Left atrial thrombus formation in patients with nonvalvular paroxysmal atrial fibrillation

The formation of left atrial thrombus (LAT) during atrial fibrillation (AF) was evaluated in 388 patients without valvular disease using transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE). Twohundred seventy-five patients had sinus rhythm (SR), while 58 had paroxysmal atrial fibrillation (PAF), and 55 had chronic atrial fibrillation (CAF). LAT was detected by TEE in 63 patients (16.2%), but it was not detected by TTE. LAT was present in 4.0% of the patients with SR, 25.9% of the patients with PAF (p<0.01 vs SR), and 67.3% of the patients with CAF (p<0.01 vs SR). PAF and CAF were each significantly more prevalent among the patients with LAT than among those without LAT. Diabetes mellitus, a prior history of stroke, smoking, and alcohol use were also more prevalent in patients with LAT than in patients without LAT. There was no significant difference in the prevalence of hypertension between the patients with and without LAT. Left ventricular dysfunction (ejection fraction < 60%) was more frequently observed in patients with LAT than in patients without LAT (15.9% and 7.8%, respectively, p=0.02). A multiple logistic regression analysis showed that PAF, CAF and drinking were independent predictors of LAT. A 7-fold increase in the odds ratio for the formation of LAT was observed for patients with PAF, whereas CAF was associated with a 50-fold greater risk. In conclusion, we confirmed that TEE is a sensitive test for detecting LAT while PAF was found to be an important risk factor for LAT formation, although the risk during PAF is much less than that during CAF.