San Francisco Syncope Rule

The San Francisco Syncope Rule (SFSR) is a clinical decision tool developed to identify emergency department patients presenting with syncope who are at risk for serious outcomes within 30 days. Published by Quinn et al. in 2004, the SFSR was designed to safely identify low-risk patients who could be discharged without extensive workup while flagging those requiring further evaluation.

Syncope accounts for approximately 1-3% of all emergency department visits. While most episodes are benign (vasovagal, orthostatic), approximately 10% of patients will experience a serious outcome within 30 days, including death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or need for a procedure.

The SFSR uses the mnemonic CHESS: Congestive heart failure history, Hematocrit less than 30%, abnormal ECG (new changes or non-sinus rhythm), complaint of Shortness of breath, and Systolic blood pressure less than 90 mmHg at triage. If none of these criteria are present, the patient is classified as low risk.

CHF captures patients with cardiac dysfunction at elevated risk for arrhythmias. Hematocrit below 30% identifies significant anemia possibly from occult hemorrhage. Abnormal ECG findings may indicate cardiac pathology. Shortness of breath suggests pulmonary pathology or cardiac decompensation. Hypotension indicates hemodynamic instability requiring investigation.

The original validation reported 96% sensitivity and 62% specificity for serious 30-day outcomes. Subsequent external validations show sensitivity ranging from 74-98%. Despite variations, the SFSR remains valuable when combined with clinical judgment.

The rule is designed as a screening tool to identify patients who can safely be discharged, not as a standalone diagnostic instrument. Patients meeting no CHESS criteria have approximately a 2% serious event rate, supporting discharge with appropriate follow-up. Any positive criterion warrants further evaluation.

It is important to note that the SFSR was validated for true syncope (transient loss of consciousness with spontaneous recovery), not for near-syncope or presyncope. Patients with ongoing symptoms, trauma from the syncopal episode, or clear neurological deficits require evaluation regardless of CHESS criteria.

This calculator evaluates all five CHESS criteria and provides a binary risk classification with the number of positive criteria to guide clinical decision-making in the evaluation of syncope patients.