Selective Modulation of the Cardiac Autonomic Nervous System

> The enlightened ruler is heedful and the good general full of caution .> > —Sun TzuNeurally mediated syncope (NMS) encompassing a reflex mechanism resulting in bradycardia or vasodilation, is the most common cause of syncope in the general population. Recurrent NMS has an adverse impact on quality of life1 and is associated with increasing healthcare costs.See Article by Rivarola et al Pharmacological or invasive therapies for NMS are only marginally effective as the conditions ripe for the reflex response are only transient and often have unintended side effects or consequences when the reflex response is inactive. Among older patients (age >40 years) with marked cardioinhibitory response, pacing seems to be helpful in reducing recurrent syncope.2 The lack of evidence for pacing in young patients, magnitude of the problem and the impact of NMS on quality of life in a young population, as well as risks associated with initial and subsequent pacemaker surgeries makes this arena a fertile ground for investigation.Several investigators have proposed autonomic modulation to blunt the vasodepressor3 or cardioinhibitory responses4,5 as an alternative solution to management of NMS. Rivarola et al6 present the findings of their single-center study of patients with recurrent syncope and predominantly a cardioinhibitory response on tilt table study or transient sinus arrest or AV block on a Holter recording. The patient population was heterogenous as 4 patients had a positive tilt test, 1 had sinus …