Thyrotoxic Atrial Fibrillation: Factors Associated with Persistence and Risk of Ischemic Stroke

Abstract

Background Atrial fibrillation (AF) is one of the commonest cardiovascular manifestations of thyrotoxicosis. A significant proportion of patients have persistent AF which may have long term consequences, for example, ischemic stroke. Methods We performed a retrospective cohort study in a regional hospital from January 2004 to June 2016 to examine the clinical characteristics and outcomes of thyrotoxic patients who presented with atrial fibrillation and to investigate possible factors associated with persistent atrial fibrillation and ischemic stoke. Results Among 1918 patients who had a diagnosis of thyrotoxicosis, 133 (6.9%) patients presented with AF. Spontaneous sinus conversion occurred in 89 (66.9%) patients in which 85 (94%) patients developed sinus conversion before or within 6 months after having achieved euthyroidism. The remaining 44 (33.1%) had persistent AF. The rate of ischemic stroke was numerically higher among patients who had persistent AF than those with spontaneous sinus conversion (15.9% versus 10.1%; log-rank 0.442, p = 0.506). Patients who sustained an ischemic stroke were older (71 ± 11 years versus 62 ± 16 years, p = 0.023) and had a trend towards higher CHA2DS2-VASc score (2.9 ± 1.7 versus 2.3 ± 1.7, p = 0.153). History of smoking (adjusted odds ratio 4.9, 95% CI [1.8,14.0], p = 0.002), a larger left atrial diameter (adjusted odd ratio 2.6, 95% CI [1.2,5.5], p = 0.014), and a relatively lower free thyroxine level at diagnosis (adjusted odd ratio 2.1, 95% CI [1.2,3.5], p = 0.008) were associated with persistence of AF on multivariate analysis. Conclusion Persistence of thyrotoxic AF occurred in one-third of patients and spontaneous sinus conversion was unlikely after six months of euthyroidism. High rate of ischemic stroke was observed among patients with persistent thyrotoxic AF and older age. Patients with factors associated with persistent AF, especially older people, should be closely monitored beyond 6 months so that anticoagulation can be initiated in a timely manner to reduce risk of ischemic stroke.

Risk of Thromboembolism in Non-Valvular Atrial Fibrillation With or Without Clinical Hyperthyroidism

“…However, the incidence of ischemic stroke is considered to be lower in paroxysmal AF patients than in those with sustained AF [28], and the different types of AF should not change the anticoagulation strategy [8]. In addition, Wong et al reported that hyperthyroid AF patients who had a restored sinus rhythm had a lower incidence of stroke than those with persistent AF [29]. In this study, information on sinus rhythm restoration was lacking.…”

Levothyroxine Treatment and the Risk of Cardiac Arrhythmias – Focus on the Patient Submitted to Thyroid Surgery

“…Once initiated, AF alters the electrical and structural properties of the atria in a manner that affects its maintenance, increasing the risk of recurrence and can alter the response to antiarrhythmic drugs (97,105). In addition, AF increases the risk of cerebrovascular stroke, peripheral embolization, and overall mortality (106)(107)(108). About 13-15% of individuals with newly developed AF have biochemical hyperthyroidism (103).…”

Higher FT4 level within the normal range predicts the outcome of cryoballoon ablation in paroxysmal atrial fibrillation patients without structural heart disease

“…However, in persistent AF patients, this increasing risk trend was nonsignificant. One explanation could be that persistent AF was associated with more advanced atrial structural remodeling and more non‐PV triggers than paroxysmal AF (Wong et al, 2017 ). Thus, thyroid hormone may be less able to modulate arrhythmogenic effects after cryoballoon‐based PVI ablation than in other scenarios (Chen et al, 2002 ).…”