External Validation of the San Francisco Syncope Rule

doi:10.1016/j.annemergmed.2006.11.012

Annals of Emergency Medicine

Volume 49, Issue 4, April 2007, Pages 420-427.e4

https://doi.org/10.1016/j.annemergmed.2006.11.012 Get rights and content

Study objective

We externally validate the ability of the San Francisco Syncope Rule to accurately identify syncope patients who will experience a 7-day serious clinical event.

Methods

Patients who presented to a single academic emergency department (ED) between 8 am and 10 pm with syncope or near-syncope were prospectively enrolled. Treating physicians recorded the presence or absence of all San Francisco Syncope Rule risk factors. Patients were contacted by telephone at 14 days for a structured interview. A 3-physician panel, blinded to the San Francisco Syncope Rule score, reviewed ED medical records, hospital records, and telephone interview forms to identify predefined serious clinical events. The primary outcome was the ability of the San Francisco Syncope Rule to predict any 7-day serious clinical event. A secondary outcome was the ability of the San Francisco Syncope Rule to predict 7-day serious clinical events that were not identified during the initial ED evaluation.

Results

Of 592 eligible patients, 477 (81%) provided informed consent. Direct telephone contact or admission/outpatient records were successfully obtained for 463 (97%) patients. There were 56 (12%) patients who had a serious 7-day clinical event, including 16 (3%) who received a diagnosis after the initial ED evaluation. Sensitivity and specificity of the San Francisco Syncope Rule for the primary outcome were 89% (95% confidence interval [CI] 81% to 97%) and 42% (95% CI 37% to 48%), respectively, and 69% (95% CI 46% to 92%) and 42% (95% CI 37% to 48%), respectively, for the secondary outcome. Estimates of sensitivity were minimally affected by missing data and most optimistic assumptions for missing follow-up information.

Conclusion

In this external validation cohort, the San Francisco Syncope Rule had a lower sensitivity and specificity than in previous reports.

Introduction

Syncope, defined as a transient loss of consciousness, may herald life-threatening events. As a result, patients presenting with syncope to emergency departments (EDs) are frequently hospitalized. Syncope accounts for 1% to 3% of all ED visits and hospital admissions from the ED.1, 2, 3, 4, 5, 6, 7 Unfortunately, current admission practices result in marginal diagnostic and therapeutic benefit8, 9 and consume enormous health care resources. Between 39% and 50% of admitted patients are discharged without an explanation for syncope,4, 10 and syncope-related admissions in the United States account for $2.4 billion in annual health care costs.¹¹

The San Francisco Syncope Rule is an instrument designed to identify patients with syncope or near-syncope who are at low risk of a short-term, serious clinical event.12, 13 Low-risk patients can potentially be discharged for an outpatient evaluation of syncope. The San Francisco Syncope Rule predictors include an abnormal ECG result, complaint of shortness of breath, hematocrit level less than 30%, systolic blood pressure less than 90 mm Hg, and a history of congestive heart failure.

In a derivation study, outcomes included any predefined clinical events within 7 days; the San Francisco Syncope Rule demonstrated 96% sensitivity (95% confidence interval [CI] 92% to 100%) and 62% specificity (95% CI 58% to 66%).¹² In a validation study, outcomes included 30-day predefined events that were diagnosed after the ED visit; the San Francisco Syncope Rule demonstrated 98% sensitivity (95% CI 89% to 100%) and 56% specificity (95% CI 52% to 60%).¹³ These studies suggest that application of the San Francisco Syncope Rule may safely decrease syncope-related admissions by 7% to 10%.

The published San Francisco Syncope Rule derivation and validation studies have been performed at the same institution. Our goal was to evaluate the accuracy of the San Francisco Syncope Rule to identify “low-risk” patients in an independent, prospective validation sample. The primary outcome included all 7-day serious clinical events. The secondary outcome included 7-day serious clinical events that were diagnosed only after the index ED visit. Analysis of the secondary outcome is important because there is little clinical utility in “predicting” serious conditions that are evident at the ED evaluation.

Section snippets

Study Design and Setting

This was a single-center, prospective, observational, cohort study that enrolled patients from April 18, 2005, to April 18, 2006. The study site is an urban, academic, Level I trauma center with an emergency medicine residency and an annual volume of 40,000 visits. The study site institutional review board approved the research protocol.

Selection of Participants

Adult patients with a complaint of syncope or near-syncope were eligible for enrollment. Syncope is defined as a sudden, transient loss of consciousness.

Results

Of the 709 patients who were screened during the study period, 592 (83%) were eligible, and 477 (81%) provided informed consent to participate. We found no important differences in age, sex, race, or ethnicity between eligible patients who provided or declined informed consent. Direct telephone follow-up was obtained in 436 patients (91%). Of the remaining 41 patients, 27 (6% of the entire cohort) had available inpatient or outpatient data for at least 2 weeks after the date of enrollment, and

Limitations

We performed a prospective cohort study designed to minimize missing data bias and maximize direct patient follow-up with a standardized protocol. Nevertheless, there are potential limitations to our study.

We excluded children, patients with DNR/DNI status, and patients without follow-up contact information, whereas these were not exclusion criteria used by the San Francisco Syncope Rule investigators. It is possible that the San Francisco Syncope Rule demonstrated different test

Discussion

We performed a prospective cohort study to externally validate the San Francisco Syncope Rule. Study strengths include a protocol to minimize missing ECG data, high rates of direct patient follow-up, a physician outcomes review panel that was blinded to data recorded by treating physicians, and explicit methods for assessing the effects of missing data on San Francisco Syncope Rule predictors and missing follow-up information. At our institution, physician application of the San Francisco

References (20)

S.C. Day et al.
Evaluation and outcome of emergency room patients with transient loss of consciousness
Am J Med
(1982)
F.P. Sarasin et al.
Prospective evaluation of patients with syncope: a population-based study
Am J Med
(2001)
B.C. Sun et al.
Direct medical costs of syncope-related hospitalizations in the United States
Am J Cardiol
(2005)
J.V. Quinn et al.
Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes
Ann Emerg Med
(2004)
J. Quinn et al.
Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes
Ann Emerg Med
(2006)
T.P. Martin et al.
Risk stratification of patients with syncope
Ann Emerg Med
(1997)
W. Kapoor et al.
Syncope in the elderly
Am J Med
(1986)
M. Brignole et al.
Management of syncope referred urgently to general hospitals with and without syncope units
Europace
(2003)
V. Casini-Raggi et al.
Vasovagal syncope in emergency room patients: analysis of a metropolitan area registry
Neuroepidemiology
(2002)
F. Ammirati et al.
Diagnosing syncope in clinical practice: implementation of a simplified diagnostic algorithm in a multicentre prospective trial: the OESIL 2 study (Osservatorio Epidemiologico della Sincope nel Lazio)
Eur Heart J
(2000)

There are more references available in the full text version of this article.

Cited by (103)

Prediction of Pacemaker Requirement in Patients With Unexplained Syncope: The DROP Score
2022, Heart Lung and Circulation
Implantable loop recorders (ILR) are increasingly utilised in the evaluation of unexplained syncope. However, they are expensive and do not protect against future syncope.
To compare patients requiring permanent pacemaker (PPM) implantation during ILR follow-up with those without abnormalities detected on ILR in order to identify potential predictors of benefit from upfront pacing.
We analysed 100 consecutive patients receiving ILR: Group 1 (n=50) underwent PPM insertion due to bradyarrhythmias detected on ILR; Group 2 (n=50) had no arrhythmias detected on ILR over >3 years follow-up. Baseline clinical characteristics, syncope history, electrocardiographic and echocardiographic parameters were assessed to identify predictors of ultimate requirement for pacing.
Group 1 (64% male, median age 70.8 years; IQR 65.5–78.8) were older than Group 2 (58% male, median 60.2 years; IQR 44.0–73.0 p=0.001) and were less likely to have related historical factors such as overheating, posture and exercise (98% vs 70% p<0.001). PR interval was also longer in Group 1 (192±51 vs 169±23 p=0.006) with greater prevalence of distal conduction system disease (30% vs 4.3% p=0.002). Significant univariate predictors for PPM insertion were distal conduction disease (p=0.007), first degree atrioventricular (AV) block (p=0.003), absence of precipitating factors (p=0.004), and age >65 years (p=0.001). Injury sustained, recurrent syncope, history of atrial fibrillation (AF) or heart failure, left atrial (LA) size and left ventricular ejection fraction (LVEF) were not predictive. These significant predictors were incorporated into the DROP score¹ (0–4). Using time-to-event analysis, no patients with a score of 0 progressed to pacing, while higher scores (3–4) strongly predicted pacing requirement (log-rank p<0.001).
The DROP score may be helpful in identifying patients likely to benefit from upfront permanent pacemaker (PPM) insertion following unexplained syncope. Larger prospective studies are required to validate this tool.
Risk Stratification of Older Adults Who Present to the Emergency Department With Syncope: The FAINT Score
2020, Annals of Emergency Medicine
Older adults with syncope are commonly treated in the emergency department (ED). We seek to derive a novel risk-stratification tool to predict 30-day serious cardiac outcomes.
We performed a prospective, observational study of older adults (≥60 years) with unexplained syncope or near syncope who presented to 11 EDs in the United States. Patients with a serious diagnosis identified in the ED were excluded. We collected clinical and laboratory data on all patients. Our primary outcome was 30-day all-cause mortality or serious cardiac outcome.
We enrolled 3,177 older adults with unexplained syncope or near syncope between April 2013 and September 2016. Mean age was 73 years (SD 9.0 years). The incidence of the primary outcome was 5.7% (95% confidence interval [CI] 4.9% to 6.5%). Using Bayesian logistic regression, we derived the FAINT score: history of heart failure, history of cardiac arrhythmia, initial abnormal ECG result, elevated pro B-type natriuretic peptide, and elevated high-sensitivity troponin T. A FAINT score of 0 versus greater than or equal to 1 had sensitivity of 96.7% (95% CI 92.9% to 98.8%) and specificity 22.2% (95% CI 20.7% to 23.8%), respectively. The FAINT score tended to be more accurate than unstructured physician judgment: area under the curve 0.704 (95% CI 0.669 to 0.739) versus 0.630 (95% CI 0.589 to 0.670).
Among older adults with syncope or near syncope of potential cardiac cause, a FAINT score of zero had a reasonably high sensitivity for excluding death and serious cardiac outcomes at 30 days. If externally validated, this tool could improve resource use for this common condition.
Clinical Benefit of Hospitalization for Older Adults With Unexplained Syncope: A Propensity-Matched Analysis
2019, Annals of Emergency Medicine
Citation Excerpt :
This does not directly change practice but suggests that we may be able to safely discharge more syncope patients. Despite substantial research efforts to develop and validate accurate risk-stratification tools,4-10 there remains considerable uncertainty in regard to which patients with syncope can be safely discharged from the ED.11 Greater than 30% of these visits result in hospitalization; for older adults (≥60 years), this proportion is greater than 50%.12
Many adults with syncope are hospitalized solely for observation and testing. We seek to determine whether hospitalization versus outpatient management for older adults with unexplained syncope is associated with a reduction in postdisposition serious adverse events at 30 days.
We performed a propensity score analysis using data from a prospective, observational study of older adults with unexplained syncope or near syncope who presented to 11 emergency departments (EDs) in the United States. We enrolled adults (≥60 years) who presented with syncope or near syncope. We excluded patients with a serious diagnosis identified in the ED. Clinical and laboratory data were collected on all patients. The primary outcome was rate of post-ED serious adverse events at 30 days.
We enrolled 2,492 older adults with syncope and no serious ED diagnosis from April 2013 to September 2016. Mean age was 73 years (SD 8.9 years), and 51% were women. The incidence of serious adverse events within 30 days after the index visit was 7.4% for hospitalized patients and 3.19% for discharged patients, representing an unadjusted difference of 4.2% (95% confidence interval 2.38% to 6.02%). After propensity score matching on risk of hospitalization, there was no statistically significant difference in serious adverse events at 30 days between the hospitalized group (4.89%) and the discharged group (2.82%) (risk difference 2.07%; 95% confidence interval –0.24% to 4.38%).
In our propensity-matched sample of older adults with unexplained syncope, for those with clinical characteristics similar to that of the discharged cohort, hospitalization was not associated with improvement in 30-day serious adverse event rates.
Prevalence of Pulmonary Embolism Among Emergency Department Patients With Syncope: A Multicenter Prospective Cohort Study
2019, Annals of Emergency Medicine
The prevalence of pulmonary embolism among patients with syncope is understudied. In accordance with a recent study with an exceptionally high pulmonary embolism prevalence, some advocate evaluating all syncope patients for pulmonary embolism, including those with another clear cause for their syncope. We seek to evaluate the pulmonary embolism prevalence among emergency department (ED) patients with syncope.
We combined data from 2 large prospective studies enrolling adults with syncope from 17 EDs in Canada and the United States. Each study collected the results of pulmonary embolism–related investigations (ie, D-dimer, ventilation-perfusion scan, or computed tomography [CT] pulmonary angiography) and 30-day adjudicated outcomes: pulmonary embolism or nonpulmonary embolism outcome (arrhythmia, myocardial infarction, serious hemorrhage, and death).
Of the 9,374 patients enrolled, 9,091 (97.0%; median age 66 years, 51.9% women) with 30-day follow-up were analyzed: 547 (6.0%) were evaluated for pulmonary embolism (278 [3.1%] had D-dimer, 39 [0.4%] had ventilation-perfusion scan, and 347 [3.8%] had CT pulmonary angiography). Overall, 874 patients (9.6%) experienced 30-day serious outcomes: 818 patients (9.0%) with nonpulmonary embolism serious outcomes and 56 (prevalence 0.6%; 95% confidence interval 0.5% to 0.8%) with pulmonary embolism (including 8 [0.2%] out of 3521 patients diagnosed during the index hospitalization and 7 [0.1%] diagnosed after the index visit). Eighty-six patients (0.9%) died, and 4 deaths (0.04%) were related to pulmonary embolism. Only 11 patients (0.1%) with a nonpulmonary embolism serious condition had a concomitant pulmonary embolism.
The prevalence of pulmonary embolism is very low among ED patients with syncope, including those hospitalized after syncope. Although an underlying pulmonary embolism may cause syncope, clinicians should be cautious about indiscriminate investigations for pulmonary embolism.
Geriatric Syncope and Cardiovascular Risk in the Emergency Department
2017, Journal of Emergency Medicine
Syncope is a transient loss of consciousness that is caused by a brief loss in generalized cerebral blood flow.
This article reviews the background, epidemiology, etiologies, evaluation, and disposition considerations of geriatric patients with syncope, with a focus on cardiovascular risk.
Although syncope is one of the most common symptoms in elderly patients presenting to the emergency department, syncope causes in geriatric patients can present differently than in younger populations, and the underlying etiology is often challenging to discern. History, physical examination, and electrocardiography (ECG) have the greatest utility in evaluating syncope. Additional testing should be guided by history and physical examination. There are multiple scoring tools developed to aid in management and these are reviewed in the article. Common predictors that would indicate a need for further work-up include a history of cardiac or valvular disease (i.e., ventricular dysrhythmia, congestive heart failure), abnormal ECG, anemia or severe volume depletion (i.e., from a gastrointestinal bleed), syncope while supine or with effort, report of palpitations or chest pain, persistent abnormal vital signs, or family history of sudden death. With advancing age, cardiovascular morbidity plays a more frequent and important role in the etiology of syncope.
The syncope work-up should be tailored to the patient's presentation. Disposition should be based on the results of the initial evaluation and risk factors for adverse outcomes.
Opportunities for Emergency Medical Services (EMS) Care of Syncope
2016, Prehospital and Disaster Medicine

View all citing articles on Scopus

Supervising editor: Allan B. Wolfson, MD

Author contributions: BCS, CMM, JRH, and WRM conceived the study. BCS and CMM obtained funding for this study. BCS, GM, TW, GZS, GZ, and SS were responsible for data collection, and BCS supervised the overall data collection process. BCS performed the data analysis and drafted the article. All authors contributed substantially to article revisions. BCS takes responsibility for the paper as a whole.

Michael Callaham, MD, recused himself from the editorial decision process for this article.

Funding and support: This study was supported by the UCLA Robert Wood Johnson Clinical Scholars Program (050721). Dr Sun is supported by a UCLA National Institute of Aging K12 award (K12AG001004) and an American Geriatrics Society Dennis Jahnigen Career Development Award. Dr Mangione was also partially supported by the UCLA Center for Health Improvement in Minority Elders/Resource Centers for Minority Aging Research, NIH/NIA (AG 02-004).

Available online January 8, 2007.

Reprints not available from the authors.

View full text

Neurology/original researchExternal Validation of the San Francisco Syncope Rule

Study objective

Methods

Results

Conclusion

Introduction

Section snippets

Study Design and Setting

Selection of Participants

Results

Limitations

Discussion

Am J Med

Am J Med

Am J Cardiol

Ann Emerg Med

Ann Emerg Med

Ann Emerg Med

Am J Med

Management of syncope referred urgently to general hospitals with and without syncope units

Europace

Vasovagal syncope in emergency room patients: analysis of a metropolitan area registry

Neuroepidemiology

Diagnosing syncope in clinical practice: implementation of a simplified diagnostic algorithm in a multicentre prospective trial: the OESIL 2 study (Osservatorio Epidemiologico della Sincope nel Lazio)

Eur Heart J

Neurology/original research
External Validation of the San Francisco Syncope Rule