Characteristics and Outcomes of Atrial Fibrillation in Patients With Thyroid Disease (from the ARISTOTLE Trial)

Whether patients with atrial fibrillation (AF) and thyroid disease are clinically distinct from those with AF and no thyroid disease is unknown. Furthermore, the effectiveness of anticoagulation for prevention of AF-related thromboembolic events in patients with thyroid disease has not been adequately studied. Patients enrolled in the Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation, which compared apixaban with warfarin in patients with AF (n = 18,201), were categorized by thyroid disease history at randomization (hypothyroidism, hyperthyroidism, and no thyroid disease). Adjusted hazard ratios derived from Cox models were used to compare outcomes by thyroid disease history. Associations between randomized treatment and outcomes by thyroid disease history were examined using Cox models with interaction terms. A total of 18,021/18,201 (99%) patients had available thyroid disease history at randomization: 1,656 (9%) had hypothyroidism, 321 (2%) had hyperthyroidism, and 16,044 (89%) had no thyroid disease. When compared with those without a history of thyroid disease, patients with hypo- or hyperthyroidism were more likely to be female (60.4% vs 32.1%; 52.0% vs 32.1%; both p <0.0001). Patients with hypothyroidism were older (73 vs 70 years, p <0.0001) and more likely to have had previous falls (8.7% vs 4.3%, p <0.0001). There was no difference in clinical outcomes by thyroid disease history. The benefit of apixaban compared with warfarin was similar regardless of thyroid disease history (interaction p >0.10). In conclusion, despite differences in baseline characteristics of patients with and without thyroid disease, their clinical outcomes were similar. The benefit of apixban compared with warfarin was preserved regardless of thyroid disease history.