Jose Ruiz, Fadi Kandah?, Maedeh Ganji, Robert F. Percy, Srinivasan Sattiraju

1. Department of Cardiology, UF Health Jacksonville, Jacksonville, Fl, United States; 2. Department of Internal Medicine,UF Health Jacksonville, Jacksonville, Fl, United States

The left atrial appendage (LAA) is the most common site of left atrial thrombus with more than 90% of thrombi formed within this structure.[1]Transesophageal echocardiography(TEE) is the gold standard imaging technique for identifying LAA thrombus, with sensitivity and specificity both of 95%-100%.[1,2]An imaging modality that is used on most cardiac patients is the transthoracic echocardiogram (TTE). While quick and noninvasive, it is not known for its ability to detect left atrial appendage thrombi. Detecting a thrombus on TTE is a great advantage as it allows for rapid initiation of anticoagulation and avoidance of cardioversion early in atrial fibrillation patients. This case demonstrates the rare occurrence of a patient who was found to be in atrial fibrillation in the setting of thyrotoxicosis who was subsequently discovered to have a left atrial appendage thrombus on TTE.

Figure 1 Transthoracic echocardiogram images. (A): Apical two chamber view during transthoracic echocardiogram without contrast showing thrombus in LAA; (B) apical two chamber with contrast showing LAA with filling defect consistent with LAA clot; (C)apical 2 chamber view without contrast showing resolution of LAA thrombus; and (D) apical two chamber view with contrast showing resolution of LAA thrombus. LAA: left atrial appendage.

A 48-year-old male with past medical history of Graves' disease presented to the hospital for worsening shortness of breath of one-week duration. In the emergency department, he was found to be in atrial fibrillation with rapid ventricular response in the setting of severe thyrotoxicosis. The patient was appropriately started on a diltiazem infusion for rate control, along with methimazole and IV steroids for management of Graves' disease. A TTE was subsequently performed and revealed a newly reduced ejection fraction of 20% with a large mobile left atrial appendage thrombus (Figure 1A &1B). Rhythm control and cardioversion was therefore deferred, and the patient was bridged to warfarin therapy. In addition, the strategy was to continue rate control strategy along with anticoagulation. Prior to discharge, the patient's thyroid function normalized and heart rate improved. A repeat TTE one month later revealed resolution of the left atrial appendage thrombus which was confirmed with contrast images (Figure 1C & 1D).

There is growing interest in non-invasive modalities to identify LAA thrombi. Cardiac CT and MRI are frequently used as an alternative in those that cannot obtain a TEE.[2]These modalities still have the disadvantages of cost and contrast exposure. An essential imaging modality used initially on almost every patient with cardiac dysfunction is the TTE.Unfortunately, the ability of the TEE to detect LAA thrombus is extremely limited, with a reported sensitivity of only about 33% to 60%.[2]In the Comprehensive Left Atrial Appendage Optimization of Thrombus (CLOTS) trial, 118 patients with atrial fibrillation were enrolled to determine ability of TTE to identify LAA thrombi. Only two patients were found to have a LA thrombus, demonstrating the scarcity of identifying thrombi through TTE.[3]In our case, the TTE images were diagnostic of detecting LAA clot. The contrast images were able to confirmed the findings. Despite resolution of clot on repeat TTE after one month, decision was made to continue warfarin given the low ejection fraction and management of clot for at least three months.

In our case, the TTE, which is used on most cardiac patients, was able to diagnose an LAA thrombus rapidly and allow for the initiation of anticoagulation without delay. With further advances in imaging modalities and technique, detecting LAA thrombi through noninvasive methods has potential to produce comparable results to TEE.