Thrombus Detection in the Left Atrial Appendage Using Contrast-Enhanced MRI: A Pilot Study

Left atrial thrombi are an important cause for embolism-related morbidity and mortality. Transesophageal echocardiography (TEE), the clinical reference, is semiinvasive; thus, we aimed to assess the value of contrast-enhanced cardiovascular MRI for the detection of thrombus in the left atrial appendage. The image quality was good for both 2D perfusion (grade 4 +/- 1) and 3D turbo fast low-angle shot (FLASH) (grade 4 +/- 1, n.s.). Compared with TEE, 2D perfusion, 3D turboFLASH, and the combination of both techniques yielded sensitivities of 47/35/44%, specificities of 50/67/67%, positive predictive values of 73/75/80%, and negative predictive values of 25/27/29%, respectively. The size of the thrombus was overestimated by 2D perfusion (66%) and by 3D turboFLASH (25%) and agreement for location and shape of thrombus was 50% and 75% for 2D perfusion and 75% and 50% for 3D turboFLASH, respectively. The TEE thrombus size was significantly larger in patients with true-positive diagnoses by 2D perfusion (148%) and by 3D turboFLASH (151%) when compared with patients with false-negative diagnoses (p < 0.05 for both). No such difference was found for image quality, time delay between TEE and MRI examination, and location and shape of thrombi. Contrast-enhanced MRI lacks diagnostic accuracy for the detection of thrombi in the left atrial appendage. Future technical improvements are essential to establish this technique as a noninvasive alternative to TEE.