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Circulation. 2017;136:e60–e122. DOI: 10.1161/CIR.0000000000000499 August 1, 2017 e67 CLINICAL STATEMENTS AND GUIDELINES

the present guideline when applicable or when appropriate. Table 2 also contains a list of other statements that may be of interest to the reader.

2 GENERAL PRINCIPLES

2.1 Definitions: Terms and Classification

For the purpose of this guideline, definitions of syncope and relevant terms are provided in Table 3.

2.2 Epidemiology and Demographics

Syncope has many causes and clinical presentations; the incidence depends on the population being evaluated. Estimates of isolated or recurrent syncope may be inaccurate and underestimated because epidemiological data have not been collected in a consistent fashion or because a consistent definition has not been used. Interpretation of the symptoms varies among the patients, observers, and healthcare providers. The evaluation is further obscured by inaccuracy of data collection and by improper diagnosis. Studies of syncope report prevalence rates as high as 41%, with recurrent syncope occurring in 13.5%.43 In a cross section of 1925 randomly selected residents of Olmsted County, Minnesota, with a median age of 62 years (all age >45 years), 364 reported an episode of syncope in their lifetime; the estimated prevalence of syncope was 19%. Females reported a higher prevalence of syncope (22% versus 15%, P<0.001).44 The incidence follows a trimodal distribution in both sexes, with the first episode common around 20, 60, or 80 years of age and the third peak occurring 5 to 7 years earlier in males.45 Predictors of recurrent syncope in older adults are aortic stenosis, impaired renal function, atrioventricular (AV) or left bundlebranch block, male sex, chronic obstructive pulmonary disorder, heart failure (HF), atrial fibrillation (AF), advancing age, and orthostatic medications,45 with a sharp increase in incidence after 70 years of age.35 Reflex syncope was most common (21%), followed by cardiac syncope (9%) and orthostatic hypotension (OH) (9%), with the cause of syncope unknown in 37%.35 In patients with New York Heart Association class III–IV HF, syncope is present in 12% to 14% of patients.46,47 In older adults, there is a greater risk of hospitalization and death related to syncope. The National Hospital Ambulatory Medical Care Survey reported 6.7 million episodes of syncope in the emergency department (ED), or 0.77% of all ED patients. Among patients >80 years of age, 58% were admitted to hospital.48 The prevalence of syncope as a presenting symptom to the ED ranged from 0.8% to 2.4% in multiple studies in both academic and community settings.49–55

Older institutionalized patients have a 7% annual incidence of syncope, a 23% overall prevalence, and a 30% 2-year recurrence rate.56 The incidence of syncope in older adults may overlap with falls, so it may be difficult to distinguish one from the other. Older adults are predisposed to falls when syncope occurs, with a 1-year fall rate of 38% among fainters versus 18.3% among nonfainters.57

2.3 Initial Evaluation of Patients With

Syncope: Recommendations

The time interval between the index syncopal event and the initial evaluation can vary significantly according to the medical necessity for evaluation and the patient’s effort in seeking evaluation. The clinical setting in which the initial evaluation takes place also varies. The patient could seek evaluation in an outpatient setting with a generalist or a specialist or in the ED at a hospital. The recommendations in the present section are intended for consideration under the general principles of what constitutes GDMT during initial evaluation, regardless of the clinical setting. These general principles for the initial evaluation are shown in Figure 1. Additional evaluation is discussed in subsequent sections according to the outcomes of initial evaluation or in the presence of specific disease conditions.

Figure 1. Syncope Initial Evaluation. *See relevant terms and definitions in Table 3. Colors correspond to Class of Recommendation in Table 1. This figure shows the general principles for initial evaluation of all patients after an episode of syncope. ECG indicates electrocardiogram.

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