From the Guidelines
Approximately 5-15% of patients with hyperthyroidism develop atrial fibrillation (AFib), with the risk being higher in older patients, particularly those over 60 years of age. The development of AFib in patients with hyperthyroidism is a significant concern, as it can lead to increased morbidity and mortality due to complications such as heart failure and thromboembolism 1. Hyperthyroidism increases AFib risk by elevating thyroid hormone levels, which directly affects cardiac tissue and increases heart rate, contractility, and blood pressure. Excess thyroid hormones enhance automaticity and triggered activity in the atria, creating an environment conducive to AFib development.
Some key points to consider in the management of AFib in patients with hyperthyroidism include:
- Treating the underlying hyperthyroidism with medications like methimazole or propylthiouracil often leads to restoration of normal sinus rhythm in about 50-60% of patients, particularly in those with recent-onset AFib 1.
- Beta-blockers such as propranolol or metoprolol are typically used to control heart rate and reduce palpitations in patients with hyperthyroidism and AFib 1.
- The decision to anticoagulate patients with hyperthyroidism and AFib should be guided by CHA2DS2-VASc risk factors, as the correlation between thyrotoxicosis and thromboembolic disease is controversial 1.
Overall, the management of AFib in patients with hyperthyroidism requires a multifaceted approach that addresses both the underlying thyroid dysfunction and the cardiac arrhythmia, with the goal of reducing morbidity and mortality and improving quality of life 1.
From the Research
Prevalence of Atrial Fibrillation in Hyperthyroidism
- The prevalence of atrial fibrillation (AF) in patients with hyperthyroidism is estimated to be between 5-15% 2 and 10-25% 3 in overtly hyperthyroid patients.
- A study found that the prevalence of hyperthyroidism was higher in patients with AF (0.9% vs 0.4%, P < .001) compared to patients without AF 4.
- Another study reported a prevalence of 16%-60% of atrial fibrillation in patients with known hyperthyroidism 5.
Risk Factors for Atrial Fibrillation in Hyperthyroidism
- Risk factors for atrial fibrillation in thyrotoxic patients include male sex, ischemic or valvular heart disease, and congestive heart failure 3.
- Subclinical hyperthyroidism and high-normal free T4 have been associated with an increased risk in the development of AF 2.
Clinical Outcomes of Atrial Fibrillation with Hyperthyroidism
- Patients with AF and hyperthyroidism have better clinical outcomes compared to AF patients without hyperthyroidism, with lower hospitalization cost, shorter mean length of stay, and lower in-hospital mortality 4.
- Hyperthyroidism is associated with AF in both univariate and multivariate analysis, and AF patients with hyperthyroidism have a lower prevalence of comorbidities such as CAD, cardiomyopathy, and hypertension 4.