Real-time Smartphone Alerts During Atrial Fibrillation Episodes with Implantable Cardiac Monitors and Wearable Devices: SMART-ALERT study.

BACKGROUND: Atrial fibrillation (AF) is a major cause of stroke, with dynamic thromboembolic risk during and shortly after episodes. Implantable cardiac monitors (ICMs) and wearable devices have emerged as tools for real-time AF detection, yet their comparative performance in supporting anticoagulation strategies remains underexplored. OBJECTIVES: This single-centre feasibility study investigated the performance of real-time AF detection and notification for episodes >30 minutes. METHODS: Phase 1 evaluated the integration of ICM and bespoke cloud-based software (SMART-ALERT) in sending automated SMS notifications (n=50) for episodes uploaded within 24 hours. Phase 2 evaluated an Apple Watch (n=23) and CART Ring (n=23) detecting and notifying participants of AF episodes. Primary outcome was the successful AF notification rates via (i) SMART-ALERT software and (ii) wearable devices. Secondary outcomes included acknowledgement rates, notification times, and adherence. RESULT: Among 4,943 AF episodes detected in 31 participants, the SMART-ALERT software successfully notified 511/691 eligible AF episodes (74%), with a 99.6% acknowledgment. In contrast, wearable devices showed poor notification performance: Apple Watch identified 76/389 episodes (19.5%) and the CART Ring 72/474 (15.1%). This performance difference was partly explained by suboptimal device adherence (Apple Watch: 66.3%; CART Ring: 23.9%), with 24.6% and 55.7% of AF episodes missed due to devices not being worn. CONCLUSION: The SMART-ALERT system demonstrated the feasibility of real-time AF detection and automated notifications, achieving a 74% notification success but facing important connectivity challenges. Wearable devices showed poor notification rates (<20%) and adherence, highlighting significant technical barriers for their current use in clinical AF monitoring.