Accuracy of Apple Watch to Measure Cardiovascular Indices in Patients with Cardiac Diseases: Observational Study.

The validity of Apple Watch for measuring heart rate (HR) and oxygen saturation (SpO) in patients with cardiac diseases is still unclear. Therefore, this study aimed to investigate the accuracy of the Apple Watch in measuring HR and SpO in patients with cardiac diseases. A cross-sectional study recruited 260 cardiac patients, including 190 with regular heart rhythm and 70 with cardiac arrhythmia. Each patient wore the Apple Watch alongside a Polar HR monitor at rest, during and after mild- to moderate-intensity exercise sessions, and wore the Apple Watch alongside a Contec pulse oximeter at rest and after exercise. The Apple Watch showed excellent validity (ICC = 0.100) in measuring the HR at rest, during mild- to moderate-intensity exercise, and after exercise in cardiac patients, as well as in measuring SpO at rest (ICC = 0.100) and after exercise (ICC = 0.92). However, the validity of the Apple Watch for measuring SpO decreased slightly after exercise (ICC = 0.85; good validity), especially in patients with an irregular heart rhythm. Overall, the Apple Watch appears valid for measuring HR and SpO at rest and after exercise, and for measuring HR during mild- to moderate-intensity training in cardiac patients.