What is the most common arrhythmia associated with hyperthyroidism?

In the context of hyperthyroidism, the most common arrhythmia is atrial fibrillation. This condition is often characterized by an increased heart rate and is frequently observed in patients with elevated levels of thyroid hormones. Hyperthyroidism can cause a hyperdynamic state, leading to increased cardiac output and alterations in heart rate regulation, which strongly predispose individuals to develop atrial fibrillation.

Sinus tachycardia can occur as a result of hyperthyroidism and is common; however, it is typically a physiological response to the increased metabolic state rather than a persistent arrhythmia. Atrial fibrillation, being more specific and persistent, reflects a more significant and complex influence of hyperthyroidism on the cardiac conduction system.

Ventricular tachycardia is less common in this context and usually occurs under more serious circumstances or underlying heart disease. Bradycardia is typically not associated with hyperthyroidism; instead, it is more common in conditions of hypothyroidism or other disturbances affecting the heart's natural pacemaker or conduction system.

Thus, the most relevant and common arrhythmia linked with hyperthyroidism is indeed atrial fibrillation, highlighting the importance of monitoring heart rhythm in patients with this endocrine disorder.