Source Document: Serrano LA, Hess EP, Bellolio MF, Murad MH, Montori VM, Erwin PJ, Decker WW. Accuracy and quality of clinical decision rules for syncope in the emergency department: a systematic review and meta-analysis. Ann Emerg Med. 2010 Oct;56(4):362-373.e1. Review. PubMed PMID: 20868906; PubMed Central PMCID: PMC2946941. 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;47:448-454. 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;43:224-232. Schladenhaufen R, Feilinger S, Pollack M, et al. Application of San Francisco Syncope Rule in elderly ED patients. Am J Emerg Med. 2008;26:773-778. Sun BC, Mangione CM, Merchant G, et al. External validation of the San Francisco Syncope Rule. Ann Emerg Med. 2007;49:420-427, e424. Dipaola FCG, Perego F, Borella M, et al. San Francisco Syncope Rule, Osservatorio Epidemiologico sulla Sincope nel Lazio risk score, and clinical judgment in the assessment of short-term outcome of syncope. Am J Emerg Med. 2010;28:432-439. Birnbaum A, Esses D, Bijur P, et al. Failure to validate the San Francisco Syncope Rule in an independent emergency department population. Ann Emerg Med. 2008;52:151-159. Cosgriff TM, Kelly AM, Kerr D. External validation of the San Francisco Syncope Rule in the Australian context. CJEM. 2007;9:157-161. Thiruganasambandamoorthy V, Hess EP, Alreesi A, et al. External validation of the San Francisco Syncope Rule in the Canadian setting. Ann Emerg Med. 2010;55:464-472. Reed MJ, Newby DE, Coull AJ, et al. The ROSE (Risk Stratification of Syncope in the Emergency Department) study. J Am Coll Cardiol. 2010;55:713-721. Colivicchi F, Ammirati F, Melina D, et al. Development and prospective validation of a risk stratification system for patients with syncope in the emergency department: the OESIL risk score. Eur Heart J. 2003;24:811-819. Grossman SA, Fischer C, Lipsitz LA, et al. Predicting adverse outcomes in syncope. J Emerg Med. 2007;33:233-239. Sun BC, Derose SF, Liang LJ, et al. Predictors of 30-day serious events in older patients with syncope. Ann Emerg Med. 2009;54: 769-778. Quinn J. In reply. Ann Emerg Med. 2006;48(6): 760-1. Reed MJ, Henderson SS, Newby BS, Gray AJ. One-Year Prognosis After Syncope and the Failure of the ROSE Decision Instrument to Predict One-Year Adverse Events. Ann Emerg Med. 2011 Feb 1.
Narrative: Background: Syncope is defined as sudden, transient loss of consciousness with failure to maintain postural tone. It accounts for 1-2% of ED visits and hospitalizations in the U.S. with subsequent health care costs in the billions of dollars. Most patients who have syncope ultimately have a benign etiology and clinical course. However a nontrivial number of patients have significant pathology such as cardiac arrhythmia or ischemia, gastrointestinal blood loss, etc. so identifying this group of patients is consequential. Most patients who are admitted for syncope do not have significant pathology, hence identifying those safe for discharge is desirable for both patients and physicians.
There have been multiple studies evaluating syncope decision rules in the past 10 years: The San Francisco syncope rule (SFSR), OESIL risk score, ROSE study (Risk Stratification of Syncope in the Emergency Department Study), Boston syncope rule, and the Syncope risk score. There is a consistent theme of ‘serious’ short-term outcome (7-23%) and the possibility of death (0.4-2.4%) following syncope across these studies.
The SFSR is by far the most robust data set as it has been externally validated 7 times: US (3 prospectively, 1 retrospective) and once each in Canada (retrospective), Australia (prospective), and Italy (prospective) with a combined pool of 4250 patients. There were 434 (10%) serious outcomes in these patients including 17 deaths (0.4%) that occurred in the 7 days following initial Emergency Department presentation. 60 of these events would not have been predicted by the rule (1.4%). The pooled sensitivity of this rule is 86%.
Myocardial infarction and undiagnosed anemia are less common but consistent etiologies found across the group. Neurologic catastrophe (stroke, intracranial hemorrhage) was an uncommon syncope presentation though represented in most studies, and while many of the rules missed it, it seems to have been obvious as a cause as it was not missed as a diagnosis in the ED in any of the studies. ED ‘bounceback’ for syncope is considered a serious outcome in the SFSR, however one could quibble with this given it is generally insignificant from a long term outcome perspective both medically and legally (7 of the 60 missed outcomes are for this reason).
Arrhythmia is by far the largest category of pathology found in syncope: ~40% of the total number of serious outcomes and 60% of the SFSR misses. Some of these arrhythmias are clearly legitimate diagnoses (documented sinus pauses, severe bradycardias, and ventricular tachycardia) and probably the root cause of many of the deaths. However this term is a bit of a garbage-basket diagnostic category as it includes everything from supraventricular tachycardias (rarely dangerous) to ventricular tachycardia (clearly dangerous) to patients who received pacers for perceived risk (unclear danger).
The SFSR is criticized as being unsafe given this miss rate (pooled sensitivity of 86%) which is just when it is clearly shown to miss significant pathology (mostly cardiac arrhythmias, 36/60 cases). Notably, there is one patient who was SFSR negative who subsequently died (cardiac arrest after inpatient hospital discharge).
San Francisco Syncope Rule Misses*
|Arrhythmia (>21 pacers placed)||36|
|Return to ED for recurrent symptoms||9|
|Structural heart disease||1|
Of considerable importance is the fact that all of the patients who were missed by the rule across the SFSR studies were admitted, except for the 9 patients who returned with recurrent syncope for which no cause was found. (Caveat: we don’t have admit/discharge data for the 23 SFSR misses from the retrospective chart review of elderly patients… data hopefully to arrive from the authors). There were no cases of undiagnosed pulmonary embolism.
Caveats: Some of the data in San Francisco Syncope rule cohort is retrospective. One of these retrospective studies did not include all syncope patients, limiting the subject pool to those over age 65. This group had higher rates of serious outcomes, unsurprisingly, so if anything this skews the overall morbidity of the combined data upward.
Many physicians have expressed discomfort with the fact that the SFSR was generated to measure serious outcomes at 7 days only, voicing concerns about medical and legal liability with a relatively short follow-up period. Quinn responded that there were minimal significant outcomes between 8-30 days in his 2 study cohorts. There were 7 total outcomes in 1475 patients (0.5%). 6 of these were for pacemaker placements that occurred in the period after discharge from the inpatient service.
Unfortunately, the SFSR does not exclude patients whose cause of syncope is obvious, as the decision tree is clear for these folks. (i.e. the patient who had syncope accompanied by obvious stroke findings) The burning unanswered question for most clinicans who evaluate syncope is what the risk is for an asymptomatic patient with a benign exam and workup after syncope. This leads to the important question: "Can the SFSR rule be used to augment disposition of such syncope patients?" While the SFSR rule has misses, none of the consequential misses were discharged from the ED giving evidence that when combined with clinical gestalt there may be utility for the SFSR. This zero 'miss' rate is likely due to an overall high admission rate, therefore a prospective study utilizing combined physician gestalt with the SFSR would be a critical step in determining whether this decision aid can perform the task that clinicians would hope to see.
Author: Joshua Quaas, MD
Published/Updated: April 23, 2011
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