How to risk stratify syncope?

Risk Stratification of Syncope

The most effective approach to risk stratify syncope is to conduct an initial evaluation with history, physical examination, orthostatic blood pressure measurements, and 12-lead ECG, followed by categorization into high, intermediate, or low risk based on specific clinical features. 1

Initial Evaluation Components

History

• Circumstances before, during, and after the event:
  • Posture (supine, sitting, standing)
  • Activity (rest, position change, exertion, during/after exertion)
  • Predisposing factors (crowded/hot places, prolonged standing, post-prandial)
  • Precipitating events (fear, pain, neck movements)
  • Prodromal symptoms (nausea, vomiting, warmth, sweating, aura, blurred vision)
  • Witness account (manner of falling, skin color, duration of unconsciousness, breathing pattern, movements)

Physical Examination

• Complete cardiovascular examination
• Orthostatic blood pressure measurements (lying, sitting, standing)
• Neurological examination when indicated

12-Lead ECG

• Mandatory in all patients with syncope (Class I recommendation) 1
• Assess for arrhythmias, conduction abnormalities, QT interval, pre-excitation, Brugada pattern

Risk Stratification Categories

High-Risk Features (Suggesting Cardiac Syncope) 1

• Demographics/History:

  • Age >60 years
  • Male sex
  • Known ischemic/structural heart disease or previous arrhythmias
  • Family history of sudden cardiac death or inheritable conditions
  • Syncope during exertion or in supine position
  • Sudden onset with brief or absent prodrome
  • Low number of episodes (1-2)
  • Palpitations preceding syncope

• Physical Examination:

  • Abnormal cardiac examination
  • Systolic BP <90 mmHg

• ECG Findings:

  • Bifascicular block (LBBB or RBBB with left anterior/posterior fascicular block)
  • Other intraventricular conduction abnormalities (QRS ≥120 ms)
  • Mobitz II second or third-degree AV block
  • Symptomatic sinus bradycardia (<50 bpm) or sinoatrial block
  • Pre-excited QRS complex
  • Prolonged or short QT interval
  • RBBB pattern with ST-elevation in V1-V3 (Brugada pattern)
  • Negative T waves in right precordial leads, epsilon waves (ARVC)
  • Non-sustained ventricular tachycardia

Low-Risk Features (Suggesting Reflex/Orthostatic Syncope) 1

• Younger age
• No known cardiac disease
• Syncope only in standing position
• Clear positional trigger
• Typical prodrome (nausea, vomiting, warmth)
• Specific triggers (dehydration, pain, medical environment)
• Situational triggers (cough, laugh, micturition, defecation)
• Frequent recurrence with similar characteristics

Management Based on Risk Stratification

High-Risk Patients

• Immediate hospitalization for further evaluation 1
• Additional cardiac testing:
  • Echocardiography when structural heart disease is suspected
  • Continuous cardiac monitoring
  • Consider electrophysiological study for suspected arrhythmic syncope 1
  • Exercise testing if syncope occurred during exertion 1

Intermediate-Risk Patients

• Structured emergency department observation protocol 1
• Consider referral to syncope specialist
• Consider implantable loop recorder for recurrent unexplained syncope 2

Low-Risk Patients

• Outpatient management 1
• Education on trigger avoidance and physical counterpressure maneuvers 2
• Consider tilt-table testing for recurrent episodes 1

Validated Risk Stratification Scores

Several clinical decision rules can assist in risk stratification:

• San Francisco Syncope Rule: Abnormal ECG, dyspnea, hematocrit <30%, systolic BP <90 mmHg, heart failure 1
• OESIL Score: Age >65 years, cardiovascular disease history, syncope without prodrome, abnormal ECG 1
• ROSE Rule: Abnormal ECG, B-type natriuretic peptide, hemoglobin, oxygen saturation, fecal occult blood 1
• Canadian Syncope Risk Score: Includes cardiac biomarkers 3

Common Pitfalls to Avoid

1. Overreliance on diagnostic testing - The diagnostic yield of routine comprehensive laboratory testing is low unless clinically indicated 2

2. Unnecessary neuroimaging - Only order when focal neurological findings are present or head injury is suspected 3

3. Failure to identify structural heart disease - Patients with structural heart disease have the highest mortality risk 4

4. Underestimating risk in elderly patients - Syncope in older adults carries greater risk of hospitalization and death 1

5. Missing red flags in seemingly benign presentations - Even with apparent reflex syncope, look for high-risk features

By systematically applying this risk stratification approach, clinicians can identify patients at high risk for adverse outcomes while avoiding unnecessary hospitalization and testing in low-risk patients.