Evolving Indications for Permanent Pacing in Patients with Vasovagal Syncope

Abstract

Patients with frequent vasovagal syncope are often resistant to medical therapy. Consensus statements from the United States and Great Britain [1,2] recommend dual chamber pacing for vasovagal syncope if patients have a positive tilt test ending in a relative bradycardia, and if pacing during a second tilt test prevents syncope. These recommendations were not tested until recently. There were concerns about how to select patients, that syncope detection algorithms are unproven, and that pacing might be unable to prevent symptoms due to vasodepression. Three recent nonrandomized studies [3–5] used pacemakers which sense initial drops in heart rate in order to activate early in the syncopal spell, and then pace at a relatively high rate. This acutely delivered relative tachycardia might provide for suf~cient cardiac output to overcome the effects of the vasodepression. One study used rate hysteresis and two used rate drop sensing. None of the studies required evidence that acute pacing during tilt testing prevented syncope. These studies showed a fairly uniform 75–90% reduction in the frequency of syncope. Given these promising results, we designed and are conducting the North American Vasovagal Pacemaker Study [6], a randomized clinical trial, to evaluate the effectiveness of dual chamber pacing with rate-drop sensing in patients at high risk of a recurrence of syncope.