How it's calculated
Any single positive criterion out of five (CHESS: history of CHF, Haematocrit <30%, abnormal ECG, Shortness of breath, Systolic BP <90 mmHg) classifies the patient as high risk for a serious outcome within 7 days.
CHESS criteria
| Criterion | Threshold |
|---|---|
| C — CHF history | Any history of congestive heart failure |
| H — Haematocrit | < 30% |
| E — ECG | Abnormal (new changes or non-sinus rhythm) |
| S — Shortness of breath | Present |
| S — Systolic BP | < 90 mmHg at triage |
Clinical use
- Used in the emergency department to help decide whether a patient presenting with syncope needs admission and further work-up, or can be safely discharged.
- Designed to be highly sensitive for serious short-term outcomes (death, MI, arrhythmia, PE, stroke, subarachnoid haemorrhage, significant haemorrhage, or a condition causing a return ED visit with admission) — a negative rule doesn't guarantee an entirely benign cause, but supports a lower-risk disposition.
- Should be applied alongside a thorough history and examination — clinical judgement can override a negative rule if there's still significant concern.
Frequently asked questions
What does CHESS stand for in the San Francisco Syncope Rule?
CHF history, Haematocrit <30%, abnormal ECG, Shortness of breath, and Systolic BP <90 mmHg — any one present classifies the patient as high risk.
What counts as an 'abnormal ECG' for this rule?
Any new changes compared to a prior ECG, or a rhythm other than sinus (e.g. atrial fibrillation), including new arrhythmias, conduction blocks, or ischaemic changes.
Has the San Francisco Syncope Rule been validated in other populations?
Performance has varied somewhat across external validation studies, with sensitivity for serious outcomes ranging more widely than the original derivation study — it should inform, not replace, overall clinical judgement.
References
- Quinn JV, et al. Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes. Ann Emerg Med. 2004;43(2):224-232.
- Quinn JV, et al. Prospective validation of the San Francisco Syncope Rule. Ann Emerg Med. 2006.