiography: for heart murmur, suspected structural heart disease, abnormal ECG, history of reduced LV function
• Holter monitoring (24–72 h or event recorder): for recurrent syncope without a clear cause
• Implantable loop recorder: for infrequent but recurrent syncope with suspected arrhythmogenic etiology
• Tilt table testing: to confirm reflex syncope when there is diagnostic uncertainty
• Carotid sinus massage: in patients > 40 years with unexplained syncope (contraindication: carotid stenosis, stroke/TIA within the last 3 months)
• Electrophysiology study (EPS): if arrhythmogenic syncope is suspected with non-diagnostic monitoring

Disposition: Inpatient or Outpatient?

The disposition decision is among the most challenging in emergency medicine. As a guide:

Hospital admission (with monitoring) for:

• Any identified or suspected cardiac cause
• Significant ECG abnormalities (see above)
• Syncope with serious injury or in a high-risk situation (e.g., while driving)
• Known structural heart disease or reduced LV function
• Hemodynamic instability in the emergency department
• Significant comorbidities posing an acute threat (e.g., severe anemia, acute hemorrhage)

Outpatient workup is reasonable for:

• Classic vasovagal syncope with typical prodromes and trigger
• Clear orthostatic syncope with an identifiable cause (e.g., medications, volume depletion)
• Situational syncope (micturition, coughing) with otherwise unremarkable findings
• Normal ECG and unremarkable clinical examination
• Low risk score

Important: Even upon discharge, a clear recommendation for outpatient follow-up must be provided (primary care physician, cardiology), especially for first-time syncope or in the absence of a definitive diagnosis.

Special Situations

Syncope in Young Patients and Athletes

In patients under 35 years with exertion-induced syncope, there is a particularly high risk for:

• Hypertrophic cardiomyopathy (HCM)
• Arrhythmogenic right ventricular cardiomyopathy (ARVC)
• Channelopathies (Long QT, Brugada, CPVT)
• Coronary artery anomalies

A thorough cardiac workup including echocardiography and, if indicated, cardiac MRI is mandatory – even with an initially normal ECG. Family history regarding sudden cardiac death is of critical importance.

Syncope in Elderly Patients

In geriatric patients, multifactorial causes are common:

• Polypharmacy as the main driver (antihypertensives, psychotropic medications, alpha-blockers)
• Autonomic dysfunction
• Carotid sinus hypersensitivity
• Fall-related injuries often outweigh the actual syncope risk itself

A thorough medication history and review of the indication for every blood pressure-affecting medication are essential here.

Syncope with Convulsive Movements

Brief myoclonus (< 15 seconds) occurs in up to 10% of all syncopes and is an expression of cerebral hypoperfusion – not an epileptic seizure. Distinguishing features:

Feature	Convulsive Syncope	Epileptic Seizure
Myoclonus	Brief, arrhythmic, < 15 s	Rhythmic, prolonged
Tongue bite	Tip of tongue (rare)	Lateral
Postictal phase	None or very brief	Prolonged confusion
Incontinence	Rare	More common
Trigger	Typical (standing, pain)	Usually absent

Algorithm Summary

1. Confirm syncope: Was this truly transient loss of consciousness with complete recovery?
2. ABCDE and stabilization: Rule out immediate life threats
3. 12-lead ECG: Immediately, for every syncope
4. Targeted history: Prodromes, triggers, position, witness report, medications, family history
5. Check for red flags: Systematically search for warning signs
6. Apply risk score: CSRS or EGSYS to support decision-making
7. Determine disposition: Inpatient monitoring vs. outpatient workup
8. Documentation and handover: Clear communication of the suspected diagnosis and further plan

Practical Training

Safe recognition and initial management of cardiac causes of syncope – from hemodynamically unstable tachycardia to high-grade AV block to Torsades de Pointes – requires not only theoretical knowledge but above all practical competency. In the ACLS course by Simulation Tirol, you train exactly these scenarios: structured ECG interpretation under time pressure, bradycardia and tachycardia algorithms, cardioversion and pacing – hands-on, in a simulation environment, and according to American Heart Association guidelines. Because recognizing cardiac syncope in the emergency department is the first step – but taking the right action in a real emergency has to be trained.