Background
Cardiac pacing is the treatment of choice for cardioinhibitory carotid sinus syndrome (CSS), but syncope recurrence occurs in up to 20% of patients within 3 years. The present study aims at assessing incidence and identifying predictors of syncope recurrence in patients receiving pacing therapy for CSS.

Methods
The Syncope Clinics of two large regional hospitals in Northern Italy, both following European Syncope Guidelines, combined to perform this study. Retrospective analysis of 3127 consecutive patients undergoing carotid sinus massage (CSM) was performed 2004–2014. Ten-second supine and standing CSM was systematically assessed in patients aged >40 years with suspected reflex syncope as part of the initial evaluation. Syncope recurrence was investigated in those paced for CSS having >6 months' available follow-up. Data were collected from clinical records and patient interviews.

Results
CSS was diagnosed in 261 patients (8.3%). Pacemakers were implanted in 158, with follow-up data available in 112: 19 (17%) experienced 73 syncope recurrences during a mean follow-up of 89 ± 42 months, yielding an incidence of 0.5 episodes per patient/year. Prodrome, predisposing situations preceding syncope and chronic nitrate therapy were more frequent in patients reporting recurrence. Prodrome and predisposing situations remained independent predictors of post-implantation recurrence on multivariable analysis.

Conclusions
CSS is a frequent cause of syncope, if CSM is performed during the initial evaluation. Most patients treated by pacing remain asymptomatic during long-term follow-up. In those who have recurrence, its incidence is very low. Prodrome and predisposing situations are predictors of post-implantation recurrence, suggesting presence of hypotensive susceptibility.