Assessment of left atrial appendage spontaneous echo contrast in patients with atrial fibrillation using two-phase cardiac CT

Objective To evaluate the ability of cardiac CT(CCT) in detecting left atrial appendage spontaneous echo contrast(LAASEC) in patients with atrial fibrillation visually and quantitatively. Methods We studied 245 inpatients with atrial fibrillation who received both two-phase CCT and transesophageal echocardiography(TEE) examinations.LAASEC was visually identified in TEE and CCT.Taking TEE as the gold standard, CCT was analyzed visually by calculating sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV), and accuracy.In addition, LAA apex, left atrial(LA)body and ascending aorta(AA) attenuation(Hounsfield units)were measured on initial CCT and LAA/AA and LAA/LA attenuation ratios were calculated.The quantitative values of LAA, LAA/AA and LAA/LA were determined on the basis of the receiver operating characteristic(ROC)curve. Results In our study of 245 patients, TEE demonstrated that grade 0 LAASEC in 113, grade 1 in 73, grade 2 in 19, grade 3 in 25, and grade 4 in 15 patients, respectively.On CCT, 162 patients were found without LAASEC and 83 patients with LAASEC.A total of grade 2-4 LAASEC in 59 patients were detected with CCT.Sensitivity, specificity, PPV, NPV and accuracy values of CCT for LAASEC (≥grade 1) were 56.8%, 92.9%, 90.3%, 64.8% and 73.5%, respectively.The area under the ROC curve for LAA, LAA/AA and LAA/LA were 0.852, 0.902, and 0.824, respectively.Quantitative identification of LAASEC (≥grade 1) yielded a sensitivity of 87.9%, specificity of 83.2%, PPV of 85.9%, NPV of 85.5% and an accuracy of 85.7% when the optimal LAA/AA ratio was 0.897. Conclusion Two-phase CCT is a promising noninvasive examination in detection of LAASEC (especially for grade 2-4). On the basis of CCT visual analysis, the accuracy for the detection of LAASEC can be improved with quantitative measurement. Key words: Spontaneous echo contrast; Cardiac CT; Atrial fibrillation; Left atrial appendage