Randomized clinical trials of neurally mediated syncope

Therapy for Neurally Mediated Syncope. Evidence for therapy of neurally mediated syncope is generally weak. Many drugs have been used for the treatment of vasovagal syncope (beta-blockers, disopyramide, scopolamine, clonidine, theophylline, fludrocortisone, ephedrine, dihydroergotamine, etilefrine, midodrine, clonidine, serotonin reuptake inhibitors, enalapril). In general, although the results have been satisfactory in uncontrolled trials or short-term controlled trials, the majority of long-term placebo-controlled prospective trials have not been able to show a benefit of the active drug over placebo. Only two well-designed double-blind placebo-controlled randomized trials have been performed-one for etilefrine and the other for atenolol-and both were unable to show a superiority of the active drug versus placebo. Four randomized clinical trials of pacing therapy-three positive and one negative-have been performed in patients affected by vasovagal syncope. The relationship between carotid sinus hypersensitivity and spontaneous, otherwise unexplained, syncope has been demonstrated. Cardiac pacing appears to be beneficial in carotid sinus syndrome; its efficacy has been demonstrated by two randomized controlled trials and confirmed by several pre-post comparative studies, one controlled trial, and one prospective observational study. There is evidence and general agreement that cardiac pacing is useful in patients with cardioinhibitory or mixed carotid sinus syndrome. Usefulness of the treatment is less well established and divergence of opinion exists with regard to cardiac pacing in patients with cardioinhibitory vasovagal syncope. The evidence fails to support the efficacy of beta-blocking drugs. As yet there are insufficient data to support the use of any other pharmacologic therapy for vasovagal syncope.