The role of implantable loop recorder in patients with cryptogenic stroke: A systematic review and meta-analysis

Objective: The objective of this study was to provide data on implantable loop recorder (ILR)-based atrial fibrillation (AF) rates, recurrent stroke rates, and predictors of AF in patients with cryptogenic stroke (CS) after 1, 6, 12, 24, and 36 months of follow-up. Methods: We searched MEDLINE/PubMed, Cochrane Central Register of Controlled Trials, EMBASE, Web of Science, and reference lists of retrieved reports, which were published by April 30, 2023, which was the date of our last search. We utilized random-effects meta-analysis for detection rates, and meta-regression analysis, t-test (for normally distributed variables), and Mann-Whitney (for skewed variables) for predictor factors. Results: Thirteen studies were analyzed, which included data from 3,377 patients with CS or embolic stroke of undetermined source. The ILR-based AF rates in patients with CS were 4.73% (95% confidence interval [CI] 3.91–5.71) at 1 month, 13.45% (95% CI 12.19–14.81) at 6 months, 17.5% (95% CI 16.25–18.82) at 12 months, 20.69% (95% CI 19–22.49) at 24 months, and 25.98% (95% CI 23.21–28.58) at 36 months. Age and CHA2DS2-VASc score were positively associated with AF detection. Specifically, the mean difference of age and CHA2DS2-VASc score in the group with AF versus the group without AF was 7.47 (95% CI 4.58–10.36, P < 0.001) and 0.75 (95% CI 0.22–1.28, P = 0.01), respectively. Finally, AF detection was positively associated with recurrent strokes with an estimated risk ratio of 1.27 (95% CI 0.69–2.31). Conclusions: There is a correlation between AF detection rate and ILR monitoring duration. One out of eight patients was diagnosed with AF after 6 months of follow-up and about one quarter after 3 years. Our results demonstrate the critical use of ILRs, especially in older patients, and in patients with high CHA2DS2-VASc scores.