Photoplethysmography for Heart Rate and Rhythm Monitoring

Photoplethysmography (PPG) is a noninvasive optical technique for assessing cardiovascular physiology that has evolved into a widely used tool embedded in modern consumer wearables. By detecting changes in blood volume through light absorption, PPG provides both heart rate and rhythm information, as well as insights into broader physiological states. While electrocardiography (ECG) remains the gold standard for arrhythmia diagnosis, PPG offers a scalable and accessible alternative for continuous monitoring. Technically, PPG signals consist of a pulsatile component reflecting arterial blood flow and a baseline component from static tissues. These signals correlate closely with ECG-derived heart rate and can be used to derive additional metrics such as heart rate variability and vascular indices. Numerous studies have demonstrated the high accuracy of PPG for heart rate measurement, though performance can be affected by motion artifacts, skin tone, and reduced signal amplitude at high heart rates. PPG has shown strong performance in detecting atrial fibrillation, with high sensitivity and specificity in both algorithm-based and physician-interpreted analyses. However, ECG confirmation remains necessary for diagnosis given variability in study quality and limitations in distinguishing other arrhythmias. Clinically, PPG is valuable for atrial fibrillation screening, symptom-rhythm correlation, and remote monitoring, particularly in hybrid systems combining PPG with ECG. Future developments include expanded arrhythmia detection, machine learning integration, and contactless monitoring technologies. Despite its promise, widespread clinical adoption is currently limited by the lack of standardized technical frameworks and validation protocols. Overall, PPG represents a powerful adjunct to ECG, with significant potential to enhance patient-centered cardiovascular care.