What is the appropriate work‑up for a patient presenting with syncope?

Syncope Work-Up: A Structured Approach

Every patient presenting with syncope requires three mandatory initial assessments: a detailed history, physical examination with orthostatic vital signs, and a 12-lead ECG—this triad alone establishes the diagnosis in 23-50% of cases and determines whether hospital admission is needed. 1

Initial Assessment Components

History Taking (Critical Elements)

Position during the event:

• Supine onset strongly suggests cardiac cause 1
• Standing onset points to reflex or orthostatic mechanisms 1

Activity and triggers:

• Syncope during exertion is high-risk and mandates immediate cardiac evaluation 1
• Warm crowded places, prolonged standing, or emotional stress suggest vasovagal syncope 1
• Situational triggers (urination, defecation, cough) indicate situational syncope 1

Prodromal symptoms:

• Nausea, diaphoresis, blurred vision, or dizziness favor vasovagal syncope 1
• Brief or absent prodrome is a high-risk feature for cardiac syncope 1
• Palpitations immediately before syncope strongly suggest arrhythmic cause 1

Medical history red flags:

• Known structural heart disease or heart failure has 95% sensitivity for cardiac syncope 1
• Family history of sudden cardiac death or inherited arrhythmia syndromes 1
• Medications: antihypertensives, diuretics, vasodilators, QT-prolonging agents 1

Physical Examination (Mandatory Findings)

Orthostatic vital signs (measure in all patients):

• Lying, sitting, and standing positions 1
• Orthostatic hypotension: systolic drop ≥20 mmHg or to <90 mmHg 1

Cardiovascular examination:

• Murmurs, gallops, rubs indicating structural heart disease 1
• Irregular rhythm suggesting arrhythmia 1

Carotid sinus massage (patients >40 years only):

• Positive if asystole >3 seconds or systolic BP drop >50 mmHg 1
• Contraindicated if history of TIA or carotid disease 1

12-Lead ECG (High-Risk Abnormalities)

• QT prolongation (Long QT syndrome) 1
• Conduction abnormalities: bundle branch blocks, bifascicular block, Mobitz II, third-degree AV block 1
• Signs of ischemia or prior myocardial infarction 1
• Brugada pattern, pre-excitation (WPW), or ARVC features 1

Risk Stratification for Disposition

High-Risk Features Requiring Hospital Admission

Admit immediately if any of the following are present:

• Age >60-65 years 1
• Known structural heart disease or heart failure 1
• Syncope during exertion or while supine 1
• Brief or absent prodrome 1
• Abnormal cardiac examination or ECG 1
• Palpitations immediately before the event 1
• Family history of sudden cardiac death or inherited cardiac conditions 1
• Systolic blood pressure <90 mmHg 1

The stakes are high: cardiac syncope carries 18-33% one-year mortality versus 3-4% for non-cardiac causes 1

Low-Risk Features Supporting Outpatient Management

• Younger age with no known cardiac disease 1
• Normal ECG and cardiac examination 1
• Syncope only when standing 1
• Clear prodromal symptoms (nausea, diaphoresis, warmth) 1
• Situational triggers (micturition, defecation, cough) 1

Targeted Diagnostic Testing (Based on Initial Evaluation)

When to Order Echocardiography

Order immediately for:

• Abnormal cardiac examination 1
• Abnormal ECG suggesting structural disease 1
• Syncope during or after exertion 1
• Known or suspected structural heart disease 1

Cardiac Monitoring Strategy

Continuous telemetry (initiate immediately for):

• Abnormal ECG 1
• Palpitations before syncope 1
• Any high-risk feature 1

Holter monitor (24-72 hours):

• Frequent symptoms likely to recur within monitoring period 1

External loop recorder:

• Infrequent symptoms expected within 2-6 weeks 1

Implantable loop recorder:

• Recurrent unexplained syncope with suspected arrhythmic cause 1
• Diagnostic yield 52% versus 20% with conventional strategies 1

Exercise Stress Testing

Mandatory for:

• Syncope during or immediately after exertion 1
• To uncover exercise-induced arrhythmias, catecholaminergic polymorphic VT, or dynamic outflow obstruction 1

Tilt-Table Testing

Consider for:

• Young patients without heart disease 1
• Recurrent unexplained syncope when reflex mechanism suspected 1
• Only after cardiac causes are excluded 1

Laboratory Testing (Targeted, Not Routine)

Avoid comprehensive laboratory panels unless specific clinical suspicion exists 1

Order targeted tests only when indicated:

• Hematocrit if volume depletion suspected 1
• Electrolytes if dehydration suspected 1
• BNP and troponin have uncertain utility even when cardiac cause suspected 1

Tests NOT Recommended (Low Yield)

Brain imaging (CT/MRI):

• Diagnostic yield only 0.24-1% 1
• Do not order unless focal neurological findings present 2, 1

EEG:

• Yield approximately 0.7% 1
• Do not order routinely 2, 1

Carotid artery imaging:

• Yield approximately 0.5% 1
• Do not order routinely 2, 1

Management of Unexplained Syncope

If initial evaluation is non-diagnostic:

1. Re-evaluate the entire work-up: obtain additional history details, repeat focused physical examination, review all prior test results 1
2. Consider specialty consultation (cardiology or neurology) when clues to underlying disease emerge 1
3. Early implantable loop recorder when arrhythmic suspicion persists despite negative initial evaluation 1

Common Pitfalls to Avoid

• Ordering brain imaging without focal neurological findings (yield <1%) 2, 1
• Comprehensive laboratory testing without clinical indication 1
• Using Holter monitoring for infrequent events (external or implantable loop recorders provide higher yield) 1
• Missing exertional syncope as a high-risk feature 1
• Neglecting orthostatic vital signs (misses treatable orthostatic hypotension) 1
• Overlooking medication effects (antihypertensives, diuretics, QT-prolonging agents) 1
• Failing to distinguish true syncope from seizure (post-ictal confusion), stroke (persistent focal deficits), or metabolic disorders 1