Progression to Higher Burden of ICM‐Detected Subclinical Atrial Fibrillation in Cryptogenic Stroke Patients

Background and Aims Prolonged monitoring with implantable cardiac monitors (ICMs) effectively detects subclinical atrial fibrillation (SCAF) in patients with cryptogenic stroke (CS). Understanding SCAF progression to higher burdens can affect decisions regarding oral anticoagulant (OAC) and antiarrhythmic therapies. This analysis aimed to quantify initial SCAF burden, its progression, and predictors of progression in CS patients. Methods This multicenter project collected demographics, stroke characteristics, and SCAF daily burden in CS patients implanted with ICM. SCAF progression was defined as an increase in daily burden from initial detection, categorized as: 5 min to 1 h, 1−6 h, 6−24 h, 24 h for < 7 days, and 24 h for ≥ 7 days. Results Of 593 patients (70.0 ± 11.3 years, 42% female, median CHA 2 DS 2 ‐VASc score 4.7 ± 1.4) monitored over a median of 24.6 months, 32.7% had SCAF detected. While initial SCAF daily burden was < 1 h in 38.7% of SCAF patients, 53.3% progressed to a higher SCAF daily burden, with 30.6% reaching the 24 h burden by 36 months. Higher CHA 2 DS 2 ‐VASc scores and stroke severity were associated with SCAF progression. OAC therapy was initiated in 91.2% patients with a maximum SCAF daily burden < 1 h, while in 98.0% of those with a maximum daily burden ≥ 1 h ( p = 0.042). Conclusions Over half of CS patients with SCAF progressed to a higher burden, and about one‐third reached a 24 h SCAF daily burden. These findings highlight the importance of continuous monitoring in CS patients for early SCAF detection and personalized therapy, considering SCAF burden progression and the patient's risk profile.