San Francisco Syncope Rule Explained

The San Francisco Syncope Rule (SFSR) is a rule for evaluating the risk of adverse outcomes in patients presenting with fainting or syncope.

The mnemonic for features of the rule is CHESS:

• C - History of congestive heart failure

• H - Hematocrit < 30%

• E - Abnormal ECG

• S - Shortness of breath

• S - Triage systolic blood pressure < 90

A patient with any of the above measures is considered at high risk for a serious outcome such as death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or any condition causing a return Emergency Department visit and hospitalization for a related event.

SFSR was retrospectively found to have 98% sensitivity and specificity of 56% for serious causes of syncope.^[1] However, external prospective validation of the criteria found sensitivity to be 74%, substantially lower than the initial study.^[2] This means that in patients with none of the above criteria, potentially serious causes of syncope were missed in over a quarter of patients. Syncope accounts for 1-2% emergency department visits. Half are hospitalized and of these, 50% have unclear diagnosis and 85% will be simply monitored.

Notes and References

Quinn J . McDermott D . Stiell I . Kohn M . Wells G . Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes . Ann Emerg Med . 47 . 5 . 448–54 . May 2006 . 16631985 . 10.1016/j.annemergmed.2005.11.019 .
Birnbaum A . Esses D . Bijur P . Wollowitz A . Gallagher EJ . Failure to Validate the San Francisco Syncope Rule in an Independent Emergency Department Population . Ann Emerg Med . 52. 2. 151–9. February 2008 . 18282636 . 10.1016/j.annemergmed.2007.12.007 .