Epicardial adipose tissue and subclinical incident atrial fibrillation in a population at risk of stroke - a cardiac magnetic resonance imaging study

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Innovation Fund Denmark. Background Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide and is associated with a substantially increased risk of morbidity and mortality, including heart failure and stroke(1,2). Epicardial adipose tissue (EAT) is believed to provide both thermoregulation and mechanical protection to the heart and coronary arteries in healthy human beings(3,4), but the role of EAT in the development and severity of AF suggests deleterious effects of EAT. Since EAT shares blood circulation with the myocardium, it offers the opportunity for paracrine- and neuroendocrine signaling(5), which contributes to an arrhythmogenic- and pro-inflammatory state. Purpose While EAT assessed by cardiac magnetic resonance imaging (CMR) has been found predictive of clinical AF(5,6), the association with subclinical AF has not yet been established. This study aimed to investigate the association between EAT, determined by CMR, and incident AF following long-term continuous heart rhythm monitoring by implantable loop recorder (ILR) in an at-risk population. Methods This study is a sub-study of the LOOP study. In total, 203 participants without a history of AF received an ILR and underwent advanced CMR. All participants were at least 70 years of age at inclusion and had at least one of the following conditions: hypertension, diabetes, previous stroke, or heart failure. Volumetric measurements of atrial- and ventricular EAT were derived from CMR, as seen in Picture 1, and the time to incident AF was subsequently determined. Results A total of 78 patients (38%) were diagnosed with AF during a median of 40 (37–42) months of monitoring. Of these, only 7 (9%) participants reported symptoms of AF during arrhythmia episodes, i.e., 91% had subclinical AF. In multivariate Cox regression analyses adjusted for age, sex, body mass index (BMI), and comorbidities, we found EAT to be an independent marker for time to AF with hazard ratios (95% confidence intervals) up to 1.66 (1.17–2.36; p = 0.005) when analyzing the risk of new-onset AF episodes lasting ≥ 24 hours. The Cox regression analyses are presented in Picture 2, where we furthermore have adjusted for left atrial size (LAMIN) and left atrial function (LATEF). Conclusion Atrial EAT assessed by volumetric measurements on CMR images was significantly associated with the incident AF episodes as detected by ILR.