Hyperthyroidism and AFib: The Acute and Long-term Effects

Hyperthyroidism can cause atrial fibrillation (AFib) through both acute and long-term mechanisms. In the acute phase, hyperthyroidism leads to sympathetic activation and increased heart rate, creating an environment for AFib to develop. The increased heart rate and decreased atrial refractory period contribute to the initiation and maintenance of AFib. Additionally, hyperthyroidism can induce fibrosis in the longer term, increasing the likelihood of AFib. While the risk of AFib is higher in severe hyperthyroidism, even subclinical hyperthyroidism poses a heightened risk.