Left Atrial Appendage Morphology as a Determinant for Stroke Risk Assessment in Atrial Fibrillation Patients: Systematic Review and Meta-Analysis

The left atrial appendage: An enigmatic friend or foe and implications of closure

The left atrial appendage (LAA) is often thought of as a vestigial organ serving as a nidus for clot formation in those with atrial fibrillation (A-fib). The LAA, however, has unique anatomy which allows it to serve special functions in the human body. Closing the LAA has been shown to decrease the risk of thromboembolic events in patients who cannot tolerate anticoagulation. Several methods of closure exist including percutaneous endocardial closure, epicardial closure, and surgical clipping. In addition to decreasing stroke risk, there appears to be physiologic changes that occur after LAA closure. This comprehensive review aims to describe the functions of the LAA, compare the different methods of closure, and propose a new method for identifying which patients may benefit from LAA closure versus anticoagulation based on each patients' individual comorbidities rather than their contraindications.

Atrial Fibrillation Detection and Load: Knowledge Gaps Related to Stroke Prevention

Atrial fibrillation is a major cause of ischemic stroke. Technological advances now support prolonged cardiac rhythm monitoring using either surface electrodes or insertable cardiac monitors. Four major randomized controlled trials show that prolonged cardiac monitoring detects subclinical paroxysmal atrial fibrillation in 9% to 16% of patients with ischemic stroke, including in patients with potential alternative causes such as large artery disease or small vessel occlusion; however, the optimal monitoring strategy, including the target patient population and the monitoring device (whether to use an event monitor, insertable cardiac monitor, or stepped approach) has not been well defined. Furthermore, the clinical significance of very short duration paroxysmal atrial fibrillation remains controversial. The relevance of the duration of monitoring, burden of device-detected atrial fibrillation, and its proximity to the acute ischemic stroke will require more research to define the most effective methods for stroke prevention in this patient population.

Echocardiography in Percutaneous Left Atrial Appendage Occlusion and Related Complications

Atrial fibrillation (AF) is a devastating disease with a large global prevalence. The left atrial appendage (LAA) is a major source of thrombi in patients with AF. Echocardiography plays an important role in identifying LAA thrombi and has become an invaluable imaging tool in planning for LAA occlusion (LAAO) in patients intolerant to anticoagulation. This review article will discuss the role of echocardiography in selecting patients for LAAO, intraprocedural monitoring, and identifying procedure-related complications.

Accuracy and Reliability of Left Atrial Appendage Morphology Assessment by Three-Dimensional Transesophageal Echocardiographic Glass Rendering Modality: A Comparative Study With Computed Tomography

BACKGROUND

Contrast-enhanced computed tomography is the reference-standard imaging technique to assess left atrial appendage (LAA) morphology. The aim of this study was to evaluate the accuracy and reliability of two-dimensional and new three-dimensional (3D) transesophageal echocardiographic rendering modalities in assessing LAA morphology.

METHODS

Seventy consecutive patients who underwent both computed tomography and transesophageal echocardiography (TEE) were retrospectively enrolled. The traditional LAA morphology classification system (LAAcs; chicken wing, cauliflower, cactus, and windsock) and a new simplified LAAcs based on the LAA bend angle were used for the analysis. LAA morphology was independently assessed by two trained readers using three different modalities: two-dimensional TEE, 3D TEE with multiplanar reconstruction, and a new 3D transesophageal echocardiographic rendering modality with improved transparency (Glass). The new LAAcs and traditional LAAcs were compared in terms of intra- and interrater reliability.

RESULTS

With the new LAAcs, two-dimensional TEE was fairly accurate in identifying LAA morphology (κ = 0.43, P < .05), with moderate interrater (κ = 0.50, P < .05) and substantial intrarater (κ = 0.65, P < .005) agreement. Three-dimensional TEE showed higher accuracy and reliability: 3D TEE with multiplanar reconstruction had almost perfect accuracy (κ = 0.85, P < .001) and substantial (κ = 0.79, P < .001) interrater reliability, while 3D TEE with Glass had substantial accuracy (κ = 0.70, P < .001) and almost perfect (κ = 0.84, P < .001) interrater reliability. Intrarater agreement was almost perfect for both 3D transesophageal echocardiographic modalities (κ = 0.85, P < .001). Accuracy was considerably lower when the traditional LAAcs was used, with 3D TEE with Glass being the most reliable technique (κ = 0.75, P < .05). The new LAAcs showed higher inter- and intrarater reliability compared with the traditional LAAcs (interrater, κ = 0.85 vs κ = 0.49; intrarater, κ = 0.94 vs κ = 0.68; P < .05).

CONCLUSIONS

Three-dimensional TEE is an accurate, reliable, and feasible alternative to computed tomography in assessing LAA morphology with the new LAAcs. The new LAAcs shows higher reliability rates than the traditional one.

Left lateral decubitus computed tomography before catheter ablation in patients with atrial fibrillation

Aim    The study aimed to determine the efficacy of cardiac computed tomography angiography (CCTA) for diagnosing left atrial appendage (LAA) thrombus before catheter ablation with the patient in the left lateral decubitus position and, also, to evaluate the risk factors for thrombus formation.Material and methods    This retrospective, cohort study included 101 patients with atrial fibrillation. All patients underwent transthoracic echocardiography (TTE) and left lateral decubitus CCTA. Transesophageal echocardiography (TEE) was performed to confirm or exclude LAA thrombus. Patients with allergic reactions to iodinated contrast media, increased serum creatinine, hyperthyroidism, pregnancy, and age&lt;18 years were excluded. The CHA2‑DS2‑VASc and HAS-BLED scores were calculated for each patient.Results    All LAA thrombi detected on CCTA were confirmed by TEE. Higher CHA2‑DS2‑VASc, HAS-BLED scores, enlarged LA, and the anteroposterior dimension of the left atrium were significantly associated with the presence of LAA thrombus. A LAA cauliflower shape was a predictor of thrombus. An increase of LAA volume by 1 ml increased the chances of LAA thrombus and cerebral ischemic infarct by 2 %. The growth of the LAA anteroposterior diameter by 1 cm increased the risk of LAA thrombus by 190 % and of cerebral infarct by 78 %. An increase in the CHA2DS2‑VASc score by 1 point increased the risk of thromboembolism and cerebral infarction by 12 %.Conclusions    CCTA performed in the left lateral decubitus position of the patient is an optimal screening tool to detect or exclude LAA thrombus before catheter ablation because of atrial fibrillation. CCTA has predictive value for risk of thrombosis formation in LAA.

Does left atrial appendage morphology and dimension differ amongst etiological stroke subtypes in patients without known atrial fibrillation? Results from the left atrial appendage morphology and dimension assessment by TEE in patients with stroke without known atrial fibrillation (LAMDA-STROKE) study

CONTEXT

Complex left atrial appendage (LAA) morphology is increasingly associated with cryptogenic ischemic stroke as compared to cardioembolic stroke due to atrial fibrillation (AF). However, data on such an association in patients with other etiological stroke subtypes in the absence of AF is limited.

AIM

The study aimed to assess the LAA morphology, dimension and other echocardiographic parameters by transesophageal echocardiography (TEE) in patients with embolic stroke of undetermined source (ESUS) and compare it with other etiological stroke subtypes without known AF.

METHODS

This was a single-Centre, observational study involving comparison of echocardiographic parameters including LAA morphology and dimension in ESUS patients (group A; n = 30) with other etiological stroke subtypes i.e., TOAST (Trial of Org 10172 in Acute Stroke Treatment) class I-IV without AF (group B; n = 30).

RESULTS

Complex LAA morphology was predominant in group A (18 patients in group A versus 5 patients in group B, p-Value = 0.001). Mean LAA orifice diameter (15.3 + 3.5 mm in group A versus 17 + 2.0 mm in group B, p-Value = 0.027) and LAA depth were significantly lower in group A (28.4 + 6.6 mm in group A versus 31.7 + 4.3 mm in group B, p-Value = 0.026). Out of these three parameters only complex LAA morphology was found to be independently associated with ESUS [OR = 6.003, 95% CI {1.225-29.417}, p = 0.027].

CONCLUSION

Complex LAA morphology is a predominant feature in ischemic stroke patients with ESUS and may contribute to an increased risk of stroke in these patients.

Impact of left atrial appendage morphology on thrombus formation in TAVI patients with atrial fibrillation

PURPOSE

We aimed to correlate left atrial appendage (LAA) morphology with thrombus formation in patients with severe aortic valve stenosis and atrial fibrillation.

METHODS

We analyzed LAA morphology and the prevalence of a thrombus in 231 patients with atrial fibrillation and severe aortic valve stenosis that were referred for pre-interventional CT scan before trans-catheter aortic valve implantation (TAVI) between 2016 and 2018. In addition, we documented neuro-embolic events depending on the presence of LAA thrombus within a follow-up of 18 months.

RESULTS

The overall distribution of different LAA morphologies was chicken-wing 25.5%, windsock 51.5%, cactus 15.6% and cauliflower 7.4%. Compared to chicken-wing morphology, patients with non-chicken-wing morphology showed a significantly higher thrombus rate (OR: 2.48, 95%; CI 1.05 to 5.86, p = 0.043). Within the 50 patients with a LAA thrombus, we observed chicken-wing (14.0%), windsock (62.0%), cactus (16.0%) and cauliflower (8.0%) configuration. In patients with LAA thrombus those with chicken-wing configuration have a higher risk (42.9%) to develop neuro-embolic events compared to non-chicken-wing configuration (20.9%).

CONCLUSION

We found a lower LAA thrombus rate in patients with chicken-wing morphology compared to patients with non-chicken-wing configuration. However, in the presence of thrombus, those patients with chicken-wing morphology showed a doubled risk for neuro-embolic events compared to patients with non-chicken-wing morphology. These results must be confirmed in larger trials but underline the importance of LAA evaluation in thoracic CT scans and could have an impact on the anticoagulation management.

Left atrial appendage closure in patients with reversed chicken-wing morphology: Anatomical features and procedural strategy

Background

Left atrial appendage (LAA) closure (LAAC) in atrial fibrillation (AF) patients with the reversed chicken-wing (RCW) LAA is challenging.

Aims

To elucidate the LAAC strategy of the RCW-LAA.

Methods

A total of 802 AF patients who were enrolled in the LAACablation registry for LAAC procedure were included, 55 of whom presented with the RCW-LAA. The WATCHMAN device was implanted using the standard protocol when the sheath depth was no less than the device depth (the simple group). For those with a sheath depth of less than the device depth (the complex group), device deployment was attempted with acceptable protrusion or after a repeated atrial transseptal puncture (re-ATP) at a more inferior and anterior position. The anatomical and procedural features were compared between groups and before and after the re-ATP.

Results

The success rate of LAAC was significantly lower in patients with the RCW-LAA than with the other morphologies (92.7% vs. 98.8%, p = 0.001). Compared with the simple group, the complex group had shorter root depth and shorter neck length, and more LAAs in the complex group were at lower position (all p < 0.05). The sheath depth after the re-ATP was significantly greater than that before the re-ATP (18.8 ± 3.4 mm vs. 14.7 ± 2.6 mm, p < 0.001). For the patients who underwent re-ATP, the sheath went significantly deeper in successful procedures than in aborted procedures (19.7 ± 3.3 mm vs. 15.8 ± 1.8 mm, p = 0.040).

Conclusions

The anatomical features of the RCW-LAA were related to the complexity of the LAAC procedure. The re-ATP at an inferior and anterior location could increase the success rate of LAAC.

ClinicalTrialsgov

NCT03788941.

Association Between Left Atrial Appendage Morphology and Function and the Risk of Ischaemic Stroke in Patients with Atrial Fibrillation

AF is the most common cardiac arrhythmia and has been identified as an independent risk factor for stroke. The European Society of Cardiology guidelines recommend a thromboembolic event risk assessment based on the CHA₂DS₂-VASc score. However, stroke also occurs in some patients with a low CHA₂DS₂-VASc score. Therefore, it is necessary to find new factors to improve thromboembolic risk stratification in AF patients. Over 90% of embolic strokes are caused by thrombi originating from the left atrial appendage (LAA). Thus, certain anatomical or functional parameters of the LAA could potentially be used to predict cardioembolic stroke. Studies have suggested that some of these factors, such as LAA morphology, number of LAA lobes, LAA dimensions, LAA volume, distance from the LAA ostium to the first bend of LAA, LAA orifice diameter, extent of LAA trabeculations, LAA takeoff, LAA flow velocity and LAA strain rate, are independently associated with a higher risk of stroke in a population of patients with AF and improve the performance of the CHA₂DS₂-VASc score. However, the results are conflicting and, so far, no new parameter has been added to the CHA₂DS₂-VASc score.

A Review of Biomarkers for Ischemic Stroke Evaluation in Patients With Non-valvular Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia worldwide and results in a significantly increased ischemic stroke (IS) risk. IS risk stratification tools are widely being applied to guide anticoagulation treatment decisions and duration in patients with non-valvular AF (NVAF). The CHA₂DS₂-VASc score is largely validated and currently recommended by renowned guidelines. However, this score is heavily dependent on age, sex, and comorbidities, and exhibits only moderate predictive power. Finding effective and validated clinical biomarkers to assist in personalized IS risk evaluation has become one of the promising directions in the prevention and treatment of NVAF. A number of studies in recent years have explored differentially expressed biomarkers in NVAF patients with and without IS, and the potential role of various biomarkers for prediction or early diagnosis of IS in patients with NVAF. In this review, we describe the clinical application and utility of AF characteristics, cardiac imaging and electrocardiogram markers, arterial stiffness and atherosclerosis-related markers, circulating biomarkers, and novel genetic markers in IS diagnosis and management of patients with NVAF. We conclude that at present, there is no consensus understanding of a desirable biomarker for IS risk stratification in NVAF, and enrolling these biomarkers into extant models also remains challenging. Further prospective cohorts and trials are needed to integrate various clinical risk factors and biomarkers to optimize IS prediction in patients with NVAF. However, we believe that the growing insight into molecular mechanisms and in-depth understanding of existing and emerging biomarkers may further improve the IS risk identification and guide anticoagulation therapy in patients with NVAF.

Statistical shape analysis of the left atrial appendage predicts stroke in atrial fibrillation

The shape of the left atrium (LA) and left atrial appendage (LAA) have been shown to predict stroke in patients with atrial fibrillation (AF). Prior studies rely on qualitative assessment of shape, which limits reproducibility and clinical utility. Statistical shape analysis (SSA) allows for quantitative assessment of shape. We use this method to assess the shape of the LA and LAA and predict stroke in patients with AF. From a database of AF patients who had previously undergone MRI of the LA, we identified 43 patients with AF who subsequently had an ischemic stroke. We also identified a cohort of 201 controls with AF who did not have a stroke after the MRI. We performed SSA of the LA and LAA shape to quantify the shape of these structures. We found three of the candidate LAA shape parameters to be predictive of stroke, while none of the LA shape parameters predicted stroke. When the three predictive LAA shape parameters were added to a logistic regression model that included the CHA₂DS₂-VASc score, the area under the ROC curve increased from 0.640 to 0.778 (p = .003). The shape of the LA and LAA can be assessed quantitatively using SSA. LAA shape predicts stroke in AF patients, while LA shape does not. Additionally, LAA shape predicts stroke independent of CHA₂DS₂-VASc score. SSA for assessment of LAA shape may improve stroke risk stratification and clinical decision making for AF patients.

Three-Dimensional Echocardiographic Left Atrial Appendage Volumetric Analysis

BACKGROUND

Left atrial appendage (LAA) echocardiographic assessment is difficult because of the complex shape and relatively small size of the LAA. Three-dimensional (3D) echocardiographic imaging can overcome the limitations of two-dimensional imaging. Pulsed-wave Doppler is the only currently standard LAA functional parameter. The aim of this study was to test a new approach for 3D echocardiographic volumetric analysis to obtain LAA ejection fraction (EF), its size and shape.

METHODS

Transesophageal two-dimensional and 3D LAA images were prospectively obtained in 159 consecutive patients. LAA volumes were measured from 3D echocardiographic images using available software. Pulsed-wave Doppler was considered the reference value for LAA function and was used for comparison with LAA EF. Comparison with cardiac computed tomography was performed in a subgroup of 32 patients. Comparisons included linear regression and Bland-Altman analyses. Repeated measurements were performed to assess measurement variability.

RESULTS

Nine patients were excluded because of suboptimal image quality (94% feasibility). Three-dimensional LAA calculated EF was in good agreement with LAA pulsed-wave measurements. Three-dimensional morphologic evaluation showed that 43% of the patients had "chicken wing," 33% "cactus," 19% "windsock," and 5% cauliflower shapes. At the time of data acquisition, patients with atrial fibrillation had nonsignificantly larger LAA end-systolic and end-diastolic volumes, leading to lower calculated EFs. Three-dimensional echocardiographic LAA end-systolic volumes were in good agreement with cardiac computed tomography (r = 0.75), with small biases (mean, -2.5 ± 3.9 ml). Reproducibility was better for larger LAA volumes.

CONCLUSIONS

A novel 3D echocardiographic approach can determine the geometry, size, and function of the LAA. A new parameter, LAA EF, provides functional quantitation.

Left atrial appendage morphology at transesophageal echocardiography: how to improve reproducibility?

BACKGROUND

Left atrial appendage (LAA) morphology, investigated by computed tomography and magnetic resonance imaging, has proved to relate to the risk of cerebrovascular events in patients with atrial fibrillation (AF). The aim of the present study was to assess reproducibility of transesophageal echocardiography (TEE) imaging in describing LAA morphology.

METHODS

Two-hundred consecutive patients referred for TEE were enrolled. In the first group of 47 (23.5%) patients LAA morphology was analyzed by conventional TEE and described as ChickenWing, Windsock, Cactus or Cauliflower. In the second group of 153 (76.5%) patients, instead, a 3D-Xplane diagnostic algorithm was performed to stratify LAA morphology as linear (ChickenWing) or complex (Windsock/Cactus and Cauliflower). Interobserver variability within three independent readers was assessed in both groups of patients and stratified by operator's experience and training. In a subgroup of 19 (12.4%) patients, the agreement of LAA morphology description by 3D-Xplane diagnostic algorithm was compared to cardiac magnetic resonance.

RESULTS

By conventional TEE the agreement among operators on LAA morphology classification was poor (ρ<0.13). The 3D-XPlane diagnostic algorithm, significantly increased interobserver agreement up to ρ=0.32 within all readers and up to ρ=0.82 among the experienced and specifically trained operators. LAA morphology description in this latter group provided strong agreement with cardiac magnetic resonance (up to ρ=0.77).

CONCLUSIONS

LAA morphology assessment is challenging by conventional TEE. To improve reproducibility, the use of the 3D-Xplane technique combined with a specific diagnostic algorithm and training of the operators is fundamental.