San Francisco Syncope Rule Calculator

How does this San Francisco syncope rule calculator work?

This is a health tool that predicts the negative outcome risk in patients suffering syncope symptoms, either that they present themselves to the clinician in the ER during a syncopal episode or outside of it. 

There are 5 variables in this San Francisco syncope rule calculator, clinical determinations that are used to assess the adverse outcome risk and these are often known under the CHESS mnemonic:

■ Congestive heart failure history;

■ Hematocrit percentage below 30%;

■ ECG abnormal findings;

■ Shortness of breath;

■ Systolic blood pressure in triage less than 90 mmHg, indicative of hypotension.

This rule has been implemented in order to make the triage process more efficient in the case of patients with a syncope episode and to reduce redundant admissions.

In the SFSR score interpretation, any of the above variables being present is a sign of high risk for the patient to be evolving toward one of the following serious outcomes:

■ Myocardial infarction (less common);

■ Stroke (most common);

■ Arrhythmia (most common);

■ Pulmonary embolism;

■ Subarachnoid hemorrhage (common);

■ Significant hemorrhage.

The patient’s syncope symptoms are not under the risk of a significant life threatening condition if none of the criteria is met but if any of the criteria or more are met, then the patient is likely to return to the ER with a more serious condition. 10% of SFSR positive patients return within 7 days with a serious outcome with a mortality rate defined generically at 0.4% but in the case of SFSR negative patients, there is a return rate of only 1.4%.

The specificity for the San Francisco rule, validated in 7 different studies, is around 56% with a sensitivity of 74-79% in determining which patients are suitable for outpatient monitoring rather than a prolonged stay in hospital.

Syncope guidelines

Syncope presentation accounts for almost 2% of ER visits. Although most cases of syncope are without any underlying serious condition, occasionally syncopal episodes can indicate a life-threatening disease.

From this, 50% of the patients are hospitalized, 50% of them in turn with diagnosis still to be determined while in around 85% of cases, the hospitalization is just taken as a measure of caution.

Syncope definition states it as a sudden, transient loss of consciousness with the inability to maintain postural tone.

The most common syncope symptoms include: lightheadedness, nausea, feelings of cold, clammy skin. The first resort is to allow the return of blood to the brain by positioning the patient with legs elevated for several minutes. This actions on the vasovagal and orthostatic hypotension. Further syncope treatment will depend on the cause of fainting and aims at diagnosing the underlying disease in order to prevent other syncopal episodes from happening.

Arrhythmia is one of the most common underlying pathologies for patients with syncope, either documented sinus pauses, severe bradycardias, and ventricular tachycardia and often represent a major mortality risk if left untreated. Unfortunately, due to the SFSR score having only around 79% sensitivity, there are several missed pathologies, this often happening in the case of arrhythmias.

References

1) Quinn J, McDermott D, Stiell I, Kohn M, Wells G. (2006) Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med; 47(5):448-54.

2) Birnbaum A, Esses D, Bijur P, Wollowitz A, Gallagher EJ.(2008) Failure to validate the San Francisco Syncope Rule in an independent emergency department population. Ann Emerg Med; 52(2):151-9.

3) Saccilotto RT, Nickel CH, Bucher HC, Steyerberg EW, Bingisser R, Koller MT. (2011) San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review. CMAJ; 183(15):E1116-26.