Complex LAA Shape Predicts Thromboembolic Risk

With the arrival of sophisticated advances in imaging technology, such as three-dimensional echocardiography, we are better able to appreciate the geometric subtleties of the left atrial appendage (LAA) and its contribution to thromboembolic risk in atrial fibrillation (AF). 

A recent studyby investigators in Japan and published in Circulation: Cardiovascular Imaging identified LAA structure as a potential congenital risk factor for stroke in AF.  Prior to undergoing catheter ablation, 564 patients were prospectively studied with transesophageal echocardiography (TEE). Only 36 (6.4%) had LAA clots at the time of the study. Of those with thrombi, the overwhelming majority (34 patients) had 3 or more LAA lobes and only 2 patients had 2 or fewer LAA lobes. 

This study found that complex LAA geometry (3 or more lobes) was the strongest independent risk factor for having a LAA thrombus (multivariate OR 2.5, 95% CI 1.50-1.08, p<.001), followed by CHADS₂ score (multivariate OR 1.75, 95% CI 1.24-2.49, p=0.002). This association held true even after adjusting for clinical risk factors and other echocardiographic markers of slow blood flow, such as “smoke” or spontaneous contrast in the LAA.  Conversely, of those patients who had 2 or fewer LAA lobes, LAA thrombi formed in only 1%.

Therefore, these findings raise for consideration whether the number of LAA lobes should be considered as part of the calculation of the CHADS₂ score when assessing thrombotic risk in patients with AF.  While we wait for results of studies to further validate the current findings, clinicians may want to consider the number of LAA lobes when classifying thromboembolic risk in patients with AF.

References:

Yamamoto M, Seo Y, Kawamatsu N, et al. Complex left atrial appendage morphology and left atrial appendage thrombus formation in patients with atrial fibrillation. Circ Cardiovasc Imaging 2014; DOI:10.1161/CIRCIMAGING.113.001317.