[Current concepts on syncope of uncertain etiology].

The starting point for evaluation of syncope is the "Initial evaluation" that consists of history, physical examination including orthostatic blood pressure measurements and standard electrocardiogram. Differentiating true syncope from other 'non-syncopal' conditions associated with real or apparent transient loss of consciousness is generally the first diagnostic challenge and influences the subsequent diagnostic strategy. The initial evaluation may lead to certain diagnosis or suspected that need to be confirmed by appropriate diagnostic tests or no diagnosis (here termed as unexplained syncope). The strategy of evaluation varies according to the severity and frequency of the episodes and the presence or absence of heart disease. The absence of suspected or certain heart disease excludes a cardiac cause of syncope with the exception of syncope accompanied by palpitations which could be due to paroxysmal tachycardia. Conversely, the presence of heart disease at the initial evaluation is a strong predictor of cardiac cause of syncope and virtually includes all cardiac syncopes, but its specificity is low as about half of patients with heart disease has a non-cardiac cause of syncope. The Implantable Loop Recorder is indicated in some cases in which diagnosis remains unexplained despite a complete work-up.