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Abstract

Objective: The objective was to evaluate the application of transesophageal echocardiography, left atrial appendage angiography, cardiac computed tomography angiography, and three-dimensional reconstruction model in the left atrial appendage occlusion. Methods: A total of 53 patients with persistent atrial fibrillation hospitalized from January 2015 to February 2019 were selected. Transesophageal echocardiography and cardiac computed tomography angiography were performed simultaneously before operation, and three-dimensional reconstruction of the left atrial appendage model was performed based on the cardiac computed tomography angiography findings. The morphology and size of the left atrial appendage were displayed by the left atrial appendage angiography during the operation. Results: Cardiac computed tomography angiography revealed filling defects in the left atrial appendage in four patients, whereas transesophageal echocardiography revealed thrombosis in two patients of the four patients. According to the cardiac computed tomography angiography results, the morphology of the left atrial appendage was classified into chicken wing–like, cauliflower-like, wind vane–like, and cactus-like. The diameters and depths of the left atrial appendage measured by cardiac computed tomography angiography and three-dimensional reconstruction model were found to be the greatest, and the orifice sizes and depths of the left atrial appendage measured by the left atrial appendage angiography were the smallest. Conclusion: Transesophageal echocardiography, left atrial appendage angiography, cardiac computed tomography angiography, and three-dimensional reconstruction model can evaluate the morphology and size of the left atrial appendage. The cardiac computed tomography angiography and three-dimensional reconstruction model could demonstrate the internal structure of the left atrial appendage more clearly.

Keywords

Atrial fibrillation left atrial appendage transesophageal echocardiography cardiac computed tomography angiography Watchman

Introduction

Atrial fibrillation (AF) is the most common type of arrhythmia.¹ Stroke is a common complication of AF and often leads to death or disability in patients, causing serious burden to the patients’ families and the society.^2,3 Prevention of stroke in patients with AF is currently one of the key strategies.^4,5 Due to low compliance and risk of bleeding, the clinical application of oral anticoagulants is limited.^6–8 Therefore, exploring new strategies to prevent stroke in patients with AF has become one of the present highly discussed topics in clinical research. Transcatheter closure of the left atrial appendage (LAA) has been used clinically as a new technique to prevent stroke in patients with non-valvular AF. Its clinical benefits and safety have also been confirmed by many clinical studies.^9–11 However, due to the changeable morphology and irregular opening of the LAA, the success rate and occlusion effect of the LAA occlusion often vary. However, full assessment of the morphology and size of the LAA before surgery can improve the success rate and effectiveness of such occlusion.^12–14 In this study, transesophageal echocardiography (TEE), LAA angiography, cardiac computed tomography angiography (CTA), and three-dimensional (3D) reconstruction model of the heart based on CTA were used to fully evaluate the morphology and structure of the LAA to improve the success rate and effect of LAA occlusion.

Study subjects and methods

Study population

A total of 53 patients with persistent AF hospitalized from January 2015 to February 2019 were selected. All patients provided written informed consent to participate in this study, and the Ethics Committee of the First Affiliated Hospital of Third Military Medical University approved the study protocol (the approval number is KY201941). All patients fulfilled the following inclusion and exclusion criteria.

Inclusion criteria: (a) Persistent non-valvular AF, (b) A CHA₂DS₂VASc score of ≥2, and (c) HAS-BLED score of ≥3 or having a contraindication to anticoagulant therapy or unwilling to receive long-term warfarin therapy.

Exclusion criteria: (a) Thrombosis in the left atrium or LAA, (b) Valvular heart disease, (c) Severe cardiac insufficiency (New York Heart Association (NYHA) IV), (d) Acute stroke within 1 month, and (e) Concomitant complicated severe hepatic and renal insufficiency.

Devices

The LAA occlusion devices used in this study were the Watchman LAA occluder and its delivery system (Boston Scientific, Toledo, OH, USA). The 3D reconstruction model of the LAA was constructed by the joint center of Southwest hospital.

TEE, cardiac CTA, and 3D reconstruction model

All patients underwent TEE to evaluate whether there was thrombus in the LAA, and the maximum orifice size and depth of the LAA were measured from different angles (0°, 45°, 90°, and 135°)(Figure 1).¹⁵ Cardiac CTA was also performed to measure the maximum orifice size and depth of the LAA. At the same time, cardiac perfusion images from cardiac CTA were obtained. The Digital Imaging and Communications in Medicine (DICOM) data were segmented by Materialise Mimics 17.0 image to construct an STL model of the LAA. The STL model of the LAA was then imported into Geomagic Studio 2013 for reverse processing to generate the STP model, which was imported into Siemens Unigraphics NX 8.5 to construct a model of the LAA to estimate the maximum orifice size and depth of the LAA. Then, according to the diameter of the occluder (≥4−6 mm) of the opening of the LAA, a suitable LAA occluder was selected.

Figure 1.

The maximum orifice size and depth of the LAA were measured with TEE from different angles: (a) 0°, (b) 45°, (c) 90°, and (d) 135°.

LAA angiography and LAA occlusion

The operation was performed under general anesthesia with TEE monitoring according to our previous study.¹⁶ The specialized Watchman LAA access sheath was inserted into the LAA through a pigtail catheter. LAA angiography was conducted at the right anterior oblique (RAO) 30° + cranial angulation (CRAN) 20° and RAO 30° + caudal angulation (CAUD)20° to measure the maximum orifice size and depth of the LAA, respectively. After confirming that the position of the LAA occlusion device is appropriate, the occlusion device was released.

Statistical analysis

All data are presented as means ± standard errors. The analysis of variance was used to evaluate the orifice sizes and depths of the LAA. SPSS 13.0 statistical software (SPSS Inc., Chicago, IL, USA) was applied. A p value < 0.05 was the threshold for statistical significance.

Results

Basic characteristics of the patients

A total of 51 patients, including 22 males and 29 females, with persistent AF were enrolled in this study. According to the cardiac CTA results, the morphology of the LAA was classified into chicken wing–like (39.2%), cauliflower-like (19.6%), wind vane–like (17.7%), and cactus-like (23.5%) (details in Table 1).

Table 1.

Patient characteristics.

Patient characteristics	All (n = 51)
Sex	Male (22)
Age (year)	69.1 ± 7.9
BMI (kg/m²)	24.2 ± 3.7
AF time (year)	2.8 ± 2.4
CHA₂DS₂VASc score	4.2 ± 1.4
HAS-BLED score	2.5 ± 0.6
Morphology of LAA
Cauliflower-like	10 (19.6%)
Cactus-like	12 (23.5%)
Chicken wing–like	20 (39.2%)
Wind vane–like	9 (17.7%)

BMI: body mass index; AF: Atrial fibrillation; LAA: left atrial appendage.

Evaluation of the morphology and size of the LAA

Evaluation of the morphology of the LAA

TEE revealed thrombosis in two patients and blood stasis in one patient, and CTA revealed filling defects in the LAA in four patients (including thrombosis in two patients). According to the research results of Wang et al., we classified the morphology of the LAA into chicken wing–like (39.2%), cauliflower-like (19.6%), wind vane–like (17.7%), and cactus-like (23.5%) by cardiac CTA and 3D reconstruction model.

Evaluation of the size of the LAA

TEE was used to measure the maximum orifice size and depth of the LAA from different angles. The measurement results are shown in Table 2. LAA angiography, cardiac CTA, and 3D reconstruction model measured the orifice size and depth of the LAA. The measurement methods are shown in Figure 2, and the measurement results are shown in Table 2.

Table 2.

The maximum orifice size and depths of the LAA measured by TEE, LAA angiography, cardiac CTA, and 3D reconstruction model.

	Maximum orifice size (mm)	Maximum depth (mm)
TEE	20.2 ± 2.5*	27.2 ± 3.0*
LAA angiography	19.4 ± 2.3	26.8 ± 2.4
Cardiac CTA	20.6 ± 2.1*	27.5 ± 2.6*
3D reconstruction model	20.4 ± 2.3*	27.3 ± 2.7*

TEE: transesophageal echocardiography; LAA: left atrial appendage; CTA: computed tomography angiography.

p < 0.05.

Figure 2.

The maximum orifice sizes and depths of the LAA measured by: (a) LAA angiography, (b) cardiac CTA, and (c) 3D reconstruction model (a: LAA orifice size, b: LAA depth).

As is seen Table 2, the orifice size and depth of LAA from LAA angiography were significantly smaller than those from TEE, cardiac CTA, and 3D reconstruction model. The orifice size and depth from cardiac CTA and 3D reconstruction model were the greatest with statistically significant differences (p < 0.05). The selection of the occluder during the operation was guided by the above data.

Discussion

Transcatheter closure of the LAA is a new method to prevent thrombotic events in patients with non-valvular AF. Its clinical benefits and safety have been confirmed by many clinical studies. However, due to the changeable morphology and irregular opening of the LAA, a residual shunt may occur during percutaneous closure of the LAA, which directly affects the outcome of the closure. Therefore, a full preoperative evaluation of the morphology and size of the LAA will help to improve the success rate of the surgery and the occlusion effect.

LAA thrombosis is a contraindication for LAA occlusion.¹⁷ TEE is a common technique for diagnosing LAA thrombosis. It has been confirmed by many studies that the sensitivity and specificity of TEE for diagnosing LAA thrombosis are 100%.¹⁸ In actual operation, the operator should rotate the probe in a large range when using the ultrasonic probe to achieve a comprehensive scan, especially on the top of the left atrium and the LAA, and pay attention to distinguish between the pectinate muscles in the LAA and small thrombi in the LAA. In our study, TEE examination revealed two cases of the LAA thrombosis and one case of the LAA blood stasis, while cardiac CTA revealed another two cases of filling defects. Considering that it is difficult for cardiac CTA to distinguish between the pectinate muscles and thrombi in the LAA, TEE might play a better role than CTA in determining LAA thrombosis.¹⁹

The anatomical structure of the LAA is complex and changeable. CTA can be used to objectively evaluate the morphological structure and variation of the LAA and make objective measurements, thereby providing a good basis for the relevant parameters of the anatomical structure of the LAA.²⁰ At the same time, the 3D structure of the LAA can be obtained through 3D reconstruction which provides the operator with a more realistic visual field perception during surgery and an important reference for LAA occlusion.²¹ Wang et al.²² classified the morphology of the LAA in AF into four types through cardiac CTA examination: chicken wing–like, accounting for 48% (most common); cactus-like, accounting for 30%; and wind vane–like, accounting for 19%, while cauliflower-like, accounting for 3%. Such morphological variations of the LAA cause difficulties in LAA occlusion. For example, the chicken wing–like LAA, which has several curves and an upward tip, is not suitable for using some epicardial device for the LAA. A cauliflower-like LAA may have some small cavities that cannot be blocked after the LAA is blocked due to multiple lobes, thus increasing the risk of residual shunt and thrombosis in the occluder. Based on this study, the 3D structure of the LAA can be clearly displayed on the basis of cardiac CTA combined with a 3D reconstruction model, and the possible situations during the operation can be predicted preoperatively, which is conducive to improving the success rate of the LAA occlusion.

At present, while performing LAA occlusion, selection of the appropriate LAA occluder is crucial to the success of the operation. The size of the occluder is mainly determined by the caliber and depth of the LAA. At present, methods for measuring the size of the LAA include cardiac CTA, TEE, and LAA angiography. There are certain differences among those various measurement methods. TEE can aid in observing and measuring the caliber and depth of the LAA from multiple angles (0°, 45°, 90°, and 135°). Furthermore, the application of 3D TEE can more accurately display the situation of the LAA. CTA can clearly show the morphology and lobulation of the LAA; the 3D reconstruction model based on it can clearly show the internal structure. Although LAA angiography is intuitive, it is subject to relative influence by the left atrial volume, and the contrast agent may affect its measurement. Nucifora G²³ confirmed that TEE measurement underestimates the size of the LAA as compared to that with cardiac CTA. López-Mínguez et al.²⁴ compared the orifice sizes and depths of the LAA measured by cardiac CTA and LAA angiography and demonstrated that cardiac CTA overestimates the size of the LAA. The results of this study show that the orifice sizes and depths of the LAA measured by cardiac CTA and 3D reconstruction model are the greatest, and the orifice size and depth of the LAA measured by LAA angiography are the smallest (p < 0.05). The cause may be related to the location of the LAA angiography catheter, the angle of projection, the amount of contrast agent injected, and the measurement method.

Therefore, the three methods (TEE, cardiac CTA, and LAA angiography) commonly used for the clinical evaluation of the morphology and size of the LAA have their respective advantages and disadvantages.²⁵ Before LAA occlusion, TEE can clearly judge whether there is thrombus in the LAA and measure the basal orifice size and depth of the LAA, thereby providing the basis for the operator to select the occluder model. Cardiac CTA can achieve more objective and accurate measurement of the morphology and lobulation of the LAA and the parameters of the LAA orifice providing more sufficient basis for judging whether LAA occlusion is feasible. Therefore, the combination of the three techniques can provide more useful information before performing LAA occlusion and can effectively improve the success rate of the LAA occlusion.

Limitations

Due to the complex anatomical structure and irregular morphology of the LAA, might be some errors in some of the measurements of the LAA.

Footnotes

Handling Editor: Yuedong Xie

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by Chongqing Science and Health Joint Project under grant nos 2018MSXM141.

ORCID iD

Li Hua Kang

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Application of transesophageal echocardiography,left atrial appendage angiography,cardiac computed tomography angiography,and three-dimensional reconstruction model in left atrial appendage occlusion