Clinical Predictors of Pacing Device Implantation in Implantable Cardiac Monitor Recipients for Unexplained Syncope

Background: Implantable cardiac monitors (ICMs) help investigate the cause of unexplained syncope, but the probability and predictors of needing a pacing device thereafter remain unclear. Methods: We retrospectively analyzed the data of patients who received ICM insertion for unexplained syncope with suspected arrhythmic etiology. The data were obtained from a nationwide database obtained between April 1, 2012 and March 31, 2020. Multivariable mixed-effects survival analysis was performed to identify predictors of pacing device implantation (PDI), and a risk score model was developed accordingly. Results: In total, 2905 patients (age: 72 years [range: 60-78]) implanted with ICMs to investigate the cause of syncope were analyzed. During the median follow-up period of 128 days (range: 68–209) days, 473 patients (16%) underwent PDI. Older age, history of atrial fibrillation, bundle branch block (BBB), and diabetes were independent predictors of PDI in multivariable analysis. A risk score model was developed with scores ranging from 0 to 32 points. When patients with the lowest quartile score (0–13 points) were used as a reference, those with higher quartiles had a higher risk of PDI (second quartile: 14–15 points, hazard ratio [HR]: 3.86, 95% confidence interval [CI]: 2.62–5.68; third quartile: 16–18 points, HR: 4.67, 95% CI: 3.14–6.94; fourth quartile: 19–32 points, HR: 6.59, 95% CI: 4.47–9.71). Conclusions: The 4 identified predictors are easily assessed during the initial evaluation of patients with syncope. They may help identify patients with a higher risk of requiring permanent PDI.