ReviewCardiac Computed Tomography Angiography for Left Atrial Appendage Closure
Section snippets
LAA Anatomy
The LAA is highly variable in anatomy, consisting of a blind-ended pouch with tapering tips and trabeculations from pectinate muscles. This morphology promotes stasis and thrombus formation, and indeed the LAA is the harbinger of > 90% of thrombi in patients with nonvalvular AF.3 The LAA length ranges 20-60 mm and the width ranges 16-59 mm.4 The LAA entrance is termed the orifice or ostium, and is often described as oval-shaped (in 68.9%), but might also be round-shaped (5.7%),
Baseline CCTA to Rule Out LAA Thrombus
Multidetector CT (MDCT) has been extensively explored to evaluate for LAA thrombus. Studies have shown conflicting results with MDCT in detecting LAA thrombus, with sensitivities of 29%-100%, specificities of 72%-98%, and positive predictive values (PPVs) of 7%-31%.11, 12, 13, 14, 15, 16 A recent meta-analysis including 19 studies with 2955 patients showed a mean sensitivity of 96%, specificity of 92%, and PPV of 41%.17 The most consistent finding was the strong negative predictive value of
Baseline CCTA Protocol for LAA Closure Preplanning
The high spatial resolution and 3D data provided by MDCT allows detailed morphologic characterization of LAA anatomy. Advantages and disadvantages of CCTA in imaging the LAA are listed in Table 1. Different CT machines and protocols have been used for LAA evaluation in the literature. For 64-detector, settings used included rotation time 400 msec, collimation 64 × 0.5 mm, tube voltage 100-135 kV, tube current 250-400 mA, and images reconstructed at 30%-35% and 75%-85% RR intervals. For
Digital Postprocessing Assessment of the LAA
Digital postprocessing analysis of the LAA and surrounding structures is useful to guide LAA closure for device selection and implantation strategy. Several image processing workstations are available, such as the VitreaWorkstation (Vital, Toshiba Medical Systems Group Co, Zoetermeer, The Netherlands), Aquarius Workstation (TeraRecon Inc, Foster City, CA), Brilliance Workspace (Philips Healthcare, Andover, MA), and the 3mensio software (Pie Medical Imaging, Maastricht, The Netherlands). These
Assessment of the LAA on CCTA for Endovascular Device Closure
To assess for suitability and sizing for percutaneous LAA closure, baseline evaluation of the LAA shape and dimensions are important. The first step is to clearly delineate the LAA ostium and obtain cross-sectional orthogonal images of this point. Conventional axial views alone are often inadequate to assess the LAA ostium, thus, MPR (preferred over MIP) is typically used. We select an oblique view in which the circumflex artery, the PV ridge, and the LAA ostium can be clearly seen in 1 image.
Preprocedural CCTA for the LARIAT (SentreHeart) Procedure
Preprocedural CCTA is necessary to exclude anatomic variants that might preclude the use of LARIAT (SentreHeart, Redwood City, CA), which can occur in up to 20% of cases. These exclusions include large LAA (> 40 mm), posteriorly rotated appendages with apex behind the pulmonary artery, multilobed LAA with combined width in different planes > 40 mm, pericardial adhesions, and posteriorly rotated heart. Volume rendering techniques can also guide pericardial access allowing visualization of the
Postsurveillance Using CCTA After LAA Closure
LAA device surveillance imaging after percutaneous closure is routinely performed to assess for residual leak, device thrombus, device positioning, surrounding structures, and pericardial effusion. CCTA is well suited to assess these features noninvasively after LAA closure. We reported the first series of CCTA follow-up with the ACP device, showing that this modality provided accurate assessment of the position and function of ACP compared with transthoracic echocardiography.28 Also, CT linear
Comparison of CCTA With TEE LAA Assessments
There are limited studies that compared LAA measurements from CCTA, TEE, and cineangiography. In a 37-patient study of ACP implants, measurements taken with the 3 techniques agreed in only 21.6% of cases. CCTA most often predicted the appropriate device size; however, it overmeasured in 21.6% of cases.30 In another series that included 53 patients who had CCTA and TEE before AF ablation, measurements from 3D segmental CT were larger compared with 2-dimensional planar CT and TEE measurements.
Radiation Exposure
The mean radiation dose using our standard LAA CCTA protocol for preprocedural planning or surveillance was approximately 5 mSv. This dosage is considered relatively low and equivalent to the annual background radiation dose of 2-5 mSv. To put in context the relationship between radiation dose and cancer risk, the potential risk of fatal cancer with 10 mSv exposure is only 1:2000. Furthermore, the 2011 position statement from the Radiologic Society of North America and the American Association
Conclusions
CCTA provides superior spatial resolution and 3D structural depiction of the LAA and surrounding structures to facilitate procedural preplanning, to rule out LAA thrombus, and provide postprocedural surveillance for LAA closure. Thus, CCTA might become a feasible noninvasive alternative to 2-dimensional TEE for these purposes. Prospective comparative studies between CCTA and TEE should be performed to further delineate the accuracy of these technologies in LAA device sizing, procedural success,
Disclosures
Dr Jacqueline Saw received research grants (from Canadian Institutes of Health Research, University of British Columbia Division of Cardiology, Boston Scientific, AstraZeneca, Abbott Vascular, St Jude Medical, and Servier), speaker honorarium (AstraZeneca, Boston Scientific, St Jude Medical, and Sunovion), consultant (Boston Scientific, St Jude Medical, AstraZeneca, Abbott Vascular), and proctorship (Boston Scientific, St Jude Medical) honoraria. The other authors have no conflicts of interest
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Cited by (32)
Watchman FLX Implantation for Challenging Left Atrial Appendage Anatomy: Case-Based Discussion
2022, Current Problems in CardiologyCitation Excerpt :A different approach is by utilization of the multidetector computed tomography (MDCT) to provide further details on LAA and using cross-sectional planes to determine the exact level of the landing zone.18 MDCT is not limited by poor acoustic windows, patient discomfort, the anesthesia limitation and it provides more accurate spatial resolution.19,20 Patients are asked to get CT assessment of LAA anatomy and structure in non-sedating states and with limited fasting.
CT assessment of the left atrial appendage post-transcatheter occlusion – A systematic review and meta analysis
2021, Journal of Cardiovascular Computed TomographyCitation Excerpt :CCTA, although currently used as a secondary modality for this purpose, provides a more robust evaluation of LAA by assessing peridevice gap as well as contrast enhancement in the LAA in the absence of a visualized gap. Multiple studies have detected higher rates of peridevice gap with CCTA.10,19,21 Our meta-analysis shows that the utilization of CCTA was associated with almost three times more likelihood of finding LAA patency after LAAOD implantation as compared to TEE.
Left Atrial Appendage Closure: Technical Considerations of Endocardial Closure
2020, Cardiac Electrophysiology ClinicsCitation Excerpt :Delaying imaging 30 to 60 seconds after contrast bolus injection during imaging acquisition is important to differentiate a true filling defect from incomplete contrast mixing with stagnant blood flow in the LAA. With delayed imaging, defects present in the LAA 60 seconds after contrast administration are more likely to represent thrombus.10 In contrast, in patients without filling defects visible in the LAA, a negative predictive value greater than 96% has been reported.
Periprocedural Imaging for Left Atrial Appendage Closure: Computed Tomography, Transesophageal Echocardiography, and Intracardiac Echocardiography
2020, Cardiac Electrophysiology ClinicsExpert Recommendations on Cardiac Computed Tomography for Planning Transcatheter Left Atrial Appendage Occlusion
2020, JACC: Cardiovascular InterventionsCitation Excerpt :The cutoff BMI value varies depending on detector design and sensitivity of the computed tomographic system. Generally, patients with BMIs >27 to 30 kg/m2 may require tube potential >100 kV (23,24), whereas others use an optional correction to the automated software based on the actual weight of the patient (20). The tube current should be adjusted to BMI following the settings recommended by each vendor and may be modulated over the cardiac cycle to save dose by using automated current modulation, a technology available on most scanner systems.
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