Volume and morphology of left atrial appendage as determinants of stroke subtype in patients with atrial fibrillation

Left Atrial Appendage Pseudothrombus Is Associated With Stroke History in Patients With Atrial Fibrillation Undergoing Cardiac Computed Tomography

BACKGROUND

In nonvalvular atrial fibrillation (NVAF), the left atrial appendage (LAA) is the source of thrombus in up to 90% of patients. LAA pseudothrombus (LAAPT), defined as a filling defect on the initial but not the 60-second delayed acquisition on cardiovascular computed tomography scan (CCT), is a recognized phenomenon in NVAF, with unknown clinical relevance. We aimed to determine the relationship between LAAPT and history of stroke in patients with NVAF.

METHODS AND RESULTS

The study included 213 consecutive patients with NVAF undergoing CCT who were assessed for LAAPT. LA and LAA dimensions and LAA morphology correlated with clinical demographics including cardiovascular risk factors, history of stroke, thromboembolic stroke, and transient ischemic attack. Mean age (±SD) was 65.1±10.5 years (range 31-89) and 150 of 213 (70.4%) were men. LAAPT was present in 59 of 213 (27.7%) patients. Greater mean LAA ostium area (5.7 versus 4.5, P<0.001), greater mean LAA ostium area:curved length (0.11 versus 0.08, P<0.001), increased LAA volume (14.0 versus 10.2, P<0.001), and lower mean LAA tortuosity index (1.17 versus 1.38, P<0.001) were all associated with the presence of LAAPT. On multivariable analysis, LAAPT on CCT (odds ratio [OR], 3.20 [95% CI, 1.40-7.20]; P<0.006) and higher CHA2DS2-VASc score (OR, 1.65 [95% CI, 1.16-2.35]; P=0.01) were associated with all strokes, with LAAPT remaining a statistically significant risk factor even after adjustment for CHA2DS2-VASc score.

CONCLUSIONS

LAAPT on CCT is common in patients with NVAF. It has a strong positive association with stroke prevalence, even after adjustment for CHA2DS2-VASc score. LAAPT on CCT may potentially allow further stratification for stroke risk, additive to the CHA2DS2-VASc score.

Slow blood-flow in the left atrial appendage is associated with stroke in atrial fibrillation patients

Background

Atrial fibrillation (AF) patients are at high risk of stroke with ∼90% clots originating from the left atrial appendage (LAA). Clinical understanding of blood-flow based parameters and their potential association with stroke for AF patients remains poorly understood. We hypothesize that slow blood-flow either in the LA or the LAA could lead to the formation of blood clots and is associated with stroke for AF patients.

Methods

We retrospectively collected cardiac CT images of paroxysmal AF patients and dichotomized them based on clinical event of previous embolic event into stroke and non-stroke groups. After image segmentation to obtain 3D LA geometry, patient-specific blood-flow analysis was performed to model LA hemodynamics. In terms of geometry, we calculated area of the pulmonary veins (PVs), mitral valve, LA and LAA, orifice area of LAA and volumes of LA and LAA and classified LAA morphologies. For hemodynamic assessment, we quantified blood flow velocity, wall shear stress (WSS, blood-friction on LA wall), oscillatory shear index (OSI, directional change of WSS) and endothelial cell activation potential (ECAP, ratio of OSI and WSS quantifying slow and oscillatory flow) in the LA as well as the LAA. Statistical analysis was performed to compare the parameters between the groups.

Results

Twenty-seven patients were included in the stroke and 28 in the non-stroke group. Examining geometrical parameters, area of left inferior PV was found to be significantly higher in the stroke group as compared to non-stroke group (p = 0.026). In terms of hemodynamics, stroke group had significantly lower blood velocity (p = 0.027), WSS (p = 0.018) and higher ECAP (p = 0.032) in the LAA as compared to non-stroke group. However, LAA morphologic type did not differ between the two groups. This suggests that stroke patients had significantly slow and oscillatory circulating blood-flow in the LAA, which might expose it to potential thrombogenesis.

Conclusion

Slow flow in the LAA alone was associated with stroke in this paroxysmal AF cohort. Patient-specific blood-flow analysis can potentially identify such hemodynamic conditions, aiding in clinical stroke risk stratification of AF patients.

The role of the pulmonary veins on left atrial flow patterns and thrombus formation

Atrial fibrillation (AF) is the most common human arrhythmia, forming thrombi mostly in the left atrial appendage (LAA). However, the relation between LAA morphology, blood patterns and clot formation is not yet fully understood. Furthermore, the impact of anatomical structures like the pulmonary veins (PVs) have not been thoroughly studied due to data acquisition difficulties. In-silico studies with flow simulations provide a detailed analysis of blood flow patterns under different boundary conditions, but a limited number of cases have been reported in the literature. To address these gaps, we investigated the influence of PVs on LA blood flow patterns and thrombus formation risk through computational fluid dynamics simulations conducted on a sizeable cohort of 130 patients, establishing the largest cohort of patient-specific LA fluid simulations reported to date. The investigation encompassed an in-depth analysis of several parameters, including pulmonary vein orientation (e.g., angles) and configuration (e.g., number), LAA and LA volumes as well as their ratio, flow, and mass-less particles. Our findings highlight the total number of particles within the LAA as a key parameter for distinguishing between the thrombus and non-thrombus groups. Moreover, the angles between the different PVs play an important role to determine the flow going inside the LAA and consequently the risk of thrombus formation. The alignment between the LAA and the main direction of the left superior pulmonary vein, or the position of the right pulmonary vein when it exhibits greater inclination, had an impact to distinguish the control group vs. the thrombus group. These insights shed light on the intricate relationship between PV configuration, LAA morphology, and thrombus formation, underscoring the importance of comprehensive blood flow pattern analyses.

A highly-detailed anatomical study of left atrial auricle as revealed by in-vivo computed tomography

The left atrial auricle (LAA) is the main source of intracardiac thrombi, which contribute significantly to the total number of stroke cases. It is also considered a major site of origin for atrial fibrillation in patients undergoing ablation procedures. The LAA is known to have a high degree of morphological variability, with shape and structure identified as important contributors to thrombus formation. A detailed understanding of LAA form, dimension, and function is crucial for radiologists, cardiologists, and cardiac surgeons. This review describes the normal anatomy of the LAA as visualized through multiple imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and echocardiography. Special emphasis is devoted to a discussion on how the morphological characteristics of the LAA are closely related to the likelihood of developing LAA thrombi, including insights into LAA embryology.

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.

Left atrial appendage dimension predicts elevated brain natriuretic peptide in nonvalvular atrial fibrillation

INTRODUCTION

BNP elevation in patients with AF is observed in the absence of heart failure; however, prior mechanistic studies have not included direct left atrial pressure measurements. This study sought to understand how emptying function of the left atrial appendage (LAA) and LAA dimension contributes to brain-natriuretic peptide elevations (BNP) in atrial fibrillation (AF) accounting for left atrial pressure (LAP).

METHODS

132 patients referredfor left atrial appendage occlusion (LAAO) were prospectively enrolled in this study. BNP levels and LAP were measured just before LAAO. Statistical analysis considered BNP, rhythm at time of procedure, LAP, LAA morphology, LAA size (ostial diameter, depth, volume), LAA emptying velocity, CHADS2-VASc score, body mass index (BMI), left ventricular ejection fraction (LVEF), estimated glomerular filtration rate (eGFR), and obstructive sleep apnea (OSA) diagnosis as covariates.

RESULTS

Bivariate statistical analysis demonstrated positive associations with age, LAA ostial diameter, depth, and volume, LAP, AF status at time of measurement, OSA, and CHADS2-VASc score. BNP was negatively associated with LVEF, eGFR, LAA emptying velocity and BMI. With multivariate logistic regression including LAP as covariate, significant relationships between BNP and AF/AFL(OR 1.99 [1.03, 3.85]), LAP (OR 1.13 [1.06, 1.20]), LAA diameter (OR 1.14 [1.03, 1.27]), LAA depth (OR 1.14 [1.07, 1.22]), and LAA emptying velocity (OR 0.97 [0.96,0.99]) were observed; however, no significant associations were seen with LAA morphology or CHADS2-VASc score.

CONCLUSIONS

BNP elevations in AF are associated with LAA size and function, but not CHADS2-VASc score or appendage morphology after accounting for changes in LAP.

Role of Cardiovascular Magnetic Resonance in the Management of Atrial Fibrillation: A Review

Atrial fibrillation (AF) is the most common arrhythmia, and its prevalence is growing with time. Since the introduction of catheter ablation procedures for the treatment of AF, cardiovascular magnetic resonance (CMR) has had an increasingly important role for the treatment of this pathology both in clinical practice and as a research tool to provide insight into the arrhythmic substrate. The most common applications of CMR for AF catheter ablation are the angiographic study of the pulmonary veins, the sizing of the left atrium (LA), and the evaluation of the left atrial appendage (LAA) for stroke risk assessment. Moreover, CMR may provide useful information about esophageal anatomical relationship to LA to prevent thermal injuries during ablation procedures. The use of late gadolinium enhancement (LGE) imaging allows to evaluate the burden of atrial fibrosis before the ablation procedure and to assess procedural induced scarring. Recently, the possibility to assess atrial function, strain, and the burden of cardiac adipose tissue with CMR has provided more elements for risk stratification and clinical decision making in the setting of catheter ablation planning of AF. The purpose of this review is to provide a comprehensive overview of the potential applications of CMR in the workup of ablation procedures for atrial fibrillation.

Patients With Larger Left Atrial Appendage Orifice Presented Worse Prognosis Contributed by Acute Heart Failure After Left Atrial Appendage Closure

Background

Left atrial appendage (LAA) closure (LAAC) could prevent stroke in patients with atrial fibrillation. However, LAAC may impair the compliance of the left atrium and result in poor prognosis. This study aimed to comparatively evaluate the prognosis of LAAC among patients with different sizes of LAA orifice.

Methods and Results

Three hundred two consecutive patients who underwent successful LAAC were included and divided into 4 groups based on LAA orifice size that was measured using transesophageal echocardiography. Clinical outcomes including thromboembolic events, major cardiocerebrovascular adverse events, and acute heart failure (AHF) were compared among 4 quartile groups and between propensity‐score matched groups of large and small LAAs. Through follow‐up of 39.6±8.4 months, survival of thromboembolic events was similar. Survival of major cardiocerebrovascular adverse events was significantly lower in the group with the largest LAA orifice (log‐rank P <0.001), including a higher incidence of AHF with New York Heart Association class III to IV (21.4%, log‐rank P =0.009). A large LAA orifice (by cutoff) could predict major cardiocerebrovascular adverse events (hazard ratio, 3.749 [95% CI, 2.074–6.779]) in most patients, except for subgroups of those aged <65 years, with paroxysmal atrial fibrillation, and/or with failed rhythm/rate control. Further compared with a propensity‐score matched small‐LAA group, the large‐LAA orifice group still presented worse survival of AHF with New York Heart Association class III to IV (log‐rank P =0.010).

Conclusions

Patients with a larger LAA orifice presented a worse prognosis after LAAC, including a higher incidence of AHF. A large LAA orifice could predict a post‐LAAC AHF event in most patients, except for young patients, patients with paroxysmal atrial fibrillation, and/or with failed rhythm/rate control.

Registration

URL: clinicaltrials.gov ; Unique identifier: NCT04185142.

Stroke risk evaluation for patients with atrial fibrillation: Insights from left atrial appendage

Left atrial appendage (LAA) is believed to be a common site of thrombus formation in patients with atrial fibrillation (AF). However, the commonly-applied stroke risk stratification model (such as. CHA2DS2-VASc score) does not include any structural or hemodynamic features of LAA. Recent studies have suggested that it is important to incorporate LAA geometrical and hemodynamic features to evaluate the risk of thrombus formation in LAA, which may better delineate the AF patients for anticoagulant administration and prevent strokes. This review focuses on the LAA-related factors that may be associated with thrombus formation and cardioembolic events.

Morphological characteristics of symptomatic and asymptomatic carotid webs

OBJECTIVE

Carotid webs (CWs) are an increasingly recognized source of recurrent stroke among young patients without conventional vascular risk factors. There have been no previous studies demonstrating that specific web morphological characteristics correlate with a higher stroke risk. The authors aim to report distinct morphological features of symptomatic and asymptomatic CWs.

METHODS

The authors performed a cross-sectional study of patients with CWs detected on CT angiography (CTA) of the neck. Patients were categorized based on whether or not they presented with stroke ipsilaterally and if it was likely to be attributable to their web. The following CW morphological variables were recorded and compared based on CTA: length, thickness, angle, and the proportion of carotid bulb lumen occupied by the web (web-to-bulb ratio [WBR]).

RESULTS

A total of 86 CWs were identified, 14 of which presented with stroke (16.3%). Patients presenting with stroke had webs that were significantly longer (4.18 mm vs 2.20 mm, p = 0.001) and were situated at more acute angles relative to the carotid wall (73.2° vs 94.9°, p = 0.004). Additionally, patients presenting with stroke had higher WBRs compared to the asymptomatic cohort (0.50 vs 0.36, p = 0.008). The optimal threshold associated with stroke was web length ≥ 3.1 mm (OR 15.2, 95% CI 3.73–61.8; p < 0.001), web angle ≤ 90.1° (OR 5.00, 95% CI 1.42–17.6; p = 0.012), and WBR ≥ 0.50 (OR 30.0, 95% CI 5.94–151; p < 0.001).

CONCLUSIONS

Patients with CWs that occupy more than half of the diameter of the carotid bulb lumen and are situated at acute angles relative to the carotid wall are more likely to present with acute ischemic stroke. Additional studies are needed to determine the long-term outcomes of these lesions.

Joint Analysis of Morphological Parameters and In Silico Haemodynamics of the Left Atrial Appendage for Thrombogenic Risk Assessment

Background. Atrial fibrillation (AF) is considered the most common human arrhythmia. In nonvalvular AF, around 99% of thrombi are formed in the left atrial appendage (LAA). Nevertheless, there is not a consensus in the community about the relevant factors to stratify the AF population according to thrombogenic risk. Objective. To demonstrate the need for combining left atrial morphological and haemodynamics indices to improve the thrombogenic risk assessment in nonvalvular AF patients. Methods. A cohort of 71 nonvalvular AF patients was analysed. Statistical analysis, regression models, and random forests were used to analyse the differences between morphological and haemodynamics parameters, extracted from computational simulations built on 3D rotational angiography images, between patients with and without transient ischemic attack (TIA) or cerebrovascular accident (CVA). Results. The analysis showed that models composed of both morphological and haemodynamic factors were better predictors of TIA/CVA compared with models based on either morphological or haemodynamic factors separately. Maximum ostium diameter, length of the centreline, blood flow velocity within the LAA, oscillatory shear index, and time average wall shear stress parameters were found to be key risk factors for TIA/CVA prediction. In addition, TIA/CVA patients presented more flow stagnation within the LAA. Conclusion. Thrombus formation in the LAA is the result of multiple factors. Analyses based only on morphological or haemodynamic parameters are not precise enough to predict such a phenomenon, as demonstrated in our results; a better patient stratification can be obtained by jointly analysing morphological and haemodynamic features.

A comprehensive comparison of various patient-specific CFD models of the left atrium for atrial fibrillation patients

BACKGROUND

Recently, advances in medical imaging, segmentation techniques, and high-performance computing have supported the use of patient-specific computational fluid dynamics (CFD) simulations. At present, CFD-compatible atrium geometries can be easily reconstructed from atrium images, providing important insight into the atrial fibrillation (AF) phenomenon, and assistance during therapy selection and surgical procedures. However, the hypothesis assumed for such CFD models should be adequately validated.

AIM

This work aims to perform an extensive study of the different hypotheses that are commonly assumed when performing atrial simulations for AF patients, as well as to evaluate and compare the range of indices that are usually applied to assess thrombus formation within the left atrium appendage (LAA).

METHODS

The atrial geometries of two AF patients have been segmented. The resulting geometries have been registered and interpolated to construct a dynamic mesh, which has been employed to compare the rigid and flexible models. Two families of hemodynamic indices have been calculated and compared: wall shear-based and blood age distribution-based.

RESULTS

The findings of this study illustrate the importance of validating the rigid atrium hypothesis when utilizing an AF CFD model. In particular, the absence of the A-wave contraction does not avoid a certain degree of passive atrial contraction, making the rigid model a poor approximation in some cases. Moreover, a new thrombosis predicting index has been proposed, i.e., M4, which has been shown to predict stasis more effectively than other indicators.

Impact of low-voltage zones on the left atrial anterior wall on the reduction in the left atrial appendage flow velocity in persistent atrial fibrillation patients

BACKGROUND

The reduction in the left atrial appendage (LAA) flow velocity is related to the presence of emboli in atrial fibrillation (AF) patients. The LAA is located on the left superior side of the left atrial (LA) anterior wall, and we investigated the relationship between the reduction in the LAA flow velocity (LAAFV) and low voltage zones (LVZs < 0.5 mV) on the LA anterior wall.

METHODS

In 146 persistent AF patients, LAAFV measurements, by transesophageal echocardiography, and catheter ablation were performed. LA mapping was performed before ablation during sinus rhythm, and the locations of any anterior-LVZs were documented.

RESULTS

Eighty-one patients had a documented LVZ on the LA anterior wall, and those with an LVZ had a significantly lower LAAFV compared to those without (anterior-LVZ(+) vs. anterior-LVZ(-) = 26 ± 11 vs. 34 ± 10 cm/s, p < 0.001), while no significant difference was observed when compared to the other LVZ regions. A low-LAAFV (≦ 20 cm/s) was observed in 36 patients, and the CHADS₂-vasc score and existence of an anterior-LVZ were associated with a low-LAAFV. In patients with anterior-LVZs, the distance between the anterior-LVZ and LAA orifice correlated with a low LAAFV (r = 0.534, p < 0.001) as compared to the surface area of the anterior-LVZ (r = - 0.288, p = 0.009).

CONCLUSIONS

In persistent AF patients, an LVZ on the LA anterior wall was associated with a low LAAFV. In addition, an anterior-LVZ located near the LAA orifice was further related to a reduction in the LAAFV.

The Impact of Left Atrium Appendage Morphology on Stroke Risk Assessment in Atrial Fibrillation: A Computational Fluid Dynamics Study

Atrial fibrillation (AF) carries out a 5-fold increase in stroke risk, related to embolization of thrombi clotting in left atrium (LA). Left atrial appendage (LAA) is the site with the highest blood stasis which causes thrombus formation. About 90 % of the intracardiac thrombi in patients with cardioembolic events originally develop in the LAA. Recent studies have been focused on the association between LAA anatomical features and stroke risk and provided conflicting results. Haemodynamic and fluid dynamic information on the LA and mostly on the LAA may improve stroke risk stratification. Therefore, the aim of this study was the design and development of a workflow to quantitatively define the influence of the LAA morphology on LA hemodynamics. Five 3D LA anatomical models, obtained from real clinical data, which were clearly different as regard to LAA morphology were used. For each LAA we identified and computed several parameters describing its geometry. Then, one LA chamber model was chosen and a framework was developed to connect the different LAAs belonging to the other four patients to this model. These new anatomical models represented the computational domain for the computational fluid dynamics (CFD) study; simulations of the hemodynamics within the LA and LAA were performed in order to evaluate the interplay of the LAA shape on the blood flow characteristics in AF condition. CFD simulations were carried out for five cardiac cycles. Blood velocity, vorticity, LAA orifice velocity, residence time computed in the five models were compared and correlated with LAA morphologies. Results showed that not only complex morphologies were characterized by low velocities, low vorticity and consequently could carry a higher thrombogenic risk; even qualitatively simple morphologies showed a thrombogenic risk equal, or even higher, than more complex auricles. CFD results supported the hypothesis that LAA geometric characteristics plays a key-role in defining thromboembolic risk. LAA geometric parameters could be considered, coupled with the morphological characteristics, for a comprehensive evaluation of the regional blood stasis. The proposed procedure might address the development of a tool for patient-specific stroke risk assessment and preventive treatment in AF patients, relying on morpho-functional defintion of each LAA type.

The Left Atrial Appendage, Including LAA Occlusion Devices Line Watchman, Amulet, and Lariat

Atrial fibrillation is a very common arrhythmia whose prevalence is expected to increase significantly as the population ages. The associated stroke risk is a major cause of morbidity and mortality. Stroke prevention by anticoagulation carries its own risks, leading to the search for alternative strategies. Multiple techniques have been developed to exclude the left atrial appendage (the main source of thromboembolism in atrial fibrillation) from the circulation. Such techniques offer the hope of stroke prevention without the risks of anticoagulation. This article describes the percutaneous approaches being currently performed in the United States. Particular emphasis is placed on the use of transesophageal echocardiography to guide these procedures.

Implications of CHA2DS2-VASc Score in Stroke Patients with Atrial Fibrillation: An Analysis of 938 Korean Patients

BACKGROUND AND AIMS

The aim of this study was to investigate the stroke mechanisms and associated conditions influencing the decision regarding stroke thromboprophylaxis in patients with atrial fibrillation (AF) plus ischemic stroke, according to the CHA2DS2-VASc score.

METHODS

We evaluated 938 consecutive patients with a diagnosis of AF plus transient ischemic attack/ischemic stroke. Based on the CHA2DS2-VASc scores, patients were stratified as score 0 or 1 (n = 151), score 2 (n = 146), score 3 (n = 213), score 4 (n = 185), or score ≥5 (n = 243).

RESULTS

Patients with a higher CHA2DS2-VASc score were more likely to have noncardioembolic stroke mechanism (p = 0.001). Large-artery atherosclerosis causing stenosis >50% was more frequently observed in the high CHA2DS2-VASc group (p < 0.001). Coronary artery disease and the use of antiplatelet agents were more prevalent in the higher group (p < 0.001). A high CHA2DS2-VASc score was associated with a higher frequency of cerebral microbleeds and a higher Fazekas grade for leukoaraiosis (p < 0.001). The HAS-BLED score was correlated with the CHA2DS2-VASc score (γ = 0.650; p < 0.001).

CONCLUSIONS

A higher CHA2DS2-VASc score is associated with noncardioembolic mechanisms of stroke and with a higher risk of bleeding. Strategies to treat macro/microangiopathy such as use of statin for plaque stabilization, as well as oral anticoagulants with a lower bleeding risk, are needed in these patients.

The Left Atrial Appendage Revised

Nonvalvular atrial fibrillation is associated with a 4- to 5-fold strokes increase and may be responsible for 15% to 20% of all strokes in the elderly. In this scenario, the left atrial appendage thrombus would be the associated with 90% of cases. The use of anticoagulants, percutaneous devices, and the left atrial appendage surgical exclusion is still an open discussion. For left atrial appendage procedures, relevant anatomic spatial relationships have to be emphasized, besides the chance of the normal physiological functioning would be eliminated with the proceedings. There are evidences that the left atrial appendage closure during routine cardiac surgery is significantly associated with an increased risk of early postoperative atrial fibrillation. Therefore, the purpose of this review is to focus basic aspects for continuous medical education. In summary, the rationale of this text is to emphasize anatomical and pharmacological aspects involved in the simple surgical exclusion of left atrial appendage under cardiopulmonary bypass. There are several operative techniques, but to conclude this revision it will present one of them based on the discussed basic sciences.

Comparison of prevalence and management of left atrial appendage thrombi under old and new anticoagulants prior to left atrial catheter ablation

BACKGROUND

The prevalence and management of left atrial appendage (LAA) thrombi associated with new anticoagulants remain to be elucidated, especially prior to atrial fibrillation (AFib) ablation. This study sought to (1) compare the prevalence of LAA thrombi and/or severe LAA contrast under vitamin K antagonist (VKA) agents and novel oral anticoagulants (NOACs), (2) evaluate the rate of LAA thrombus resolution after anticoagulation modification, and (3) determine the predictive factors of LAA thrombi and severe LAA contrast in patients prior to LA AFib ablation.

METHODS

Between January 2013 and March 2016, 576 consecutive patients referred for AFib ablation were included, and the prevalence of transesophageal echocardiography-detected thrombi was similar under NOACs (2.1%) and VKA agents (2.6%).

RESULTS

Thrombus resolution was obtained in 50% of cases following anticoagulation modification. Through multivariate exact logistic regression analysis with relevant clinical and echocardiographic features, age (P<.001), LAA hypocontractility (P<.001), and left ventricular ejection fraction (P=.007) were found to be independently associated with the occurrence of LAA thrombus. The relevant factors independently associated with LAA thrombus or severe contrast were LAA hypocontractility (P<.001) and age (P<.001).

CONCLUSIONS

The prevalence of transesophageal echocardiography-detected thrombi in patients referred for AFib ablation is similar under NOACs (2.1%) and VKA agents (2.6%). Under VKA therapy with 3-4 international normalized ratio, 50% of thrombi dissolved. Independent predictive factors of procedure contraindication included age, LAA hypocontractility, and left ventricular ejection fraction.

Comparison of Morphologic Features and Flow Velocity of the Left Atrial Appendage Among Patients With Atrial Fibrillation Alone, Transient Ischemic Attack, and Cardioembolic Stroke

The left atrial appendage (LAA) is a major source of emboli responsible for cardioembolic stroke (CES). We hypothesized that there could be differences in the morphologic and functional features of LAAs among patients with atrial fibrillation (AF) alone, patients with cardioembolic transient ischemic attack (CETIA), and patients with CES. Patients with AF and CETIA/CES were included in either a CETIA group or a CES group. Patients with AF without past histories of stroke were included in an AF/non-CVA (cerebrovascular accident) group. Cardiac computerized tomography and transesophageal echocardiography were employed for morphologic and functional assessments of LAAs. Cauliflower LAA morphology increased and chicken wing LAA morphology decreased in frequency in the following order: AF/non-CVA, CETIA, and CES group. LAA orifice diameters were larger in the CETIA and CES groups than in the AF/non-CVA group. LAA flow velocity was higher in the CES group than in the other groups. Multiple multinominal regression analyses showed that the cauliflower morphology was associated with CETIA and CES; however, after LAA orifice diameters and flow velocity were adjusted, LAA morphology was associated with neither of them. Receiver operating characteristic curve analysis showed that LAA orifice diameter and flow velocity accurately predicted CETIA (c-statistic 0.839) and CES (c-statistic 0.896), respectively. In conclusion, cauliflower LAA morphology is associated with an increased risk of CETIA and CES through its large LAA orifice diameters and low LAA flow velocity. There are clear differences in LAA orifice diameters and flow velocity among patients with AF alone, CES, and CETIA.

Multimodality Cardiac Imaging for the Assessment of Left Atrial Function and the Association With Atrial Arrhythmias

Several cardiac imaging modalities are able to visualize the left atrium (LA) and, therefore, allow for quantification of both structural and functional properties of this cardiac chamber. In echocardiography, only the maximal LA volume is included in the assessment of diastolic function at the current moment. Numerous studies, however, have shown that functional measures may be superior to the maximal LA volume in several aspects and to possess clinical value even in the absence of structural abnormalities. Such functional measures could prove particularly useful in the setting of predicting atrial fibrillation, which will be a point of focus in this review. Pivotal cardiac magnetic resonance imaging studies have revealed high correlation between LA fibrosis and risk of atrial fibrillation recurrence after catheter ablation, and subsequent multimodality imaging studies have uncovered an inverse relationship between LA reservoir function and degree of LA fibrosis. This has sparked an increased interest into the application of advanced imaging modalities, including both speckle tracking echocardiography and tissue tracking by cardiac magnetic resonance imaging. Even though increasing evidence has supported the use of functional measures and proven its superiority to the maximal LA volume, they have still not been adopted in clinical guidelines. The reason for this discrepancy may rely on the fact that there is little to no agreement on how to technically perform deformation analysis of the LA. Such technical considerations, limitations, and alternate imaging prospects will be addressed in this review.

Association of Left Atrial Enlargement with Cortical Infarction in Subjects with Patent Foramen Ovale

Background and Purpose

Left atrial dysfunction has been reported in patients with patent foramen ovale (PFO). Here we investigated the role of left atrial dysfunction in the development of embolic stroke in patients with PFO.

Methods

We identified consecutive patients with embolic stroke of undetermined sources except for PFO (PFO+ESUS). Healthy subjects with PFO served as controls (PFO+control). A stratified analysis by 10-year age group and an age- and sex- matching analysis were performed to compare echocardiographic markers between groups. In the PFO+ESUS group, infarct patterns of PFO-related stroke were determined (cortical vs. cortico-subcortical) and analyzed in correlation with left atrial function parameters.

Results

A total of 118 patients and 231 controls were included. The left atrial volume indices (LAVIs) of the PFO+ESUS patients were higher than those of the PFO+controls in age groups of 40–49, 50–59, and 60–69 years (P<0.001, P=0.003, and P=0.027, respectively), and in the age- and sex-matched analysis (P=0.001). In the PFO+ESUS patients, a higher (>28 mL/m²) LAVI was more associated with the cortical infarct pattern (P=0.043 for an acute infarction and P=0.024 for a chronic infarction, both adjusted for age and shunt amount). The degree of right-to-left shunting was not associated with infarct patterns, but with the posterior location of acute infarcts (P=0.028).

Conclusions

Left atrial enlargement was associated with embolic stroke in subjects with PFO. Left atrial physiology might contribute to the development of PFO-related stroke and need to be taken into consideration for optimal prevention of PFO-related stroke.

Asian Patients with Stroke plus Atrial Fibrillation and the Dose of Non-Vitamin K Oral Anticoagulants

After recent randomized control trials (RCTs), non-vitamin K oral anticoagulants (NAOAs) are now widely being used in patients with atrial fibrillation (AF) worldwide. However, current guidelines for the use of NOACs in patients with AF are derived mostly using a Caucasian population and non-stroke patients. Relatively few Asian patients with AF and stroke are included in the recent RCTs. As a result, the optimal use of NOACs in this particular group of patients is remains to be settled. The optimal dose of NOACs and response to current dose of NOACs of Asian patients with AF and stroke may differ from those of westerners and patients without stroke. We reviewed available research on NOACs by searching PubMed and ClinicalTrials.gov published in English up to December 2015. In this review, the characteristics of Asian AF patients with prior stroke/transient ischemic attack, which might influence the efficacy and safety profiles of NOACs, are discussed. In addition, we summarize the risk factors for bleeding complications on NOACs, which are related or unrelated with the blood level of NOACs. Lastly, we provide recent data of reduced dose of NOACs from RCTs or large cohorts. The results reviewed herein call for clinical trials to test whether a reduced dose of NOACs is beneficial in Asian patients with AF and stroke. In the meantime, further researches are needed to establish the safety and efficacy of dose-adjusted NOACs considering both blood levels of NOACs and fragility of patients in Asian patients with AF and stroke.

Considerations When Subtyping Ischemic Stroke in Asian Patients

Both the incidence and prevalence of stroke in Asia are steadily increasing, and the burden of stroke is particularly high in Asian countries. Although strokes in Asians and Caucasians share many common features, there are some differences that are probably due to differences in lifestyle and genetic background. While there have been advances in the stroke classification system, the assignment of Asian stroke patients to etiological categories has received little attention. The current classification system may not be well suited to Asian patients with ischemic stroke because the proportions and relative importance of stroke subtypes may differ with race and ethnicity. This review addresses concerns about the use of the current stroke classification system in Asian patients with ischemic stroke, and proposes a classification system that is more specific to the Asian population, in conjunction with discussing advances in diagnostic techniques.