Hyperthyroidism related AF patients at high risk of ischemic stroke, finds study

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia in patients. An estimation of the prevalence of AF in the United States ranges from about 2.7 million to 6.1 million. It is estimated to rise to 12.1 million in 2030. 5% – 15% of patients with hyperthyroidism cases report AF.

Previous observational studies with small populations have reported a high incidence of ischemic stroke in hyperthyroidism-related AF patients and claimed the need for anticoagulation treatment.

A retrospective study by Dr Kyu Kim, MD and team has revealed that hyperthyroidism-related AF patients are at high risks of ischemic stroke and systemic embolism akin to usual AF. Further the risk of ischemic stroke was reduced by treating hyperthyroidism.

The findings of the study are published in American Heart Journal.

The objective of the study was to evaluate the long-term risk of ischemic stroke/systemic embolism of hyperthyroidism-related AF.

The study was a retrospective population-based cohort study, which included records of 1,034,099 atrial fibrillation patients between 2005 and 2016 from the Korean National Health Insurance Service database. After exclusion, we identified 615,724 oral anticoagulation-naïve patients aged ≥18 years with new-onset non-valvular atrial fibrillation, of whom 20,773 had hyperthyroidism-related atrial fibrillation. After 3:1 propensity score matching, ischemic stroke and systemic embolism occurrences were compared between hyperthyroidism-related and non-hyperthyroidism-related ("nonthyroidal") atrial fibrillation patients.

The results of the study were

• A total of 615,724 oral anticoagulation-naïve AF patients of whom 20,773 had hyperthyroidism-related AF. Median follow-up duration was 5.9 years.

• Hyperthyroidism-related AF patients had significantly higher risks of ischemic stroke and systemic embolism than nonthyroidal AF patients (1.83 vs 1.62 per 100-person year, hazard ratio[HR], 1.13; 95% confidence interval[CI], 1.07 to 1.19; P < 0.001).

• This risk was 36% higher in hyperthyroidismrelated than in nonthyroidal AF patients within 1 year of atrial fibrillation diagnosis (3.65 vs 2.67 per 100-person year, HR, 1.36; 95% CI, 1.24 – 1.50; P < 0.001).

• This difference was also observed in the CHA2DS2-VASc score subgroup analysis. The risk of ischemic stroke and systemic embolism significantly decreased in patients treated for hyperthyroidism (HR, 0.64; 95% CI, 0.58 to 0.70; P < 0.001).

Dr Kim, and team concluded that "Hyperthyroidism-related AF patients have high risks of ischemic stroke and systemic embolism like nonthyroidal AF, especially when initially diagnosed. This risk is reduced by treating hyperthyroidism."

Reference: https://doi.org/10.1016/j.ahj.2021.08.018