All patients consecutively referred with the first episode of transient and short-lasting loss of consciousness will have a diagnostic workup for the assessment of the most common causes of syncope, and will be evaluated for the presence of pulmonary embolism (PE) with the use of an internationally accepted algorithm including a pre-test clinical probability (PTP according to the method of Wells et al.) and a high-sensitivity quantitative D-dimer assay. If the PTP is low and D-dimer negative, PE will be excluded. All other patients will undergo confirmatory diagnostic tests (either computerized tomography or ventilation/perfusion lung scanning) in order to confirm or rule out the presence of PE.

Inclusion Criteria:

• first episode of syncope

Exclusion Criteria:

• previous episodes of syncope
• ongoing anticoagulation
• age younger than 18 years
• pregnancy