Atrial fibrillation burden in clinical practice, research, and technology development: a clinical consensus statement of the European Society of Cardiology Council on Stroke and the European Heart Rhythm Association.

Atrial fibrillation (AF) is one of the most common cardiac diseases and a complicating comorbidity for multiple associated diseases. Many clinical decisions regarding AF are currently based on the binary recognition of AF being present or absent with the categorical appraisal of AF as continued or intermittent. Assessment of AF in clinical trials is largely limited to the time to (first) detection of an AF episode. Substantial evidence shows, however, that the quantitative characteristic of intermittent AF has a relevant impact on symptoms, onset, and progression of AF and AF-related outcomes, including mortality. Atrial fibrillation burden is increasingly recognized as a suitable quantitative measure of intermittent AF that provides an estimate of risk attributable to AF, the efficacy of antiarrhythmic treatment, and the need for oral anticoagulation. However, the diversity of assessment methods and the lack of a consistent definition of AF burden prevent a wider clinical applicability and validation of actionable thresholds of AF burden. To facilitate progress in this field, the AF burden Consensus Group, an international and multidisciplinary collaboration, proposes a unified definition of AF burden. Based on current evidence and using a modified Delphi technique, consensus statements were attained on the four main areas describing AF burden: Defining the characteristics of AF burden, the recording principles, the clinical relevance in major clinical conditions, and implementation as an outcome in the clinic and in clinical trials. According to this consensus, AF burden is defined as the proportion of time spent in AF expressed as a percentage of the recording time, undertaken during a specified monitoring duration. A pivotal requirement for validity and comparability of AF burden assessment is a continuous or near-continuous duration of monitoring that needs to be reported together with the AF burden assessment. This proposed unified definition of AF burden applies independent of comorbidities and outcomes. However, the disease-specific actionable thresholds of AF burden need to be defined according to the targeted clinical outcomes in specific populations. The duration of the longest episode of uninterrupted AF expressed as a time duration should also be reported when appropriate. A unified definition of AF burden will allow for comparability of clinical study data to expand evidence and to establish actionable thresholds of AF burden in various clinical conditions. This proposed definition of AF burden will support risk evaluation and clinical treatment decisions in AF-related disease. It will further promote the development of clinical trials studying the clinical relevance of intermittent AF. A unified approach on AF burden will finally inform the technology development of heart rhythm monitoring towards validated technology to meet clinical needs.