Reliability of single-lead electrocardiogram interpretation to detect atrial fibrillation: insights from the SAFER Feasibility Study

Abstract Background and Aims Single-lead electrocardiograms (ECGs) can be recorded using widely available devices such as smartwatches and handheld ECG recorders. Such devices have been approved for atrial fibrillation (AF) detection. However, little evidence exists on the reliability of single-lead ECG interpretation. We aimed to assess the level of agreement on detection of AF by independent cardiologists interpreting single lead ECGs, and to identify factors influencing agreement. Methods In a population-based AF screening study, adults aged ≥65 years old recorded four single-lead ECGs per day for 1-4 weeks using a handheld ECG recorder. ECGs showing signs of possible AF were identified by a nurse, aided by an automated algorithm. These were reviewed by two independent cardiologists who assigned participant- and ECG-level diagnoses. Inter-rater reliability of AF diagnosis was calculated using linear weighted Cohen’s kappa ( κ w ). Results Out of 2,141 participants and 162,515 ECGs, only 1,843 ECGs from 185 participants were reviewed by both cardiologists. Agreement was moderate: κ w = 0.42 (95% CI, 0.32 – 0.52) at participant-level; and κ w = 0.51 (0.46 – 0.56) at ECG-level. At participant-level, agreement was associated with the number of adequate-quality ECGs recorded, with higher agreement in participants who recorded at least 67 adequate-quality ECGs. At ECG-level, agreement was associated with ECG quality and whether ECGs exhibited algorithm-identified possible AF. Conclusion Inter-rater reliability of AF diagnosis from single-lead ECGs was found to be moderate in older adults. Strategies to improve reliability might include participant and cardiologist training and designing AF detection programmes to obtain sufficient ECGs for reliable diagnoses. What’s New We observed moderate agreement between cardiologists when diagnosing AF from single-lead ECGs in an AF screening study. This study indicates that for every 100 screening participants diagnosed with AF by two cardiologists, there would be complete disagreement over the diagnosis of 70 further participants. We found that the quality of ECG signals greatly influenced the reliability of single-lead ECG interpretation. In addition, when multiple ECGs were acquired from an individual, the reliability of participant-level diagnoses was influenced by the number of adequate-quality ECGs available for interpretation.