Patients referred for radiofrequency pulmonary vein antral isolation undergo contrast-enhanced multidetector computed tomography (MDCT) to assess pulmonary vein and left atrial anatomy as well as transesophageal echocardiography (TEE) to detect intraatrial thrombus. We sought to determine the accuracy of MDCT to qualitatively and quantitatively detect severe spontaneous echo contrast (SEC) or thrombus by TEE in the left atrial appendage (LAA).

Two hundred twenty-three consecutive MDCT and TEE studies performed within 7 days of each other were retrospectively identified. The LAA was evaluated by MDCT for filling defects and by TEE for thrombus or SEC. Severe SEC or thrombus on TEE was considered positive. In patients with preserved ejection fraction, the Hounsfield unit (HU) density of a 1-cm² region of interest was measured in the LAA and ascending aorta (AA) of the same slice to calculate an LAA/AA HU ratio.

Visually identified filling defects in LAA by MDCT correspond to severe SEC and thrombus with a sensitivity, specificity, positive predictive value, and negative predictive value of 93%, 85%, 31%, and 99%, respectively. Multidetector CT missed severe SEC detected by TEE in one examination; all thrombi, however, were correctly identified. There is a significant inverse association between mean LAA/AA HU ratios with increasing grades of SEC or thrombus (P < .001). Using an LAA/AA HU ratio cutoff of 0.25, the positive predictive value and specificity increased to 75% and 96%, respectively, while preserving a high negative predictive value (96%).

Multidetector CT can qualitatively and quantitatively identify and distinguish severe LAA SEC/thrombus from lesser grades of SEC.