Left Atrial Appendage Occlusion for Stroke Prevention

Rule-based definition of muscle bundles in patient-specific models of the left atrium

Atrial fibrillation (AF) is the most common arrhythmia encountered clinically, and as the population ages, its prevalence is increasing. Although the CHA2DS2- VASc score is the most used risk-stratification system for stroke risk in AF, it lacks personalization. Patient-specific computer models of the atria can facilitate personalized risk assessment and treatment planning. However, a challenge faced in creating such models is the complexity of the atrial muscle arrangement and its influence on the atrial fiber architecture. This work proposes a semi-automated rule-based algorithm to generate the local fiber orientation in the left atrium (LA). We use the solutions of several harmonic equations to decompose the LA anatomy into subregions. Solution gradients define a two-layer fiber field in each subregion. The robustness of our approach is demonstrated by recreating the fiber orientation on nine models of the LA obtained from AF patients who underwent WATCHMAN device implantation. This cohort of patients encompasses a variety of morphology variants of the left atrium, both in terms of the left atrial appendages (LAAs) and the number of pulmonary veins (PVs). We test the fiber construction algorithm by performing electrophysiology (EP) simulations. Furthermore, this study is the first to compare its results with other rule-based algorithms for the LA fiber architecture definition available in the literature. This analysis suggests that a multi-layer fiber architecture is important to capture complex electrical activation patterns. A notable advantage of our approach is the ability to reconstruct the main LA fiber bundles in a variety of morphologies while solving for a small number of harmonic fields, leading to a comparatively straightforward and reproducible approach.

Left atrial appendage occlusion in a mirror-image dextrocardia: A case report and review of literature

BACKGROUND

In mirror-image dextrocardia, the anterior-posterior position of the cardiac chambers and great vessels is maintained, but the left-right orientation of the abdominal organs is reversed. The abnormal anatomy of the heart poses surgical challenges and problems in dealing with surgical risk and monitoring complications. There are few reports on closure of the left atrial appendage (LAA) in dextrocardia and no reports on the application of enhanced recovery after surgery (ERAS) following LAA occlusion (LAAO) procedures.

CASE SUMMARY

The objective for this case was to ensure perioperative safety and accelerate postoperative recovery from LAAO in a patient with mirror-image dextrocardia. ERAS was guided by the theory and practice of nursing care. Atrial fibrillation was diagnosed in a 77-year-old male patient, in whom LAAO was performed. The 2019 guidelines for perioperative care after cardiac surgery recommend that the clinical nursing procedures for patients with LAAO should be optimized to reduce the incidence of perioperative complications and ensure patient safety. Music therapy can be used throughout perioperative treatment and nursing to improve the anxiety symptoms of patients.

CONCLUSION

The procedure was uneventful and proceeded without complications. Anxiety symptoms were improved.

3D Printing in Modern Cardiology

BACKGROUND

3D printing represents an emerging technology in the field of cardiovascular medicine. 3D printing can help to perform a better analysis of complex anatomies to optimize intervention planning.

METHODS

A systematic review was performed to illustrate the 3D printing technology and to describe the workflow to obtain 3D printed models from patient-specific images. Examples from our laboratory of the benefit of 3D printing in planning interventions were also reported.

RESULTS

3D printing technique is reliable when applied to high-quality 3D image data (CTA, CMR, 3D echography), but it still needs the involvement of expert operators for image segmentation and mesh refinement. 3D printed models could be useful in interventional planning, although prospective studies with comprehensive and clinically meaningful endpoints are required to demonstrate the clinical utility.

CONCLUSION

3D printing can be used to improve anatomy understanding and surgical planning.

Value of left atrial diameter with CHA2DS2-VASc score in predicting left atrial/left atrial appendage thrombosis in non-valvular atrial fibrillation

Fundamentos

A fibrilação atrial é a arritmia persistente mais comum e é o principal fator que leva ao tromboembolismo.

Objetivo

Investigar o valor do diâmetro do átrio esquerdo combinado com o escore CHA2DS2-VASc na predição da trombose atrial esquerda/trombose de apêndice atrial esquerdo na fibrilação atrial não valvar.

Métodos

Trata-se de estudo retrospectivo. 238 pacientes com fibrilação atrial não valvar foram selecionados e divididos em dois grupos: trombose e não trombose. Determinou-se o escore CHA2DS2-VASc. Valores de p<0,05 foram considerados estatisticamente significativos.

Resultados

A análise de regressão logística multivariada revelou que histórico de acidente vascular cerebral/ataque isquêmico transitório, doença vascular, escore CHA2DS2-VASc, DAE, DDFVE e FEVE foram fatores de risco independentes para trombose atrial esquerda/trombose de apêndice atrial esquerdo (p<0,05). A análise da curva ROC ( Receiver Operating Characteristic ) revelou que a área sob a curva para o escore CHA2DS2-VASc na predição de trombose atrial esquerda/trombose de apêndice atrial esquerdo foi de 0,593 quando o escore CHA2DS2-VASc foi ≥3 pontos, e a sensibilidade e especificidade foram 86,5% e 32,6%, respectivamente, enquanto a área sob a curva para o DAE na predição de trombose atrial esquerda/trombose de apêndice atrial esquerdo foi 0,786 quando o DAE foi ≥44,17 mm, e a sensibilidade e especificidade foram 89,6% e 60,9%, respectivamente. Entre os diferentes grupos CHA2DS2-VASc, a taxa de incidência de trombose atrial esquerda/trombose de apêndice atrial esquerdo em pacientes com DAE ≥44,17 mm foi maior do que em pacientes com DAE <44,17 mm (p <0,05).

Conclusão

O escore CHA2DS2-VASc e o DAE estão correlacionados com a trombose atrial esquerda/trombose de apêndice atrial esquerdo na fibrilação atrial não valvar. Para pacientes com escore CHA2DS2-VASc de 0 ou 1, quando o DAE é ≥44,17 mm, o risco de trombose atrial esquerda/trombose de apêndice atrial esquerdo permaneceu alto. (Arq Bras Cardiol. 2020; [online].ahead print, PP.0-0)

Boundary-Condition Analysis of an Idealized Left Atrium Model

The most common type of cardiac arrhythmia is atrial fibrillation (AF), which is characterised by irregular and ineffective atrial contraction. This behaviour results into the formation of thrombi, mainly in the left atrial appendage (LAA), responsible for thromboembolic events. Very different approaches are considered as therapy for AF patients. Therefore, it is necessary to yield insight into the flow physics of thrombi formation to determine which is the most appropriate strategy in each case. Computational Fluid Dynamics (CFD) has proven successful in getting a better understanding of the thrombosis phenomenon, but it still requires validation by means of accurate flow field in vivo atrial measurements. As an alternative, in this paper it is proposed an in vitro flow validation, consisting in an idealised model that captures the main flow features observed in the human LA which, once combined with Particle Image Velocimetry (PIV) measurements, provides readily accessible, easy to emulate, detailed velocity fields. These results have been used to validate our laminar and Large Eddy Simulation (LES) simulations. Besides, we have run a parametric study of different boundary conditions sets previously employed in the literature. These data can be used as a benchmark for further development of LA CFD models.

Correlation between LAA Morphological Features and Computational Fluid Dynamics Analysis for Non-Valvular Atrial Fibrillation Patients

The left atrial appendage (LAA) is a complex cardiovascular structure which can yield to thrombi formation in patients with non-valvular atrial fibrillation (AF). The study of LAA fluid dynamics together with morphological features should be investigated in order to evaluate the possible connection of geometrical and hemodynamics indices with the stroke risk. To reach this goal, we conducted a morphological analysis of four different LAA shapes considering their variation during the cardiac cycle and computational fluid dynamics (CFD) simulations in AF conditions were carried out. The analysis of main geometrical LAA parameters showed a huger ostium and a reduced motility for the cauliflower and cactus shapes, as well as a lower velocity values from the CFD analysis. Such findings are in line with literature and highlight the importance of coupling dynamics imaging data with CFD calculations for providing information not available at clinical level.

Role of CT imaging in left atrial appendage occlusion for the WATCHMAN™ device

Computed tomography (CT) plays a key role in the peri-procedural planning of left atrial appendage occlusion (LAAO) device placement and post-procedural evaluation. The geometric variability of the interatrial septum, left atrium, and the left atrial appendage morphology can be fully visualized and intuitively appreciated through CT-derived, patient-specific 3D model unique to each individual's anatomy. This review further defines the strengths and limitations of CT peri-procedural imaging in the planning of LAAO.

Current aspects of TIA management

Transient Ischaemic Attack (TIA) if untreated carries a high risk of early stroke and is associated with poorer long-term survival [1]. There is emerging evidence of a reduction in stroke risk following TIA. Time critical investigations and management, as well as service organisation remain key to achieving good outcomes. Patients are diagnosed with TIA if they have transient, sudden-onset focal neurological symptoms which usually completely and rapidly resolve by presentation. The tissue based definition of TIA guides the fact that patients with residual symptoms should be considered as potentially having a stroke, with urgent evaluation regarding eligibility for thrombolysis and/or endovascular clot retrieval (ECR). Essential investigations for all patients with TIA should include early brain imaging, ECG, and carotid imaging in patients with anterior circulation symptoms. After brain imaging, exclusion of high risk indicators and immediate administration of an antiplatelet agent, subsequent attention to other mechanistic factors can be managed safely as part of a structured clinical pathway supervised by stroke specialists. This is in line with the recently revised Stroke Foundation Clinical Guidelines for Stroke Management (2017).

Simultaneous Functional and Morphological Assessment of Left Atrial Appendage by 3D Virtual Models

Purpose

The left atrial appendage (LAA) is responsible for thrombus formation in patients with atrial fibrillation. The evaluation of both LAA function and morphology is crucial for the patient characterization and the preprocedural planning of LAA closure intervention. Despite the availability of 3D imaging modalities, the current standard image analysis is based on manual delineation of the LAA contours on 2D views.

Methods

In this study, a comprehensive approach based on a full 3D analysis of the tomographic dataset by surface extraction and processing (3D-S) is presented. The proposed method allows extracting functional and morphologic information in the entire cardiac cycle by minimalizing manual user interaction. The proposed methodology has been validated on ten computer tomography datasets.

Results

The proposed 3D-S method was feasible in all cases. Reproducibility was improved with respect to the reference 2D manual procedure (2D-S) (coefficient of variation 2.9 vs. 4.1% for diastolic ostium area; 3.8 vs. 6.1% for systolic ostium area; 2.4 vs. 5.3% for diastolic LAA volume; 2.7 vs. 5.9% for systolic LAA volume; and 7.7 vs. 17.1% for LAA ejection fraction). No significant differences were found between 2D-S and 3D-S measurements.

Conclusions

In this study, we introduced a fully 3D approach for LAA characterization, allowing the simultaneous assessment of LAA function and geometry. The proposed approach could be used to improve the patient selection and the best sizing of the device for LAA closure and to allow a patient-specific 3D printing.

Atrial Fibrillation and Risk of Dementia: Epidemiology, Mechanisms, and Effect of Anticoagulation

Atrial fibrillation (AF) is one of the cardiovascular risk factors for dementia. Several longitudinal studies have reported an association between AF and dementia independently of stroke history. Although the mechanisms underlying this association are not fully understood, proposed mechanisms include cerebral hypoperfusion, inflammation, genetic factors, cerebral microbleeds, and recurrent silent cerebral ischemia. Oral anticoagulation can be used to minimize risk of cognitive decline and dementia, given that brain insults can be caused by chronic microemboli or microbleeds. However, controversy on the effects of warfarin and direct oral anticoagulants on this risk exists. This article will address these aspects, with data on the studies already published and a critical view on this subject.

Thromboembolic events and need for anticoagulation therapy following left atrial appendage occlusion in patients with electrical isolation of the appendage

INTRODUCTION

Electrical isolation of the left atrial appendage (LAA) is an important adjunctive ablation strategy in patients with nonparoxysmal atrial fibrillation (AF). Patients who have impaired LAA contractility following isolation may require long-term oral anticoagulant (OAC) therapy irrespective of their CHADS₂ -VASc score. Percutaneous LAA occlusion (LAAO) is a potential alternative to life-long OAC therapy. We aimed to assess the rate of OAC discontinuation and thromboembolic (TE) events following percutaneous LAAO in patients who underwent LAA electrical isolation (LAAI).

METHODS

This is a retrospective two-center study of patients who underwent percutaneous LAAO following LAAI. Patients with at least 3-month follow-up were included in the study. The antithrombotic therapy and TE events at the time of the last follow-up were noted.

RESULTS

The LAA was successfully occluded in 162 (with Watchman device in 140 [86.4%] and Lariat in 22 [13.6%]). A total of 32 patients had leaks detected on the 45-day transesophageal echocardiogram (TEE); 21 (15%) Watchman and 11 (50%) Lariat cases (P = 0.0001). Two (one Watchman and one Lariat) of the 32 leaks were more than 5 mm. After the 45-day TEE, 150 (92.6%) patients were off-OAC. No TE events were reported in the 150 patients who stopped the anticoagulants. Four (2.47%) patients experienced stroke following the LAAO (three Watchman and one Lariat) procedure while on-OAC, two of which were fatal. At the median follow-up of 18.5 months, 159 (98.15%) patients were off-anticoagulant.

CONCLUSION

Up to 98% of patients with LAAI could safely discontinue OAC after undergoing the appendage closure procedure.

Evaluating the morphology of the left atrial appendage by a transesophageal echocardiographic 3-dimensional printed model

The novel 3-dimensional printing (3DP) technique has shown its ability to assist personalized cardiac intervention therapy. This study aimed to determine the feasibility of 3D-printed left atrial appendage (LAA) models based on 3D transesophageal echocardiography (3D TEE) data and their application value in treating LAA occlusions.Eighteen patients with transcatheter LAA occlusion, and preprocedure 3D TEE and cardiac computed tomography were enrolled. 3D TEE volumetric data of the LAA were acquired and postprocessed for 3DP. Two types of 3D models of the LAA (ie, hard chamber model and flexible wall model) were printed by a 3D printer. The morphological classification and lobe identification of the LAA were assessed by the 3D chamber model, and LAA dimensions were measured via the 3D wall model. Additionally, a simulation operative rehearsal was performed on the 3D models in cases of challenging LAA morphology for the purpose of understanding the interactions between the device and the model.Three-dimensional TEE volumetric data of the LAA were successfully reprocessed and printed as 3D LAA chamber models and 3D LAA wall models in all patients. The consistency of the morphological classifications of the LAA based on 3D models and cardiac computed tomography was 0.92 (P < .01). The differences between the LAA ostium dimensions and depth measured using the 3D models were not significant from those measured on 3D TEE (P > .05). A simulation occlusion was successfully performed on the 3D model of the 2 challenging cases and compared with the real procedure.The echocardiographic 3DP technique is feasible and accurate in reflecting the spatial morphology of the LAA, which may be promising for the personalized planning of transcatheter LAA occlusion.