Echocardiographic imaging plays an important role in the selection of the patient according to anatomy, in verifying the presence of exclusion criteria to the procedure such as presence of a thrombus inside the left atrial appendage, and in device selection.

Multiplanar transesophageal echocardiography (TEE) is performed to define LAA size and anatomy. The LAA is imaged from the mid-esophageal view through 180° (in particular at 0°, 45–60°, 90°, and 120–135°) to define the maximum LAA width and maximum depth of the dominant lobe. The need of a complete 180° scan is due to the highly variable anatomy of the LAA, showing the presence of more than one lobe in 80 % of left atrial appendages (Fig. 16.2) [2]; it is not unusual that a LAA that shows one lobe at 45–60° then reveals the presence of more than one lobe or a “broccoli-like” aspect at 120–135° (Fig. 16.3); moreover, the ostium of the LAA is typically oval shaped; therefore, diameters on the various planes can vary significantly, in some cases up to a 12 mm difference between the diameters obtained at 0° and 135° [3].

A further help for the visualization of the LAA, in particular for determination of shape and dimension of the orifice, comes from the 3D TEE [4, 5]; the two main modalities to perform this exam are [3]:

Multidetector computed tomography (MDCT) with contrast injection is an alternative to echocardiography, producing high-quality 3D images of the LAA anatomy, with a sensitivity for the detection of LAA thrombi comparable with TEE [6]; in our department, we don’t use MDCT to avoid further radiation exposure or contrast administration. As an alternative, some authors use cardiac magnetic resonance imaging (MRI) to study the LAA; however, the role of this methodology needs to be better defined [7].

During the procedure, after the transseptal puncture, comparison of TEE measurements with angiography (two projections) is usually performed in our department (Fig. 16.6).

The two commercially available devices need the following measurements: