Medically unexplained syncope and its relationship to psychiatric disorders.

Currently, a series of diagnostic tests are available for investigating syncopal episodes. However, in approximately 30% of patients with syncope, the extensive investigations fail to reveal a definite etiology. Recent evidence suggests that a significant portion of these patients may suffer from psychiatric illnesses that lead to recurrent syncope. In the present review, the authors discuss the relationship between medically undetermined syncope and psychiatric illnesses, such as major depression, panic, anxiety and somatization disorders. The patients most likely to develop syncope as a result of psychiatric illnesses are primarily women under the age of 40 years, with multiple previous syncopal episodes and marked presyncopal symptomatology. Although psychiatric syncope should be considered an exclusion diagnosis, it should be remembered, as the referral to a specialist for the institution of a therapy targeting the baseline disease leads to a better prognosis and decreases the occurrence of syncopal episodes. Syncope is defined as a sudden and transient loss of both consciousness and postural tone, with subsequent complete and spontaneous recovery, which does not require cardiopulmonary resuscitation . It is the clinical result of the critical and transient decrease of blood flow to the neurons responsible for maintaining consciousness . Syncope is a frequent condition, accounting for 1% to 6% of all hospital admissions and for 3% of the visits to the emergency department in the United States . In the Framingham Study , which evaluated a cohort study of more than 5,000 patients during 26 years of follow-up, Savage et al suggest that approximately 3% of the population will experience a syncopal episode during their lives. The incidence of this condition can be even higher, approaching 37%, if young patients are evaluated. The prevalence of syncope increases with age, ranging from 0.7% in individuals between 35 and 44 years of age to 5.6% in individuals ≥ 5 years of age. In this same age group, the annual incidence is 6%, with a recurrence rate of 30% . Neurocardiogenic syncope, triggered by the stimulation of intramyocardial receptors, has been recognized as the most frequent, accounting for 50% of the diagnoses . The situational syncopes (postmicturition, cough, swallowing or defecation), as well as the carotid sinus syncope, are also neurally mediated. Other possible causes include heart diseases (obstruction and arrhythmias), neurologic diseases (stroke, seizures) and those related to drug use or metabolic disorders (use of vasodilators and hypoglycemia). Thus, the causes of syncope range from benign conditions to potentially fatal diseases. However, in spite of the use of multiple diagnostic tests, in approximately 30% of the patients, a defined etiology for the syncopal episodes is still lacking . Psychiatric illnesses have been underestimated as possible causes of syncope. Actually, results of 3 cohort studies published in the early 80s (fig. 1) show psychiatric diseases accounting for 1% to 7% of all causes of syncope . However, recent evidence suggests that the prevalence of psychiatric disorders in patients with medically undetermined syncope (MUS) can be as high as 26% . In addition, recurrent syncopes resulted in a psychosocial impact similar to that observed in other chronic debilitating diseases . Thus, this review aims to underscore the relationship between syncope and psychiatric illnesses, to describe the patients most likely to develop syncope and to establish the psychosocial and prognostic impact and the specific management of this disease.