Characterization, Pathogenesis, and Clinical Implications of Inflammation-Related Atrial Myopathy as an Important Cause of Atrial Fibrillation

Abstract

Historically, atrial fibrillation has been observed in clinical settings of prolonged hemodynamic stress, eg, hypertension and valvular heart disease. However, recently, the most prominent precedents to atrial fibrillation are metabolic diseases that are associated with adipose tissue inflammation (ie, obesity and diabetes mellitus) and systemic inflammatory disorders (ie, rheumatoid arthritis and psoriasis). These patients typically have little evidence of left ventricular hypertrophy or dilatation; instead, imaging reveals abnormalities of the structure or function of the atria, particularly the left atrium, indicative of an atrial myopathy. The left atrium is enlarged, fibrotic and noncompliant, potentially because the predisposing disorder leads to an expansion of epicardial adipose tissue, which transmits proinflammatory mediators to the underlying left atrium. The development of an atrial myopathy not only leads to atrial fibrillation, but also contributes to pulmonary venous hypertension and systemic thromboembolism. These mechanisms explain why disorders of systemic or adipose tissue inflammation are accompanied an increased risk of atrial fibrillation, abnormalities of left atrium geometry and an enhanced risk of stroke. The risk of stroke exceeds that predicted by conventional cardiovascular risk factors or thromboembolism risk scores used to guide the use of anticoagulation, but it is strongly linked to clinical evidence and biomarkers of systemic inflammation.

Keywords: atrial fibrillation; atrial myopathy; stroke.

Figure 1

Hemodynamic and inflammatory stresses can lead to atrial fibrillation by distinct pathophysiological pathways. LA indicates left atrium; LV, left ventricle or left ventricular.

Figure 2

Chronic systemic inflammatory disorders and metabolic disorders that are linked to adipose tissue inflammation can lead to expansion of epicardial fat mass, which can cause a left atrial myopathy and its clinical consequences. LA indicates left atrium.