Effect of Hyperthyroidism on the Hypercoagulable State and Thromboembolic Events in Patients with Atrial Fibrillation

Abstract

Objective: To clarify whether hyperthyroidism (HT) itself confers an additional effect on the hypercoagulable state and the risk of ischemic stroke among patients with hyperthyroid atrial fibrillation (AF). Methods: We prospectively evaluated plasma D-dimer levels and thromboembolic events among three groups of patients (hyperthyroid AF, n = 62; nonthyroid AF, n = 107, and HT without AF, n = 100). Plasma D-dimer levels were used to evaluate the hypercoagulable state. Results: The D-dimer level was significantly higher in patients with hyperthyroid AF than in nonthyroid AF (0.66 ± 0.06 vs. 0.34 ± 0.02 mg/l, p < 0.001) and HT without AF (0.66 ± 0.06 vs. 0.27 ± 0.02 mg/l, p < 0.001). During a 3-year follow-up, patients with hyperthyroid AF had a significantly higher incidence of ischemic stroke compared with patients with nonthyroid AF (hazard ratio, HR: 3.2, 95% confidence interval, CI: 1.01-5.59, p = 0.04). Cox regression analysis revealed that age (HR: 2.5, 95% CI: 1.01-1.21, p = 0.05), CHADS₂-VAS score (HR: 5.5, 95% CI: 1.51-7.43, p = 0.01) and anticoagulation (HR: 0.45, 95% CI: 0.07-0.54, p = 0.01) were independent predictors of risk for the occurrence of ischemic stroke. Conclusions: The present study suggests that HT may enhance the hypercoagulable state and the risk of ischemic stroke in patients with AF.

Hyperthyroid Atrial Fibrillation: Does It Matter for Stroke Risk?

“…In a recent issue of Cardiology , Chen et al [1] reported on hypercoagulable state and stroke risk in hyperthyroid atrial fibrillation (AF). The existing evidence is not completely settled as to whether hyperthyroid AF is associated with a hypercoagulable state and constitutes an excess stroke risk, since the existing studies are small and observational in nature.…”

“…The authors found that the annual incidence of ischemic stroke was highest among hyperthyroid AF patients at 7.6% versus 3.6 and 0.7% in the non-thyroid AF and hyperthyroidism without AF groups, respectively [1]. Although the study groups were matched for stroke risk according to the CHA 2 DS 2 -VASc score, the Cox proportional hazards analysis indicated that hyperthyroid AF patients were at significantly higher stroke risk than non-thyroid AF patients with a hazard ratio of 3.2 (95% CI 1.01-5.59, p = 0.04), indicating that hyperthyroid AF is predictive of stroke risk above and beyond the CHA 2 DS 2 -VASc score.…”

“…The study by Chen et al [1] has many strengths, including consecutive patient selection and prospective follow-up. Additionally, control groups were properly selected and matched to the hyperthyroid AF cohort on the basis of gender, age, hypertension and diabetes, in an apparent nested case-control design.…”

“…Clearly, the investigation by Chen et al [1] is limited by the small sample size and number of events. The low rate of anticoagulation limits the applicability of the study findings in other practice settings.…”

Brief Review: Atrial Fibrillation in Hyperthyroidism Increases Propensity to Stroke

“…The D-dimer levels were significantly higher in hyperthyroid with AF than in the other 2 groups. Over a period of 3 years, the follow-up showed higher incidence of ischemic stroke, when compared with nonthyroid AF (hazard ratio, HR: 3.2, 95% confidence interval, CI: 1.01 -5.59, P = 0.04) (19). Dekker et al looked at allcause mortality in hyperthyroidism, which they found it to be the highest in the first 3 months postdiagnosis (HR:4.62, 95% CI: 4.40 -4.85), moreover, they reported an elevated mortality in the 3-year (long-term) follow-up (HR: 1.35, 95% CI: 1.33 -1.37).…”