The benefit of pacemaker therapy in patients with neurally mediated syncope and documented asystole: a meta-analysis of implantable loop recorder studies

Abstract

Although the efficacy of cardiac pacing in patients with neurally mediated syncope (NMS) and documented asystole is established, a more robust point estimate of the benefit, which is not possible with any individual study, is lacking. We undertook a meta-analysis of individual participant data from four studies that reported follow-up data on syncope recurrence with cardiac pacing in patients with NMS who had had an electrocardiographic (ECG) documentation of an asystolic event by means of implantable loop recorder (ILR). Of a total of 1046 patients, who had ILR implanted, 383 (36.6%) patients had an ECG documentation of a diagnostic event during mean follow-up of 13 ± 10 months. Of these, 201 (52%) patients, corresponding to 19.2% of the total ILRs, had an asystolic event of 12.8 ± 11.0 s duration documented and met the criteria for pacemaker therapy. Follow-up was available in 121 (60%) of those patients with asystolic events. Syncope recurred after pacing in 18 (14.9%) patients with an actuarial rate of 13% [95% confidence interval (CI) ±6] at 1 year, 21% (95%CI ±10) at 2 years, and 24% (95%CI ±11) at 3 years. On multivariable Cox regression analysis, positive tilt test response was the only significant predictor of syncope recurrence with a hazard ratio (95% CI) of 4.3 (1.4-13). On the contrary, type of asystolic event (sinus arrest or atrioventricular block), prodrome, cardiac abnormalities, number and duration of history of syncope, age, and gender were not predictors of recurrence of syncope. A long asystolic pause, suitable for pacemaker therapy, was found in one of five patients with ILR. After pacemaker implantation, most of these patients remained free of syncope recurrence for up to 3 years. The benefit of pacemaker was greater in patients with negative tilt test.