Shape Of Left Atrial Appendage Research Articles

Correlation between left atrial appendage morphology based on fractal dimension quantification and its hemodynamic parameters in patients with atrial fibrillation

To investigate the relationship between left atrial appendage (LAA) morphology, quantified based on fractal dimension (FD), and LAA hemodynamic parameters in patients with atrial fibrillation (AF), in an effort to reveal the effect of LAA shape on blood flow. 225 patients with AF who underwent cardiac computed tomography angiography (CTA) and transesophageal echocardiography (TEE) were enrolled. LAA morphology was quantified based on FD on cardiac CTA images, and LAA hemodynamic parameters, including injection fraction (EF), filling peak flow velocity (FV), maximum speed of emptying (PEV), and wall motion velocity (WMV), were assessed using TEE. We divided the patients with AF into two groups based on a mean LAA FD of 1.32: the low FD group (n=124) and the high FD group (n=101). Compared to the low FD group, there were more patients with LAA circulatory stasis/thrombus (P=0.008) in the high FD group, as well as lower LAA FV (P=0.004), LAA PEV (P=0.007), and LAA WMV (P=0.007). LAA FD was an independent and significant determinant of LAA EF (β=-11.755, P=0.001), LAA FV (β=-17.364, P=0.004), LAA PEV (β=-18.743, P<0.001), and LAA WMV (β=-7.740, P=0.001) in multiple linear regression analysis. LAA FD is an essential determinant of LAA hemodynamic parameters, suggesting that the relatively complex morphology of the LAA may influence its hemodynamics, which can correlate with embolic events.

Association of Left Atrial Appendage Morphology and Function With Stroke and Transient Ischemic Attack in Atrial Fibrillation Patients

We aimed to correlate left atrial appendage (LAA) structure and function with the history of stroke/transient ischemic attack (TIA) in patients with atrial fibrillation (AF). We analyzed data of 649 patients with AF who were scheduled for catheter ablation. Patients underwent cardiac CT and transesophageal echocardiography prior to ablation. LAA morphologies depicted by cardiac CT were categorized into four groups: cauliflower, chicken wing, swan and windsock shapes. Mean age was 61.3±10.5 years, 33.9% were female. Prevalence of stroke/TIA was 7.1%. After adjustment for the main risk factors, LAA flow velocity ≤35.3 cm/sec (OR=2.18; 95%CI=1.09-4.61; p=0.033) and swan LAA shape (OR=2.69; 95%CI=0.96-6.86; p=0.047) independently associated with higher risk of stroke/TIA, while windsock LAA morphology proved to be protective (OR=0.32; 95%CI=0.12-0.77; p=0.017) as compared to cauliflower LAA shape. When comparing the differences between LAA morphology groups, we measured significantly smaller LAA orifice area (389.3±137.7 mm2 in windsock vs 428.3±158.9 ml in cauliflower, p=0.021) and LAA volume (7.4±3.0 mm2 in windsock vs 8.5±4.8 mm2 in cauliflower, p=0.012) in patients with windsock LAA morphology, while LAA flow velocity did not differ significantly. Reduced LAA function and swan LAA morphology were independently associated with higher prevalence of stroke/TIA, while windsock LAA shape proved to be protective. When comparing the differences between the various LAA morphology types, significantly lower LAA volume and LAA orifice area were measured in windsock LAA shape as compared to cauliflower LAA shape.

Variations in the Size and Shape of Left Atrial Appendage: A Cross-sectional Study-based on Autopsy Specimens and their Endocasts

Variations in the Size and Shape of Left Atrial Appendage: A Cross-sectional Study-based on Autopsy Specimens and their Endocasts

A Study on Variations in Size and Shape of Left Atrial Appendage from Formalin-fixed Cadavers

Introduction: Atrial appendages were once considered vestigial structures with no significant role in atrial function. However, they are now recognized as significantly impacting various pathophysiological conditions, including cardiac thromboembolism and arrhythmias. The left atrial appendage (LAA), in particular, has been found to have significant variations in shape and size, and its relationship with nearby structures, such as the pulmonary veins (PVs), is crucial in planning interventional and surgical procedures in and around the LAA. Although most studies examining variations in the LAA are image-based, few have focused on anatomical studies. Materials and Methods: In this study, we examined heart specimens from 54 cadavers for anatomical dissection at a tertiary care teaching hospital. After removing the heart from the pericardial cavity, we opened the left atrium and examined its interior. Observations were made regarding the LAA orifice and PV orifices, and measurements were taken. Subsequently, we removed the LAA along with a portion of the left atrial wall, observed its shape and number of lobes, and took measurements. To classify the shape, we used a system proposed by Wang et al. based on resemblance to familiar objects. Categorical variables were expressed as percentages and continuous as mean and standard deviation. The institutional research committee and the institutional ethics committee approved the study. Results: The most common shape variant observed was the Chicken Wing type, followed closely by the Windsock type. Specimens with Cauliflower or Cactus morphology were rare, with the Cactus variant being the least common. The LAA orifice was round or oval shaped in most cases. In most cases, the LAA orifice was at the same or lower level as the left superior PV orifice, with a prominent ridge between the two orifices in most patients. We observed most of the appendages to be trilobed, with considerable variations in length and diameter. We found two specimens with unusual morphologies but no specimens with accessory appendages. Conclusions: Based on our study, there are significant differences in findings compared to some of the previous studies reporting the shape variations of LAA. However, our findings are matching with those of some other earlier studies. The variations in the shape and size of LAA orifices and their relationship to PV orifices are similar to those reported in earlier studies. The distribution of variations in the size of LAA was also similar to those reported in earlier studies. Conducting larger studies to explore these variations could aid in designing and developing therapeutic interventions in the LAA.

Radiomics Based on Single-Phase CTA for Distinguishing Left Atrial Appendage Thrombus from Circulatory Stasis in Patients with Atrial Fibrillation before Ablation.

Differentiation of left atrial appendage thrombus (LAAT) and left atrial appendage (LAA) circulatory stasis is difficult when based only on single-phase computed tomography angiography (CTA) in routine clinical practice. Radiomics provides a promising tool for their identification. We retrospectively enrolled 204 (training set: 144; test set: 60) atrial fibrillation patients before ablation, including 102 LAAT and 102 circulatory stasis patients. Radiomics software was used to segment whole LAA on single-phase CTA images and extract features. Models were built and compared via a multivariable logistic regression algorithm and area under of the receiver operating characteristic curves (AUCs), respectively. For the radiomics model, radiomics clinical model, radiomics radiological model, and combined model, the AUCs were 0.82, 0.86, 0.90, 0.93 and 0.82, 0.82, 0.84, 0.85 in the training set and the test set, respectively (p < 0.05). One clinical feature (rheumatic heart disease) and four radiological features (transverse diameter of left atrium, volume of left atrium, location of LAA, shape of LAA) were added to the combined model. The combined model exhibited excellent differential diagnostic performances between LAAT and circulatory stasis without increasing extra radiation exposure. The single-phase, CTA-based radiomics analysis shows potential as an effective tool for accurately detecting LAAT in patients with atrial fibrillation before ablation.

Cardiac magnetic resonance imaging for preprocedural planning of percutaneous left atrial appendage closure.

Percutaneous closure of the left atrial appendage (LAA) facilitates stroke prevention in patients with atrial fibrillation. Optimal device selection and positioning are often challenging due to highly variable LAA shape and dimension and thus require accurate assessment of the respective anatomy. Transesophageal echocardiography (TEE) and x-ray fluoroscopy (XR) represent the gold standard imaging techniques. However, device underestimation has frequently been observed. Assessment based on 3-dimensional computer tomography (CTA) has been reported as more accurate but increases radiation and contrast agent burden. In this study, the use of non-contrast-enhanced cardiac magnetic resonance imaging (CMR) to support preprocedural planning for LAA closure (LAAc) was investigated. CMR was performed in thirteen patients prior to LAAc. Based on the 3-dimensional CMR image data, the dimensions of the LAA were quantified and optimal C-arm angulations were determined and compared to periprocedural data. Quantitative figures used for evaluation of the technique comprised the maximum diameter, the diameter derived from perimeter and the area of the landing zone of the LAA. Perimeter- and area-based diameters derived from preprocedural CMR showed excellent congruency compared to those measured periprocedurally by XR, whereas the respective maximum diameter resulted in significant overestimation (p < 0.05). Compared to TEE assessment, CMR-derived diameters resulted in significantly larger dimensions (p < 0.05). The deviation of the maximum diameter to the diameters measured by XR and TEE correlated well with the ovality of the LAA. C-arm angulations used during the procedures were in agreement with those determined by CMR in case of circular LAA. This small pilot study demonstrates the potential of non-contrast-enhanced CMR to support preprocedural planning of LAAc. Diameter measurements based on LAA area and perimeter correlated well with the actual device selection parameters. CMR-derived determination of landing zones facilitated accurate C-arm angulation for optimal device positioning.

Does the wall thickness of the left atrial appendage and its isthmus depend on their macroscopic characteristics?

Knowledge in interrelations between gross anatomy of the left atrial appendage (LAA) and thickness of the walls of LAA and periauricular area enables decreasing operational risks in LAA ostium occluding and «Cox-Maze» surgery for atrial fibrillation. The aim of the study was to identify significant interrelations between the macroscopic characteristics of the LAA (size, shape, number of lobes) and the parameters of the wall thickness of the LAA and its isthmus. Material and methods. The study includes 50 heart specimens of patients died from non-cardiac diseases. We examined 60 anatomical sections from 30 hearts by means Olympus SZX2-ZB10 microscope, and histological slices from 20 hearts. Results. The layers of the LAA wall were thinner than those in the isthmus. The thickness of LAA walls did not show direct correlation with the external dimensions of LAA. We found inverse correlation (Rs = – 0.4, p &lt; 0,05) between the thickness of the myocardium, endocardium and some external sizes of LAA. The wall thickness of «chicken wing», «cauliflower» and «arrowhead» was the same. The wall of single-lobe LAA was thinner than that of two-lobed LAA (p = 0.036). The LAA isthmus wall was thinner (p = 0.03) in hearts with «cauliflower» LAA compared to hearts with LAA resembled a «chicken wing». Differences in wall thickness in LAA of various shapes were due to the degree of subepicardial fatty tissue development. Intracardiac operations should be done with the utmost care in patients with «cauliflower» LAA and single-lobe LAA to avoid damage of the LAA and periauricular area. Conclusions. The research found clinically significant interrelations between the LAA wall thickness and the number of its lobes as well as between the LAA isthmus wall thickness and LAA shape variants.

Real-time 3D echocardiographic transilluminated imaging combined with artificially intelligent left atrial appendage measurement for atrial fibrillation interventional procedures.

Aims: This study investigated the feasibility and accuracy of real-time three-dimensional (3D) echocardiographic transilluminated imaging (TrueVue Glass) in left atrial appendage (LAA) anatomical morphology and artificial intelligence (AI)-assisted 3D automated LAA measurement (3D Auto LAA) software in the preoperative evaluation of LAA occlusion (LAAO) in patients with atrial fibrillation (AF). Method and results: Thirty-seven patients with AF were selected. Two-dimensional (2D) and real-time 3D transesophageal echocardiography (RT3D-TEE) were performed preoperatively, using conventional 3D, the new 3D TrueVue Glass mode, and cardiac computed tomography angiography (CCTA) to assess and type the morphology of LAA. Physiological parameters were measured using traditional 2D and 3D manual (3D Manual LAA), 3D Auto LAA, and CCTA. TrueVue Glass for LAA outer contour display was compared with CCTA. Comparisons were based on correlation and consistency in measuring the maximum diameter (LZ max), minimum diameter (LZ min), area (LZ area), and circumference (LZ cir) of LAA landing zone (LZ). Times and variabilities were compared. The concordance rate for external shape of LAA was 97.14% between TrueVue Glass and CCTA. 3D Auto LAA and 3D Manual LAA have a stronger correlation and higher consistency in all parameters. 3D Auto LAA showed higher intra- and interobserver reproducibility and allowed quicker analysis (p < 0.05). LAAO was performed in 35 patients (94.59%), and none of which had serious adverse events. Conclusion: TrueVue Glass is the first non-invasive and radiation-free visualization of the overall external contour of LAA and its adjacent structures. 3D Auto LAA simplifies the measurement, making the preoperative assessment more efficient and convenient while ensuring the accuracy and reproducibility. A combination of the two is feasible for accurate and rapid assessment of LAA anatomy and physiology in AF patients and has practical application in LAAO.

Rehearsal simulation to determine the size of device for left atrial appendage occlusion using patient-specific 3D-printed phantoms

Left atrial appendage (LAA) occlusion (LAAO) is used to close the finger-like extension from the left atrium with occlusion devices to block the source of thrombosis. However, selection of the devices size is not easy due to various anatomical changes. The purpose of this study is patient-specific, computed tomography angiography (CTA)-based, three-dimensionally (3D) printed LAAO phantoms were applied pre-procedure to determine the size. Ten patients were enrolled prospectively in March 2019 and December 2020. The cardiac structure appearing in CTA was first segmented, and the left atrium and related structures in the LAAO procedure were modeled. The phantoms were fabricated using two methods of fused deposition modeling (FDM) and stereolithography (SLA) 3D printers with thermoplastic polyurethane (TPU) and flexible resin materials and evaluated by comparing their physical and material properties. The 3D-printed phantoms were directly used to confirm the shape of LAA, and to predict the device size for LAAO. In summary, the shore A hardness of TPU of FDM was about 80–85 shore A, and that of flexible resin of SLA was about 50–70 shore A. The measurement error between the STL model and 3D printing phantoms were 0.45 ± 0.37 mm (Bland–Altman, limits of agreement from − 1.8 to 1.6 mm). At the rehearsal, the estimations of device sizes were the exact same with those in the actual procedures of all 10 patients. In conclusion, simulation with a 3D-printed left atrium phantom could be used to predict the LAAO insertion device size accurately before the procedure.

Left atrial appendage shape impacts on the left atrial flow hemodynamics: A numerical hypothesis generating study on two cases

Background and objectivesThe left atrial appendage (LAA) is the most common region for thrombus formation in atrial fibrillation (AF). Morphological parameters such as shape, size, and LAA volume can cause insufficient effectiveness of available therapeutic options. This study aimed to examine blood flow inside LAA and its removal effects. Computational fluid dynamic (CFD) simulations were carried out on two patients with different morphologies. MethodsTwo patients' CT was used to reconstruct the 3D geometries of the left atrium (LA) and left atrial appendage (LAA). Then, the geometries were refined in the mentioned software, and the LAA in some models was removed. Next, in generated 3D volume mesh, sinus rhythm (SR) and atrial fibrillation (AF) outflow velocity were imposed at the mitral valve as boundary conditions. Finally, CFD simulation was conducted to analyzing blood flow within LA with/without LA. ResultsThe results confirmed that velocity and vorticity decreased under AF conditions inside the LA domain for both patients. However, removing LAA may cause unpredictable consequences, due to different shape and volume of LAA. LAA removal had insignificant effects on velocity and vorticity within LA in SR-mitral outflow. However, removing LAA increased the blood flow rate by 9.15% and vorticity by 7.27% for patient one under AF rhythm (SR)-outflow. In contrast, for patient two, LAA removal in both AF and SR decreased velocity and vorticity within the LA domain. In SR-mitral outflow, velocity dropped by 18.8 %, and vorticity by 13.2%. Also, under AF velocity and vorticity decreased by 23.33% and 18.6% respectively. Meanwhile, the results indicated that the vorticity magnitude increased inside the LAA under AF associated with the risk of thrombus formation, particularly for patient one under AF. The distal part of LAA in both patients was the most common region for blood stasis because of the lowest velocity magnitude. ConclusionOverall, the morphology of LAA could be the critical parameter to determine the possibility of thrombosis formation, particularly under AF conditions. High volume, low blood flow velocity and two-lobe-appendage are more likely to have blood stasis. Furthermore, the morphology difference can affect the LAA removal result and make it more complicated. So, it could be challenging to generalize LAA removal as a therapeutic option for different patients. The implication of this CFD observation needs more investigation.

Thickness of the left atrial wall surrounding the left atrial appendage orifice.

The aim of this study was to investigate the thickness of the left atrial wall surrounding the left atrial appendage (LAA) orifice. The tissue thickness around the LAA orifice was measured at four points (superior, inferior, anterior, and posterior) in 200 randomly selected autopsied human hearts. The thickest tissue was observed at the anterior point (3.17 ± 1.41 mm), followed by the superior (2.47 ± 1.00 mm), inferior (2.22 ± 0.80 mm) and posterior (2.22 ± 0.83 mm). The chicken wing LAA type was associated with the lowest thickness at the superior point compared to the cauliflower and arrowhead shapes (p = .024). In hearts with an oval LAA orifice, the atrial wall was significantly thicker in all points than in specimens with a round LAA orifice (p > .05). Both the LAA orifice anteroposterior diameter and orifice surface area were negatively correlated with the tissue thickness in the anterior (r = -.22, p = .004 and r = -.23, p = .001) and posterior points (r = -.24, p = .001 and r = -.28, p = .005). Endocardial surface roughness was commonly in the inferior pole of the LAA orifice (75.5% of cases), while they are much less prevalent in other sectors around the orifice (anterior: 17.5%), superior: 4.0%, and posterior: 1.5%). Although a significant heterogeneity in the atrial wall thickness around the LAA orifice was observed, the thickness in the respective points is quite conservative and depends only on LAA orifice size and shape, as well as LAA body shape. Thin atrial wall and endocardial surface roughness might challenge invasive procedures within this region.

Prediction of Left Atrial Appendage occluder size based on 3D printed models

Abstract Funding Acknowledgements Type of funding sources: None. Background occlusion of the left atrial appendage (LAA) is an established method in the prevention of thromboembolic complications in patients with atrial fibrillation and high bleeding risk. There is a huge anatomical variability of LAA and choosing the right type and size of the occluder may be challenging and result in a time-consuming procedure with repeated repositioning of the selected device, or a need to use another device. These aspects may lead to a prolonged or more aggressive manipulation resulting in periprocedural complications and a suboptimal result. The current technology of 3D printing allows us to obtain a real model of the LAA and to simulate the course of implantation. Purpose in a post-hoc analysis to compare occluder sizes predicted as optimal by simulation on a 3D-printed LAA model to actually implanted LAA occluders, and analyse potential benefits of such simulations. Methods We analysed 32 consecutive patients after a TEE-guided implantation of the Amulet occluder in whom a CT cardiac scan had been performed prior to the procedure. Based on the CT, an LAA 3D model was printed out post-hoc for each patient. Two experienced operators blinded to the procedural results simulated the implantation ex-vivo and agreed on the most appropriate size of the occluder to fit in the LAA. If the simulation-based size matched the size of the primary operator`s choice and this occluder was actually implanted („intention-to-implant and implanted"), the match was considered positive; otherwise it was negative. The number of positive and negative matches and corresponding procedural characteristics were analysed. Results The positive match was found in 9 (28.1%) cases. Out of 23 (71.9%) negative matches, there were 11 (47.8%) implantations using a bigger-than-simulated and 12 (52.2%) smaller-than-simulated occluder; in 2 (8.7%) cases the actually implanted occluder matched the simulated size but was a 2nd -choice occluder. In positive-match cases compared to negative-match cases, there was a statistically significant less need for an occluder reposition (median 0.0 vs 1.0, p = 0,02), and a trend to a shorter procedural time (average 66.7+ 13.3 min vs 85.2 + 32.8 min, p = 0.112) and less contrast agent consumption (average 188.9 + 67.9ml vs 220.9 + 112.4ml, p = 0.43). Conclusion The preliminary results of our study suggest that a CT-based 3D modelling of the LAA shape and simulating the LAA occlusion procedure ex-vivo have a potential to become useful tools to reduce procedural time and complications. Our results might serve as a rational for a prospective study. Abstract Figure. Occluder in the 3D model

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

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. 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. 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±3.9ml). Reproducibility was better for larger LAA volumes. A novel 3D echocardiographic approach can determine the geometry, size, and function of the LAA. A new parameter, LAA EF, provides functional quantitation.

Morphology of the Left Atrial Appendage: Introduction of a New Simplified Shape-Based Classification System

The left atrial appendage (LAA) is a heart structure with known prothrombogenic and pro-arrhythmogenic properties. The aim of this study was to evaluate the specific anatomy of the LAA and to create a simple classification system based on the shape of its body. This study investigated 200 randomly selected autopsied human hearts (25.0% females, 46.6±19.1 years old). Three (3) types of LAAs were distinguished: the cauliflower type (no bend, limited overall length, compact structure [36.5%]); the chicken wing type (substantial bend in the dominant lobe [37.5%]), and the arrowhead type (no bend, one dominant lobe of substantial length [26.0%]). Additional accessory lobes were present in 55.5% of all LAAs. Significant variations between category types were noted in LAA length (chicken wing: 35.7±9.8 mm, arrowhead: 30.8±10.1 mm, cauliflower: 22.3±9.6 mm [p<0.001]) and in the thickness of pectinate muscles located within the LAA apex (arrowhead: 1.2±0.7 mm; cauliflower: 1.1±0.6 mm; chicken wing: 0.9±0.6 mm [p<0.001]). Left atrial appendage volume and orifice size were not affected by the type of LAA shape. The age of the donor was positively correlated with LAA volume (r=0.29, p=0.005), body length (r=0.26, p=0.012), and area of the orifice (r=0.36, p<0.001). Donors with an oval LAA orifice were significantly older than those with round orifices (50.2±16.6 vs 43.7±20.4 years [p=0.014]) and had significantly heavier hearts (458.2±104.8 vs 409.6±114.1g [p=0.002]). This study delivered a new simple classification system of the LAA based on its body shape. An increase in age and heart weight was associated with LAA enlargement and a more oval-shaped orifice. Results of current study may help to estimate the different thrombogenic properties associated with each LAA type and be an assistance during planning and performing interventions on LAA.

Applicability of computed tomography preoperative assessment of the LAA in LV summit ablations

PurposeVentricular arrhythmias originating from the left ventricular summit (LVS) may present with challenges for catheter ablation. Recently, the left atrial appendage (LAA) became a new vantage point for mapping and ablating arrhythmias from that region, but data of possible usefulness is limited.MethodsFrom September to December 2019, we retrospectively analyzed 48 consecutive patient hearts (20 male; mean age 57.9y ± 11.56) undergoing diagnostic coronary vessel imaging in 64 dual-source computer tomography angiography (CTA). Distances from the LAA to the LVS, LAA shape type, and coronary arteries in the LVS region were measured. Also, we compared the true LVS area from CTA with a calculated formula derived from LVS definition.ResultsThe mean LVS area calculated from the formula was 291.58 mm2 (± 115.5) while the true area calculated from CT was 263.33 mm2 (± 99.49) (p = 0.44). The mean inaccessible area was 133.42 mm2 (± 72.89), accessible 95.67 mm2 (± 72.77). The mean LAA coverage over LVS was 196.08 mm2—which is approximately 75% of LVS size in general. The most common LAA shape was chicken wing (50%); windsock has the highest accessible area coverage on average (80.23%), followed by chicken wing (59.88%), broccoli (47.72%), and cactus (46.98%). The mean distance from LAA to the surface was 5.14 mm (1.5 to 10 mm) and was not correlated with BMI. LAA has a 98% coverage over the point of transition between the great cardiac vein and anterior interventricular vein.ConclusionAngio-CT assessment of the LAA over the LVS structures may be helpful in decision making before an ablation procedure. LAA appears to be a promising mapping approach in LVS arrhythmias.

Image-Based Flow Simulations of Pre- and Post-left Atrial Appendage Closure in the Left Atrium.

For patients with atrial fibrillation, the left atrial appendage (LAA) is often the site of thrombus formation due to low atrial ejection fraction that triggers strokes and other thromboembolic events. Recently introduced percutaneous LAA occlusion procedure is known to reduce LAA-induced strokes. Despite having the procedure, there are still 11% of the patients who continue to suffer from future strokes or transient ischemic attacks, not accounting for the procedural related complications. The high failure rate is largely due to the variabilities in LAA's shape, size, and contractility which may result in ineffectiveness of this procedure. To correctly identify the candidates and evaluate the effectiveness of the procedure, we rely on patient-specific CT scans which provides the exact LA and LAA geometries and predictive hemodynamic analysis to assist in evaluating quantitative flow parameters pre- and post-LAA occlusion procedures. Hemodynamic parameters are critical to predict adverse hemodynamic flow patterns in LAA as well as the effectiveness of LAA closure in individual patient. The aim of this paper is to establish an image-based patient-specific computational fluid dynamic (CFD) simulation framework specific to the prediction of treatment outcomes of LAA closure with atrial fibrillation. This framework utilizes automated LA/LAA image segmentation which yields significant reduction in image processing. One set of patient data with successful procedure outcome is used to illustrate the potential of the proposed framework. The proposed LAA occlusion simulation framework is composed of several components: (1) a novel image segmentation procedure, which is fully-automated to identify LA/LAA geometries from CT images, (2) a finite-element mesh generation procedure which transforms the surface geometry into a 3-D volume mesh and properly identified boundary planes, (3) performing CFD simulations with atrial fibrillation flow boundary conditions, and (4) analyzing flow characteristics (velocity, flow patterns, streamlines, vortices) within the LA for before and after LAA closure. Based on the LA/LAA segmentation of a 65 year old female patient with chronic atrial fibrillation, a CFD analysis was pursued to examine flow characteristics upon LAA closure. The results showed that the flow velocity magnitudes were significantly reduced by a maximum factor of 2.21, flow streamlines were greatly stabilized, and mitral outflow appeared to be more organized. Vortices were dramatically reduced in size, number, intensity, as well as duration. During diastole, the peak vortex diameter was reduced from 2.8 to 1.5 cm, while the vortex duration was reduced from 0.210 to 0.135 s. These flow characteristics all indicated a reduced risk in future thrombus formation and strokes based on the established relationship between flow and thrombus formation. For the patient case under study, the effectiveness of the procedure is predicted and found to be consistent with the actual procedural outcome. This framework successfully predicted patient-specific outcome of a LAA closure procedure for one patient with atrial fibrillation. It can be further developed into a useful tool for pre-procedural planning and candidate selection. More patient data are necessary for further validation studies.

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.

Morphologic and functional features of left atrial appendage in Iranian population: an echocardiographic study.

Introduction: Cardioembolic events are accompanied by left atrial appendage (LAA) in patients suffering from atrial fibrillation (AF); therefore, the LAA closure is implemented as a preventive strategy. The detection of LAA morphologies and function is a paramount step before establishing the LAA closure. Herein, we sought to determine the morphologic features of the LAA in an Iranian population using echocardiographic evaluation. Methods: Seventy-two near-normal heart patients were investigated by conducting a cross-sectional study. All patients were examined using the 2-dimensional and 3-dimensional transesophageal echocardiography (2D- and 3D-TEE) method. The anatomical features and functions of LAA were examined. All images were stored and analyzed offline. Results: The patients’ mean age was 39 ± 15.5 year and 33 (45.8%) were female. The most frequent shape of LAA was wind sock . More LAA lobes was observed in patients with AF compared to those with NSR. In comparison with AF group, the NSR had higher LAA flow velocity (P < 0.01). The paroxysmal AF had greater LAA flow velocity and LAA ejection fraction in comparison with the chronic AF (39 ± 19 vs. 75 ± 22, P < 0.01; and 49±4 vs. 72±14, P < 0.003; respectively). The paroxysmal AF had smaller systolic LAA orifice area in comparison with the chronic AF (P < 0.02). Conclusion: The morphologic features of LAA in Iranian population were within the range of other studies and LAA length and orifice diameters in 2D- and 3D-TEE were consistent. In addition, AF influenced the morphologies and functions of LAA compared to sinus rhythm.

Sensitivity analysis of geometrical parameters to study haemodynamics and thrombus formation in the left atrial appendage.

The left atrial appendage (LAA) is a complex and heterogeneous protruding structure of the left atrium (LA). In atrial fibrillation patients, it is the location where 90% of the thrombi are formed. However, the role of the LAA in thrombus formation is not fully known yet. The main goal of this work is to perform a sensitivity analysis to identify the most relevant LA and LAA morphological parameters in atrial blood flow dynamics. Simulations were run on synthetic ellipsoidal left atria models where different parameters were individually studied: pulmonary veins and mitral valve dimensions; LAA shape; and LA volume. Our computational analysis confirmed the relation between large LAA ostia, low blood flow velocities and thrombus formation. Additionally, we found that pulmonary vein configuration exerted a critical influence on LAA blood flow patterns. These findings contribute to a better understanding of the LAA and to support clinical decisions for atrial fibrillation patients.