Association of inflammation with atrial fibrillation in hyperthyroidism

The bidirectional relationship of thyroid disease and atrial fibrillation: Established knowledge and future considerations

Atrial fibrillation (AF) tends to occur frequently in patients with thyroid disease, primarily hyperthyroidism. In hyperthyroidism, increased levels of thyroid hormones, via intra- and extranuclear mechanisms, have profound effects on cardiac electrophysiology. Hypothyroidism carries a lower risk for AF and is mainly associated with the overtreatment of hypothyroid patients. New-onset AF is frequently the only manifestation of thyroid disease, which renders screening for thyroid dysfunction in that scenario clinically useful. Managing thyroid disease and comorbid AF is essential. This includes thyroid hormones control along with conventional AF therapy. However, there are several open issues with this comorbid duo. The optimal management of thyroid disease and its impact on AF burden remains obscure. There is scanty information on clear-cut benefits for therapy of subclinical thyroid disease and screening of asymptomatic patients. Furthermore, the immunogenetic overlap between the autoantibodies in Graves' disease and AF genesis may lead to novel therapeutic implications. The objective of this review is to summarize the up-to-date epidemiology, pathogenesis, pathophysiology and management of interacting thyroid disease and AF.

Focus on Autoimmune Myocarditis in Graves' Disease: A Case-Based Review

The manifestations of hyperthyroidism-related myocardial damage are multitudinous, including arrhythmia, dilated cardiomyopathy, valvular diseases, and even cardiogenic shock. Acute myocarditis induced by thyrotoxicosis had been reported in a few studies. However, attention on its prevalence and underlying mechanisms is sorely lacking. Its long-term harm is often ignored, and it may eventually develop into dilated cardiomyopathy and heart failure. We report a case of Graves' disease with a progressive elevation of hypersensitive cardiac troponin-I at several days after discontinuation of the patient's anti-thyroid drugs. Cardiac magnetic resonance imaging (CMRI) showed inflammatory edema of some cardiomyocytes (stranded enhanced signals under T2 mapping), myocardial necrosis (scattered enhanced signals under T1 late gadolinium enhancement) in the medial and inferior epicardial wall, with a decreased left ventricular systolic function (48%), which implied a possibility of acute myocarditis induced by thyrotoxicosis. The patient was then given a transient glucocorticoid (GC) treatment and achieved a good curative effect. Inspired by this case, we aim to systematically elaborate the pathogenesis, diagnosis, and treatment of hyperthyroidism-induced autoimmune myocarditis. Additionally, we emphasize the importance of CMRI and GC therapy in the diagnosis and treatment of hyperthyroidism-related myocarditis.