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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 6  |  Issue : 1  |  Page : 2-6

Prospective validation of San Francisco Syncope Rule in Indian population


1 Associate Professor, Department of Cardiology, Government Medical College, Kottayam, Kerala, India
2 Senior Resident, Department of Cardiology, Government Medical College, Kottayam, Kerala, India
3 Professor, Department of Cardiology, Government Medical College, Kottayam, Kerala, India

Date of Web Publication26-Dec-2016

Correspondence Address:
Narayanapillai Jayaprasad
Department of Cardiology, Government Medical College, Kottayam - 686 008, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2250-3528.196642

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  Abstract 

Context: The San Francisco Syncope Rule (SFSR) was proposed as a risk stratification tool for patients presenting to the emergency department (ED) with syncope.
Aims: The aim of this study was to validate the SFSR in Indian population for predicting serious outcomes in patients presenting with syncope or near syncope. Secondary aim was to identify whether the admission rate can be safely reduced by applying this rule in the ED.
Settings and Design: This was a prospective observational study conducted among patients attending the ED of a teaching hospital with syncope or near syncope.
Subjects and Methods: Physicians prospectively applied the SFSR after usual evaluation, and patients were followed up to determine whether they had a serious outcome within 30 days of their ED visit.
Statistical Analysis Used: Sensitivity, specificity, positive and negative predictive values of the rule for predicting serious outcomes were calculated.
Results: A total of 210 patients were included in the study. There were 86 (41%) males and 124 (59%) females. Average age was 60.6 years. A total number of patients admitted were 110 out of 210 patients (52%). At least one SFSR predictor was positive in 90 (43%) patients out of 210. A total of 23 patients (11%) had at least one serious outcome at 30 days of ED visit. SFSR had a sensitivity of 95.65% and a specificity of 63.64% to predict serious outcome in the study population.
Conclusions: The SFSR is valid in Indian population and application of the rule could reduce the hospital admission rates for syncope.

Keywords: Risk stratification, San Francisco Syncope Rule, syncope


How to cite this article:
Jayaprasad N, Madhavan S, Baiju S, Jayaprakash V L. Prospective validation of San Francisco Syncope Rule in Indian population. J Clin Prev Cardiol 2017;6:2-6

How to cite this URL:
Jayaprasad N, Madhavan S, Baiju S, Jayaprakash V L. Prospective validation of San Francisco Syncope Rule in Indian population. J Clin Prev Cardiol [serial online] 2017 [cited 2020 Nov 29];6:2-6. Available from: https://www.jcpconline.org/text.asp?2017/6/1/2/196642


  Introduction Top


Syncope accounts for approximately 3% of emergency department (ED) visits and 1%-6% of all hospital admissions. [1] In ED evaluation, it is challenging to decide which patients require in-hospital management for potentially life-threatening etiologies as against those who are safe for discharge. While most potential causes of syncope are benign and self-limited, some etiologies are associated with significant morbidity and mortality. Cardiovascular causes are the most common life-threatening conditions associated with syncope, and these can be divided by causal factor into arrhythmogenic, structural, and ischemic. [2]

Several studies have attempted to stratify syncope patients with regard to risk for life-threatening events. [3],[4] Quinn et al. published the San Francisco Syncope Rule (SFSR) as a means of predicting patients with serious outcomes at 1 week following the episode. [3] The five SFSR variable predictors are history of congestive heart failure (CHF), hematocrit <30%, abnormal electrocardiogram (ECG) results, complaint of shortness of breath, and systolic blood pressure (SBP) <90 mm Hg during triage. Identification of patients at risk of short-term (7-day) adverse events helps prevent unnecessary admissions so that low-risk patients can potentially be discharged for outpatient evaluation of syncope. The SFSR had a sensitivity of 96% and specificity of 62%. Validation studies conducted among various populations showed conflicting results. [5],[6],[7],[8] There are wide variations in the performance of the rule across different validation studies with sensitivity varying from 69% to 100% while specificity from 33% to 57%.

There has been no validation study of the rule in the Indian population for identifying high-risk syncope patients presenting to the ED. Hence, the aim of the study was to test whether SFSR is valid in our population for predicting serious outcomes in patients presenting with syncope or near syncope. The secondary aim was to identify whether the admission rate can be safely reduced by applying this rule in the ED.


  Subjects and Methods Top


This was a prospective observational study conducted in a Government Tertiary Care Hospital from March 2015 to August 2015. Consecutive patients presenting with syncope or near syncope in the ED were included in the study. After detailed clinical examination, all patients were evaluated with ECG, blood hemoglobin, packed cell volume, and other relevant investigations including Holter analysis, treadmill testing, coronary angiography, computed tomography (CT) scan, and electroencephalogram needed to diagnose serious outcomes. Exclusion criteria included head injury preceding the loss of consciousness, coma, definite seizure, associated diseases with expected survival <6 months (malignancies, terminal illnesses), and intoxication.

All the enrolled patients were evaluated for the five components of the SFSR.

Definitions of the five variables are given below:

  • Triage SBP <90 mmHg: Defined as SBP <90 mmHg measured by ED nurse triaging the patient
  • History of shortness of breath: Defined as patient suffering from shortness of breath at any time during the visit
  • History of CHF: Defined as present or past history of CHF and reported by the patient or elicited by the medical personnel
  • Abnormal ECG: Defined as any nonsinus rhythm, which could be identified on the 12 lead ECG or during cardiac monitoring in the ED; or any new change compared to a prior ECG
  • Hematocrit <30%.
The list of serious outcomes included any of the following: death, myocardial infarction (MI), arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, any significant bleeding, any procedural intervention to treat a related cause of syncope, any condition causing or likely to cause a return emergency visit, or hospitalization for a related event within 30 days.

Serious outcomes were defined as follows:

  • Death: Death from any cause
  • MI: Defined as an increase in troponin level or ECG changes consistent with ischemia/infarction and with an accompanying diagnosis of MI
  • Arrhythmia: Defined as any rhythm abnormality (previously known or new) captured on monitoring and thought to have a temporal relationship to the symptom or that required treatment
  • Pulmonary embolism: Diagnosis made by CT scan of the chest
  • Stroke: Defined by the presence of a persistent neurologic deficit with symptoms temporally related to the syncope episode
  • Subarachnoid hemorrhage: Confirmed by CT imaging of the brain
  • Significant hemorrhage: Defined as a detected source of bleeding requiring transfusion
  • Any procedural intervention to treat a related cause of syncope
  • Any condition causing or likely to cause a return emergency visit
  • Hospitalization for a related event within 30 days.
All patients were prospectively followed up at 30 days for serious outcomes by outpatient clinic review or telephonic interview.

Clinically significant structural heart diseases were confirmed on two-dimensional echocardiography and thought to be significant to cause syncope. Major cardiac procedures included percutaneous coronary interventions, coronary artery bypass graft operations, valve surgeries, and pacemaker insertions that were carried out to treat the cause of syncope.

Baseline characteristics of the study population were assessed with respect to age, sex, whether admitted or discharged, presence or absence of SFSR predictors. After 30 days evaluation, study population was divided into two groups: (1) those with serious outcomes and (2) those without serious outcomes. Between-group differences of the baseline characteristics, management advice, and presence of SFSR predictors were evaluated. Sensitivity and specificity of the rule for predicting serious outcomes were calculated from the number of patients from different groups.


  Results Top


A total of 210 patients were included in the study. There were 86 (41%) males and 124 (59%) females. Total number of patients requiring admission were 110, of the total 210 patients (52%) while 100 (48%) were evaluated as outpatients. Of the 210 patients, 46 were smokers who were all male and 56 were alcoholics (all male patients). Systemic arterial hypertension was noted in 110 (52%) patients and diabetes was present in 89 (42%) patients out of the total 210 patients in the study. Fifty-one (24%) patients had a history of previous coronary artery disease. Among the 210 patients, 11 patients had valvular heart disease. Eight patients had calcific aortic stenosis, one patient each had bicuspid aortic valve stenosis, rheumatic heart disease - mitral regurgitation, and mitral valve prolapse. Out of the 210 patients, serious outcomes were identified in 23 patients (11%). No serious outcomes were present in 187 patients (89%). All the 23 patients with serious outcomes were admitted. Eighty-seven (47%) patients from no serious outcome group were admitted and 100 patients were evaluated as outpatients. Demographic characteristics and risk factors are given in [Table 1].
Table 1: Characteristics of study population


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Prevalence of san francisco syncope rule predictors

The prevalence of SFSR predictors in the study population is given in [Table 2]. At least one SFSR predictor was positive in 90 (43%) patients out of 210. Twenty-two (95.6%) out of 23 patients with serious outcomes had SFSR positivity. SFSR was positive in 68 (36%) out of 187 patients without serious outcome.
Table 2: Prevalence of San Francisco Syncope Rule predictors


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Serious outcomes

A total of 23 patients had at least on serious outcome at 30 days of ED visit. This constituted about 11%. The numbers of various serious outcomes measured are given in [Table 3].
Table 3: List of serious outcomes


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San francisco syncope rule predictors and outcome

Among the admitted patients, the SFSR was positive in ninety patients out of the 110 admitted (82%). From the total of 210 patients included, 110 were admitted (52%). SFSR positive patients admitted constituted 43% admissions only. By applying SFSR, the number of admissions would have been reduced by 9% (20 patients). Among the 23 patients with serious outcome, SFSR was positive in 22 and negative in one. The only patient with serious outcome with no SFSR predictor developed cerebrovascular accident in the hospital. Among the 187 patients with no serious outcomes, SFSR was positive in 68 and negative in 119. In this study, the SFSR had a sensitivity of 95.65% (95% confidence interval [CI] 78.05%-99.89%), specificity of 63.64% (95% CI 56.30%-70.53%), positive likelihood ratio of 2.63 (95% CI 2.14-3.24), negative likelihood ratio of 0.07 (95% CI 0.01-0.47), positive predictive value of 24.44% (95% CI 16.00% to 34.64%), and negative predictive value of 99.17% (95% CI 95.44% to 99.98%).

SFSR performance in the study population is given in [Table 4].
Table 4: San Francisco Syncope Rule performance


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  Discussion Top


During ED evaluation, the cause of syncope often remains unclear and management must focus on identification of the underlying condition and risk stratification to differentiate among patients safe for discharge and those who require evaluation and in-hospital management. However, methods of evaluation vary from center to center, and there is no uniform consensus on the best strategy to triage these patients in the ED. Many admissions for syncope are unwanted and inefficient. After admission, approximately half of syncope patients may still have unclear diagnoses, and only about half of the hospitalized patients undergo any specific investigation such as tilt table or electrophysiologic studies. [9],[10] Risk stratification with simple guidelines that are clinically derived is an important tool to help with physician decision-making and improve the efficiency of the use of patient care resources.

There have been multiple studies to risk-stratify syncope in ED. The SFSR has, by far, been the most studied. However, the validation studies have produced mixed results. [5],[6],[7],[8] This is the first validation study of SFSR in the Indian population. In this prospective validation study among patients with syncope, it is demonstrated that patients who develop serious outcomes can be accurately predicted by the SFSR. The rule is not complex and is easily remembered by a simple mnemonic: CHESS (history of CHF, hematocrit <30%, abnormal ECG, a patient complaint of shortness of breath and a triage SBP <90 mm Hg). Moreover, the rule reinforces most of the key risk factors identified in retrospective studies and guidelines.

In our study, the SFSR performed well with a sensitivity of 95.65% (95% CI = 78.05%-99.89%) and a specificity of 63.64% (95% CI = 56.30%-70.53%). The sensitivity and specificity were comparable to the original study (96% and 62%). Negative predictive value was 99.17% which indicates that the rule is very useful in reducing admissions in the ED. Standardized guidelines were recently developed for ED-based syncope risk stratification studies using an expert consensus process involving 24 panelists from five clinical subspecialties across eight countries. [11] These guidelines included study eligibility, outcomes, ECG abnormalities, and predictors. According to these guidelines, the tool should be able to identify outcomes during ED evaluation, 7 days as well as 7-30-day period. Based on the above guideline, we used serious outcomes at 30 days from ED visit instead of the 7-day outcome in the original cohort. We found that absolute admission rates could be decreased by 9% in the low-risk group with the implementation of the decision rule. The major advantage of SFSR in this study was that 22 out of 23 patients with serious outcomes had at least one predictor. Thus, using SFSR in ED will help avoid inadvertent discharge from ED of a patient who is prone for a serious outcome.

Limitations of the study

  • Even though we have tried to include all consecutive patients there might have been omissions from the ED as evaluation of syncope often involve multiple specialties
  • Long-term outcomes were not evaluated
  • Significance of multiple predictors in the same patient was not studied as we were assessing the predictive value of variables as a group.

  Conclusions Top


In this prospective observational study of patients attending the ED with syncope or near syncope, serious outcomes were present in 11% of the study population. We found that the SFSR had a sensitivity of 95.65% and specificity of 63.64%. The SFSR is valid in Indian population and application of the rule could reduce the hospital admission rates for syncope evaluation significantly.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Day SC, Cook EF, Funkenstein H, Goldman L. Evaluation and outcome of emergency room patients with transient loss of consciousness. Am J Med 1982;73:15-23.  Back to cited text no. 1
    
2.
Kapoor WN, Karpf M, Wieand S, Peterson JR, Levey GS. A prospective evaluation and follow-up of patients with syncope. N Engl J Med 1983;309:197-204.  Back to cited text no. 2
    
3.
Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA. Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes. Ann Emerg Med 2004;43:224-32.  Back to cited text no. 3
    
4.
Grossman SA, Fischer C, Lipsitz LA, Mottley L, Sands K, Thompson S, et al. Predicting adverse outcomes in syncope. J Emerg Med 2007;33:233-9.  Back to cited text no. 4
    
5.
Quinn J, McDermott D, Stiell I, Kohn M, Wells G. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med 2006;47:448-54.  Back to cited text no. 5
    
6.
Sun BC, Mangione CM, Merchant G, Weiss T, Shlamovitz GZ, Zargaraff G, et al. External validation of the San Francisco Syncope Rule. Ann Emerg Med 2007;49:420-7, 427.e1-4.  Back to cited text no. 6
    
7.
Cosgriff TM, Kelly AM, Kerr D. External validation of the San Francisco Syncope Rule in the Australian context. CJEM 2007;9:157-61.  Back to cited text no. 7
    
8.
Tan C, Sim TB, Thng SY. Validation of the San Francisco Syncope Rule in two hospital emergency departments in an Asian population. Acad Emerg Med 2013;20:487-97.  Back to cited text no. 8
    
9.
Blanc JJ, L'Her C, Touiza A, Garo B, L'Her E, Mansourati J. Prospective evaluation and outcome of patients admitted for syncope over a 1 year period. Eur Heart J 2002;23:815-20.  Back to cited text no. 9
    
10.
Pires LA, Ganji JR, Jarandila R, Steele R. Diagnostic patterns and temporal trends in the evaluation of adult patients hospitalized with syncope. Arch Intern Med 2001;161:1889-95.  Back to cited text no. 10
    
11.
Sun BC, Thiruganasambandamoorthy V, Cruz JD; Consortium to Standardize ED Syncope Risk Stratification Reporting. Standardized reporting guidelines for emergency department syncope risk-stratification research. Acad Emerg Med 2012;19:694-702.  Back to cited text no. 11
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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