Workup for Syncope
The initial evaluation of syncope should include a detailed history, physical examination, orthostatic blood pressure measurements, and standard ECG, which can establish a diagnosis in up to 50% of cases and guide risk stratification for further management. 1
Initial Evaluation
History Taking
The history should focus on specific aspects that help differentiate types of syncope:
Circumstances prior to attack 1:
- Position (supine, sitting, standing)
- Activity (rest, posture change, during/after exercise, during/after urination/defecation/coughing/swallowing)
- Predisposing factors (crowded/warm places, prolonged standing, post-prandial period)
- Precipitating events (fear, pain, neck movements)
Onset symptoms 1:
- Nausea, vomiting, abdominal discomfort
- Cold sensation, sweating
- Aura, neck/shoulder pain, blurred vision
During attack (from witness) 1:
- Falling pattern (slumping vs. kneeling)
- Skin color (pallor, cyanosis, flushing)
- Duration of unconsciousness
- Breathing pattern
- Movements (tonic, clonic, myoclonus, automatism)
- Tongue biting
End of attack 1:
- Recovery symptoms (nausea, sweating, confusion)
- Injuries, chest pain, palpitations, incontinence
Background information 1:
- Family history of sudden death
- Previous cardiac disease
- Neurological conditions
- Metabolic disorders
- Current medications
Physical Examination
- Complete cardiovascular examination (murmurs, signs of heart failure)
- Neurological examination
- Orthostatic blood pressure measurements (supine and standing)
- Carotid sinus massage in patients >40 years (when appropriate)
Initial Testing
- Standard 12-lead ECG
- Orthostatic vital signs (decrease in systolic BP ≥20 mmHg or to <90 mmHg defines orthostatic hypotension) 1
Risk Stratification and Further Evaluation
High-Risk Features (Require Hospitalization) 1
Presence of severe structural heart disease
Abnormal ECG findings:
- Sinus bradycardia <40 bpm
- Sinoatrial blocks or pauses >3 seconds
- Mobitz II or third-degree AV block
- Alternating left and right bundle branch block
- Rapid paroxysmal SVT or VT
- Pacemaker malfunction
Clinical features suggesting cardiac syncope:
- Syncope during exertion or while supine
- Palpitations preceding syncope
- Family history of sudden death
- Chest pain associated with syncope
Diagnostic Pathway Based on Initial Evaluation
1. For Suspected Cardiac Syncope 1
- Echocardiography
- Prolonged ECG monitoring (Holter, event recorder, implantable loop recorder)
- Exercise stress testing (especially if syncope is exercise-related)
- Electrophysiological studies (if above tests are non-diagnostic)
2. For Suspected Neurally-Mediated Syncope 1
- Tilt table testing (especially in younger patients with recurrent episodes)
- Carotid sinus massage (particularly in older patients)
- Consider implantable loop recorder for recurrent unexplained episodes
3. For Suspected Orthostatic Hypotension 1
- Repeated orthostatic BP measurements (preferably in morning or shortly after syncope)
- 24-hour ambulatory BP monitoring if BP instability is suspected
- Autonomic function testing in selected cases
4. For Unexplained Syncope After Initial Evaluation 1
- Implantable loop recorder (particularly effective with 34% diagnostic yield) 1
- Psychiatric assessment if multiple somatic complaints or suspected anxiety/stress disorders
- Reappraisal of the entire workup if diagnosis remains elusive
Special Considerations
Elderly Patients 1
- More likely to have orthostatic hypotension, carotid sinus hypersensitivity, or cardiac syncope
- Multiple risk factors often present
- Cognitive assessment may be necessary
- Medication review is crucial (polypharmacy common)
Common Pitfalls to Avoid
- Overuse of neuroimaging (CT/MRI) and EEG in patients without focal neurological signs 2
- Relying on short-term ECG monitoring when symptoms are infrequent
- Failure to perform orthostatic BP measurements
- Missing medication-induced causes, especially in elderly patients
- Not distinguishing syncope from seizures or other non-syncopal causes of loss of consciousness
By following this systematic approach to syncope evaluation, physicians can establish a diagnosis in the majority of cases while minimizing unnecessary testing and hospitalizations, ultimately improving patient outcomes by identifying and treating potentially life-threatening causes.