Pacing for neurally mediated syncope: Is placebo powerless?

Abstract

Background: After two recent controlled trials failed to prove superiority of cardiac pacing over placebo in patients affected by neurally mediated syncope, a widely accepted opinion is that cardiac pacing therapy is not very effective and that a strong placebo effect exists. Aim To measure the effect of placebo pacing therapy. Method and results: We compared the recurrence rate of syncope during placebo vs. no treatment in controlled trials of drug or pacing therapy. Syncope recurred in 38% of 252 patients randomized to placebo pooled from five trials vs. 34% of 881 patients randomized to no treatment pooled from eight trials. The corresponding recurrence rate with active cardiac pacing was 15% in 203 patients from six trials. Conclusions: Placebo is not an effective therapy for neurally mediated syncope. Different selection criteria in patients who are candidates for cardiac pacing - for example, presence, absence, or severity of the cardioinhibitory reflex may separate positive from negative trials. © 2007 Oxford University Press.