Syncope is defined as a sudden and transient loss of consciousness and postural tone with spontaneous recovery without the assistance of a therapeutic intervention. It is estimated that the lifetime prevalence of syncope could reach approximately 50% of the general population. In the United States, it is estimated that one to two million patients are evaluated for syncope annually. This represents anywhere from three to five percent of all emergency room visits and one to six percent of all hospital admissions.

Mayo Clinic.

       Dr. Shen and his colleagues at the Mayo Clinic conducted the Syncope Evaluation in the Emergency Department Study (SEEDS). The genesis of the study was based on the central question whether an area designated for syncope evaluation in the emergency department or a syncope unit could affect the diagnostic yield and the rate of hospital admissions for syncope patients with intermediate-risk profiles for a poor prognosis. The hypothesis was that a syncope unit equipped with diagnostic resources that target the common causes of syncope would improve the diagnostic yield and reduce the hospital admission rate compared to patients undergoing a standard work-up.

Causes of Syncope
       The SEEDS study defined 10 diagnostic categories that were based on the pathophysiological mechanisms and therapeutic targets. These ten categories were: 1) bradyarrhythmias; 2) ventricular arrhythmias; 3) supraventricular tachyarrhythmias; 4) structural cardiac or cardiopulmonary causes; 5) neurocardiogenic or situational syncope; 6) carotid sinus hypersensitivity; 7) cerebrovascular disease; 8) orthostatic intolerance; 9) syncope-like conditions such as psychogenic or hyperventilation; and 10) unknown.
       During the initial emergency room evaluation, patients were stratified into one of three categories: high risk, intermediate risk, and low risk (Table 1). High-risk patients are deemed appropriate for hospital admission, intermediate risk are potential hospital admissions, and low-risk patients met the guidelines that meant hospital admission was not required. Patients that were enrolled in the study experienced syncope of intermediate risk for adverse cardiovascular outcomes. According to the current practice, most of these patients are routinely admitted for inpatient evaluation.

Table 1. Emergency Department Risk Stratification of Patients with Syncope of Unknown Cause.

- High-risk group: Chest pain compatible with acute coronary syndrome Signs of congestive heart failure Moderate/severe valvular disease History of ventricular arrhythmias ECG/cardiac monitor findings of ischemia Prolonged QTc (> 500 ms) Trifascicular block or pauses between 2–3 seconds Persistent sinus bradycardia between 40–60 beats/minute Atrial fibrillation and non-sustained ventricular tachycardia without symptoms Cardiac devices (pacemaker or defibrillator) with dysfunction Intermediate-risk group: Age >= to 50 years old With previous history of: Coronary artery disease Myocardial infarction Congestive heart failure Cardiomyopathy without active symptoms or signs on cardiac medications Bundle branch block or Q wave without acute changes on ECG Family history of premature (< 50 years old), unexplained sudden death Symptoms not consistent with a reflex-mediated or vasovagal cause Cardiac devices without evidence of dysfunction Physician's judgment that suspicion of cardiac syncope is reasonable Low-risk group: Age < 50 years old With no previous history of: Cardiovascular disease Symptoms consistent with reflex-mediated or vaso-vagal syncope Normal cardiovascular examination Normal ECG findings ECG = electrocardiographic

Study Design
       This study was designed to operate in three phases. Phase 1 occurred from the time of arrival in the emergency department to the dismissal from the emergency department. The patients presenting with syncope were placed on cardiac monitor, given nasal oxygen, and started on an IV. A complete history was obtained, a physical examination was given, and an ECG was obtained. Then the patients were randomized to routine emergency room evaluation or to the syncope unit to receive continuous cardiac monitoring for up to six hours. Echocardiograms were obtained on those patients with abnormal cardiovascular examinations or an abnormal ECG. A tilt table test was recommended in patients who had a history of cardiac disease, an abnormal ECG, presented with symptoms atypical for cardiogenic syncope, or in patients without known or confirmed cardiac disease presenting with symptoms atypical for neurocardiogenic syncope or orthostatic intolerance. Phase 2 of the study included the period of time of emergency department dismissal to the completion of the index event evaluation (whether in hospital or in outpatient clinic). Phase 3 of the study was the time period of follow-up.

Syncope Unit Design
       The design of the syncope unit was based on the common causes of syncope and the available diagnostic tools suitable in an emergency room setting. A multidisciplinary approach is critical for the evaluation of syncope in the emergency room since there are numerous causes. For this study, the physicians involved included those from the emergency room, cardiologists, and electrophysiologists who share expertise in triage, diagnosis, therapy options, and education. A neurologic examination was not part of this study, because neurological conditions such as seizure or stroke were differentiated from the syncope unit based on clinical presentation.

Phase 1: Primary Endpoints
       Phase 1 of the study ended with the dismissal from the emergency department. For the patients enrolled in the syncope unit, sixty-seven percent of these individuals had an identified cause for their syncope as compared to 10% in the standard care group. See Table 2 for the breakdown of diagnosis during phase 1 and phase 2 of the evaluation. Neurocardiogenic syncope was the most frequent diagnosis in the syncope unit (21 patients or 41%). Two patients had arrhythmogenic cause (one ventricular tachycardia and one transient bradycardia). In the standard care group, five patients (10%) had the presumptive diagnosis established in the emergency room. Two were presumed to have vasovagal syncope and the other three were diagnosed with dehydration. All five of these patients experienced recurrent symptoms while receiving standard care in the emergency department.
       Hospital admissions varied significantly between the two populations. The syncope unit patients had a 43% admission rate, whereas there was a 98% rate in the standard care group.

Phase 2: Completion of Index Event Evaluation
       At the conclusion of the index evaluation, the overall rates for presumed causes of syncope were similar between the two randomized groups. This finding is not surprising since all patients, regardless of how they were randomized, were expected to have undergone similar evaluation by the conclusion of the index evaluation. Although the mean hospital length of stay was similar between the two groups, the total inpatient hospital days were reduced by more than 50% in the syncope unit group.

Phase 3: Follow-up Outcomes
       During a mean follow-up of 18 months, mortality, recurrent syncope, and a combined mortality and recurrent syncope rates were not different between the randomized groups.

Major Findings
       This study was designed as a prospective, single-center, randomized study, looking at patients with intermediate risk syncope that is unexplained upon admission. This study demonstrated four main findings.
1. There was a significantly higher diagnosis yield and a decreased hospital admission rate in the syncope unit as compared to the standard care.
2. At the conclusion of the study, the net diagnostic yield was similar in the two groups.
3. The total length of hospital admission was reduced by > 50% for patients in the syncope unit as compared to the conventional group. This was directly related to the decreased hospitalization rate.
4. Follow-up outcomes for all-cause mortality and recurrent syncope were similar for the two groups.

Conclusion
       This syncope unit study provided the first evidence that a designated unit in the emergency department to evaluate intermediate risk syncope can be an effective option as compared to conventional approach. Many similarly equipped units have been established across the United States for the evaluation of chest pain, and these have been shown to be cost-effective and safe. Utilizing a multidisciplinary collaboration in the syncope unit provided efficient and effective evaluation, as well as triage of the patients. With rapidly growing health care costs, this novel model can significantly reduce inpatient hospital days and optimize patient care in the emergency department.