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An 83 year old man presented with left hemiplegia and atrial fibrillation. Cranial computed tomography and magnetic resonance imaging (MRI) showed cerebral infarction at the area of right middle cerebral artery. We used MRI (Signa, 1.5T, General Electric, Milwaukee, Wisconsin) for visualising the left atrial appendage (LAA). On the MRI of triple inversion recovery (IR) fast spin echo (FSE) sequence, the images of the left side of the heart are clearly seen in a long axis view. LAA is imaged on the left ventricular basal anterior wall. Mass with high signal intensity in the LAA is visible and distinctive from the LAA wall (below left). Anticoagulant treatment was initiated, and aphagia and dysarthria improved after four days of warfarin. The thrombus in the LAA was confirmed by transoesophageal echocardiography (TOE) and its size was observed to be relatively small. The MRI was repeated and the LAA thrombus disappeared (below right).
Although TOE is well established as the method for evaluation of LAA thrombi, this method is semi-invasive and cannot be used at the acute phase of cerebral infarction. Black blood technique is used to evaluate cardiac anatomy, and triple IR FSE sequence can be used to reduce more blood signal and related artefacts including fat. In our case, LAA thrombus could be detected by using this method without gadolinium injection. The non-invasive nature and safety of MRI makes it ideal for serial follow up of thrombi in LAA, even in acute cerebral infarction with a complication of aphagia or dysarthria.