Which test is commonly used to assess left atrial thrombus before cardioversion of atrial fibrillation?

• A. Transthoracic echocardiography (TTE)
• B. Transesophageal echocardiography (TEE)
• C. Cardiac MRI
• D. CT angiography

Answer: (B)

Before restoring cardioversion in atrial fibrillation, it’s essential to rule out a left atrial thrombus to lower the risk of stroke. The test most commonly used for this purpose is transesophageal echocardiography. The reason is its probe sits in the esophagus, right behind the heart, which provides very close, clear views of the left atrium and especially the left atrial appendage where clots tend to form. This yields high-resolution, real-time images and strong accuracy for detecting thrombus, more so than transthoracic echocardiography, which often can’t visualize the appendage well because of chest wall and lung interference. Cardiac MRI or CT angiography can detect thrombus too, but they’re not the standard upfront choice for pre-cardioversion assessment due to longer exam times, availability, and potential need for contrast or radiation. So, transesophageal echocardiography is the preferred test to safely guide whether to proceed with cardioversion.