Left Atrial Appendage Geometry Research Articles

Left atrial appendage geometry and function using transesophageal three-dimensional echocardiography in atrial fibrillation: a new approach to characterize left atrial thrombogenic milieu

Abstract Background Little data is available on the evaluation of left atrial appendage (LAA) geometry and function using three-Dimensional (3D) transoesophageal echocardiography (TEE). Purpose We hypothesized that 3D LAA geometry evaluated using dedicated TEE software could be integrated in the evaluation of the thromboembolic milieu in patients hospitalized for atrial fibrillation (AF). Methods We prospectively studied 206 hospitalized patients with AF with two-dimensional transthoracic echocardiography (TTE) and 3D TEE of the LAA within 24 hours of admission. 3D parameters were analysed off-line using Tomtec software (4D Cardio-View, Generic Volume, Philips) (Figure 1). Patients were divided into two groups according to the presence (n = 35) or absence (n = 171) of LAA sludge/thrombus on admission. Results Patients with LAA sludge/thrombus had more frequently a history of heart failure together with higher values of BNP, CRP and hemoglobin. These patients received less frequently angiotensin II receptor antagonist treatment on admission. Concerning the echocardiographic characteristics, patients with LAA sludge/thrombus exhibited higher left atrial (LA) volume, lower left ventricular ejection fraction (LVEF) and cardiac output. In the 2D TEE study they had lower LAA emptying and filling flow velocities compared to those without sludge/thrombus. 3D TEE showed overall higher 3D end-systolic (ES) and end-diastolic (ED) LAA measurements (ostium area, length, volume), and more frequently the absence of a chicken wing morphology. There were no intergroup differences regarding the number of LAA lobes (Table 1). Conclusion 3D characterization of LAA geometry and function depicts a degree of appendage remodeling in AF that appears to be associated with the degree of thrombogenicity. Further investigation is needed to determine the impact of this remodeling on outcomes in these patients.

Characterization of left atrial appendage geometry and function using three-dimensional transesophageal echocardiography in patients in atrial fibrillation

Few data are available on left atrial appendage (LAA) remodeling using three-dimensional (3D) transoesophageal echocardiography (TEE) in patients in atrial fibrillation (AF). The aim of this study was to evaluate LAA thrombogenic milieu, LAA velocities, spontaneous echocardiographic contrast/thrombus, 3D LAA geometry and volume in AF. We prospectively evaluated patients 206 hospitalized for AF with two-dimensional (2D) transthoracic and 3D TEE of the LAA within 24 hours of admission. 3D parameters were off-line analysed using Tomtec software (4D Cardio-View, Generic Volume, Philips) (Fig. 1). Patients were divided into two groups according to the type of AF at admission: paroxysmal AF (62 patients) or persistent AF (144 patients). Patients with persistent AF had higher BMI, more prevalent hypertension and diabetes, as well as history of AF, heart failure, renal failure. They had also higher CHA2DS2-VASc. Patients with persistent AF at admission had lower LVEF, higher left atrial volume, higher E and E/e′ and pulmonary arterial systolic pressure. Patients with persistent AF had more severe LAA spontaneous echo contrast/sludge, lower LAA emptying and filling flow velocity, and higher 3D LAA measurements (ostium area, length, volume) (Table 1). 3D evaluation of the LAA may reflect atrial remodeling in AF and seems to be associated with the burden of AF. Follow-up data are needed to determine the impact of such abnormalities in the risk stratification of such patients.

Thermally responsive hydrogel for atrial fibrillation related stroke prevention

Atrial fibrillation induced stroke accounts for up to 15% of all strokes. These strokes are caused approximately 90% of the time by clot formation in the left atrial appendage (LAA). To prevent these clots, the most common approach is to administer blood thinners. However, contraindications prevent some people from being able to have blood thinners. Devices have been developed to seal the LAA to prevent clot formation in these patients. Current devices, such as the LARIAT® tie off the LAA theoretically preventing blood from entering the LAA. These have had limited clinical success mainly due to failure to completely close the LAA leaving holes and orifices for thrombi to form. To overcome this lack of complete closure, many surgeons use off-label approaches, classically filling the LAA filamentous coils, to cover these holes. Although this usually helps largely cover the holes, placement is challenging, the coils can migrate, the holes are not fully closed as there is space within and around the coils that don't fully mold to the LAA geometry. Furthermore, the coils can develop device related thrombi defeating their purpose. Therefore, these are not fully sufficient to complement the closure techniques in closing the LAA. To address limitation of the closure devices and coil sealing of remaining holes, we developed a thermally responsive hydrogel (Thermogel) that solidifies once injected into the LAA to uniformly and fully close off the LAA thus preventing clot formation and device related thrombi. This Thermogel consists of three portions: 1) a structural component composed of thiolated Pluronic F127 for gel to solid transition following injection, 2) Heparin for anticoagulation, and 3) Dopamine for adhesion to the surrounding endothelium in the turbulent flow encountered in cardiovascular applications. Here we have demonstrated that Thermogel, in conjunction with the LARIAT®, is capable of filling the defects in small and large animals through catheter injection. Thermogel was biocompatible and led to atrophy of the LAA at 5 weeks in a large animal model. Given the advantages of this Thermogel for sealing this defect and ability to be delivered through an endovascular approach, Thermogel presents a viable adjuvant to current occlusion-based treatments for sealing cardiovascular defects.

How Could Pre-Procedural Imaging Guide Successful Left Atrial Appendage Closure?

REFER TO THE PAGE 211-218 Atrial fibrillation (AF) is the most common sustained arrhythmia and strongly associated with ischemic stroke.1) In patients with AF, the main site of thrombus formation is the left atrial appendage (LAA).2) Autopsy and surgical data have suggested that about 90% of atrial thrombi in AF patients originate from the LAA.3) There are two reasonable ways to prevent ischemic stroke events in patients with AF. The first is maintenance of anticoagulation. The second is to isolate the LAA as a major embolic source from the systemic circulation. Multiple randomized, controlled trials have suggested that oral anticoagulation (OAC) decrease the risk of stroke in patients with AF.4) However, long-term OAC is contraindicated in 14% to 44% of AF patients with risk of stroke.5) Because there are various barriers against maintenance of long-term OAC such as the risk of bleeding, inconvenience of dose adjustments, drug interactions, and restrictions on diet.6) Other novel anticoagulants are also limited by the side effects, and the risk of bleeding from systemic administration of these agents.7) Because the LAA is a separate anatomic structure, it may be relatively easily isolated from systemic circulation by excision or ligation. Recently, less invasive technique using percutaneous transcatheter have been introduced for LAA isolation by occlusion of this anatomical structure with implantable devices.8) The PROTECT AF (Watchman Left Atrial Appendage System for Embolic Protection in Patients with Atrial Fibrillation) trial was planned to determine whether systemic anticoagulation with warfarin, the most commonly used anticoagulant, could be replaced by LAA closure with a percutaneously positioned device. This final results of the PROTECT AF trial followed up for an accumulated exposure of 1588 patient-years revealed LAA closure with the Watchman device to be non-inferior to systemic anticoagulation with warfarin regarding prevention of stroke, systemic embolism, and cardiovascular death.9) On the basis of these data, LAA closure has been decided a class IIb recommendation in the 2014 ACC/ASA guideline as an alternative strategy to prevent stroke. For this procedure to be accepted as an alternative, there must be a high success rate. Although success rate of the LAA closure is generally high, peri-device leakage of LAA persists due to incomplete closure.9),10) During percutaneous LAA closure for stroke prophylaxis, the geometric variability of the LAA ostium may result in an incomplete seal of the LAA. To understand the technical limitations of LAA closure, it is important to consider the anatomical variations of the LA and LAA geometry. The geometry of LA and LAA, a detailed knowledge of its anatomical characteristics and relationship might be very useful when planning the procedure. As LA and LAA geometry is complex, there are limited available data about the predictors of successful procedure. The anatomical relationship of LAA and interatrial septum (IAS) may affects the success rate of device implantation.11) In this issue, Chung et al.12) introduced 3-dimensional anatomical relation of IAS and LAA orifice as a predictor of peri-device leakage after LAA closure. One of the novel and interesting aspects of this study is that they use new novel analysis program for accurate measurement of 3-dimensional relationship between IAS and LAA orifice and found that 3-dimensional angulation between IAS and LAA significantly associated with development of peri-device leakage after LAA occlusion. In this study, the angle between the IAS plane and the line linking the LAA orifice midline and foramen ovale was measured using 3-dimensional geometric cardiac CT analysis. Measurement of this new parameter can provide more detail geometric information and predict success of the procedure. In addition, it might be helpful to select catheter and to decide the direction of IAS puncture site. This study is the first study that anatomical relationship of IAS and LAA orifice might affect peri-device leakage. However, clinical implication of peri-device leakage after LAA occlusion is unclear. Despite some previous studies suggested that the incomplete LAA occlusion was not associated with cardioembolic stroke event,10) understanding the clinical impact of peri-device leakage would be critical. As the authors commented in the limitation, larger sample size, prospective and long-term follow up data are needed to determine the clinical implication of peri-device leak after LAA occlusion. Despite some limitations, this study results suggested that novel anatomical parameter could be measured by their new software and this parameter is useful to predict peri-device leakage after LAA device closure.

Percutaneous ligation of the left atrial appendage results in atrial electrical substrate modification

Debulking of electrically active atrial tissue may reduce the mass of fibrillating tissue during atrial fibrillation, eliminate triggers, and promote maintenance of normal sinus rhythm (NSR). We investigated whether left atrial appendage (LAA) ligation results in modification of atrial electrical substrate. Healthy male mongrel dogs (N = 20) underwent percutaneous epicardial LAA ligation. The ligation system grabber recorded LAA local electrograms (EGM) continuously before, during, and after closure. Successful ligation with a preloaded looped suture was confirmed intraprocedurally by LAA Doppler flow cessation on transesophageal echocardiography (TEE) and loss of LAA electrical activity, and after procedure by direct necropsic visualization. P-wave duration on surface electrocardiograms was measured immediately before and after LAA closure. Percent P-wave duration reduction was correlated with preclosure LAA internal dimensions measured by TEE and external dimensions measured on necropsy specimens to investigate associations of LAA geometry with the extent of electrical substrate modification. LAA ligation was successful in all dogs and accompanied by loss of LAA EGM. P-wave duration reduced immediately on ligation (mean 75 ms preligation to 63 ms postligation; mean difference ± standard error, 12 ± 1 ms; P < 0.0001). Percent P-wave reduction was associated with larger LAA longitudinal cross-sectional area (R(2) = 0.263, P = 0.04) and smaller external circumference (R(2) = 0.687, P = 0.04). All dogs were in sinus rhythm. Percutaneous LAA ligation results in its acute electrical isolation and atrial electrical substrate modification, the degree of which is associated with LAA geometry. These electrical changes raise the possibility that LAA ligation may promote NSR by removing LAA substrate and triggers.

Geometry of left atrial appendage assessed with multidetector-row computed tomography: implications for transcatheter closure devices

To assess the left atrial appendage (LAA) geometry with multidetector-row computed tomography (MDCT) and its implications for selection of closure devices. One hundred and ninety-seven patients who underwent MDCT prior to catheter ablation for atrial fibrillation were evaluated. Feasibility for Watchman and Amplatzer Cardiac Plug (ACP) devices was assessed based on the maximal cross-sectional diameter and perimeter of the ostium and at 10 mm depth and on the LAA diameter on the MDCT plane resembling the transoesophageal echocardiography (TEE) view. Mean maximal diameters of the ostium and at 10 mm depth were 28.7±4.4 mm and 24.6±4.5 mm, respectively, resulting in feasibilities of 80.7%, 84.8% and 91.4% for the Watchman, the ACP and for either one of the two devices, respectively. Mean perimeters of the ostium and at 10 mm depth were 79.1±12.2 mm and 69.8±11.6 mm, resulting in feasibilities of 87.8%, 92.9% and 96.4% for the Watchman, the ACP and for either one of the two devices, respectively. Mean TEE-like MDCT LAA diameter was 22.0±3.3 mm, resulting in feasibilities of 93.9%, 97% and 99.0% for the Watchman, the ACP and for either one of the two devices, respectively. The feasibility of current devices is high, based on MDCT measurements of the LAA, with no difference for either one of the devices.

Three-dimensional assessment of left atrial appendage orifice geometry and potential implications for device closure

Transcatheter placement of left atrial closure device is an attractive therapy for patients with atrial fibrillation (AF), to avoid anticoagulation and reduce cerebrovascular events; however peri-device leaks occur. The geometry of the left atrial appendage (LAA) is not well understood, largely owing to limitations of 2-dimensional imaging techniques. We sought to better define the LAA orifice geometry, by performing 3-dimensional multi-detector computed tomography measurements. We prospectively recruited 105 consecutive patients referred for pulmonary vein ablation (PVA) and age-matched controls. Area, short and long-axis measurements were performed. Eccentricity was calculated as 1-(short axis/long axis). Multiple clinical variables were tested for their ability to predict appendage orifice eccentricity using univariate linear regression models. The PVA cohort demographics included; 25 (24%) females, mean age 59 years (SD = 10), median height (1.55-2.03), weight 89 (56-139) kg and body surface area 2.1 (1.61-2.58). In the PVA cohort, there was a significant difference between the long and short-axis; median short-axis dimension was 20.5 (12.9-35.4) mm, versus long-axis median 30.4 (17.7-43.8) (p < 0.001). Mean eccentricity score was 0.4. When compared with controls, there was a significant difference in the short and long-axis measurements (p < 0.001) as well as eccentricity (p = 0.04). All clinical variables tested showed limited ability to predict appendage eccentricity (p = NS). LAA ostium is an elliptical structure in the setting of AF with a high eccentricity index and uniformly significant differences between short and long-axis. There were significant differences between these parameters when compared with controls. A deeper appreciation of LAA geometry and eccentricity may allow for reduction in peri-closure leaks.

Geometry of left atrial appendage assessed with multi-detector row computed tomography: implications for transcatheter closure devices

Purpose: Transcatheter left atrial appendage (LAA) occlusion is a feasible alternative to long-term anticoagulation therapy for stroke prevention in patients with atrial fibrillation (AF). Currently, implantation of the Amplatzer Cardiac Plug (ACP) and the Watchman device is planned and guided by echocardiography and fluoroscopy. However, the implications of sizing the LAA with 3D imaging techniques, such as multi-detector row computed tomography (MDCT) are unknown. Methods: 197 patients who underwent MDCT prior to AF ablation were evaluated. Measured indices included key parameters that define procedural feasibility: the maximal cross-sectional diameter and the perimeter of the LAA at level of the ostium and at 10 mm depth, the maximal LAA-length and the LAA diameter on the MDCT plane that resembles the transesophageal echocardiography (TEE) view. Following manufacturer's recommendations the feasibility for each device was assessed based on the maximal diameter, perimeter and the TEE-like MDCT LAA-diameter. Results: The mean maximal diameters of ostium and at 10 mm depth were 28.7±4.4 and 24.6±4.5 mm, resulting in a feasibility of 80.7% for the Watchman, of 84.8% for the ACP and of 91.4% for either one of the two. The mean perimeters of ostium and at 10 mm depth were 79.1±12.2 and 69.8±11.6 mm, resulting in a feasibility of 87.8% for the Watchman, of 92.9% for the ACP and of 96.4% for either one of the two. The mean TEE-like MDCT LAA-diameter was 22.0±3.3 mm, resulting in a feasibility of 93.9% for the Watchman, of 97% for the ACP and of 99.0% for either one of the two (Figure). ![Figure][1] Feasibility Histogram LAA occluders Conclusion: The maximal cross-sectional diameter, perimeter and the TEE-like LAA-diameter measured with MDCT would lead to a respective 91.4%, 96.4% and 99.0% feasibility for transcatheter LAA-occlusion. [1]: pending:yes

Analysis of the Left Atrial Appendage by Three-Dimensional Transesophageal Echocardiography

This study was designed to determine the ability and reliability of 3-dimensional (3D) transesophageal echocardiography (TEE) to assess the geometry and size of the left atrial appendage (LAA). Three-dimensional TEE may allow more accurate assessment of, and provide additional information on, LAA morphology compared to 2-dimensional TEE. Validation studies for LAA morphology data derived from 3D TEE were performed using 10 isolated porcine LAA specimens. Of 107 enrolled patients, 55 patients were in sinus rhythm (normal sinus rhythm), in whom 3D transesophageal echocardiographic images were obtained from full-volume mode imaging, and in 52 patients with atrial fibrillation, zoom-mode imaging was used. LAA orifice area, depth, and volume and the number of LAA lobes were assessed on reconstructed 3D imaging. Left atrial volume was calculated using 2-dimensional echocardiographic imaging. In experimental studies, excellent correlations (r >0.90, p <0.001) between the measurements by full-volume or zoom-mode imaging and reference data were observed in all parameters. The mean LAA orifice long diameter was 29.7 +/- 7.4 mm, the mean short diameter was 20.6 +/- 5.9 mm, the mean orifice area was 5.1 +/- 2.5 cm(2), the mean LAA depth was 38.5 +/- 8.2 mm, and the mean volume was 9.2 +/- 5.6 ml. The most frequent number of LAA lobes was 2 (n = 52), followed by 3 (n = 28), 1 (n = 18), and 4 (n = 3). Left atrial volume was weakly correlated with LAA orifice long diameter (r = 0.33, p = 0.001), short diameter (r = 0.40, p <0.001), area (r = 0.39, p <0.001), LAA depth (r = 0.21, p = 0.03), and volume (r = 0.36, p = 0.001). In conclusion, 3D TEE is a reliable modality to evaluate LAA geometry and provides detailed information to quantify varied LAA characteristics.

Real-Time Three-Dimensional Transesophageal Echocardiography of the Left Atrial Appendage: Initial Experience in the Clinical Setting

The aim of this study was to determine the feasibility and accuracy of a new real-time 3-dimensional (RT3D) matrix-array transesophageal echocardiographic probe for the determination of left atrial appendage (LAA) geometry. Sixty-six consecutive patients (mean age, 53 +/- 17 years) referred for 2-dimensional (2D) transesophageal echocardiography (TEE) underwent additional RT3D TEE. The feasibility of RT3D TEE for LAA geometry was studied in the first 37 patients, and 2D and RT3D transesophageal echocardiographic quantification of the LAA were compared in the subsequent 29 patients. The LAA orifice diameter and depth were measured using biplane 2D TEE, and LAA orifice area was calculated as an ellipse. LAA orifice area and depth were measured in 3D and correlated to 2D measurement and were also correlated to 64-slice cardiac computed tomography (CT) in 8 patients. All 66 patients underwent RT3D matrix-array TEE without complication. In the feasibility study, the LAA was well visualized in 95%. In the quantitation study, 2D TEE underestimated LAA orifice area compared with 3D imaging (3.1 +/- 1.3 vs 4.2 +/- 2.2 cm(2); r = 0.55). LAA depth by 2D and 3D imaging were well correlated (3.7 +/- 0.7 vs 3.4 +/- 0.7 cm; r = 0.77). LAA orifice area on CT was well correlated with area on 3D TEE (r = 0.98) but not with area 2D TEE (r = 0.13). Bland-Altman analysis demonstrated that 2D TEE systematically underestimated LAA orifice area compared with 3D TEE (mean bias, -1.0 cm(2), with wide limits of agreement [-4.6 to 2.6 cm(2)]). In the 8 patients who underwent both 3D TEE and CT, the mean bias was 0.15 cm(2), with narrow limits of agreement (-0.50 to 0.20 cm(2)). RT3D TEE for the visualization and quantitative analysis of LAA orifice area is feasible and correlates well with 64-slice cardiac CT.

Abstract 4291: Left Atrial Appendage Occlusion: Early Clinical Results with a New Clip

Background: Atrial fibrillation (AF) is a common arrhythmia and as such a significant risk factor for stroke originating from the left atrial appendage (LAA). The purpose of this study is to evaluate surgical LAA occlusion with a new clip in patients with AF undergoing open heart surgery (OHS) at 3 month follow-up with cardiac multidetector computed tomography (MDCT). Patients and Methods: From 9/2007 to 5/2008, patients undergoing OHS with AF were enrolled in a trial for concomitant clip placement (LAA clip, Atricure Inc., Westchester, Ohio (USA)). The LAA clip is composed of titanium rods with nitinol hinges, surrounded by polyester braiding, applied epicardially on the LAA. LAA geometry and perfusion was assessed by trans-esophageal echocardiography (TEE). Postoperative and 3 month follow-up MDCT was compared to preoperative data to assess Clip location, LAA perfusion and cardiac anatomy. Results: 30 patients underwent LAA Clip placement through a median sternotomy. Clip deployment was successful in all (n=30), no device related complications occurred. LAA measurement and clip placement took less than 30 seconds and one attempt. After deployment TEE confirmed absence of LAA perfusion in all. Operative mortality was 6% (n=2) and was unrelated to clip placement. Pre-discharge (n=28) and 3 month follow-up (n=18) MDCT demonstrated stable clip location, absent LAA perfusion and normal surrounding cardiac structures. Conclusion: LAA Clip occlusionis safe, easy and straightforward. LAA occlusion remains effective and durable, per TEE and MDCT. When applied in a minimally invasive fashion LAA clip occlusion might offer a valuable tool for stroke prevention in selected patients.

Abstract 1869: Real-Time Three-Dimensional Echocardiography of the Left Atrial Appendage: Initial Experience in Humans with Validation by 64-Slice Computed Tomography

Background: Real-time left atrial appendage (LAA) quantification is increasingly important with the advent of LAA occluder devices for stroke prevention. However, accurate quantification is difficult using 2D-TEE because measurements must be made in multiple views, and LAA orifice cannot be viewed directly. We aimed to determine the accuracy of LAA geometry measured by a new matrix-array (mTEE) probe which can provide unique real-time 3D (RT3D) views of the LAA. Methods: 29 consecutive patients (age 53±18) referred for 2D-TEE underwent additional RT3D-mTEE (Philips ie33; frame rate 8–10/s). The LAA orifice diameter and LAA depth were measured from biplane 2D images, and 2D LAA orifice area was calculated as an ellipse. LAA orifice area and LAA depth were measured in 3D and correlated to 2D. In 8 patients who had cardiac CT available, 2D- and 3D-TEE LAA measurements were correlated with 64-slice CT. All LAA measurements were made at atrial end-diastole. Results: All 29 patients underwent RT3D-mTEE without complication. The LAA was well-visualized in 3D in 26/29 (90%). Because the shape of the LAA orifice in 3D was an ellipsoid with an irregular contour, 2D images resulted in underestimation of area vs. 3D (3.0±1.2 vs. 4.2±2.2 cm 2 ). LAA depth by 2D and 3D correlated well (3.7±0.7 vs. 3.4±0.7; r=0.72, p=0.001). CT LAA orifice area correlated well with 3D-TEE (r=0.98, p&lt;0.0001) but not with 2D-TEE (p=0.78). Conclusions: RT3D-TEE for analysis of LAA geometry is safe and feasible and appears to be more accurate than 2D-TEE. RT3D-TEE provides unique visualization of the LAA orifice in real-time, making it the ideal tool for intra-procedural sizing and placement of LAA occluder devices.