The Influence of Monitoring Strategy on Assessment of Ablation Success and Post-ablation Atrial Fibrillation Burden Assessment: Implications for Practice and Clinical Trial Design.

Background: Various non-invasive intermittent rhythm monitoring strategies have been used to assess arrhythmia recurrences in trials of atrial fibrillation (AF) ablation. We determined whether a frequency and duration of non-invasive rhythm monitoring could be identified that accurately detects arrhythmia recurrences and approximates the AF burden derived from continuous monitoring using an implantable cardiac monitor (ICM). Methods: The rhythm history of 346 patients enrolled in the CIRCA-DOSE trial was reconstructed. Using computer simulations, we evaluated event-free survival, sensitivity, negative predictive value, and AF burden of a range of non-invasive monitoring strategies, including those used in contemporary AF ablation trials. Results: A total of 126,290 monitoring days were included in the analysis. At 12 months, 164 patients experienced atrial arrhythmia recurrence as documented by the ICM (1-year event-free survival 52.6%). Most non-invasive monitoring strategies used in AF ablation trials had poor sensitivity for detecting arrhythmia recurrence. Sensitivity increased with the intensity of monitoring, with serial (3) short-duration monitors (24-/48-hour ECG monitors) missing a substantial proportion of recurrences (sensitivity 15.8% [95% confidence interval (CI) 8.9-20.7%] and 24.5% [95% CI 16.2-30.6%], respectively). Serial longer-term monitors (14-day ECG monitors) more closely approximated the gold-standard ICM (sensitivity 64.6% [95% CI 53.6-74.3%]). AF burden derived from short-duration monitors significantly over-estimated the true AF burden in patients with recurrences. Increasing monitoring duration resulted in improved correlation and concordance between non-invasive estimates of the invasive AF burden (R2 = 0.85 and interclass correlation coefficient = 0.91 for serial [3] 14-day ECG monitors vs ICM). Conclusions: Detection of arrhythmia recurrence following ablation is highly sensitive to the monitoring strategy employed, between-trial discrepancies in outcomes may reflect different monitoring protocols. Based on measures of agreement, serial long-term (7-14 day) intermittent monitors accumulating at least 28 days of annual monitoring provide estimates of AF burden comparable to ICM. However, ICMs outperform intermittent monitoring for arrhythmia detection, and should be considered the gold standard for clinical trials.