Components of clinical trials for vasovagal syncope

The time is ripe for adequately powered, randomized, placebo-controlled cli nical trials in vasovagal syncope. Vasovagal syncope is a common syndrome, the symptoms of which can be troublesomely frequent. Ii is usually diagnose d by tilt-table testing, although this has persistent problems with both se nsitivity and specificity. patients with syncope and positive tilt tests ha ve been the subjects of numerous studies of natural history, risk stratific ation, and treatment. This payer discusses studies of treatments for vasova gal syncope in the context of a classification of the levels of evidence th at can be gleaned from clinical studies. The reasons for placebo-controlled trials al e reviewed, as is the evidence for various methods of risk strat ification. Data for power calculations are presented for the primary outcom e, the time to the first syncope recurrence. Strengths and weakness of the four main types of outcomes for clinical trials are compared. (C) 2001 The European Society of Cardiology.