Atrial fibrillation density: A novel measure of atrial fibrillation temporal aggregation for the characterization of atrial fibrillation recurrence pattern

Aim: The atrial fibrillation (AF) burden presents a step towards a quantitative approach to AF, however, the temporal distribution of AF episodes over time cannot be expressed with the AF burden alone. We present the concept of AF density, a novel measure to evaluate and describe the temporal pattern of AF recurrence. Methods: AF episodes and rhythm histories captured by continuous monitoring devices in a large collective of 647 patients with AF were evaluated and reconstructed. Results: For the calculation of the AF density, the minimum time required to develop each proportion of the patient's total burden is calculated. AF density is defined as the ratio of the cumulative deviation of the patient's actual burden development from the hypothetical uniform burden development to that of the hypothetical maximum possible burden aggregation for that level of burden from the hypothetical uniform burden development. The AF density as the ratio of the above mentioned areas is a dimensionless quantity and assumes values between 0 and 1, with values close to 0 denoting low burden aggregation, whereas values close to 1 denoting maximal burden temporal aggregation. Conclusions: We present a methodology that evaluates the temporal distribution pattern of AF recurrence which may aid, together with the AF burden, to a better classification and description of AF recurrence patterns. The latter may be of interest in the evaluation of the risk of thromboembolism that AF patients face. Larger studies are required to investigate if AF density can influence patient specific outcomes.