Masimo W1

The Masimo W1 is a wearable smartwatch that records single-channel ECG rhythms and displays them on the device. It detects atrial fibrillation and sinus rhythm, provides heart rate and pulse oximetry measurements, and wirelessly transmits data to a compatible smartphone app. It is intended for healthcare professionals, patients with known or suspected heart conditions, and health-conscious individuals in hospitals, clinics, long-term care facilities, and homes.

The subject device adds an Atrial Fibrillation (AFib) Classification Feature that analyzes single-channel ECG waveforms to detect irregular heartbeat patterns characteristic of AFib. The AFib detection software relies on the principle that AFib rhythms are defined as 'irregularly irregular' heartbeat patterns. All other technological characteristics—ECG signal detection, pulse oximetry using Masimo SET technology, and hardware components—remain unchanged from the predicate device K240229.

The device complies with IEC 60601-1 for electrical safety, IEC 60601-1-2 for electromagnetic compatibility, and is classified as an internally powered CF Applied Part with IP24 ingress protection per IEC standards. Software verification and validation testing followed FDA Guidance 'Content of Premarket Submissions for Software Device Software Functions' (June 2023), and the device was categorized as requiring Basic Documentation Level.

The subject device is substantially equivalent to predicates K240229 (Masimo W1), K201456 (Withing Scan Monitor), and K201168 (Samsung ECG Monitor) because it uses identical principles of operation for ECG detection and pulse oximetry, maintains the same single-channel Lead I-equivalent waveform, and shares intended use (recording, storing, and displaying ECG for informational purposes in adults 22+). The only functional addition—AFib classification—is substantially equivalent because secondary and tertiary predicates already perform AFib detection; clinical testing demonstrates the subject device achieves 99.3% sensitivity and 100% specificity for AFib detection, which is comparable to or exceeds the tertiary predicate's 98.1% sensitivity. ECG waveform quality shows 98% qualitative agreement with gold-standard 12-lead ECG and similar QRS morphology, supporting equivalence.