Risk of ischaemic stroke in thyrotoxic atrial fibrillation

Objective Atrial fibrillation (AF) is the most common cardiac complication of thyrotoxicosis and is strongly implicated in thromboembolic events. However, the incidence of stroke in thyrotoxic AF remains unclear. Herein, we aimed to investigate the risks of mortality and ischaemic stroke between patients with thyrotoxic AF and nonthyrotoxic AF. Designs and Methods From Taiwan's National Health Insurance Research Database, 1868 patients with the concomitant diagnoses of AF and thyrotoxicosis identified between 2001 and 2010 were compared to 7472 patients with nonthyrotoxic AF using propensity score matching for age, sex and comorbidities. Results There was no significant difference in either CHA(2)DS(2)-VASc score or anticoagulant usage between the groups. Alternatively, the thyrotoxic group contained more beta-blocker/digoxin users, whereas the nonthyrotoxic group contained more statin users. Patients with thyrotoxic AF exhibited lower risks of all-cause mortality (HR: 0.66, CI: 0.59-0.73, P < .0001) and ischaemic stroke (HR: 0.73, CI: 0.64-0.84, P < .0001) than those with nonthyrotoxic AF, especially thyrotoxic patients with CHA(2)DS(2)-VASc scores >= 1. Comorbidities, including diabetes, hyperlipidaemia, hypertension and coronary artery disease, contributed to all-cause mortality in patients with nonthyrotoxic AF; however, this effect was diminished in thyrotoxic AF. Conclusions Patients with thyrotoxicosis and AF have a lower risk of stroke than patients with nonthyrotoxic AF. Treatment for thyrotoxicosis is also crucial as the prescription of anticoagulants based on CHA2DS2-VASc scores.