Retrospective validation of the San Francisco Syncope Rule for prediction of short-term serious outcomes in adult syncope patients

Abstract

Syncope is defined as sudden transient loss of consciousness with spontaneous, complete recovery. Syncope is usually associated with loss/of postural tone leading to falling. Of the various risk stratification instruments available, the San Francisco Syncope Rule is the only one that has been prospectively derived and validated, included all serious outcomes, focuses on short-term outcomes rather than long-term outcomes and adhered to the accepted guidelines for developing a clinical decision rule. This thesis is on retrospective validation of the San Francisco Syncope rule. The study will also attempt to refine the rule if needed and collect basic epidemiological characteristics of syncope patients presenting to a tertiary care emergency department. The objectives of this study were: (1) To assess the performance of the San Francisco Syncope Rule when applied retrospectively to Canadian syncope patients. (2) To assess the potential, impact on resource utilization (in the form of admission rates) if the San Francisco Syncope Rule was applied in Canada. (3) To determine, if needed, the potential for refining the San Francisco Syncope Rule to improve its performance. (4) To describe the basic epidemiological characteristics of emergency department syncope visits to a tertiary care emergency department. The main outcome of the study was to evaluate the performance characteristics of the San Francisco Syncope Rule in its ability to predict serious outcomes within 30 days. The outcome was a composite serious outcome that included anyone of the serious outcomes: death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant bleeding anywhere, any procedural intervention to treat a related cause of syncope, any condition causing/likely to cause a return emergency visit or hospitalization for a related event within 30 days. 505 patient visits were included in the study. 49 (9.7%) of these visits were associated with serious outcomes with 22 (44.9%) occurring in the emergency department and 27 (55.1%) occurring outside the emergency department either during their inpatient stay or outside the hospital. The sensitivity and specificity of the San Francisco Syncope Rule for all serious outcomes was 90% (95% CI 78, 95) and 40% (95% CI 39, 41), for the serious outcomes occurring after discharge from the emergency department was 96% (95% CI 82, 99) and 40% (95% CI 39, 40). 12.3% of the study patients were admitted to the hospital. The rule would have required 63% of the study patients to be admitted. Exploration for refining the rule yielded a preliminary decision rule by recursive partitioning with 3 variables: (1) Age ≥ 65 years, (2) Lowest emergency department systolic blood pressure < 80 mm of Hg and (3) abnormal electrocardiogram [defined as non-sinus rhythm (supraventricular tachycardia, multifocal atrial tachycardia, atrial flutter, atrial fibrillation, junctional rhythm, idioventricular rhythm), significant atrioventricular block (second and third degree), bifasicular block, first degree atrioventricular block in the presence of left or right bundle branch block and cardiac monitor abnormalities]. This preliminary rule had a sensitivity 100% ((95% CI 93, 100) and 53% (95% CI 52, 53) for predicting serious outcomes within 30 days of the emergency visit for syncope. Using this new rule will require 52% of the patients to be admitted to the hospital. Syncope and pre-syncope were common complaints presenting to the emergency department accounting for I% of all emergency visits. The San Francisco Syncope Rule did not perform as well as previously reported. It is feasible to develop a better clinical decision rule based on the San Francisco Syncope Rule to improve the sensitivity and specificity. It also possible to prospectively clarify and improve the performance the 'abnormal electrocardiogram' variable. (Abstract shortened by UMI.