Permanent Pacemaker Therapy for Neurally Mediated Syncope

Neurally mediated syncope (also known as fainting and vasovagal syncope) is by far the most common cause of transient loss of consciousness. Fainting is almost always benign, and most people who faint have nontraumatic syncope episodes occasionally throughout their lives with minimal adverse consequences. Most episodes of fainting occur in the erect posture and have typical warning symptoms such as light-headedness or nausea that allow the individual to avoid serious injury if he or she loses consciousness. In a small number of people, however, fainting is a serious medical problem; typically, these are patients with episodes that occur with little or no warning or occur very frequently. Recurrent neurally mediated syncope can mean the inability to drive or to work, and syncope episodes can cause serious injury, albeit rarely. In such patients, neurally mediated syncope is a significant medical problem for which there are no easy solutions.Article see p 2566Reflex vasodilation and bradycardia are the 2 main pathophysiological mechanisms underlying neurally mediated syncope, often acting together. Most pharmacological therapies are directed at limiting the vasodilation component; however, there is little evidence that medical therapies (fluid loading, β-blockers, fludrocortisone, or midodrine) are effective; a recent meta-analysis concluded that there are no proven effective pharmacological therapies for the prevention of neurally mediated syncope.1 There is modest evidence that countermaneuvers such as leg crossing can help some patients.2 Because transient bradycardia or asystole is often observed during neurally mediated syncope, cardiac pacing has been evaluated to treat severely symptomatic patients with frequent events. The challenge of pacemaker therapy for this condition, however, is that vasodilatation may still cause fainting, even after bradycardia is prevented by …