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San Francisco Syncope Rule

Identifying emergency patients with syncope at risk of short-term serious outcomes (CHESS)

Sources last checked: 2026-11-03

San Francisco Syncope Rule

Identifying emergency patients with syncope at risk of short-term serious outcomes (CHESS)

Does the rule apply?
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Derived for 7-day and validated for 30-day serious outcomes in one US centre; external validation showed lower and variable sensitivity. Arrhythmia was the most common missed serious outcome. The rule does not replace an ECG-based and clinical assessment.

Source: Quinn JV, Stiell IG, McDermott DA 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.Open

Interpretation

Rule not applicableThe patient is outside the population the rule was derived and validated in, so the rule makes no statement for this patient.
Low risk by the ruleNone of the five CHESS criteria. In the 2006 validation the rule was 98 % sensitive for 30-day serious outcomes; a 2011 systematic review found a pooled sensitivity of 87 % (95 % CI 79–93 %), so a negative rule does not exclude a serious cause.
High risk by the ruleAt least one CHESS criterion present. Specificity was 56 % in the 2006 validation (pooled 52 % in the 2011 review), so many high-risk patients have no serious outcome.

What is the San Francisco Syncope Rule?

The San Francisco Syncope Rule (CHESS) flags emergency patients with syncope who are at risk of short-term serious outcomes. Quinn and colleagues derived it from 684 visits at one teaching hospital (Ann Emerg Med 2004) and validated it prospectively in 791 visits (2006), where it was 98 % sensitive and 56 % specific for 30-day serious outcomes. A 2011 systematic review of 12 studies found a lower pooled sensitivity of 87 %.

When to use it

  • ED patients with syncope or near-syncope, as one input to the disposition decision.
  • Teaching the high-risk features of syncope: heart failure, anaemia, ECG abnormality, dyspnoea, hypotension.
  • Comparing with or complementing the Canadian Syncope Risk Score.

When not to use it

  • Loss of consciousness from trauma, alcohol or drugs, or a definite seizure.
  • As the only reason to discharge a patient — false negatives, mostly arrhythmias, occurred in external cohorts.
  • When a serious cause is already evident from the initial assessment.

How it is calculated

High risk if ANY of (CHESS): history of Congestive heart failure; Haematocrit < 30 %; ECG abnormal (new changes or non-sinus rhythm); Shortness of breath; Systolic BP < 90 mmHg at triage.

Clinical pearls and limitations

  • Derived for 7-day and validated for 30-day serious outcomes in one US centre; external validation showed lower and variable sensitivity. Arrhythmia was the most common missed serious outcome. The rule does not replace an ECG-based and clinical assessment.
  • CHESS: Congestive heart failure, Haematocrit < 30 %, ECG abnormal, Shortness of breath, Systolic BP < 90 mmHg.
  • An abnormal ECG means new changes or any non-sinus rhythm.
  • The rule was derived for 7-day outcomes and validated for 30-day outcomes.
  • In the 2011 review the probability of a serious outcome with a negative rule was ≤ 5 %, and ≤ 2 % when no cause had been found in the ED.

Frequently asked questions

What does CHESS stand for in syncope?

Congestive heart failure history, Haematocrit < 30 %, ECG abnormal (new changes or non-sinus rhythm), Shortness of breath, and Systolic blood pressure < 90 mmHg at triage.

How accurate is the San Francisco Syncope Rule?

98 % sensitive and 56 % specific in the 2006 validation; a 2011 systematic review pooled 87 % sensitivity and 52 % specificity, with wide heterogeneity between studies.

Can a patient with a negative San Francisco Syncope Rule be discharged?

The rule alone is not sufficient; external studies missed serious outcomes, mainly arrhythmias. Disposition rests on the full clinical assessment.

Evidence and guidelines

  1. Primary source: Quinn JV, Stiell IG, McDermott DA 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.
  2. Quinn J, McDermott D, Stiell I et al. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med 2006;47(5):448-454.
  3. Saccilotto RT, Nickel CH, Bucher HC et al. San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review. CMAJ 2011;183(15):E1116-E1126.

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