Left Atrial Appendage Ablation Research Articles

An enhanced and objective approach to advancing the classification system for left atrial appendage morphology in atrial fibrillation

Abstract The left atrial appendage (LAA) is an important part of the heart that can contribute to the formation of blood clots and the development of arrhythmias. Managing the LAA is crucial in clinical practice. Besides oral anticoagulation, one approach is LAA occlusion, which can reduce the risk of blood clots in selected patients. Another approach is LAA ablation, which has been proposed in addition to pulmonary vein isolation (PVI) and might improve the success of treating atrial fibrillation (AF). Different types of LAA morphology have been identified, and these differences can affect the choice of treatment and strategies for individual patients. To refine current classification system, a new approach has been proposed. The study utilized an observational single-center trial with blinded retrospective analysis of cardiac computed tomography angiography (CCTA) images from cryoballoon PVI patients. Statistical analysis included baseline characteristics and left atrium/LAA measurements. An LAA bounding box was introduced to enhance the current classification system, particularly focusing on distinguishing "chicken-wing" and "windsock," as well as "cauliflower" and "cactus" morphologies. From 2012 to 2016 a total of 1.103 patients underwent second generation cryoballoon PVI. Prior to PVI, CCTA was available for 725 (65.7%) patients with sufficient quality for measuring in 473 (65.2%). Mean age was 66.3±9.5 years; Paroxysmal AF was present in 277 (58.6%) participants. The distribution of LAA morphological types was as follows: "windsock" 51%, "chicken-wing" 20%, "cauliflower" 15%, and "cactus" 13%. Inter-rater reliability, assessed using Cohen's Kappa with Landis and Koch criteria, demonstrated substantial agreement (Kappa = 0.69; p<0.001). "Chicken-wing" morphology had the largest LAA volume at 9.9 (7.9; 12.8) mL, followed by "windsock" morphology with an LAA volume of 9.7 (7.7; 13.1) mL. "Cactus" and "cauliflower" morphologies had considerably smaller LAA volumes, measuring 5.4 (4.6; 7.5) mL and 5.6 (4.4; 7.6) mL, respectively. Bounding box parameters were utilized to distinguish between "windsock" and "chicken-wing" as well as "cauliflower" and "cactus" morphologies. "Windsock" had a maximal LAA depth of 44.3±7.1 mm, while "chicken-wing" measured 40.1±8.6 mm (p<0.001). The sinus values for the bounding box were 0.40±0.06 for "windsock" and 0.44±0.08 for "chicken-wing" (p<0.001). For "cauliflower," the LAA depth averaged 30.42±5.0 mm, whereas for "cactus," it measured 33.4±4.3 mm (p<0.001). The mean sinus of the bounding box was 0.48±0.08 for "cauliflower" and 0.44±0.07 for "cactus" (p<0.05). The utilization of novel bounding box parameters has the potential to aid in the differentiation between different LAA morphologies, such as 'chicken-wing' and 'windsock', as well as 'cactus' and 'cauliflower', especially in cases where the current classification system may not provide clear distinctions.

Abstract 15925: Comparative Mortality, Safety, and Cost Among Stroke Patients Who Received Implantable Loop Records Compared to Continuous External Cardiac Monitors

Background: Implantable loop recorders (ILR) are increasingly used to screen for atrial fibrillation (AF) among patients with stroke, but real-world outcomes are lacking. Goal: To determine comparative effectiveness, safety, and costs of ILR compared with continuous external monitors (CEM) and Holter monitors in a real-world setting of patients with stroke. Methods: This retrospective cohort analysis used the Optum Labs Data Warehouse, which contains longitudinal, de-identified administrative claims. The cohort included patients with recent stroke who received cardiac monitoring from 1/1/2016 - 6/30/2021, comparing those with ILR to those with CEM (>48 hours to 30 days) or Holter (≤48 hours). Eligibility criteria included: ischemic stroke during 6 month baseline; continuous enrollment with medical and pharmacy coverage; no evidence of pacemaker, implantable cardioverter-defibrillator, AF, left atrial appendage ablation, or oral anticoagulants. The primary outcome was 12-month all-cause mortality, secondary outcomes included new diagnosis of AF + initiation of anticoagulants, hemorrhagic stroke, and total and device-related costs. Final analyses were adjusted for CHA 2 DS 2 -VASc score. Results: Among 48,801 individuals, 18.9% received ILR, 59.5% CEM, and 21.6% Holter. Groups had similar demographics and comorbidities (Table). Compared to those with CEM, the ILR group had higher odds of a new diagnosis of AF plus initiation of anticoagulants (OR 2.27; (95% CI 2.09, 2.48)), and hemorrhagic stroke (OR of 1.60 (95% CI 1.34, 1.93)). There was no difference in mortality. Unadjusted direct medical cost of monitoring was substantially higher in the ILR group ($13,975) compared to CEM ($449) and Holter ($149). Conclusions: Although the use of ILRs was associated with increased detection and treatment for AF, there was no impact on all-cause mortality. ILR was associated with increased hemorrhagic stroke and higher costs.

Long-Term Stroke Risk in Patients Undergoing Left Atrial Appendage Ablation With and Without Complete Isolation.

Background: Catheter ablation (CA) for atrial fibrillation (AF), may require ablation beyond the pulmonary veins. Prior data suggest that additional LA ablation, particularly left atrial appendage (LAA) ablation, may alter atrial function leading to increased risk of ischemic stroke or transient ischemic attack (IS/TIA). We sought to study the long-term risk of IS/TIA in patients receiving ablation at the LAA compared to those receiving PVI alone and those receiving PVI with additional non-LAA locations.Methods: 350 patients who underwent CA for AF from 2008 to 2018 were included in the study. Locations of ablation in LA evaluated were the posterior wall, anterior wall, inferior wall, inter-atrial septum, lateral wall and the left atrial appendage (LAA). Patients undergoing LAA ablation were further divided as complete isolation (LAAi) and without complete isolation (LAAa).Results: Mean follow up of 4.8 years. In entire cohort, risk of IS/TIA was 1.62/100 patient-years (pys). The risk was highest in patients with LAAi (3.81/100 pys), followed by ablation LAAa (3.74/100 pys). Amongst all LA locations, only LAAi (HR 3.32, p = 0.03) and LAAa (HR 3.18, p = 0.02) were statistically significant predictors of IS/TIA after adjusting for OAC (Oral anticoagulant) use and baseline CHA2DS2VASc score.Conclusions: During long term follow-up, only ablation at the left atrial appendage with and without complete isolation was independently associated with an increased risk of IS/TIA in patients undergoing CA for AF. Potential strategies to reduce stroke risk, such as LAA closure, should be considered in these patients.

STS Adult Cardiac Surgery Database: 2021 Update on Outcomes, Quality, and Research

The Society of Thoracic Surgeons Adult Cardiac Surgery Database is the most mature and comprehensive cardiac surgery database. It has been the foundation for quality measurement and improvement activities in cardiac surgery, facilitated the generation of accurate risk adjusted performance benchmarks and serves as a platform for novel research. Recent enhancements have added to the database's functionality, ease of use, and value to multiple stakeholders. This report is the sixth in a series of annual reports that provide updated volumes, outcomes, database-related developments, quality improvement initiatives, and research summaries using the Adult Cardiac Surgery Database in the past year.

Durability of cryoballoon left atrial appendage isolation: Acute and invasive remapping electrophysiological findings.

The left atrial appendage (LAA) has been identified as a potential source of atrial fibrillation (AF) and has been described as the "fifth" pulmonary vein (PV). We report our initial experience in LAA isolation (LAAI) using the cryoballoon (CB) and data on durability of CB-LAAI. Patients treated with a CB-LAAI were retrospectively identified. Six weeks after electrical LAAI, patients were scheduled for staged percutaneous LAA closure. During the second procedure, a subset of patients underwent invasive remapping of the LAA. A total of 32 patients (21 males, 68±10 years old) were treated with CB-LAAI. Acute LAAI was achieved in 29 of 32 (91%) patients: single-shot LAAI was observed in 18 of 32 (56%) patients. Acute procedural sustained LAAI was related with a significantly shorter time to LAAI (sustained LAAI: 84±50s vs nonsustained LAAI: 166±76s, P=0.004). Mean procedure and fluoroscopy time were 61±29 and 8±6min, respectively. One left-sided phrenic nerve palsy occurred. In 25 of 32 (78%) patients, a second procedure for percutaneous LAA closure device implantation was performed. In 22 patients, persistency of LAAI was tested: durable LAAI was documented in 16/22 patients (73%). In the present report, CB LAA isolation followed by staged LAA closure appeared to be safe and feasible but more data are required. Time to LAAI played a role in predicting acute sustained LAAI rate. CB LAA ablation leads to 73% of durable LAA isolation.

A Review of the Anatomical and Histological Attributes of the Left Atrial Appendage with Descriptive Pathological Examination of Morphology and Histology.

The left atrial appendage (LAA) has a key role in the embolic complications of atrial fibrillation (AF). It has been studied extensively, from recent interest in the thrombotic implications of various LAA morphologies to LAA occlusion and ablation.We collected eleven post-mortem LAA samples for visual analysis, two were not included due to poor sample quality. On examination of the nine remaining samples, several common patterns of pectinate muscle orientation were noted. The LAA samples were noted to have a smooth circumferential neck of muscular tissue giving rise to a dominant singular smooth trunk of papillary muscle in 6 cases and two trunks in 3 cases. These trunks were either shallow (5 samples) or more muscular and raised (4 samples). Shallow trunks tended to be wider than the raised trunks and may even be circumferential (2 samples). The main trunk arborized to give off papillary muscle branches down to third or fourth order branches. The samples were visually assessed for the percentage of smooth papillary muscle versus non-papillary recesses and were found to have ≤50% smooth muscle in 3 samples, 50-75% in 3 samples and >75% in 3 samples. We performed histological analysis of further LAA samples collected during cardiac surgery in a parallel study. We identified a distinct pattern of myocyte orientation from the neck, mid-section and apical section of the LAA demonstrating arborization of myocyte fibers with minimal communication in distal segments of the LAA. We feel that this information may help understanding of the issues surrounding LAA ablation strategies.

Cardiac CT assessment of tissue thickness at the ostium of the left atrial appendage predicts acute success of radiofrequency ablation.

Tissue thickness at the site of ablation is a determinant of lesion transmurality. We reported the feasibility, safety, and efficacy of longstanding persistent atrial fibrillation ablation, incorporating deliberate left atrial appendage (LAA) isolation and occlusion, and identified systematic differences in ostial LAA tissue thickness in a matched cohort of cadaveric specimens. Preprocedural cardiac computed tomography (CCT) scans were acquired from 22 patients undergoing LAA isolation and subsequent occlusion. Using a novel CCT wall thickness algorithm, LAA ostial wall thickness was assessed in vivo, compared with measurements from the cadaveric specimens, and analyzed for differences between regions that demonstrated acute electrical reconnection and those that did not. Mean tissue thickness calculated for each LAA ostial quadrant was 2.1 (±0.6) mm (anterior quadrant), 1.9 (±0.4) mm (superior quadrant), 1.5 (±0.4) mm (posterior quadrant), and 1.8 (±0.7) mm (inferior quadrant). Tissue was significantly thicker in the anterior (P=0.004) and superior quadrants (P=0.014) than the posterior quadrant. Higher thickness measurements were recorded from quadrants demonstrated to be thicker from histology. Tissue was significantly thicker in regions that demonstrated acute electrical reconnection (1.9 (±0.6) mm) when compared with those that did not (1.6 (±0.5) mm) (P=0.008). CCT imaging may be used to detect differences in wall thickness at different atrial locations and success of LAA ablation may be affected by local tissue thickness. Atrial wall thickness may need to be considered as a metric to guide titration of radiofrequency energy for safe and successful ablation.

Impact of left atrial appendage ridge ablation on the complex fractionated electrograms in persistent atrial fibrillation.

The left atrial appendage (LAA) is a possible key contributor to the maintenance of persistent atrial fibrillation (PsAF). The effect of LAA ostial ablation on global left atrial higher-frequency sources remains unclear. Complex fractionated electrograms (CFEs) and dominant frequency (DF) maps acquired with a NavX system in 58 PsAF patients were enrolled and examined before and after LAA posterior ridge ablation, which followed a stepwise linear ablation. High-density left atrial mapping identified continuous CFE sites in 50 % and high-DFs (≥ 8 Hz) in 53 % of patients at the LAA posterior ridge. In 44 patients in whom AF persisted despite pulmonary vein isolation (PVI) and linear ablation, LAA ablation significantly increased the mean CFE cycle length from 98 ± 29 to 108 ± 30 ms (P<0.0001) and decreased DF from 6.1 ± 0.8 to 5.9 ± 0.8 Hz (P<0.005) within the coronary sinus (CS). A multivariate analysis showed single-procedure failures could be predicted by the left atrial volume index and absence of continuous CFEs at the LAA posterior ridge region. The percent decrease in the global left atrial DF after LAA posterior ridge ablation was significantly lower in the patients with than in those without an enlarged left atrium (LA) (>90 mL/m(2)) (median 0 vs 4.8 %; P<0.01) and significantly lower in the patients with than in those without the absence of continuous CFEs in the LAA posterior ridge region (median 0.6 vs 4.8 %; P<0.05). These findings suggested that an approach incorporating an LAA posterior ridge ablation was effective in modifying higher-frequency sources in the global LA in PsAF patients, but a lesser effect was documented in patients with electroanatomical remodeling of the LA.

Impact of beating heart left atrial ablation on left-sided heart mechanics

The cut-and-sew Cox-Maze procedure is the gold standard for surgical treatment of atrial fibrillation, but it is associated with long-term impairment of left atrial mechanical function. We developed a bipolar, irrigated radiofrequency ablation device. We hypothesized that beating heart radiofrequency left atrial ablation would result in minimal acute changes in left atrial hemodynamics. Six healthy subjects were studied. Combination pressure-conductance catheters were inserted into the left atrium and ventricle. With the use of the device, atrial ablation was performed on the beating heart without cardiopulmonary bypass, including electrical isolation of the posterior left atrium and atrial appendage myocardium. Simultaneous left-sided heart pressure-volume and intracardiac echocardiography data were acquired before ablation, after left atrial appendage ablation alone, and after all ablation (with and without appendage occlusion). The derived indices of left-sided heart mechanical function were examined. Relative to baseline, no significant diminishment in pressure-volume or intracardiac echocardiography-derived indices of global left-sided heart mechanical function were observed after ablation, with or without appendage occlusion. Mitral valve morphology and function were not significantly altered. A significant diminishment of atrial appendage systolic flow was noted after appendage ablation in association with spontaneous echocardiographic contrast in this region. In this model, ablation does not seem to compromise global left-sided heart mechanical function. However, these findings mask regional diminishment in atrial appendage systolic function. This observation demonstrates that electrical isolation of the appendage should be accompanied by its occlusion or excision. Appendage occlusion after ablation does not seem to compromise left-sided heart mechanical function.