The San Francisco Syncope Rule (SFSR)

The San Francisco Syncope Rule is a clinical decision tool designed to identify patients presenting with syncope (fainting) or near-syncope who are at high risk for serious short-term adverse outcomes within 30 days.

The rule relies on a memorable 5-item checklist. If a patient meets any single one of these criteria, they are classified as high risk and typically require hospital admission or further diagnostic workup.

The CHESS Mnemonic Criteria

A patient is considered High Risk if they possess any of the following clinical features:

  • C - Congestive Heart Failure: A known history of congestive heart failure (CHF).

  • H - Hematocrit less than 30%: Initial laboratory evaluation showing an objective anemia.

  • E - Electrocardiogram (ECG) Abnormal: Any non-sinus rhythm on the initial ECG or monitor, or any new acute ECG changes compared to a previous tracing.

  • S - Shortness of Breath: A subjective complaint or objective evidence of dyspnea accompanying the syncopal event.

  • S - Systolic Blood Pressure less than 90 mmHg: Hypotension documented during initial triage in the emergency department.

Clinical Interpretation and Performance

  • High Risk (Any Criteria Present): The patient carries a higher likelihood of short-term serious outcomes (such as severe arrhythmias, myocardial infarction, significant hemorrhage, or sudden death) and should generally be admitted for observation or accelerated evaluation.

  • Low Risk (Zero Criteria Present): In the original derivation studies, patients with a score of 0 were considered safe for discharge.

Clinical Note: While the original studies demonstrated a sensitivity near 96%, subsequent external validation studies showed lower real-world sensitivity (around 74% to 87%). Because it can miss potentially serious cardiac causes, the rule should always complement, rather than replace, careful clinical judgment.

San Francisco Syncope Rule References

  • Quinn, J. V., Stiell, I. G., McDermott, D. A., et al. (2004). Derivation of the San Francisco Syncope Rule to predict serious outcomes in patients with syncope. Annals of Emergency Medicine, 43(2), 224-232.

  • Quinn, J., McDermott, D., Stiell, I., et al. (2006). Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Annals of Emergency Medicine, 47(5), 448-454.

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