International Study on Syncope of Uncertain Etiology

Inclusion Criteria: * Suspected or certain neurally-mediated syncope, based on the Guidelines of the ESC TF on Syncope. * 3 syncope episodes in the last 2 years. * Severe clinical presentation of syncope requiring treatment initiation in the judgement of the investigator. * Age \>30 years. * Patients have undergone carotid sinus massage, and ILR implantation. Exclusion Criteria: * ILR not implanted for any reason; in this case, the patients are still followed in the ILR-not implanted group. * Carotid sinus syndrome. * Suspected or certain cardiac syncope. * Symptomatic orthostatic hypotension diagnosed by standing blood pressure measurement. * Loss of consciousness different from syncope (e.g. epilepsy, psychiatric, metabolic, drop-attack, TIA, intoxication, cataplexy). * Steal syndrome. * Psychologically or physically (due to any other illness) unfit for participation in the study according to the opinion of the investigator. * Patient compliance doubtful. * Patients who are geographically or otherwise inaccessible for follow-up. * Patient unwilling or unable to give informed consent; * Pregnancy. * Life expectancy \< 1 year due to non-cardiac cause