From the Guidelines
Yes, hyperthyroidism can cause atrial fibrillation (AFib).
Mechanism and Risk
- Hyperthyroidism is associated with a threefold increased risk of atrial fibrillation and consequent heart failure, as thyroid hormone can directly affect the factors that determine oxygen consumption of the myocardium 1.
- The relationship between hyperthyroidism and cardiovascular abnormality is well known, and patients with hyperthyroidism have an increased risk of developing chronic stable angina and coronary artery spasm 1.
- A study reported a 3-fold increased risk of atrial fibrillation over 10 years in men and women at least 60 years of age with serum TSH of 0.1 mIU/L or lower with endogenous and exogenous subclinical hyperthyroidism 1.
Clinical Implications
- Successful treatment of the underlying hyperthyroidism often eliminates AFib 1.
- In patients with hyperthyroidism, the development of AFib can lead to a rate-related or tachycardia-induced cardiomyopathy, and prompt recognition and effective management of cardiac and other organ-system manifestations are important 1.
- The preferred treatment in these patients is nonselective β-blockers (propanolol), or diltiazem, verapamil, or ivabradine if β-blockers are contraindicated 1.
From the Research
Hyperthyroidism and Atrial Fibrillation
- Hyperthyroidism is a well-known independent risk factor for atrial fibrillation (AFib) 2, 3.
- Studies have shown that both overt and subclinical hyperthyroidism can increase the risk of developing AFib 2.
- The risk of AFib is associated with thyroid-stimulating hormone (TSH) levels, with higher TSH levels corresponding to a lower risk of AFib 2.
- Free thyroxine (FT4) levels within the normal range have also been shown to have a graded association with the risk of AFib 2.
Clinical Outcomes of Atrial Fibrillation with Hyperthyroidism
- Patients with AFib and hyperthyroidism have been found to have better clinical outcomes compared to those with AFib without hyperthyroidism 4.
- AFib patients with hyperthyroidism tend to be younger and more likely to be female, with a lower prevalence of comorbidities such as coronary artery disease and hypertension 4.
- Hyperthyroidism has been associated with lower hospitalization costs, shorter mean length of stay, and lower in-hospital mortality in AFib patients 4.
Prevalence and Associated Factors of Atrial Fibrillation in Hyperthyroidism Patients
- The prevalence of AFib among hyperthyroidism patients has been reported to be around 14% 5.
- Factors associated with an increased risk of AFib in hyperthyroidism patients include older age, female sex, and high serum FT4 levels 5.
- Other studies have also identified factors such as male sex, increasing age, ischemic heart disease, congestive heart failure, and heart valve disease as being associated with an increased risk of AFib in hyperthyroidism patients 3.