Sky Labs, a health-tech startup based in South Korea, announced that its ring-shaped smart medical device, CART-I (Cardio Tracker), demonstrated higher sensitivity than the Apple Watch in detecting atrial fibrillation (AFib) in a recent clinical study. The study’s findings were published in Heart Rhythm O2, a peer-reviewed international journal.
The comparative study, conducted across three hospitals in the UK (Oxford University Hospital, University Hospital Southampton, and Queen Elizabeth Hospital), involved approximately 500 patients and evaluated CART-I and Apple Watch under the same clinical protocol.

Researchers assessed the sensitivity and specificity of each device’s automatic AFib detection algorithms using single-lead electrocardiograms (SL-ECG) data, which was subsequently interpreted by physicians. Results showed that Sky Labs‘ CART-I achieved 84.6% sensitivity, while Apple Watch recorded 69.1% under the same protocol. Both devices also demonstrated high performance in physician interpretation of SL-ECGs: the Apple Watch scored 95.4% sensitivity, and CART-I recorded 94.3%.
