Elsevier

Canadian Journal of Cardiology

Volume 32, Issue 8, August 2016, Pages 1033.e1-1033.e9
Canadian Journal of Cardiology

Review
Cardiac Computed Tomography Angiography for Left Atrial Appendage Closure

https://doi.org/10.1016/j.cjca.2015.09.020Get rights and content

Abstract

Atrial fibrillation is prevalent and percutaneous left atrial appendage (LAA) closure is increasingly performed worldwide. This procedure is technically challenging and the success and procedural complexities depend on anatomy of the LAA and surrounding structures. These are readily depicted on cardiac computed tomography angiography (CCTA), which offers unique imaging planes. CCTA allows not only preplanning anatomic LAA assessment, but can also be used to evaluate for pre-existing LAA thrombus, and done postprocedure for surveillance for device-related thrombus, residual leak, and complications. In this article, we review the practical utility of CCTA for LAA closure.

Résumé

Puisque la fibrillation auriculaire est répandue, la fermeture de l’appendice auriculaire gauche (AAG) par voie percutanée est de plus en plus pratiquée à l’échelle mondiale. Le succès et les complexités de cette intervention techniquement difficile dépendent de l’anatomie de l’AAG et des structures environnantes. Celles-ci sont facilement distinguées à l’angiographie cardiaque par tomodensitométrie (angiographie cardiaque par TDM), qui offre des plans d’imagerie uniques. L’angiographie cardiaque par TDM permet non seulement la préplanification de l’évaluation anatomique de l’AAG, mais peut également être utilisée pour évaluer le thrombus préexistant dans l’AAG, et effectuée en post-intervention pour la surveillance du thrombus lié au dispositif, de la fuite résiduelle et des complications. Dans le présent article, nous passons en revue l’utilité pratique de l’angiographie cardiaque par TDM pour la fermeture de l’AAG.

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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