Transesophageal echocardiography plays a key role in the selection of suitable patients for cardioversion.
If a transesophageal echocardiography is conducted prior to cardioversion of a patient with a persistent non-valvular atrial fibrillation, we expect in 12 % of the patients a thrombus in the left atrial appendage (Antithrombotic therapy in atrial fibrillation, American College of Chest Physicians Evidence Based Practice Guidelines, Chest 2008, 133, 5465-5925)
The core lab of the ACUTE – study (Assessment of Cardioversion using transoesophageal echocardiography; N Engl J Med,2001;344:1411-20.) has excluded 13,8% of the patients, who were randomised to the cardioversion group because of a thrombus.

Thrombi are therefore common in patients with non-valvular atrial fibrillation before cardioversion.
However, it is not always easy to distinguish thrombi from spontaneous echo contrast, from small trabeculae and from artifacts. In addition, there are not only echogenic but more difficult to diagnose hypoechoic thrombi too.

We are thus confronted with similar problems as in the detection of thrombi in the left ventricle.
Many studies of left ventricular thrombi demonstrate the value of contrast agents. But here are a few studies dealing with left atrial thrombi and their detection using contrast agents together with transesophageal echocardiography. Giso von der Recke et. al. (J. Am Soc Echocardiogr 2002; 15:1256-61) performed in a small group of patients (n = 42) with an unclear finding in a conventional transoesophageal examination an additional contrast study with a System V from GE and a mechanical index of 0.4. Despite the limited technical capabilities of the TEE – probe compared to the current devices, a thrombus was established in 9, and excluded in 25 patients.

The manual for echocardiography of the german society of cardiology recommends:
“If thrombi can not be excluded … in the left heart chambers, a contrast study is indicated“ (Manual zur Indikation und Durchführung der Echokardiographie, Clin Res Cardiol Suppl 4:3–51 (2009), S.40).
The following examples will illustrate the clinical potential of ultrasound contrast agents in transesophageal echocardiography.