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 (SpO₂) in patients with cardiac diseases is still unclear. Therefore, this study aimed to investigate the accuracy of the Apple Watch in measuring HR and SpO₂ 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 SpO₂ at rest (ICC = 0.100) and after exercise (ICC = 0.92). However, the validity of the Apple Watch for measuring SpO₂ 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 SpO₂ at rest and after exercise, and for measuring HR during mild- to moderate-intensity training in cardiac patients.