What are the San Francisco syncope rules for managing patients with syncope?

San Francisco Syncope Rule for Risk Stratification

The San Francisco Syncope Rule (SFSR) is a validated clinical decision tool that identifies patients at high risk for serious outcomes within 7 days of syncope presentation, using five key risk factors: abnormal ECG, congestive heart failure, shortness of breath, hematocrit <30%, and systolic blood pressure <90 mmHg.

Components of the San Francisco Syncope Rule

The SFSR uses the mnemonic "CHESS" to identify high-risk patients:

• C: History of Congestive Heart Failure
• H: Hematocrit <30%
• E: Abnormal ECG (new changes or non-sinus rhythm)
• S: Shortness of breath
• S: Systolic blood pressure <90 mmHg at triage

Risk Stratification Performance

According to validation studies, the SFSR demonstrates:

• Sensitivity: 98% in the original validation cohort 1
• Specificity: 56% in the original validation cohort 1
• Negative predictive value: 99% for serious outcomes

However, it's important to note that subsequent external validation studies have shown variable performance:

• A Canadian validation study found sensitivity of 90% and specificity of 33% 2
• Another independent validation study found lower sensitivity (74%) 3
• An Asian population validation showed 94.2% sensitivity 4

Clinical Application

When to Apply the Rule

Apply the SFSR to adult patients presenting with syncope or near-syncope after initial evaluation, excluding patients with:

• Trauma-related loss of consciousness
• Alcohol or drug-associated loss of consciousness
• Definite seizures
• Persistent altered mental status

Decision Making Algorithm

1. Perform initial evaluation including history, physical examination, and ECG
2. Apply the SFSR by checking for the five risk factors
3. Risk stratification:
   • High risk: Presence of ANY of the five risk factors
   • Low risk: Absence of ALL five risk factors

Management Based on Risk

• High-risk patients (any SFSR criteria present): Consider hospital admission for further evaluation and monitoring
• Low-risk patients (no SFSR criteria present): Consider outpatient management with appropriate follow-up

Integration with Other Risk Stratification Tools

The 2017 ACC/AHA/HRS guidelines for syncope management acknowledge several risk stratification tools including the SFSR 5. Other validated tools include:

• OESIL score
• EGSYS score
• Boston Syncope Rule
• STePS
• ROSE rule

Important Caveats and Pitfalls

1. ECG interpretation is crucial: The definition of "abnormal ECG" varies across studies but generally includes any rhythm other than normal sinus rhythm, conduction delays, presence of Q waves, ST abnormalities, or prolonged QT interval 5

2. Validation inconsistencies: Be aware that independent validation studies have shown variable performance, with some showing lower sensitivity than the original validation 3

3. Admission rate impact: Implementing the SFSR may increase admission rates in some settings (from 12.3% to 69.5% in one Canadian study) 2

4. Clinical judgment remains essential: The rule should be used as an aid to clinical decision-making, not as the sole determinant of disposition 4

5. Serious outcomes definition: The rule aims to predict serious outcomes within 7 days including death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or any condition causing return ED visit and hospitalization 6

By using the San Francisco Syncope Rule as part of a comprehensive evaluation strategy, clinicians can more effectively identify patients at risk for serious outcomes and make appropriate disposition decisions that balance patient safety with resource utilization.