IMPACT OF THYROID DYSFUNCTION IN PATIENTS WITH ATRIAL FIBRILLATION
Authors: Ferreira Luiza Silva , Correa Stefanny Machado , Santos Luan Bernardino Montes , Bernardes Bernardo Machado , Borba Maisa Cristine de Oliveira , Rezende João Matheus Elias , Folgosi Fernanda , Souza Marco Tulio Lopes de , Bastos Wanghelys Leyzer , Franzoni Isabella , Silveira Lucas Gonçalves , Bernardi Chaiany Caroline , Procópio Daniela Pereira , Silveira Marcos Antônio Moreno , Marques Bruna Karyn Perne , Troncha Ludmilla Lais Pereira 
Published: February 2024

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in clinical practice, affecting approximately 2% of the general population and increasing the risk of stroke, heart failure and mortality. AF is often associated with several clinical conditions, including thyroid dysfunction, which can alter metabolism, function and cardiac structure. Thyroid dysfunction can be classified as hypothyroidism (low production of thyroid hormones) or hyperthyroidism (excess production of thyroid hormones), both of which can cause or worsen AF. The mechanism by which thyroid dysfunction affects AF is complex and involves electrophysiological, hemodynamic, inflammatory and structural changes in the atria. Appropriate diagnosis and treatment of thyroid dysfunction can improve AF control and reduce thromboembolic and hemorrhagic complications. However, the prevalence, incidence, risk factors, prognosis and management of AF in patients with thyroid dysfunction are still controversial topics in the literature. Objective: to evaluate the impact of thyroid dysfunction in patients with AF, addressing the following aspects: epidemiology, pathophysiology, diagnosis, treatment and clinical outcomes. Methodology: This review was carried out in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) protocol. The PubMed, Scielo and Web of Science databases were searched, using the following descriptors: "atrial fibrillation", "thyroid dysfunction", "hypothyroidism", "hyperthyroidism" and "thyrotoxicosis". Articles published in the last 10 years, in Portuguese, English or Spanish, that addressed the proposed topic were included. Articles that were not original, did not have sufficient data or were not relevant to the research question were excluded. Results: 18 studies were selected. The diagnosis of AF in patients with thyroid dysfunction requires confirmation of the heart rhythm by electrocardiogram (ECG) and assessment of serum thyroid hormone levels (TSH, free T4 and free T3). Treatment of AF in patients with thyroid dysfunction aims to restore and maintain sinus rhythm, control ventricular rate, prevent thromboembolic events, and correct thyroid dysfunction. Therapeutic options include antiarrhythmic drugs, antithyroid drugs, anticoagulant drugs, electrical cardioversion, catheter ablation, and surgical thyroid treatment. The clinical outcomes of AF in patients with thyroid dysfunction are influenced by the type, severity and duration of thyroid dysfunction, as well as rhythm, frequency and anticoagulation control. AF in patients with thyroid dysfunction is associated with a higher risk of arrhythmia recurrence, heart failure, stroke and mortality. Conclusion: Thyroid dysfunction is a frequent and important clinical condition in patients with AF, as it can cause or worsen arrhythmia, as well as increase the risk of complications. Appropriate diagnosis and treatment of thyroid dysfunction can improve AF control and reduce adverse outcomes. However, there are still gaps in knowledge about the epidemiology, pathophysiology, prognosis and management of AF in patients with thyroid dysfunction, which require further studies of high quality and clinical relevance.