Nine RCTs (430 patients) were included in the review.
Two studies were double-blinded and six reported allocation concealment.
Compared with control treatment, pacemaker therapy was associated with a significant reduction of recurrent vasovagal syncope (OR 0.15, 95% CI: 0.05, 0.42, p=0.0004); there was evidence of statistical heterogeneity (p=0.0009; I2=69.6%). The benefit was found in studies comparing active pacemaker with medical therapy or no therapy (OR 0.09, 95% CI: 0.04, 0.22, p<0.00001), as well as in trials comparing pacemaker algorithms (OR 0.04, 95% CI: 0.01, 0.23, p=0.0004), whereas no advantage was shown in double-blinded trials in which patients received a pacemaker but the control group had inactive pacing. Awareness of permanent pacemaker implantation was associated with a significant lower incidence of recurrent syncope (OR 0.16, 95% CI: 0.06, 0.40, p=0.0001). Therefore, the authors suggested that the primary mechanism of benefit from permanent pacemaker therapy is an expectation response.
In the subgroup of patients with baseline cardioinhibitory response on tilt-table testing, pacemaker therapy reduced the risk of recurrent syncope (OR 0.21, 95% CI: 0.05, 0.88, p=0.03); there was evidence of statistical heterogeneity (p=0.02; I2=61.6%).
Overall, the rate of complications following pacemaker procedures was 7.0% (95% CI: 4.6, 10.6). There was no evidence of statistically significant publication bias using Begg’s rank correlation test or Egger’s test. The authors suggested that the asymmetry on the funnel plot was due to methodological differences between the studies.