What is the initial workup for a patient presenting with syncope?

Syncope Workup

Initial Evaluation: The Three Essential Components

Every patient presenting with syncope requires a detailed history, physical examination with orthostatic blood pressure measurements, and a 12-lead ECG—this triad alone establishes the diagnosis in 23-50% of cases and is the only testing universally recommended. 1, 2

History Taking: Specific Questions That Matter

Focus your history on these critical elements that distinguish syncope types and guide risk stratification:

Before the event:

• Position during syncope (supine suggests cardiac; standing suggests reflex or orthostatic) 1, 2
• Activity (exertional syncope is high-risk and suggests cardiac etiology; post-micturition/defecation suggests situational) 1, 2
• Triggers (warm crowded places, prolonged standing, fear, pain suggest vasovagal; neck turning suggests carotid sinus hypersensitivity) 1, 2

Onset symptoms (prodrome):

• Presence or absence of warning symptoms is critical—absence of prodrome suggests cardiac syncope and is a high-risk feature 2, 3
• Nausea, diaphoresis, blurred vision, dizziness suggest neurally-mediated syncope 1, 2
• Palpitations before syncope suggest arrhythmic cause 1, 2

During the event (eyewitness account):

• Duration of unconsciousness (prolonged suggests seizure, not syncope) 1
• Skin color (pallor suggests syncope; cyanosis suggests seizure or cardiac) 1
• Movements (brief myoclonic jerks can occur in syncope; prolonged tonic-clonic suggests seizure) 1

Recovery phase:

• Rapid, complete recovery without confusion confirms syncope (prolonged confusion suggests seizure) 1, 3
• Muscle aches, incontinence can occur in both syncope and seizure 1

Background:

• Family history of sudden cardiac death or inherited arrhythmias (high-risk feature) 2, 3
• Known structural heart disease or heart failure 1, 2
• Medications (antihypertensives, diuretics, QT-prolonging agents, antiarrhythmics) 1, 2

Physical Examination: What to Assess

Orthostatic vital signs:

• Measure blood pressure and heart rate in lying, sitting, and standing positions 2, 3
• Orthostatic hypotension is defined as systolic BP drop ≥20 mmHg or to <90 mmHg upon standing 4

Cardiovascular examination:

• Auscultate for murmurs (aortic stenosis), gallops (heart failure), irregular rhythm 2, 4
• Systolic BP <90 mmHg at presentation is a high-risk feature 2, 3

Carotid sinus massage:

• Perform in patients >40 years old with recurrent syncope 1, 2

12-Lead ECG: Mandatory in All Patients

The ECG identifies the cause in approximately 7% of patients and stratifies risk in the remainder. 5

High-risk ECG findings suggesting arrhythmic syncope:

• Sinus bradycardia <50 bpm, sinoatrial block, sinus pauses >3 seconds 1, 2
• Any degree of AV block (2nd or 3rd degree, bifascicular block) 1, 2
• QRS duration >120 ms with bundle branch block 1, 2
• QTc prolongation (>460 ms in women, >440 ms in men suggests long QT syndrome) 1, 6
• Brugada pattern (ST elevation in V1-V3) 6, 5
• Epsilon wave or T-wave inversion V1-V3 (arrhythmogenic right ventricular cardiomyopathy) 1, 6
• Q waves suggesting prior MI or ventricular hypertrophy 1, 6
• Pre-excitation pattern (Wolff-Parkinson-White syndrome) 6, 5

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Risk Stratification: Who Needs Admission vs. Outpatient Management

High-Risk Features Requiring Hospital Admission

Admit patients with any of the following: 2, 3

• Abnormal ECG (any of the findings listed above) 2, 3
• Age >60-65 years 2, 3
• Known structural heart disease or heart failure 2, 3
• Syncope during exertion or while supine 2, 3
• Absence of prodromal symptoms 2, 3
• Family history of sudden cardiac death or inherited cardiac conditions 2, 3
• Systolic blood pressure <90 mmHg 2, 3
• Brief or absent prodrome 2
• Low number of episodes (1-2 lifetime episodes more concerning than many) 1

Low-Risk Features Appropriate for Outpatient Management

Consider outpatient evaluation for patients with all of the following: 2, 3

• Younger age with no known cardiac disease 2, 3
• Normal ECG 2, 3
• Syncope only when standing 2, 3
• Clear prodromal symptoms (nausea, diaphoresis, warmth) 2, 3
• Specific situational triggers (micturition, defecation, cough, swallowing) 2, 3
• Presumptive reflex-mediated (vasovagal) syncope 2

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Additional Testing: Only When Clinically Indicated

Tests to Order Based on Specific Clinical Suspicion

Echocardiography:

• Order when structural heart disease is suspected based on abnormal cardiac exam, abnormal ECG, or history of heart disease 1, 2
• Mandatory for syncope during or after exertion 1, 2

Cardiac monitoring (Holter, event recorder, implantable loop recorder):

• Order when arrhythmic syncope is suspected (palpitations before syncope, abnormal ECG, structural heart disease) 1, 2
• Selection of device depends on symptom frequency—Holter for daily symptoms, event recorder for weekly symptoms, implantable loop recorder for infrequent events 2, 7

Exercise stress testing:

• Mandatory for syncope during or immediately after exertion 1, 2

Tilt-table testing:

• Consider for recurrent unexplained syncope in young patients without heart disease when reflex mechanism is suspected 1, 2

Targeted laboratory tests:

• Only order based on clinical suspicion—comprehensive panels are not useful 2, 3
• Hematocrit if bleeding or anemia suspected 2
• Electrolytes, BUN, creatinine if dehydration suspected 2
• Cardiac biomarkers (troponin, BNP) only if cardiac cause suspected, not routinely 2

Tests to Avoid: Low Yield Without Specific Indication

Do not routinely order: 2, 3

• Brain imaging (CT/MRI) unless focal neurological findings or head trauma (diagnostic yield only 0.24-1%) 2, 3
• EEG unless features suggesting seizure (diagnostic yield only 0.7%) 2, 3
• Carotid ultrasound unless focal neurological findings (diagnostic yield only 0.5%) 2, 3
• Comprehensive laboratory panels without specific clinical indication 2, 3

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Common Pitfalls to Avoid

• Failing to distinguish true syncope from seizure or other causes of transient loss of consciousness—verify all four criteria: complete LOC, transient with rapid onset, spontaneous complete recovery, loss of postural tone 1, 3
• Ordering brain imaging, EEG, or carotid ultrasound without neurological findings—these have extremely low yield in syncope 2, 3
• Ordering comprehensive laboratory testing without clinical indication—targeted testing only 2, 3
• Overlooking medication effects as contributors to syncope (antihypertensives, diuretics, QT-prolonging drugs) 1, 2
• Failing to recognize that syncope at rest or during exertion is high-risk and demands cardiac evaluation 2, 4
• Not selecting appropriate cardiac monitoring based on symptom frequency—match the device to event frequency 2, 7