Vasovagal syncope

Background: Vasovagal syncope is the most common type of syncope and is one of the most difficult types to manage. Purpose: This article reviews the status of mechanisms, diagnosis, and mana gement of vasovagal syncope. Data Sources: MEDLINE search for English-language and German-language artic les on vasovagal syncope published up to June 1999. Study Selection: case reports and series, clinical trials, research investi gations, and review articles from peer-reviewed journals. Data Extraction: Findings were summarized and discussed individually. Summa ries were made in table format. Statistical analysis of combined data was i nappropriate because of differences among studies in patient selection, tes ting, and follow-up. Data Synthesis: The population of patients with vasovagal syncope is highly heterogeneous. Triggers of vasovagal syncope are likely to be protean, and many potential central and peripheral triggers have been identified. The s pecific mechanisms underlying the interactions among decreased preload, sym pathetic and parasympathetic modulation, vasodilation, and cardioinhibition remain unknown. Tilt-table testing is a widely used diagnostic tool. The t est results should be interpreted in the context of patients' clinical pres entations and with an understanding of the sensitivity and specificity of t he test. Assessment of therapeutic outcomes has been difficult, primarily b ecause of patient heterogeneity, the large number of pharmacologic agents a vailable for therapy, and the sporadic nature of the syndrome complex. Conclusions: Vasovagal syncope is a common clinical syndrome that has compl ex and variable mechanisms and is difficult to manage. Advancements are bei ng made in laboratory investigations of its triggering mechanisms. Randomiz ed, controlled trials of pharmacologic and nonpharmacologic interventions a re needed. Mechanism-targeted therapeutic trials may improve clinical outco mes.