Pacing for syncope: what role? which perspective?
1 Arrhythmologic Centre, Department of Cardiology, Ospedali del Tigullio, 16033 Lavagna, Italy
2 Department of Cardiology, Ospedale Umberto I, Mestre, Italy
3 Department of Cardiology, University Hospital, Brest, France
* Corresponding author. Tel: +39 0185 329 567; fax: +39 0185 306 506. E-mail address: mbrignole{at}asl4.liguria.it
Cardiac pacing is the most effective therapy to prevent syncopal recurrences when syncope is due to bradycardia. Causes of bradycardia-induced syncope are intrinsic [primary dysfunction of the atrioventricular (AV) conduction system and of sinus node function] and extrinsic (vagal reflexes). Intrinsic and extrinsic mechanisms often coexist in the same patient, especially in the case of sick sinus syndrome. Although formal randomized controlled trials have not been performed, cardiac pacing is commonly considered very effective and therefore accepted as therapy of choice in all patients in whom an AV block is responsible for syncope. Cardiac pacing is also commonly indicated in patients in whom syncope is caused by sick sinus syndrome or carotid sinus syndrome. However, owing to the frequently associated vasodepressor reflex, syncope still recurs during long-term observation in 
20% of the patients. Despite several controlled trials, the indications for cardiac pacing are still controversial in patients with vasovagal syncope (VVS). To date, cardiac pacing may be only indicated in selected older patients affected by VVS who present with severe recurrent impredictable syncopal attacks affecting quality of life. Also in these patients some rare syncopal recurrence should be expected over the long term.
Key Words: Atrioventricular block • Bradycardia • Sinus node dysfunction • Carotid sinus syndrome • Neurally mediated syncope • Vasovagal syncope