Differences in the structural characteristics and distribution of epicardial adipose tissue between left and right atrial fibrillation

Epicardial adipose tissue density predicts the presence of atrial fibrillation and its recurrence after catheter ablation: three-dimensional reconstructed image analysis

Epicardial adipose tissue (EAT) induces inflammation in the atria and is associated with atrial fibrillation (AF). Several studies have examined the relationship between EAT volume (EAT-V) and density (EAT-D) and the presence of AF after catheter ablation. However, conclusions have been inconsistent. This study included 43 consecutive patients who underwent catheter ablation for AF and 30 control patients. EAT-V and EAT-D around the entire heart, entire atrium, left atrium (LA), and right atrium (RA) were measured in detail using reconstructed three-dimensional (3D) EAT images from dual-source computed tomography (CT). None of the measurements of EAT-V differed significantly between patients with AF and controls or between patients with recurrent AF and those without. On the other hand, all measurements of EAT-D were higher in patients with AF than in controls (entire atrium, p < 0.001; RA, p < 0.001; LA, p = 0.002). All EAT-D measurements were associated with the presence of AF. Among patients with AF who underwent ablation, all EAT-D measurements were higher in patients with recurrent AF than in those without. The difference was significant for EATRA-D (p = 0.032). All atrial EAT-D values predicted recurrent AF (EATRA-D: hazard ratio [HR], 1.208; 95% confidence interval [95% CI], 1.053-1.387; p = 0.007; EATLA-D: HR, 1.108; 95% CI 1.001-1.225; p = 0.047; EATatrial-D: HR, 1.174; 95% CI 1.040-1.325; p = 0.010). The most sensitive cutoffs for predicting recurrent AF were highly accurate for EATRA-D (area under the curve [AUC], 0.76; p < 0.01) and EATatrial-D (AUC = 0.75, p < 0.05), while the cutoff for EATLA-D had low accuracy (AUC, 0.65; p = 0.209). For predicting the presence of AF and recurrent AF after catheter ablation, 3D analysis of atrial EAT-D, rather than EAT-V, is useful.

Standardized 2D atrial mapping and its clinical applications

The visualization and comparison of electrophysiological information in the atrium among different patients could be facilitated by a standardized 2D atrial mapping. However, due to the complexity of the atrial anatomy, unfolding the 3D geometry into a 2D atrial mapping is challenging. In this study, we aim to develop a standardized approach to achieve a 2D atrial mapping that connects the left and right atria, while maintaining fixed positions and sizes of atrial segments across individuals. Atrial segmentation is a prerequisite for the process. Segmentation includes 19 different segments with 12 segments from the left atrium, 5 segments from the right atrium, and two segments for the atrial septum. To ensure consistent and physiologically meaningful segment connections, an automated procedure is applied to open up the atrial surfaces and project the 3D information into 2D. The corresponding 2D atrial mapping can then be utilized to visualize different electrophysiological information of a patient, such as activation time patterns or phase maps. This can in turn provide useful information for guiding catheter ablation. The proposed standardized 2D maps can also be used to compare more easily structural information like fibrosis distribution with rotor presence and location. We show several examples of visualization of different electrophysiological properties for both healthy subjects and patients affected by atrial fibrillation. These examples show that the proposed maps provide an easy way to visualize and interpret intra-subject information and perform inter-subject comparison, which may provide a reference framework for the analysis of the atrial fibrillation substrate before treatment, and during a catheter ablation procedure.

Quantification of right atrial fibrosis by cardiac magnetic resonance: verification of the method to standardize thresholds

INTRODUCTION AND OBJECTIVES

Late gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) allows noninvasive detection of left atrial fibrosis in patients with atrial fibrillation (AF). However, whether the same methodology can be used in the right atrium (RA) remains unknown. Our aim was to define a standardized threshold to characterize RA fibrosis in LGE-CMR.

METHODS

A 3 Tesla LGE-CMR was performed in 53 individuals; the RA was segmented, and the image intensity ratio (IIR) calculated for the RA wall using 1 557 767 IIR pixels (40 994±10 693 per patient). The upper limit of normality of the IIR (mean IIR+2 standard deviations) was estimated in healthy volunteers (n=9), and patients who had undergone previous typical atrial flutter ablation (n=9) were used to establish the dense scar threshold. Paroxysmal and persistent AF patients (n=10 each) were used for validation. IIR values were correlated with a high-density bipolar voltage map in 15 patients undergoing AF ablation.

RESULTS

The upper normality limit (total fibrosis threshold) in healthy volunteers was set at an IIR = 1.21. In the postablation group, 60% of the maximum IIR pixel (dense fibrosis threshold) was calculated as IIR = 1.29. Endocardial bipolar voltage showed a weak but significant correlation with IIR. The overall accuracy between the electroanatomical map and LGE-CMR to characterize fibrosis was 56%.

CONCLUSIONS

An IIR > 1.21 was determined to be the threshold for the detection of right atrial fibrosis, while an IIR > 1.29 differentiates interstitial fibrosis from dense scar. Despite differences between the left and right atria, fibrosis could be assessed with LGE-CMR using similar thresholds in both chambers.

Progressive and Simultaneous Right and Left Atrial Remodeling Uncovered by a Comprehensive Magnetic Resonance Assessment in Atrial Fibrillation

Background Left atrial structural remodeling contributes to the arrhythmogenic substrate of atrial fibrillation (AF), but the role of the right atrium (RA) remains unknown. Our aims were to comprehensively characterize right atrial structural remodeling in AF and identify right atrial parameters predicting recurrences after ablation. Methods and Results A 3.0 T late gadolinium enhanced-cardiac magnetic resonance was obtained in 109 individuals (9 healthy volunteers, 100 patients with AF undergoing ablation). Right and left atrial volume, surface, and sphericity were quantified. Right atrial global and regional fibrosis burden was assessed with validated thresholds. Patients with AF were systematically followed after ablation for recurrences. Progressive right atrial dilation and an increase in sphericity were observed from healthy volunteers to patients with paroxysmal and persistent AF; fibrosis was similar among the groups. The correlation between parameters recapitulating right atrial remodeling was mild. Subsequently, remodeling in both atria was compared. The RA was larger than the left atrium (LA) in all groups. Fibrosis burden was higher in the LA than in the RA of patients with AF, whereas sphericity was higher in the LA of patients with persistent AF only. Fibrosis, volume, and surface of the RA and LA, but not sphericity, were strongly correlated. Tricuspid regurgitation predicted right atrial volume and shape, whereas diabetes was associated with right atrial fibrosis burden; sex and persistent AF also predicted right atrial volume. Fibrosis in the RA was mostly located in the inferior vena cava-RA junction. Only right atrial sphericity is significantly associated with AF recurrences after ablation (hazard ratio, 1.12 [95% CI, 1.01-1.25]). Conclusions AF progression associates with right atrial remodeling in parallel with the LA. Right atrial sphericity yields prognostic significance after ablation.

Cardiac Computed Tomography-Based Epicardial Adipose Tissue Assessment Reveals Association With Electroanatomical Voltage Mapping in Patients With Atrial Fibrillation

BACKGROUND

Epicardial adipose tissue (EAT) around the left atrium (LA) can change the electric conduction of the LA, potentially leading to atrial fibrillation (AF).

AIM

The aim of this study was to evaluate whether an association existed between EAT and the electrophysiological properties of adjacent atrial myocardium in patients with AF.

METHOD

A total of 201 consecutive patients referred for initial AF catheter ablation were prospectively included. A preprocedural computed tomography scan was performed to assess total and LA-EAT parameters. Detailed point-by-point voltage mapping using an electroanatomical mapping system was realised to assess the LA low-voltage zone (LVZ), defined as an area with bipolar electrograms ≤0.5 mV during sinus rhythm.

RESULTS

Ninety-one (91) patients (45.3%) presented at least one LVZ. They had a significantly more severe AF pattern (p=0.04) than patients without LVZ, and little difference existed with regard to other clinical variables. Patients with LVZ presented significantly more total EAT volume (162.4±71.3 mL vs 135.5±57.2 mL; p=0.03) and LA-EAT volume (26.4±15.9 mL vs 20.9±10.5 mL; p<0.01) than no-LVZ patients. Multivariable logistic regression analyses revealed total EAT volume index to be an independent predictor of the presence of LVZ (odds ratio [OR] 1.01; 95% confidence interval [CI] 1.01-1.04; p<0.01) and LA-EAT percentage to be an independent predictor of severe LVZ (OR 1.34; 95% CI 1.18-1.64; p<0.001).

CONCLUSIONS

The EAT volume and its distribution around the LA may indicate the presence and severity of LVZ. The assessment of the volume of EAT and its distribution may lead to better risk stratification in patients with AF.

Imaging assessment of the right atrium: anatomy and function

The right atrium (RA) is the cardiac chamber that has been least well studied. Due to recent advances in interventional cardiology, the need for greater understanding of the RA anatomy and physiology has garnered significant attention. In this article, we review how a comprehensive assessment of RA dimensions and function using either echocardiography, cardiac computed tomography, and magnetic resonance imaging may be used as a first step towards a better understanding of RA pathophysiology. The recently published normative data on RA size and function will likely shed light on RA atrial remodelling in atrial fibrillation (AF), which is a complex phenomenon that occurs in both atria but has only been studied in depth in the left atrium. Changes in RA structure and function have prognostic implications in pulmonary hypertension (PH), where the increased right ventricular (RV) afterload first induces RV remodelling, predominantly characterized by hypertrophy. As PH progresses, RV dysfunction and dilatation may begin and eventually lead to RV failure. Thereafter, RV overload and increased RV stiffness may lead to a proportional increase in RA pressure. This manuscript provides an in-depth review of RA anatomy, function, and haemodynamics with particular emphasis on the changes in structure and function that occur in AF, tricuspid regurgitation, and PH.

Diverse Adiposity and Atrio-Ventricular Dysfunction across Obesity Phenotypes: Implication of Epicardial Fat Analysis

Obesity has been conceptualized as a highly heterogeneous condition. We aim to investigate chamber-specific effects of obesity on the heart and relevant outcomes. A total of 2944 symptom-free individuals (age: 47.5 ± 10.0 years), free of known cardiovascular diseases were classified into four categories based on body mass index (BMI) (as normal-weight (NW) vs. overweight/obese (O)) and metabolic status (metabolically-healthy (MH) vs. unhealthy (MU)). Epicardial adipose thickness (EAT) using echocardiography method. Speckle-tracking based atrio-ventricular (LA/LV) deformations including global longitudinal strain (GLS) and peak atrial longitudinal strain (PALS) were also analyzed. MUNW had higher cardiometabolic risks and more impaired diastolic and GLS/PALS than MHNW phenotype. Both MHO and MUO phenotypes exhibited worst atrial functions. Greater EAT was independently associated with worse GLS and PALS after correcting for various anthropometrics, LV mass and LA volume, respectively, with unfavorable LA effects from EAT being more pronounced in the NW phenotypes (both p interactions < 0.05). During a median follow-up period of 5.3 years, BMI/EAT improved the reclassification for atrial fibrillation (AF) incidence (p for net reclassification improvement < 0.05) mainly in the NW phenotypes (p interaction < 0.001). Categorization of clinical obesity phenotypes based on excessive visceral adiposity likely provides increment prognostic impacts on atrial dysfunction, particularly in non-obese phenotypes.

Higher Incidence of Atrial Fibrillation in Left Ventricular-to-Right Atrial Shunt Patients

Background: The possible association between atrial fibrillation (AF) and left ventricular-to-right atrial shunt (LVRAS) has never been reported yet. The present study investigated the incidence of AF in LVRAS. Methods: This was a retrospective study of consecutive patients undergoing echocardiography at a single tertiary center. Clinical data, laboratory results and echocardiography parameters such as right atrial area (RAA), right ventricular end diastolic diameter (RVDD) and left atrial diameter (LAD) were compared between LVRAS group and non-LVRAS patients, and between AF and non-AF patients. Propensity score matching was performed to decrease the effect of confounders. Logistic regression analysis and mediation analysis were used to estimate the relationship between LVRAS and AF. Results: A total of 3,436 patients were included, and the incidence of LVRAS was 1.16% (n = 40). The LVRAS group had significantly larger RAA, RVDD and LAD compared with non-LVRAS group. Those who suffered from AF showed larger RAA, RVDD and LAD compared with those who maintained sinus rhythm. Multivariable logistic regression showed that gender (OR: 0.608), age (OR: 1.048), LAD (OR: 1.111), mean pulmonary artery blood pressure (mPAP, OR: 1.023), TR (OR: 2.309) and LVRAS (OR: 12.217) were significant factors for AF. RAA could partially mediate the relationship between LVRAS and AF according to the result of mediation analysis. Conclusions: Our study suggested that LVRAS, TR, LAD, mPAP, age and male were risk factors for AF. RA enlargement might underlie mechanism in the higher incidence of AF in LVRAS patients. These findings should be confirmed in larger prospective studies.

Interatrial distance predicts the necessity of additional carina ablation to isolate the right-sided pulmonary veins

Background

Ablation of the pulmonary vein (PV) carina is occasionally required for PV isolation (PVI). Marshall bundle and epicardial connections between the right-sided PV (RtPV) carina and right atrium (RA) may be one of the mechanisms that necessitates carina ablation.

Objective

We sought to clarify anatomical characteristics predictive of the necessity of carina ablation.

Methods

Forty-five consecutive patients undergoing radiofrequency catheter ablation of atrial fibrillation were prospectively included in this study. Left atrial (LA) and PV size and morphology, and interatrial distance in the posterior aspect, were measured on cardiac computed tomography (CT) images.

Results

For right-sided PVI, the patients were divided into 2 groups based on the necessity of RtPV carina ablation, Carina-ABL group (n = 21) and Non-Carina-ABL group (n = 24). The distance between the anterior portion of the RtPV carina and RA was shorter in the Carina-ABL group vs in the Non-Carina-ABL group (7.7 ± 1.7 mm/m² vs 9.5 ± 2.3 mm/m²; P = .005), whereas other anatomical parameters (LA and RA volumes, right inferior PV angle, and ostial diameters of the RtPVs) did not differ between the groups. For left-sided PVI, the ostial diameter and circumference of the left superior PV were smaller in the Carina-ABL group (n = 13) vs the Non-Carina-ABL group (n = 32) (8.6 ± 2.1 mm/m² vs 7.3 ± 1.5 mm/m²; P = .044, and 34.9 ± 6.0 mm/m² vs 30.1 ± 5.1 mm/m²; P = .017, respectively).

Conclusions

A shorter interatrial distance for right-sided PVI and a smaller PV ostium for left-sided PVI were associated with the necessity of additional carina ablation. The presence and location of the epicardial fibers may be affected by the atrial and PV geometry.

Epicardial adipose tissue and atrial fibrillation: pathophysiological mechanisms, clinical implications, and potential therapies

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is associated with increased cardiovascular morbidity and mortality. Epicardial adipose tissue (EAT) serves as a biologically active organ with important endocrine and inflammatory function. Review An accumulating body of evidence suggests that EAT is associated with the initiation, perpetuation, and recurrence of AF, but the precise role of EAT in AF pathogenesis is not completely elucidated. Pathophysiological mechanisms involve adipocyte infiltration, profibrotic and pro-inflammatory paracrine effects, oxidative stress, neural mechanisms, and genetic factors.

CONCLUSIONS

Notably, EAT accumulation seems to be associated with stroke and adverse cardiovascular outcomes in AF. Weight loss, specific medications and ablation of ganglionated plexi (GP) seem to be potential therapies in this setting.

Biatrial volume, estimated using magnetic resonance imaging, predicts atrial fibrillation recurrence after ablation

INTRODUCTION

The predictive value of left atrial volume (LAV) in atrial fibrillation (AF) is known, but the relationship of right atrial volume (RAV) and biatrial volume (BAV) with AF recurrence after pulmonary vein isolation (PVI) is not clear. Cardiac magnetic resonance (CMR) imaging allows us to more precisely quantify atrial volume. We investigated LAV, RAV, and BAV as predictors of AF recurrence following PVI in AF patients.

METHODS AND RESULTS

We assessed 100 AF patients (age = 59.8 ± 9.5 years, 74 males, 26 females) who underwent nonenhanced CMR before their first PVI. LAV and RAV were measured using CMR. All patients were in sinus rhythm during CMR. BAV was calculated as the sum of LAV and RAV. During the 8-month follow-up, AF recurrence occurred in 23 patients. LAV, RAV, and BAV were significantly greater in patients with AF recurrence than in those without (LAV, 103.7 ± 25.8 vs 81.8 ± 24.2 mL, P < 0.001; RAV, 109.4 ± 27.0 vs 82.2 ± 19.6 mL, P < 0.001; BAV, 213.1 ± 46.7 vs 164.1 ± 38.7 mL, P < 0.001). Multivariate logistic regression analysis revealed that increased LAV, RAV, and BAV were significantly correlated with AF recurrence. The area under the receiver operation characteristic curve for BAV showed the largest value compared to that of LAV or RAV alone.

CONCLUSIONS

LAV, RAV, and BAV were independent predictors of AF recurrence after PVI. Quantifying BAV may additionally improve prognostic stratification compared with LAV or RAV.

Mechanistic implication of decreased plasma atrial natriuretic peptide level for transient rise in the atrial capture threshold early after ICD or CRT-D implantation

PURPOSE

Despite the use of steroid-eluting leads, a transient but not persistent rise in the atrial/ventricular capture threshold (TRACT/TRVCT) can occur early after pacemaker implantation in patients with sick sinus syndrome. This study aimed to assess the prevalence, predictors, and mechanisms of TRACT/TRVCT in patients with heart failure undergoing implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT) implantation.

METHOD

One hundred twenty consecutive patients underwent ICD (N = 70) or CRT (N = 50) implantation. Capture threshold was measured at implantation, 7-day, 1-month, and 6-month post-implantation. TRACT/TRVCT was defined as a threshold rise at 7 days by more than twice the height of the threshold at implantation, with full recovery during follow-up. Atrial and brain natriuretic peptide (ANP and BNP) levels were measured before implantation.

RESULTS

TRACT and TRVCT were observed in 13 (11%) and 10 (8%) patients, respectively. Patients with TRACT had lower ANP level (median 72 [42-105] vs. 99 [49-198] pg/mL, P = 0.06), lower ANP/BNP ratio (0.29 [0.20-0.36] vs. 0.50 [0.33-0.70], P < 0.01), lower atrial sensing amplitude (2.0 ± 0.8 vs. 2.7 ± 1.3 mV, P = 0.02), and lower left ventricular ejection fraction (32 ± 12 vs. 40 ± 14%, P = 0.04) than those without TRACT. TRACT recovered within 1 month, whereas TRVCT recovered within 6 months. In multivariable analysis, ANP/BNP ratio was the only independent predictor of TRACT (OR, 0.018; 95% CI, 0.001-0.734; P = 0.034).

CONCLUSIONS

Atrial degenerative change characterized by lower ANP/BNP ratio was associated with the occurrence of TRACT in patients with heart failure. TRVCT could also occur, but it required a longer recovery time than TRACT.

Underrecognized entity of the transient rise in the atrial capture threshold early after dual-chamber pacemaker implantation

BACKGROUND

Steroid-eluting pacemaker leads suppress acute rises in pacing threshold by preventing inflammatory processes. However, we occasionally encounter not persistent but transient rise in the atrial capture threshold (TRACT) early after pacemaker implantation. We believe that this phenomenon is underrecognized in clinical practice and may potentially lead to unnecessary reintervention. We aimed to clarify the prevalence, predictors, and possible mechanisms of TRACT.

METHODS AND RESULTS

We reviewed clinical records from 239 consecutive patients who underwent dual-chamber pacemaker implantation for sick sinus syndrome (SSS) (N = 102) or atrioventricular block (AVB) (N = 137). Atrial capture threshold was measured at implantation and 7 days, 2 months, and 8 months postimplantation. TRACT was defined as a rise in the threshold at day 7 to ≥twice that at implantation, with an absolute value ≥1.0 V/0.4 ms, and full recovery by 8 months into follow-up. TRACT was observed in 15 patients (6%), of whom13 (87%) suffered from SSS but not AVB. Patients with TRACT had greater body mass index (BMI) (25 ± 5 kg/m² vs 23 ± 4 kg/m² , P = 0.01), larger left atrium (42 ± 5 mm vs 38 ± 7 mm, P = 0.03), and were more likely to suffer from paroxysmal atrial fibrillation (60% vs 31%, P = 0.02) than those without TRACT. In multivariable logistic regression analysis, BMI and SSS were the independent predictors of TRACT (odds ratio [OR], 1.172; 95% confidence interval [CI], 1.019-1.349; P = 0.03 and OR, 11.53; 95% CI, 2.010-66.21; P = 0.006, respectively).

CONCLUSIONS

The distinct phenomenon of TRACT was not rare in clinical practice early after dual-chamber pacemaker implantation, and its occurrence was strongly associated with SSS.