The following are key points to remember from a position statement on cardiac computed tomography (CCT) following left atrial appendage occlusion (LAAO):

1. CCT is used in both preoperative planning and postprocedural follow-up after transcatheter LAAO, a procedure that is becoming increasingly common for stroke prevention in atrial fibrillation (AF). Based on a comprehensive review of literature and expert consensus, this paper provides a standardized approach to acquisition and interpretation of CCT following LAAO.
2. Advantages of CCT over transesophageal echocardiography (TEE) in post-LAAO evaluation include CCT’s noninvasive nature and rapid acquisition of high-resolution, isotropic images. However, CCT cannot quantify flow velocities across and adjacent to LAAO devices.
3. Intravenous iodinated contrast is required for CCT following LAAO. In patients with estimated glomerular filtration rate <30 mL/min/1.73 m², the authors recommend careful consideration of the risk of kidney injury.
4. A 64-slice CT scanner with a cardiac package is the minimum requirement for LAAO imaging. Higher-slice and dual-source scanners may improve image quality and reduce radiation exposure. Prospective electrocardiogram triggering is generally recommended to minimize radiation exposure. The authors emphasize the importance of a consistent acquisition protocol, usually with biphasic contrast injection.
5. A multiplanar reformat double-oblique method is recommended for CCT post-processing.
6. One limitation of CT is that it is difficult to discriminate between benign endothelialization and thrombus formation on the LA surface of LAAO devices. Hypo-attenuated thickening (HAT) on the atrial surface of a device should be classified according to location, extent, morphology, and device-specific design. Low-grade HAT is currently considered a precursor to device endothelialization. Features of high-grade HAT, which is considered device-related thrombus (DRT) and warrants anticoagulation, include thickness >3 mm, pedunculation, and surface irregularity.
7. Timing of follow-up imaging after LAAO has varied among studies. The Society of Cardiovascular Angiography and Interventions and Heart Rhythm Society recommend TEE or CCT at 45-90 days post-procedure. European societies strongly recommend imaging at 6-24 weeks post-procedure and suggest imaging at 12 months post-procedure. One-third of DRT cases are diagnosed >6 months following LAAO, but many of these are incidentally discovered, and the diagnostic yield of systematic late imaging follow-up is likely low.
8. Reporting of LAAO device position may include qualitative and quantitative evaluation of implantation depth, device alignment relative to the LAA wall, and relationship with neighboring anatomical structures, including the left upper pulmonary vein (LUPV) ridge. Deep implants (>10 mm from LUPV ridge) have been associated with DRT. Excessive device protrusion into the left atrium (>30% proximal to the landing zone for Watchman devices) is associated with device instability. The LAAO device should be coaxial to the wall of the main appendage lobe; malalignment is associated with peridevice leak (PDL).
9. When PDL is present, CCT reporting should include cross-sectional area and diameters. CCT appears to report larger PDL sizes than TEE.
10. Patient-level risk factors for DRT following LAAO include advanced age, female sex, nonparoxysmal AF, chronic kidney disease, history of stroke, and high CHA₂DS₂-VASc score.

Clinical Topics: Arrhythmias and Clinical EP, Interventions and Imaging, Noninvasive Imaging

Keywords: Atrial Appendage, Computed Tomography, Coronary Occlusion

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