Device-Detected Atrial Fibrillation in Patients With and Without Cryptogenic Ischemia: The ANTARCTICA Pooled Analysis

BACKGROUND: Insertable cardiac monitoring (ICM) detects atrial fibrillation (AF) in substantial proportions of cryptogenic stroke, noncryptogenic ischemic stroke without known AF, and nonstroke patients who are at risk of underlying AF. Given differences in patient characteristics across studies, there may be differences in AF detection rates on ICM across these subgroups that have not been identified. We investigate whether AF detection rates on ICM are higher in cryptogenic stroke or transient ischemic attack (C-IS/TIA) patients compared with individuals with noncryptogenic stroke or without stroke, when accounting for differences in study populations. METHODS: This is an individual-participant data meta-analysis of prospective studies and randomized controlled trials of ICM in C-IS/TIA, noncryptogenic ischemic stroke, and nonstroke patients. Multilevel multivariable logistic regression models were used to test whether C-IS/TIA is associated with increased AF detection relative to other categories. We performed multiple imputation to derive values for variables with <20% missing data and used Rubin's rules to estimate adjusted odds ratios by combining 100 postimputation data sets. The primary outcome was detection of AF. The attributable risk was derived by application of Bayes' Theorem. RESULTS: Two randomized controlled trials and 12 prospective studies were included with a total of 1562 C-IS/TIA patients and 474 non-C-IS/TIA patients. In adjusted multilevel logistic regression analyses, AF detection was higher in C-IS/TIA patients (adjusted odds ratio, 1.90 [95% CI, 1.18-3.06]; P=0.009), indicating that 47% of AF detected in C-IS/TIA is pathogenic. Limiting the comparator group to ischemic stroke or history of stroke yielded similar results (adjusted odds ratio, 2.83 [95% CI, 1.47-5.44]; P=0.002). Days to AF detection were significantly shorter in C-IS/TIA patients (median 65 versus 169; P<0.001). CONCLUSIONS: In this individual-participant data meta-analysis of patients undergoing ICM, AF detection was higher in C-IS/TIA patients, with shorter time to AF detection compared with noncryptogenic/nonstroke individuals. These findings suggest that some of the AF detected in patients with C-IS/TIA may be pathogenic.