Motion of left atrial appendage as a determinant of thrombus formation in patients with a low CHADS2 score receiving warfarin for persistent nonvalvular atrial fibrillation

Left atrial appendage angiography for stroke risk prediction in patients with atrial fibrillation

BACKGROUND

The current risk stratification schemes for stroke in patients with atrial fibrillation (AF) are insufficient for an accurate assessment of stroke risk.

AIMS

This study evaluates the association between the mechanical function of the left atrial appendage (LAA), as assessed by angiography, and the risk of stroke.

METHODS

We conducted a cross-sectional study to assess the mechanical function of the LAA by measuring the left atrial appendage ejection fraction (LAAEF) and grading the contrast retention (CR) using angiography.

RESULTS

A total of 746 patients referred for a left atrial appendage occlusion (LAAO) procedure with (n=151; stroke group) or without (n=595; control group) a history of stroke were included in the analysis. LAAEF was significantly lower (14% [9-19] vs 20% [12-33]; p<0.001) and grade 3 CR was more common (66.9% vs 33.9%; p<0.001) in patients with a history of stroke. Multivariable analysis showed that CR was independently associated with stroke in patients with AF (grade 2 vs grade 1=7.29; 95% confidence interval [CI]: 2.84-21.65; p<0.001; grade 3 vs grade 1=16.45; 95% CI: 6.16-51.02; p<0.001). The receiver operating characteristics curve demonstrated that CR identified patients with stroke more accurately than the CHA2D-VASc score (C-statistic 0.712 vs 0.512; p<0.001), and the combination of CR and the CHA2DS2-VASc score provided the best performance (C-statistic 0.871 vs 0.829 [CHA2DS2-VASc score alone]; p=0.048) Conclusions: Impaired mechanical function of the LAA, indicated by a low LAAEF and CR, is associated with a history of stroke in patients with AF. Assessment of CR using LAA angiography helps improve the stratification scheme for stroke risk prediction.

Mechanisms and Prediction of Ischemic Stroke in Atrial Fibrillation Patients

Atrial fibrillation (AF) is the most common arrhythmia in adults worldwide and represents an important burden for patients, physicians, and healthcare systems. AF is associated with substantial mortality and morbidity, due to the disease itself and its specific complications, such as the increased risk of stroke and thromboembolic events associated with AF. The temporal relation between AF episodes and stroke is nonetheless incompletely understood. The factors associated with an increased thromboembolic risk remain unclear, as well as the stroke risk stratification. Therefore, in this review, we intend to expose the mechanisms and physiopathology leading to intracardiac thrombus formation and stroke in AF patients, together with the evidence supporting the causal hypothesis. We also expose the risk factors associated with increased risk of stroke, the current different risk stratification tools as well as future prospects for improving this risk stratification.

Left Atrial Appendage Mechanical Dispersion Assessed by Speckle-Tracking Echocardiography as a Determinant of Left Atrial Appendage Blood Stasis in Patients With Atrial Fibrillation

Aims

We sought to investigate the relationship of left atrial appendage (LAA) mechanical dispersion (MD) with LAA dense spontaneous echo contrast (SEC) or thrombus, and to compare its usefulness in the identification of thrombogenesis with left atrial (LA) MD or LA/LAA strain parameters in patients with atrial fibrillation (AF).

Methods

We conducted a cross-sectional study of 493 consecutive patients with AF [65(58.5–71.0) years, male 66.9%] who underwent echocardiography prior to catheter ablation. We measured the LAA and LA global longitudinal strain (GLS) using speckle-tracking echocardiography (STE). LAA MD and LA MD was defined as the standard deviation (SD) of time to peak positive strain corrected by the R-R interval.

Results

Patients with LAA dense SEC/thrombus (n = 70) had significantly higher LAA MD than controls (n = 423) [median 14.2(11.6–16.8)% vs 9.4(6.2–12.1)%, p &lt; 0.01]. Multivariable analysis showed that LAA MD was independently associated with LAA dense SEC/thrombus in four different models (Odds ratio, 1.23–1.24; p &lt; 0.01), and provided additional diagnostic value over clinical and standard echocardiographic parameters. Whereas, LA MD was not independently associated with LAA dense SEC/thrombus and had no incremental value over other LA/LAA mechanical parameters.

Conclusion

LAA mechanical dispersion was an independent determinant of LAA dense SEC/thrombus in AF patients, incremental to conventional risk factors and superior to LA mechanical dispersion.

Left Atrial Appendage Function Assessment by Tissue Doppler Transesophageal Echocardiography in Acute Ischemic Stroke Patients

Background: Strokes due to Cardioembolic causes are the most severe in ischemic stroke subtypes. LAA flow patterns and function could be assessed accurately by TEE. The study aimed to present the importance of Transesophageal echocardiography in the assessment of LAA function and its relation to cardioembolic stroke. Methods: 120 patients were enrolled in the study and were subdivided into 3 subgroups, each group included 40 patients. Group A; patients had a stroke with normal sinus rhythm, Group B; patients had a stroke with atrial fibrillation, and Group C; normal control subjects. The study participants were evaluated by medical history, physical examination, standard 12-leads electrocardiogram, a transesophageal echocardiographic detailed evaluation of the LAA, and brain CT and/or MRI for patients with stroke. Results: both stroke patients with AF and sinus rhythm had significantly higher LAA mean orifice diameter and higher LAA length than control patients, significantly lower mean LAA medial wall tissue Doppler upward and downward motion velocities than control patients and that patients with stroke and AF had significantly lower mean LAA pulsed wave emptying and filling velocities than both patients with stroke and sinus rhythm and control patients. Presence of LAA thrombi, spontaneous echo contrast, and stroke recurrence were higher in stroked AF patients than stroke patients with sinus rhythm. Conclusion: increased LAA orifice diameter, LAA length, and reduced filling and emptying velocities and upward and downward motion velocities of the medial wall of LAA as detected by TEE are associated with stroke and cardio embolization.  

Coronary CTA to Investigate Predictive Value of Left Atrial Appendage for Cardiogenic Stroke in Patients with Nonvalvular Atrial Fibrillation

PURPOSE

To investigate the predictive value of changes in LAA size and function for cardiogenic stroke (CS) in patients with NVAF by coronary CTA examination. Materials and Method. 179 patients with NVAF were selected and grouped according to the outbreak of acute ischemic stroke and TIA within 2 years after coronary CTA examination. Those who met the criteria for CS were selected as cases (87 patients), and those neither stroke nor TIA as controls (92 patients). LAA size of selected patients was measured and data postprocessing was performed. The differences of baseline data and LAA parameters between groups were analyzed. The impacts of BMI, hyperlipidemia, the duration of AF, the LAAOA Index, and the LAAEF on CS were assessed by binary logistic regression. The predictive abilities of LAAOA Index, LAAEF, and the combined predictor were assessed by ROC curves.

RESULTS

Proportions of BMI ≥ 25, prevalence of hyperlipidemia, duration of AF, and LAAODmax, LAAODmin, LAAOA, LAAVmax, and LAAVmin with their correction index were greater in cases than controls. The LAAEF was lower in cases than that in controls. The binary logistic regression model showed an increase in LAAOA Index (P = 0.005) and a decrease in LAAEF (P < 0.001) were independent risk factors for CS. ROC curve analysis showed that the optimal cutoff values of LAAOA Index and LAAEF to predict CS were 3.16 cm²/m² and 38.71%, with AUC value of 0.712 and 0.734, respectively. The LAAOA Index-LAAEF combined predictor (AUC value = 0.786) was likely superior to either LAAOA Index or LAAEF.

CONCLUSIONS

Coronary CTA can provide additional valuable parameters, as a by-product of coronary artery assessment without additional radiation dose, for the risk assessment of CS in patients with NVAF. Coronary CTA may make up for the limitation of single indicator of CHA₂DS₂-VASc in guiding anticoagulation program, to reduce the incidence of embolism and bleeding events.

Impact of left atrial appendage location on risk of thrombus formation in patients with atrial fibrillation

Most strokes in patients with atrial fibrillation (AF) are thought to arise from thrombus formation in the left atrial appendage (LAA). Assessing the hemodynamics in LAA and left atrium (LA) may provide some insights in the evaluation of the risk of thrombus formation. This study aims to find out the impact of different LAA locations with respect of LA on the risk of thrombus formation within LAA in patients with AF. Three different LAA locations at LA were modeled and a fully coupled fluid-structure interaction analysis was performed. A discrete phase method was used for particle residence analysis to evaluate risk of the thrombus formation. The results showed that LAA positions on the LA affected the LAA flow velocity distribution, passive contraction ability, and particle residence. In particular, the left pulmonary veins (PVs) had a greater influence on the LAA hemodynamics than the right PVs. The LAA had the lowest contractibility when it was located between left superior and left inferior PVs, and in this case, a larger number of particles were resided, which indicated a higher risk of thrombus formation. The present work provides a quantitative way to evaluate the risk of thrombus formation within LAA in patients with AF.

A new risk model of assessing left atrial appendage thrombus in patients with atrial fibrillation - Using multiple clinical and transesophageal echocardiography parameters

BACKGROUNDS

Predicting left atrial appendage thrombus (LAAT) in non-valvular atrial fibrillation (NVAF) patients need more precisely quantified risk models. In this study, we attempted to review the risk markers for LAAT and develop a simple and reliable model for LAAT prediction.

METHODS

The study included 307 patients with NVAF who were scheduled for transesophageal echocardiography (TEE) to exclude LAA thrombus before synchronized electrical cardioversion or radiofrequency ablation for atrial fibrillation (AF). We analyzed the relationship between echo, clinical parameters and the presence or absence of LAAT.

RESULTS

A total of 33 patients were found having LAAT (10.7%, 33/307). The age, left atrial appendage emptying velocity (LAAEV), left atrial or left atrial appendage spontaneous echocardiographic contrast (SEC), less than moderate to severe mitral regurgitation (≤mild MR), and left atrial enlargement showed association with LAAT. The multivariate logistic regression analysis revealed that LAAEV, SEC and ≤mild MR were independent risk factors of the LAAT. We used LAAEV ≤ 21.5 cm/s, SEC and ≤mild MR to construct a combined predictive model for LAAT in NVAF patients (the area under receiver operator characteristic curve: 0.88; 95% confidence interval: 0.82-0.95, P < 0.0001).

CONCLUSION

Comprehensive evaluation of LAAEV, SEC, and MR with associated LAAT may help risk stratifying the NVAF patients, especially if the LAA imaging quality was suboptimal for identifying thrombus. These parameters may facilitate the decision-making process at the time of TEE.

Predicting Left Atrial Appendage Thrombus from Left Atrial Volume and Confirmation by Computed Tomography with Delayed Enhancement

Assessing thromboembolic risk is crucial for proper management of patients with atrial fibrillation. Left atrial volume is a promising predictor of cardiac thrombosis. To determine whether left atrial volume can predict left atrial appendage thrombus in patients with atrial fibrillation, we conducted a prospective study of 73 patients. Left atrial and ventricular volumes were evaluated by cardiac computed tomography with retrospective electrocardiographic gating and then indexed to body surface area. Left atrial appendage thrombus was confirmed or excluded by cardiac computed tomography with delayed enhancement. Seven patients (9.6%) had left atrial appendage thrombus; 66 (90.4%) did not. Those with thrombus had a significantly higher mean left atrial end-systolic volume index (139 ± 55 vs 101 ± 35 mL/m2; P =0.0097) and mean left atrial end-diastolic volume index (122 ± 45 vs 84 ± 34 mL/m2; P =0.0077). On multivariate logistic regression analysis, left atrial end-systolic volume index (per 10 mL/m2 increase) was significantly associated with left atrial appendage thrombus (odds ratio [OR]=1.24; 95% CI, 1.03-1.50; P =0.02); so too was the left atrial end-diastolic volume index (per 10 mL/m2 increase) (OR=1.29; 95% CI, 1.05-1.60; P =0.02). These findings suggest that increased left atrial volume increases the risk of left atrial appendage thrombus. Therefore, patients with atrial fibrillation and an enlarged left atrium should be considered for cardiac computed tomography with delayed enhancement to confirm whether thrombus is present.

Periprocedural Imaging for Left Atrial Appendage Closure: Computed Tomography, Transesophageal Echocardiography, and Intracardiac Echocardiography

Percutaneous left atrial appendage closure is increasingly performed for stroke prevention for patients with nonvalvular atrial fibrillation with contraindications to oral anticoagulation. The success and complication rates with left atrial appendage closure have dramatically improved with maturing experience, growing procedural familiarity, and preprocedural planning. Multimodality imaging involving cardiac computer tomography angiography, transesophageal echocardiography, or intracardiac echocardiography in conjunction with fluoroscopy has improved the efficacy, procedural success, and safety of left atrial appendage closure in recent years. Proceduralists need to familiarize themselves with the various modalities and understand their complimentary roles and their limitations.

Novel Echocardiographic Biomarkers in the Management of Atrial Fibrillation

Purpose of Review

Atrial fibrillation (AF) is the most common arrhythmia in adults. The number of patients with AF is anticipated to increase annually, mainly due to the aging population alongside improved arrhythmia detection. AF is associated with a significantly elevated risk of hospitalization, stroke, thromboembolism, heart failure, and all-cause mortality. Echocardiography is one of the key components of routine assessment and management of AF. Therefore, the aim of this review is to briefly summarize current knowledge on “novel” echocardiographic parameters that may be of value in the management of AF patients.

Recent Findings

Novel echocardiographic biomarkers and their clinical application related to the management of AF have been taken into consideration. Both standard parameters such as atrial size and volume but also novels like atrial strain and tissue Doppler techniques have been analyzed.

Summary

A number of novel echocardiographic parameters have been proven to enable early detection of left atrial dysfunction along with increased diagnosis accuracy. This concerns particularly experienced echocardiographers. Hence, these techniques might improve the prediction of stroke and thromboembolic events among AF patients and need to be further developed and disseminated. Nonetheless, even the standard imaging parameters could be of significant value and should not be discontinued in everyday clinical practice.

Characteristics of Anatomy and Function of the Left Atrial Appendage and Their Relationships in Patients with Cardioembolic Stroke: A 3-Dimensional Transesophageal Echocardiography Study

BACKGROUND

Increasing attention is being paid to the left atrial appendage (LAA) in the context of risk stratification in cardioembolic stroke (CES) and the requirement for meticulous planning of percutaneous closure device implantation. However, detailed systematic assessment of the LAA remains limited.

METHODS

This study evaluated the anatomy and function of LAA using 3-dimensional transesophageal echocardiography (3D-TEE) on 194 consecutive patients older than 50 years old hospitalized exclusively for CES. Patients were stratified into 3 groups on the basis of cardiac rhythm: (1) chronic atrial fibrillation (AF), n = 53; (2) paroxysmal AF, n = 26; and (3) no detected AF, n = 115.

RESULTS

Significant differences between the groups were observed for anatomical (orifice area [OA], depth, diastolic volume) and functional parameters (ejection fraction [EF], flow velocity [FV]), as measured by 3D-TEE. The anatomical parameters were consistently the greatest, and functional parameters were the poorest, in the group with chronic AF. There were significant inverse correlations between them (r = -.33, P = .0003 for depth and EF; r = -.27, P = .0020 for depth and FV; r = -.22, P = .016 for OA and EF; and r = -.38, P < .0001 for OA and FV).

CONCLUSIONS

LAA morphology and function were strongly affected by cardiac rhythm disturbances. Patients with chronic AF had the greatest LAA dimensions, areas, and volumes as well as the lowest LAA functions. An inverse correlation was observed between LAA size and function.

Incidence of left atrial abnormalities under treatment with dabigatran, rivaroxaban, and vitamin K antagonists

Background

Non-vitamin K antagonist oral anticoagulants (NOACs) such as dabigatran or rivaroxaban are alternatives to vitamin K antagonists (VKAs) for prevention of stroke and systemic embolism in patients with atrial fibrillation (AF) and atrial flutter (AFL). Incidences of risk factors for left atrium (LA) and left atrial appendage (LAA) thrombus formation, such as dense spontaneous echo contrast (SEC), low LAA velocity (LAAV) <20 cm/s under treatment with dabigatran and rivaroxaban in comparison with VKAs are unknown.

Methods

We studied 306 patients with AF (94 %) and AFL (6 %) undergoing transesophageal echocardiography. Patients received VKAs (n = 138), dabigatran (n = 68), or rivaroxaban (n = 100) for at least 3 weeks prior to investigation. Time in therapeutic range was 67 % for VKA. Mean CHADS₂ score and CHA₂DS₂-VASc score were 1.3 and 2.5, respectively. Left atrial abnormality was defined as either dense SEC, low LAAV <20 cm/s, or thrombus.

Results

Any LA abnormality occurred in 9, 3, and 5 % of patients receiving VKA, dabigatran, and rivaroxaban, respectively. The most frequent abnormality was LAA thrombus (VKA: 4 %, dabigatran: 0 %, rivaroxaban: 2 %) and low LAAV of less than 20 cm/s (VKA: 4 %, dabigatran: 1 %, rivaroxaban: 1 %), followed by dense SEC (VKA: 2 %, dabigatran: 1 %, rivaroxaban: 2 %). Results of uni- and multivariate analyses revealed a numerically lower but not significantly different frequency of any LA abnormality under dabigatran (OR 0.4, 95 % Cl 0.08 − 1.88, p = 0.25) and rivaroxaban (OR 0.65, 95 % Cl 0.22 − 1.98, p = 0.45) compared to VKA.

Conclusion

With respect to the incidence of LA abnormalities, dabigatran and rivaroxaban are not inferior to VKA.

Regional function analysis of left atrial appendage using motion estimation CT and risk of stroke in patients with atrial fibrillation

AIMS

The aim of this article is to determine the association between left atrial appendage (LAA) regional dysfunction using image-based motion-estimation computed tomography (CT) (iME) and a prior history of stroke or transient ischaemic attack (TIA) in patients with atrial fibrillation (AF).

METHODS AND RESULTS

In this single-centre retrospective case-control study, among patients referred for AF ablation who underwent pre-ablation cardiac CT with retrospective ECG gating, we identified 18 patients with a prior history of stroke or TIA at the time of CT scan and 18 age- and gender-matched controls. All the patients were in sinus rhythm at the time of CT scan. Four-dimensional motion vector field was estimated from the CT images using iME. To assess myocardial deformation, area change ratio (A) and area change rate (AR) were calculated over the endocardial surface of the LAA. There was no significant difference in the baseline patient characteristics between the stroke/TIA group and the control group (67.6 ± 8.1 years old, 66.7% male, 16.7% persistent AF). LAA maximum (Amax; 23.8 ± 33.0 vs. 52.9 ± 41.2%, P = 0.02) and pre-atrial contraction area change ratio (ApreA; 13.7 ± 17.7 vs. 30.9 ± 29.2%, P = 0.04) were significantly lower in the stroke/TIA group than in the control group, respectively. The difference in LAA Amax and ApreA remained significant in multivariate analysis (P = 0.03 and P = 0.04, respectively).

CONCLUSION

LAA regional dysfunction is associated with stroke/TIA in AF patients. Our results offer a basis for a prospective study to determine the role of LAA regional dysfunction by iME in predicting cerebrovascular events such as stroke or TIA.

The left atrial appendage: anatomy, function, and noninvasive evaluation

The left atrial appendage (LAA) is a finger-like extension originating from the main body of the left atrium. Atrial fibrillation (AF) is the most common clinically important cardiac arrhythmia, occurring in approximately 0.4% to 1% of the general population and increasing with age to >8% in those >80 years of age. In the presence of AF thrombus, formation often occurs within the LAA because of reduced contractility and stasis; thus, attention should be given to the LAA when evaluating and assessing patients with AF to determine the risk for cardioembolic complications. It is clinically important to understand LAA anatomy and function. It is also critical to choose the optimal imaging techniques to identify or exclude LAA thrombi in the setting of AF, before cardioversion, and with current and emerging transcatheter therapies, which include mitral balloon valvuloplasty, pulmonary vein isolation, MitraClip (Abbott Laboratories, Abbott Park, Illinois) valve repair, and the implantation of LAA occlusion and exclusion devices. In this review, we present the current data regarding LAA anatomy, LAA function, and LAA imaging using the currently available noninvasive imaging modalities.

Embryology and Anatomy of the Left Atrial Appendage: Why Does Thrombus Form?

The left atrial appendage (LAA) is a long tubular structure that opens into the left atrium. In patients with atrial fibrillation, the LAA develops mechanical dysfunction and fibroelastotic changes on the endocardial surface. The complex anatomy of the LAA makes it a good site for relative blood stasis. In addition, systemic factors exacerbate the hypercoagulable state, eventually resulting in endothelial dysfunction, release of tissue factor, and production of inflammatory cytokines and oxidative free radicals, and eventually initiating the coagulation cascade. Thus, the LAA is susceptible to thrombus formation and is the most common source of systemic thromboembolism.

AF Detected on Implanted Cardiac Implantable Electronic Devices: Is There a Threshold for Thromboembolic Risk?

OPINION STATEMENT

Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with elevated thromboembolism risk caused by multiple pathophysiologies, including a hypercoagulable state, structural heart changes, left atrial appendage stasis, inflammation, and endothelial dysfunction. With the exception of lone AF, most other categories of AF, whether paroxysmal or persistent, have been shown to share a high thromboembolism risk. Risk stratification schemes such as CHADS2 and CHA2DS2-VASc scores help to identify the level at which anticoagulation may mitigate thromboembolism risk. AF may be episodic and asymptomatic; therefore, AF diagnosis that depends entirely on office electrocardiogram (ECG) may be easily missed. With the increasing use of pacemakers, implantable cardioverter defibrillators (ICDs), and insertable loop recorders (ILRs) for diagnosis and treatment of arrhythmias, AF has been incidentally detected with increasing frequency. However, the sensitivity and specificity for detection of AF, especially brief episodes, vary from one type of device to another, and rhythm confirmation should be considered. Several recent studies have examined device-detected AF and have tried to follow associated clinical outcomes. In this paper, we review studies that have addressed device-detected AF and associated thromboembolism risk to try to identify the burden of AF that is associated with an elevated risk of thromboembolism and may therefore warrant anticoagulation therapy.