Atrial fibrillation (AFib) is a prevalent cardiac arrhythmia associated with significant morbidity and mortality. Continuous monitoring for AFib is essential for early detection and management to prevent complications such as stroke and heart failure. The Apple Watch offers an irregular rhythm notification (IRN) feature, utilizing photoplethysmography, to identify prolonged episodes of irregular rhythm suggestive of AFib. The watch also has an AFib history feature, where the wearer is able to track their heart events; this gives the patient an estimate of the frequency and duration of their irregular heartbeats.
The United States Food and Drug Administration recently approved the Apple Watch as the first digital health technology under the Medical Device Development Tools program to check estimates of AFib in the context of clinical studies. This is groundbreaking, as Apple is the first company to have an FDA-approved medical health technology tool, and the Apple Watch is a pioneer in its realm.
In this study published in the Journal of Cardiovascular Electrophysiology, participants with a history of nonpermanent AFib and either an insertable cardiac monitor (ICM) or cardiac implanted electronic device (CIED) were enrolled and fitted with an Apple Watch Series 5 for six months. AFib episodes detected by ICM/CIED were compared to those detected by IRN. Primary endpoints included sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of IRN by subject for AFib episodes lasting ≥1 h.
The study revealed a low false positive rate and high specificity of IRN for detecting AFib in patients with known AFib. However, sensitivity, particularly for shorter AFib episodes, was modest. These findings suggest that while IRN may be effective for AFib screening in individuals without prior AF, its utility for disease management in those with known AFib may be limited by lower sensitivity. Moreover, the study highlighted the importance of continuous wear and improved algorithm sensitivity to enhance IRN's effectiveness in detecting AFib, especially for shorter episodes.
The Apple Watch IRN demonstrated high specificity but modest sensitivity for detecting AFib in patients with known AFib. While it may serve as a useful screening tool, its accuracy for disease management in this population requires further improvement. Future advancements focusing on continuous wear and enhanced algorithm sensitivity may enhance IRN's effectiveness in detecting AFib and facilitating timely intervention to prevent adverse outcomes.
Sources: Center for Disease Control, Journal of Cardiovascular Electrophysiology, United States Food and Drug Administration