Thromboembolic risk in atrial flutter. The FLASIEC (FLutter Atriale Società Italiana di Ecografia Cardiovascolare) multicentre study.

AIMS: Patients with atrial flutter are believed to be at lower risk of thromboembolism than patients with atrial fibrillation. However, the incidence of atrial thrombi and the need for anticoagulation in patients with atrial flutter is not well established. METHODS AND
RESULTS: A prospective observational multicentre study was undertaken to assess the frequency of atrial thrombi and spontaneous echocontrast and the prevalence for aortic complex atherosclerotic lesions in a cohort of unselected patients with atrial flutter. We evaluated 134 patients (102 male, aged 70+/-9 years); exclusion criteria were history of atrial fibrillation, rheumatic mitral valve disease and mitral mechanical prosthesis. The median of atrial flutter duration was 33 days. Twelve patients had been taking warfarin for more than 7 days. One hundred and twenty-four patients (94%) underwent a transoesophageal echocardiogram, which revealed left atrial appendage thrombi in two patients (1.6%) and right atrial thrombi in one patient (1%). At least moderate left atrial echocontrast was found in 16/124 patients (13%). Complex atherosclerotic aortic plaques were detected in 10 patients (8%). Atrial flutter conversion was attempted in 93/134 patients (69%). At the 1-month follow-up, two patients experienced a thromboembolic event following restoration of sinus rhythm.
CONCLUSIONS: Atrial thrombi and echocontrast, and complex aortic atherosclerotic plaques are relatively uncommon in patients with atrial flutter. Post-cardioversion embolism was observed in two patients in our study population.