Am J Cardiol. 2014 Jan 1;113(1):173-7
Patients with atrial fibrillation, who are referred for radiofrequency pulmonary vein antral isolation, frequently undergo transesophageal echocardiography (TEE) to detect and/or exclude left atrial or left atrial appendage (LAA) thrombus and cardiac computed tomographic angiography (CCTA) to define and/or evaluate left atrial and pulmonary venous anatomy. Previous studies have reported CCTA to have high sensitivity and negative predictive value (NPV) for detecting thrombus in the LAA. Previous studies determining an optimal LAA/ascending aorta (AA) Hounsfield unit (HU) density ratio for detection of LAA thrombus have been small, with limited numbers of thrombi. We thus sought to determine both the optimal cutoff for LAA HU density and LAA/AA HU density ratio in detecting LAA thrombus compared with TEE in a multicenter population. We included 84 patients who had undergone CCTA and TEE. LAA was evaluated by 64-row CCTA qualitatively (visual filling defect) and quantitatively (measurement of LAA HU density and LAA/AA HU density ratio), using a 1-cm area of interest in the same axial plane. Results were compared with TEE visualization of thrombus or spontaneous echo contrast. Qualitative identification of thrombus in LAA by CCTA compared with TEE detection of thrombus had a sensitivity of 100%, a specificity of 77.9%, a positive predictive value (PPV) of 51.6%, an NPV of 100%, and a total accuracy of 82.1%. The optimal LAA HU density cutoff for thrombus detection was 119 with a sensitivity of 88%, a specificity of 86%, PPV 56%, and an area under the curve of 0.923 (p = 0.0004). The optimal LAA/aorta HU ratio was 0.242 with a sensitivity of 87%, a specificity of 88%, a PPV of 64%, and an area under the curve of 0.921 (p = 0.0011). There is no significant difference (p = 0.72) between both areas under the curve, and both measurements improved the specificity and PPV compared with qualitative measures. Multidetector computed tomography is an imaging technique that can exclude LAA thrombus with very hig! h NPV. Quantitative measurement of LAA HU density (cutoff 119) or LAA/aorta HU density ratio (cutoff 0.242) improves accuracy of positively detecting LAA thrombus. This technique is especially useful when delayed scanning is not performed and LAA is found incidentally after the patient scanning is complete.