A systematic review on recurrent cardioinhibitory vasovagal syncope: Does pacing therapy break the fall?

Vasovagal reflex is the most common cause of syncope. Pacemaker with rate drop response (RDR) or closed-loop stimulation (CLS) anti-syncope algorithms have been studied in recurrent vasovagal syncope (VVS), with conflicting results. We aim to investigate the role of pacemaker therapy and anti-syncope pacing mode in cardioinhibitory recurrent VVS. MEDLINE, Cochrane Library and registered clinical trials were searched for single or double-blind randomized controlled trials on pacing as a treatment for recurrent VVS. Five studies were eligible, overall enrolling 228 patients. After pooling data from all trials, pacemaker therapy showed a 63% reduction in syncope recurrence compared to control [Risk Ratio (RR): 0.37; 95% CI: 0.14-0.98; I2  = 67%)]. Subgroup analyses suggested that the effect was greater in single-blind studies (RR: 0.07; 95% CI: 0.01-0.52, I2  = 0%). When comparing pacing algorithms, the results from RDR versus no pacing trials (n = 2) did not show a significant reduction in syncope recurrence (RR: 0.73; 95% CI: 0.25-2.16, I2 60 = 75%). In contrast, the data from the CLS versus standard pacing trials (n = 3) evidenced a statistically meaningful reduction in syncopal burden (RR: 0.18; 95% CI: 0.07-0.47, I2  = 0%). It is unclear whether pacemaker therapy reduces syncopal burden in cardioinhibitory recurrent VVS. However, our results suggest effectiveness of CLS pacing mode.