Atrial flutter and thromboembolic risk: a systematic review

Atrial flutter confers a thromboembolic risk, but contrary to atrial fibrillation the relationship has only been addressed in few studies. This study performs an up to date systematic review of the literature to investigate the association between atrial flutter and thromboembolic events. Articles were found by MEDLINE, EMBASE search and a manual search of references list in included articles. International guidelines, meta-analyses, reviews, case reports, studies reporting thromboembolic events in relation to ablation, or cardioversion procedures, echocardiography, and observational studies were found eligible in this review. A total of 52 articles were included in this review. During cardioversion, thromboembolic event rates varied from 0% to 6% with a follow-up from 1 week to 6 years. Echocardiographic studies reported prevalence of thrombus material from 0% to 38% and a prevalence of spontaneous echo contrast (SEC) from 21% to 28%. One ablation study in non-anticoagulated patients reported thromboembolic events at 13.9%. Observational studies reported an overall elevated stroke risk (risk ratio 1.4, 95% CI 1.35 to 1.46) and mortality risk (HR 1.9, 95% CI 1.2 to 3.1) with long time follow-up compared with a control group in both studies. Given the limitations and heterogeneity of the data, a meta-analysis was not a part of this systematic review. Notwithstanding the limitations of observational studies and indirect data from echocardiographic studies, this systematic review confirms that clinical thromboembolic events, left atrial thrombus and SEC are highly prevalent in atrial flutter.