Impact of atrial high-rate episodes on the risk of future stroke

Atrial fibrillation (AF) is the most common type of arrhythmia. The definition of AF in patients with cardiac implantable electronic devices (CIEDs) is not clear, and the appropriate treatment guideline for patients with episodes of AF has not been established yet. Additionally, little is known about the incidence of AF and embolic stroke events in Japanese patients with CIEDs. The purposes of this study were to identify the incidence of embolic stroke events in Japanese patients with and without AF events detected by CIEDs and to examine the risk factors of embolic stroke events.

We retrospectively analyzed the database of our CIED clinic. Every 6 months, episodes of AF were checked by CIEDs. Using univariate (Student's t-test and Fisher's exact test) and multivariate analyses, we examined the characteristics and incidence of embolic stroke events and investigated the relationship between episodes of AF and the incidence of embolic stroke events.

In this study, we enrolled 348 consecutive patients who had no prior history of AF and were not administering anticoagulants (follow-up period, 65±58 months; age, 70±16 years; male sex, 64%; implantable cardioverter defibrillator, 55%). The mean CHADS₂ and CHA₂DS₂-VASc scores were 1.7±1.1 and 2.8±1.5 points, respectively. Fifty-five patients (16%) had AF events detected by CIEDs that lasted for ≥30s, and 23 patients (6.6%) had embolic stroke during the follow-up period. Multivariate analysis demonstrated that independent predictors for embolic stroke were a left atrial diameter ≥40mm [odds ratio (OR) 3.1, 95% confidence interval (CI) 1.2-7.9, p=0.016] and episodes of AF (OR 5.3, 95% CI 2.2-13, p=0.0003).

Embolic stroke events are common in Japanese patients with CIEDs. AF events lasting ≥30s and an enlarged left atrium are the risk factors of embolic stroke in this population.