Real-world validation of smartphone-based photoplethysmography for heart rate monitoring in atrial fibrillation

Abstract

Abstract Introduction Photoplethysmography (PPG) based smartphone applications facilitate heart rate monitoring that may enable physicians to guide rate control in patients with atrial fibrillation (AF). Despite extensive validation of PPG-derived heart rate, validation studies in the presence of AF are lacking, particularly in unsupervised free-living conditions. Purpose To evaluate the accuracy of PPG-derived heart rate using a smartphone application in patients with an established diagnosis of AF, both during sinus rhythm and AF, in a real-world setting. Methods Consecutive patients undergoing AF ablation were enrolled four weeks prior to the procedure. They were instructed to assess their heart rate twice daily during eight weeks with a one-minute finger-over-the-camera smartphone-PPG recording. The reference heart rate was obtained from two 30-seconds handheld single-lead electrocardiogram (ECG) recordings performed immediately before and after the PPG recording. Measurements were valid if the heart rate did not change by more than 10% between the first and second ECG and maintained sinus rhythm or AF consistently. Results In total, fifty patients (age 63 ±11 years, 68% male) performed 3407 high-quality PPG measurements accompanied with two high-quality ECGs measurements both in sinus rhythm or AF. After excluding 223 measurements due to inconsistent heart rate between the first and second ECG, 3184 measurements remained. The mean heart rate (71.5 ± 17.3 beats per minute (bpm)) was significantly higher during AF (94.7 ± 19.4 bpm) compared to sinus rhythm (65.7 ± 10.7 bpm) (p-value < 0.001). The heart rate assessment was accurate within a 10% margin in 93.8% of PPG measurements. Inaccurate heart rate assessments were more frequent in AF (161/637; 25.3%) compared to sinus rhythm (35/2547; 1.4%) (p-value < 0.001). PPG underestimated the heart rate in sinus rhythm with 0.4 bpm (95% CI: -0.3 to -0.5 bpm) and in AF with 6.6 bpm (95% CI: -5.8 to -7.4 bpm). The deviation of PPG-derived heart rate from the ECG-derived true heart rate was significantly greater during AF (root mean square error (RMSE) = 11.8 bpm) compared to sinus rhythm (RMSE = 2.2 bpm) (p-value < 0.001). The heart rate correlation plots and corresponding Bland-Altman plots demonstrate a skewed underestimation of the heart rate in AF with PPG, particularly for high heart rates. Conclusions Heart rate can accurately be derived from PPG recordings using a smartphone application in real-world conditions. However, PPG measurements may underestimate high heart rates in the presence of AF.Heart Rate in Sinus RhythmHeart Rate in Atrial Fibrillation