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In the evaluation of patients with syncope, the critical first step is a detailed medical history. A diagnostic strategy based on initial evaluation is warranted. The importance of the initial evaluation goes well beyond its capability to make a diagnosis as it determines the most appropriate subsequent diagnostic pathways and risk evaluation.
THE DIAGNOSTIC STRATEGY BASED ON THE INITIAL EVALUATION
According to the Guidelines on Syncope of the European Society of Cardiology (ESC)1,2 the “initial evaluation” of a patient presenting with syncope consists of taking a careful history, and a physical examination, including orthostatic blood pressure measurements and standard electrocardiogram (ECG).
Three key questions should be addressed during the initial evaluation:
Is loss of consciousness attributable to syncope or not? Differentiating true syncope from “non-syncopal” conditions associated with real or apparent transient loss of consciousness is generally the first diagnostic challenge and influences the subsequent diagnostic strategy.
Are there features in the history that suggest the diagnosis? Accurate history taking alone is a key stage and often leads to the diagnosis or may suggest the strategy of evaluation.
Is heart disease present or absent? The absence of signs of suspected or overt heart disease virtually excludes a cardiac cause of syncope with the exception of syncope accompanied by palpitations which could be due to paroxysmal tachycardia (especially paroxysmal supraventricular tachycardia). Conversely, the presence of heart disease at the initial evaluation is a strong predictor of a cardiac cause of syncope, but its specificity is low as about half of patients with heart disease have a non-cardiac cause of syncope.3
Table 1 provides the clinical classification of the principal known causes of syncope proposed by the Task Force on Syncope of the ESC.1,2 The subdivision of syncope is based on pathophysiology as follows:
“Neurally-mediated (reflex) syncope” refers to a reflex response …