Left atrial appendage morphofunctional indices could be predictive of arrhythmia recurrence post-atrial fibrillation ablation: a meta-analysis

BACKGROUND

Left atrium changes are implicated in atrial fibrillation (AF) substrate and are predictive of AF outcomes. Left atrial appendage (LAA) is an integral component of left atrial structure and could be affected by atrial cardiomyopathy. We aimed to elucidate the association between LAA indices and late arrhythmia recurrence after atrial fibrillation catheter ablation (AFCA).

METHODS

The MEDLINE database, ClinicalTrials.gov, medRxiv and Cochrane Library were searched for studies evaluating LAA and late arrhythmia recurrence in patients undergoing AFCA. Data were pooled by meta-analysis using a random-effects model. The primary endpoint was pre-ablation difference in LAA anatomic or functional indices.

RESULTS

A total of 34 studies were found eligible and five LAA indices were analyzed. LAA ejection fraction and LAA emptying velocity were significantly lower in patients with AF recurrence post-ablation [SMD = - 0.66; 95% CI (- 1.01, - 0.32) and SMD = - 0.56; 95% CI (- 0.73, - 0.40) respectively] as compared to arrhythmia free controls. LAA volume and LAA orifice area were significantly higher in patients with AF recurrence post-ablation (SMD = 0.51; 95% CI 0.35-0.67, and SMD = 0.35; 95% CI 0.20-0.49, respectively) as compared to arrhythmia free controls. LAA morphology was not predictive of AF recurrence post-ablation (chicken wing morphology; OR 1.27; 95% CI 0.79-2.02). Moderate statistical heterogeneity and small case-control studies are the main limitations of our meta-analysis.

CONCLUSIONS

Our findings suggest that LAA ejection fraction, LAA emptying velocity, LAA orifice area and LAA volume differ between patients suffering from arrhythmia recurrence post-ablation and arrhythmia free counterparts, while LAA morphology is not predictive of AF recurrence.

Left Atrial Appendage Volume Predicts Atrial Fibrillation Recurrence after Radiofrequency Catheter Ablation: A Meta-Analysis

BACKGROUND

The influence of left atrial appendage volume (LAAV) on the recurrence of atrial fibrillation (AF) following radiofrequency catheter ablation remains unclear.

OBJECTIVES

We performed a meta-analysis to assess whether LAAV is an independent predictor of AF recurrence following radiofrequency catheter ablation.

METHODS

The PubMed and the Cochrane Library databases were searched until March 2022 to identify publications evaluating LAAV in association with AF recurrence after radiofrequency catheter ablation. Seven studies that fulfilled the specified criteria of our analysis were found. We used the Newcastle-Ottawa Scale to evaluate the quality of the studies. The pooled effects were evaluated depending on standardized mean differences (SMDs) or hazard ratios (HRs) with 95% confidence intervals (CIs). P values < 0.05 were considered statistically significant.

RESULTS

A total of 1017 patients from 7 cohort studies with a mean follow-up 16.3 months were included in the meta-analysis. Data from 6 studies (943 subjects) comparing LAAV showed that the baseline LAAV was significantly higher in patients with AF recurrence compared to those without AF (SMD: -0.63; 95% CI: -0.89 to -0,37; all p values < 0.05; I2= 62.6%). Moreover, higher LAAV was independently associated with a significantly higher risk of AF recurrence after radiofrequency catheter ablation (HR: 1.10; 95% CI: 1.02 to 1.18).

CONCLUSIONS

The meta-analysis showed that there is a significant correlation between LAAV and AF recurrence after radiofrequency catheter ablation, and the role of LAAV in AF patients should not be ignored in clinical practice.

Left atrial appendage function and structure predictors of recurrent atrial fibrillation after catheter ablation: A meta-analysis of observational studies

Background

The results of studies evaluating the left atrial appendage (LAA) function and structure as predictors of atrial fibrillation (AF) recurrence after catheter ablation (CA) are contradictory. Therefore, we performed a meta-analysis to assess whether the LAA function and structure can predict the recurrence of AF after CA.

Methods

The PubMed, EMBASE, Web of Science, and Cochrane library databases were used to conduct a comprehensive literature search. Finally, 37 studies encompassing 11 LAA parameters were included in this meta-analysis.

Results

Compared with those in the non-recurrence group, the recurrence group had increased LAA volume (SMD 0.53, 95% CI [0.36, 0.71] p < 0.00001), LAA volume index, LAA orifice area, and LAA orifice short/long axis and decreased LAA emptying flow velocity (SMD -0.54, 95% CI [-0.68, -0.40], P < 0.00001), LAA filling flow velocity, and LAA ejection fraction, while there was no significant difference in LAA morphology or LAA depth.

Conclusion

Large LAA structure of pre-ablation (LAA volume, orifice area, orifice long/short axis, and volume index) and decreased LAA function of pre-ablation (LAA emptying flow velocity, filling flow velocity, ejection fraction, and LASEC) increase the odds of AF recurrence after CA.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42022324533].

Effect of pulmonary vein isolation on left atrial appendage flow in paroxysmal atrial fibrillation

BACKGROUND

Left atrial appendage (LAA) functional modification in the context of pulmonary vein isolation has been a focus point of research and LAA emptying flow velocity (LAAEFV) is considered to reflect LAA contractility, stunning, and fibrosis.

OBJECTIVE

In the present study, we sought to prospectively evaluate short-term LAAEFV changes after radiofrequency (RF) or cryoballoon ablation in paroxysmal AF.

METHODS

This was a prospective substudy of the Effect of Cryoballoon and RF Ablation on Left Atrial Function (CryoLAEF) study (ClinicalTrials.gov Identifier: NCT02611869). Thirty patients, randomly assigned to RF or cryoablation, were prospectively followed. Transesophageal echocardiograms were performed at baseline and at 3 months postablation to measure LAAEFV.

RESULTS

All measurements were performed in sinus rhythm. Overall, LAAEFV was 44.2 [38.5-62.8] cm/s at baseline and was increased to 70.8 [64.8-77.6] cm/s at 3 months' postablation (P < 0.001). Baseline LAAEFV was 52.5 [37.7-68.0] cm/s in the RF group and 42.8 [38.7-52.9] cm/s in the CryoBalloon group (P  =  0.653). At 3 months, the corresponding values were 68.5 [61.9-76.6] cm/s and 73.9 [69.2-79.9] cm/s, respectively (P  =  0.081 for the difference between the two groups at 3 months). The median change in LAAEFV was 11.0 [4.7-26.2] cm/s in the RF group versus 29.6 [15.8-37.0] cm/s in the CryoBalloon group (P  =  0.033).

CONCLUSION

LAA function is improved after catheter ablation with RF or balloon cryoablation in patients with paroxysmal AF, evaluated while in sinus rhythm both at baseline and on follow-up.

Association Between Left Atrial Stiffness Index and Atrial Fibrillation Recurrence in Patients Undergoing Left Atrial Ablation

Background—

Atrial fibrillation (AF) is associated with significant abnormalities of left atrial (LA) systolic and diastolic function. This study describes a novel measure, LA stiffness index, that estimates LA diastolic function and its association with clinical outcomes of catheter ablation.

Methods and Results—

A total of 219 AF patients referred for ablation (59% paroxysmal, mean CHA 2 DS 2 VASc score 1.7±1.4) were enrolled. Atrial pressure and volume loops were prepared from invasive pressure measures and cardiac magnetic resonance imaging volumetric data during sinus rhythm for all patients. An LA stiffness index was created, defined by the ratio of change in LA pressure to volume during passive filling of LA (ΔP/ΔV). Patients were followed prospectively. Mean LA stiffness index for AF patients was 0.6±0.5 mm Hg/mL (paroxysmal AF 0.51±0.4 and persistent AF 0.73±0.6; P <0.001). Linear regression analysis showed a rise in the stiffness index with age, increasing at a rate of 0.02 mm Hg/mL per year ( P <0.001). The LA stiffness index was higher in patients with previous LA ablation(s) for AF (0.51±0.35 versus 0.83±0.70; P <0.001). Forty of 160 patients had recurrence after AF ablation with a mean follow-up of 10.4±7.6 months. Patients with recurrence had higher stiffness index than those without recurrence (0.83±0.46 versus 0.40±0.22; P <0.001).

Conclusions—

LA stiffness index, a novel measure to assess LA diastolic function, increases with age and is higher in persistent AF and in the setting of repeat AF ablation. Greater LA stiffness index was independently associated with recurrence of AF after LA ablation.

Pulmonary vein sleeve cell excitation-contraction-coupling becomes dysynchronized by spontaneous calcium transients

Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia. Substantial evidence indicates that cardiomyocytes located in the pulmonary veins [pulmonary vein sleeve cells (PVCs)] cause AF by generating ectopic electrical activity. Electrical ablation, isolating PVCs from their left atrial junctions, is a major treatment for AF. In small rodents, the sleeve of PVCs extends deep inside the lungs and is present in lung slices. Here we present data, using the lung slice preparation, characterizing how spontaneous Ca2+ transients in PVCs affect their capability to respond to electrical pacing. Immediately after a spontaneous Ca2+ transient the cell is in a refractory period and it cannot respond to electrical stimulation. Consequently, we observe that the higher the level of spontaneous activity in an individual PVC, the less likely it is that this PVC responds to electrical field stimulation. The spontaneous activity of neighbouring PVCs can be different from each other. Heterogeneity in the Ca2+ signalling of cells and in their responsiveness to electrical stimuli are known pro-arrhythmic events. The tendency of PVCs to show spontaneous Ca2+ transients and spontaneous action potentials (APs) underlies their potential to cause AF.

The Effect of Catheter Ablation on Left Atrial Size and Function for Patients with Atrial Fibrillation: An Updated Meta-Analysis

BACKGROUND

Catheter ablation (CA) for atrial fibrillation (AF) is now an important therapeutic modality for patients with AF. However, data regarding changes in left atrial (LA) function after CA have indicated conflicting results depending on the AF types, follow-up period, and the analytical imaging tools. The objective of this review was to analyze the effect of CA on the LA size and function for patients with AF.

METHODS

We searched for studies regarding LA size and function pre- and post-ablation in PubMed, Embase, the Cochrane Library, and Web of Knowledge through May 2014. LA function was measured by LA ejective fraction (LAEF), LA active ejective fraction (LAAEF), or both. Total and subgroup analyses were implemented using Cochrane Review Manager Version 5.2. Weighted mean differences with 95% confidence intervals were used to express the results of continuous outcomes using fixed or random effect models. I2 was used to calculate heterogeneity. To assess publication bias, Egger's test and Begg's funnel plot were performed using Stata 12.0.

RESULTS

Twenty-five studies (2040 enrolled patients) were selected for this meta-analysis. The LA diameter (LAD), maximum LA volume, and minimal LA volume were significantly decreased post-ablation, as compared with those at a pre-ablation visit. Compared with the pre-ablation outcomes, we found no significant differences in LAEF/LAAEF at a post-ablation follow-up. Decreases in LA volume and LAEF remained significant post-ablation for paroxysmal AF (PAF); however, the LAEF was insignificant changes in persistent AF (PeAF). Heterogeneity was significant in spite which individual study was excluded. A publication bias was not found. In a meta-regression analysis, we did not find any factor that contributed to the heterogeneity.

CONCLUSION

With CA, LA volumes and LAD were decreased significantly in patients with AF; LAEF was not significant changes in patients with PeAF but decreased in those with PAF.

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.

Spontaneous, pro-arrhythmic calcium signals disrupt electrical pacing in mouse pulmonary vein sleeve cells

The pulmonary vein, which returns oxygenated blood to the left atrium, is ensheathed by a population of unique, myocyte-like cells called pulmonary vein sleeve cells (PVCs). These cells autonomously generate action potentials that propagate into the left atrial chamber and cause arrhythmias resulting in atrial fibrillation; the most common, often sustained, form of cardiac arrhythmia. In mice, PVCs extend along the pulmonary vein into the lungs, and are accessible in a lung slice preparation. We exploited this model to study how aberrant Ca(2+) signaling alters the ability of PVC networks to follow electrical pacing. Cellular responses were investigated using real-time 2-photon imaging of lung slices loaded with a Ca(2+)-sensitive fluorescent indicator (Ca(2+) measurements) and phase contrast microscopy (contraction measurements). PVCs displayed global Ca(2+) signals and coordinated contraction in response to electrical field stimulation (EFS). The effects of EFS relied on both Ca(2+) influx and Ca(2+) release, and could be inhibited by nifedipine, ryanodine or caffeine. Moreover, PVCs had a high propensity to show spontaneous Ca(2+) signals that arose via stochastic activation of ryanodine receptors (RyRs). The ability of electrical pacing to entrain Ca(2+) signals and contractile responses was dramatically influenced by inherent spontaneous Ca(2+) activity. In PVCs with relatively low spontaneous Ca(2+) activity (<1 Hz), entrainment with electrical pacing was good. However, in PVCs with higher frequencies of spontaneous Ca(2+) activity (>1.5 Hz), electrical pacing was less effective; PVCs became unpaced, only partially-paced or displayed alternans. Because spontaneous Ca(2+) activity varied between cells, neighboring PVCs often had different responses to electrical pacing. Our data indicate that the ability of PVCs to respond to electrical stimulation depends on their intrinsic Ca(2+) cycling properties. Heterogeneous spontaneous Ca(2+) activity arising from stochastic RyR opening can disengage them from sinus rhythm and lead to autonomous, pro-arrhythmic activity.