Do the Left Atrial Substrate Properties Correlate with the Left Atrial Mechanical Function? A Novel Insight from the Electromechanical Study in Patients with Atrial Fibrillation

Low atrial natriuretic peptide to brain natriuretic peptide ratio is associated with left atrial remodeling

AIMS

Atrial natriuretic peptide (ANP) deficiency is thought to be one of the causes of heart failure induced by atrial fibrillation (AF). Although ANP deficiency is thought to occur as a result of atrial remodeling, data to explain this mechanism are limited. The purpose of this study was to investigate the association between ANP and left atrial remodeling or prognosis of heart failure in patients with AF ablation.

METHODS

In total, 373 consecutive patients who underwent initial ablation for persistent AF [age, 67 ± 10 years; female, 97 (26%)] were retrospectively enrolled. ANP and brain natriuretic peptide (BNP) were measured before the procedure and the ANP/BNP ratio was calculated. Left atrial volume index, left atrial appendage emptying velocity, and left atrial low-voltage areas (LVAs) were used as left atrial-remodeling parameters. The primary outcome of heart failure was defined as the composite of all-cause death or hospitalization due to worsening heart failure.

RESULTS

The median ANP level was 116 (71-178) pg/ml and the median ANP/BNP ratio was 0.65 (0.46-1.00). The ANP/BNP ratio decreased with increasing left atrial volume index or LVAs and with decreasing left atrial appendage emptying velocity. During the 5-year follow-up, freedom from the primary outcome was significantly lower in patients with ANP/BNP ratio ≤0.65 than in those with ANP/BNP ratio >0.65 (84.6% versus 95.6%, P  < 0.01).

CONCLUSION

Secretion of ANP relative to BNP decreased with progression of left atrial remodeling in patients with AF ablation. Furthermore, prognosis of heart failure was poor in patients with a low ANP/BNP ratio.

Left atrial epicardial adipose tissue is closely associated with left atrial appendage flow velocity in patients with nonvalvular atrial fibrillation

Epicardial adipose tissue (EAT) can play an important role in the occurrence and development of atrial fibrillation and stroke. In this study, we explored the relationship between left atrial epicardial adipose tissue (LA-EAT) and left atrial appendage flow velocity (LAA-FV) in patients with nonvalvular atrial fibrillation (NV-AF). A total of 145 patients with NV-AF who underwent their first radiofrequency ablation were enrolled. They underwent left aortopulmonary vein computed tomography angiography (CTA) and transesophageal echocardiography (TEE) before AF ablation. Left atrial (LA) electroanatomical mapping was performed intraoperatively to assess left atrial voltage. Univariate regression analysis showed that LAA-FV was lower in patients with a low voltage zone (LAA-FV; 35.02 ± 10.78 cm/s vs. 50.60 ± 12.17 cm/s, P < 0.001). A multiple linear regression model showed that the left atrial low voltage zone (β = − 0.311 P < 0.001), LA-EAT volume (β = − 0.256 P < 0.001), left atrial appendage shape (β = − 0.216 P = 0.041), LAVI (β = − 0.153 P = 0.041), and type of atrial fibrillation (paroxysmal vs. persistence) (β = − 0.146 P < 0.048) were independent predictors of LAA-FV. In NV-AF patients, the increase in LA-EAT volume is related to the decrease in LAA-FV.

P wave duration ≥150 ms predicts poor left atrial function and ablation outcomes in non-paroxysmal atrial fibrillation

BACKGROUND

It remains unknown whether P wave duration (PWD) ≥ 150 ms measured after extensive radiofrequency catheter ablation (RFCA) can identify non-paroxysmal atrial fibrillation (non-PAF) patients at increased risk of atrial tachyarrhythmia recurrence. We investigated the predicting power of PWD and its association with left atrial (LA) reverse remodeling in patients with non-PAF undergoing pulmonary vein isolation with LA linear ablation.

METHODS

We retrospectively evaluated 136 patients who underwent RFCA for drug-refractory non-PAF. Electroanatomic mapping was acquired during AF. Low-voltage area (LVA) was defined as an area with bipolar voltage ≤0.5 mV. Electrocardiography and echocardiography were performed during sinus rhythm 1 day and 3 months after RFCA. PWD was measured using amplified 12‑lead electrocardiography. Prolonged PWD was defined as maximum PWD ≥ 150 ms.

RESULTS

Over a mean follow-up duration of 48 ± 35 months, 28 patients experienced atrial tachyarrhythmia recurrence. PWD was positively correlated with LVA (r = 0.527, p < 0.001) and inversely correlated with LA emptying fraction (r = -0.399, p < 0.001). PWD was shortened and LA emptying fraction (LAEF) was increased in patients without atrial tachyarrhythmia recurrence during follow-up. Atrial tachyarrhythmia-free survival was significantly more likely in patients without a prolonged PWD (83.5% vs 60.7%, p = 0.002). Multivariate analysis showed that LAEF and PWD were independent predictors of atrial tachyarrhythmia recurrence.

CONCLUSIONS

PWD ≥ 150 ms measured after RFCA can identify patients with non-PAF at increased risk of atrial tachyarrhythmia recurrence. PWD is correlated with LVA and LAEF and reflects LA reverse remodeling.

Impact of Left Atrial Sphericity Index on the Outcome of Catheter Ablation for Atrial Fibrillation

Left atrial sphericity index (LASI) is one significant geometric remodeling parameter to evaluate the prognosis of atrial fibrillation (AF). We aimed to determine whether transthoracic echocardiography (TTE)-derived LASI may help predict the outcomes following AF radiofrequency catheter ablation (RFCA). This prospective study enrolled 190 consecutive AF patients who underwent TTE 24 h before RFCA. LASI was calculated as the ratio of left atrial maximum volume to spherical volume. After 1-year follow-up, 56 patients (29.5%) relapsed. Multivariate Cox regression showed that LASI (hazard ratio = 1.48, 95% Cl 1.15-1.92, P = 0.003) was an independent predictor of AF recurrence. Stratifying patients into four subgroups with different LAVI showed that high LASI value indicated a high risk of recurrence, especially in patients with mildly and moderately enlarged atria (the recurrence rate was 0% vs. 26.3%, P = 0.049; 9.5% vs. 40.9%, P = 0.018, respectively). In conclusion, TTE-derived LASI may be useful to predict AF recurrence after RFCA.

Correlation between the left atrial low-voltage area and the cardiac function improvement after catheter ablation for paroxysmal atrial fibrillation

BACKGROUND

The impact of the left atrial low-voltage area (LVA) on the cardiac function improvement following ablation for atrial fibrillation (AF) is unclear.

METHODS

In 49 patients with paroxysmal AF who underwent ablation, the left ventricular stroke volume index (SVI) was repeatedly measured using an impedance cardiography until 6 months after ablation. We defined the cardiac function improvement as a 20% increase in the SVI. The LVA (the area with the voltage amplitude of <0.5 mV) was assessed before ablation.

RESULTS

The reduced baseline SVI (<33 mL/m2) was observed in 18 (37%) patients. The SVI increased following ablation (from 36 ± 5 to 39 ± 6 mL/m2, P < .001). We observed the cardiac function improvement in 14 (29%) patients. The LVA was smaller in patients with the improved cardiac function than in those without (8.3% ± 5.2% vs 14.0% ± 8.5%, P = .026). The multivariate analysis revealed that only the LVA was independently associated with the cardiac function improvement (odds ratio, 0.878; 95% confidence interval: 0.778-0.991, P = .036). Furthermore, LVAs of the anterior (7.9% ± 7.6% vs 18.2% ± 15.5%, P = .022), septal (12.0 ± 7.3% vs 20.7% ± 13.8%, P = .031), and roof walls (6.9% ± 6.0% vs 16.9% ± 15.2%, P = .022) were smaller in patients with the improved cardiac function than in those without.

CONCLUSIONS

The LVA was related to the cardiac function improvement following ablation in patients with paroxysmal AF.

Young Patients with Unknown Stroke and Little P Wave in ECG

Here we report two young patients with atrial fibrillation/atrial flutter complicated with cardiogenic cerebral embolism. Electrophysiological study revealed a large area of low-voltage zone or area of electric silence in both sides of the atrium during restoration of sinus rhythm, and the echocardiogram showed loss of mechanical function of the atrium. The electrical-mechanical dysfunction of the atrium was considered to be the cause of embolic event in this type of patient who was "very low" stroke risk atrial fibrillation or atrial flutter. The idiopathic, fibrotic atrial cardiomyopathy may be underlying in these patients.

U-Shaped Relationship Between Left Atrium Size on Echocardiography and 1-Year Recurrence of Atrial Fibrillation After Radiofrequency Catheter Ablation - Prognostic Value Study

BACKGROUND

The larger the left atrium anteroposterior dimension (LAD) and left atrium volume (LAV), the stronger the association with recurrent atrial fibrillation (AF) after radiofrequency catheter ablation (RFCA). Patients with a smaller left atrium (LA) size, however, also have increased AF recurrence.Methods and Results:In 521 patients, routine 48-h Holter electrocardiogram and echocardiography were obtained at each outpatient visit every 3 months for 12 months. On multivariate analysis, AF type, LAD, and LAV calculated using the ellipsoid model/body surface area (LAVe/BSA) were independent predictors of AF recurrence. Patients were divided into 7 groups at 0.4-cm increments of LAD: ≤3 cm, LAD≤3 cm, 3.0<LAD≤3.4 cm, 3.4<LAD≤3.8 cm, 3.8<LAD≤4.2 cm, 4.2<LAD≤4.6 cm, 4.6<LAD≤5.0 cm; and LAD>5.0 cm. Compared with the 3.4-3.8-cm group, the adjusted HR were 3.88 (95% CI: 2.02-7.46, P<0.001), 1.03 (95% CI: 0.50-2.12, P=0.939), 0.96 (95% CI: 0.52-1.77, P=0.901), 1.36 (95% CI: 0.72-2.57, P=0.347), 3.04 (95% CI: 1.67-5.53, P<0.001), and 4.07 (95% CI: 1.93-8.60, P<0.001), respectively. Similarly, we divided LAVe/BSA into 8 groups and also observed a U-shaped curve for AF recurrence.

CONCLUSIONS

Both larger and smaller LAD and LAVe/BSA were associated with a higher risk of AF recurrence 1 year after RFCA. The association of LA size and AF recurrence after RFCA is represented by a U-shaped curve.

Left atrial voltage mapping: defining and targeting the atrial fibrillation substrate

Low atrial endocardial bipolar voltage, measured during catheter ablation for atrial fibrillation (AF), is a commonly used surrogate marker for the presence of atrial fibrosis. Low voltage shows many useful associations with clinical outcomes, comorbidities and has links to trigger sites for AF. Several contemporary trials have shown promise in targeting low voltage areas as the substrate for AF ablation; however, the results have been mixed. In order to understand these results, a thorough understanding of voltage mapping techniques, the relationship between low voltage and the pathophysiology of AF, as well as the inherent limitations in voltage measurement are needed. Two key questions must be answered in order to optimally apply voltage mapping as the road map for ablation. First, are the inherent limitations of voltage mapping small enough as to be ignored when targeting specific tissue based on voltage? Second, can conventional criteria, using a binary threshold for voltage amplitude, truly define the extent of the atrial fibrotic substrate? Here, we review the latest clinical evidence with regard to voltage-based ablation procedures before analysing the utility and limitations of voltage mapping. Finally, we discuss omnipole mapping and dynamic voltage attenuation as two possible approaches to resolving these issues.

Association of left atrial function with incident atypical atrial flutter after atrial fibrillation ablation

BACKGROUND

Symptomatic left atrial (LA) flutter (LAFL) is common after atrial fibrillation (AF) ablation.

OBJECTIVE

The purpose of this study was to examine the association of baseline LA function with incident LAFL after AF ablation.

METHODS

The source cohort included 216 patients with cardiac magnetic resonance (CMR) before initial AF ablation between 2010 and 2013. Patients who underwent cryoballoon or laser ablation, patients with AF during CMR, and those with suboptimal CMR, or missing follow-up data were excluded. Baseline LA volume and function were assessed by feature-tracking CMR analysis.

RESULTS

The final cohort included 119 patients (mean age 58.9 ± 11 years; 76.5% men; 70.6% patients with paroxysmal AF). During a median follow-up of 421 days (interquartile range 235-751 days), 22 patients (18.5%) had incident LAFL. Baseline LA volume was similar between the 2 groups. In contrast, baseline reservoir, conduit, and contractile function of the LA were significantly impaired in patients with incident LAFL. Baseline global peak longitudinal atrial strain (PLAS) <22.65% predicted incident LAFL with 86% sensitivity and 68% specificity (C statistic 0.76). In a multivariable model adjusting for age, heart failure, and LA volume, PLAS (hazard ratio 0.9 per % increase in PLAS; P = .003) and LA linear lesions (hazard ratio 2.94; P = .020) were independently associated with incident LAFL. The coexistence of PLAS <22.65% and linear lesions was associated with 9-fold increased hazard of incident LAFL.

CONCLUSION

Baseline LA function and linear lesions were independently associated with incident LAFL after AF ablation. Linear lesions should be limited to selected cases, especially in patients with impaired LA function.

Lack of Correlations between Electrophysiological and Anatomical-Mechanical Atrial Remodeling in Patients with Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) progressively leads to electrical remodeling (ER) and anatomical-mechanical remodeling (AR), whose relationships in humans remain poorly known.

METHODS

ER and AR were compared in patients undergoing percutaneous radiofrequency (RF) ablation for AF. ER was defined by right and left appendage activation rates as a surrogate for atrial refractory periods. AR was approached by left atrial (LA) diameters and area and left atrial appendage (LAA) area and contractile function (mean emptying flow velocity) (LAAFV) before RF ablation. Mean duration between successive LAA contractions was considered as LAA mechanical rate.

RESULTS

Forty-one patients (31 men, age: 64 ± 9 years) with paroxysmal (27%), persistent (61%), or long-persistent AF (12%) were prospectively included (ejection fraction: 44 ± 16%). Parameters exploring AR were highly correlated to each other: LA area (28 ± 7 cm(2) ), LAA area (5.7 ± 2.25 cm(2) ), LA transverse (49 ± 7 mm), and anteroposterior diameter (59 ± 13 mm) or LAAFV (29 ± 13 cm/s; P < 0.05 for each comparison). Parameters exploring ER were also highly correlated: right atrial appendage (RAA; 181 ± 39 ms) and LAA (176 ± 33 ms) activation rates (P < 0.0001). There was no significant correlation between any ER and AR parameter. Only LAA mechanical rate (174 ± 36 ms) was correlated to LAA or RAA activations rates (P ≤ 0.01).

CONCLUSION

ER and AR are not mutually related, atrial activation rate being not correlated to LA or LAA size or function. Thus, the mechanisms leading to AF-induced atrial remodeling may differ for anatomical and electrophysiological aspects.

Left atrial appendage exclusion for atrial fibrillation

Percutaneous left atrial appendage (LAA) closure is being increasingly used as a treatment strategy to prevent stroke in patients with atrial fibrillation (AF) who have contraindications to anticoagulants. Several approaches and devices have been developed in the last few years, each with their own unique set of advantages and disadvantages. In this article, the published studies on surgical and percutaneous approaches to LAA closure are reviewed, focusing on stroke mechanisms in AF, LAA structure and function relevant to stroke prevention, practical differences in procedural approach, and clinical considerations surrounding management.

Left atrial asynchrony and mechanical function in patients with mitral stenosis before and immediately after percutaneous balloon mitral valvuloplasty: a real time three-dimensional echocardiography study

OBJECTIVE

This study evaluated the feasibility of assessing left atrium (LA) function and asynchrony in patients with rheumatic mitral stenosis (MS) before and immediately after percutaneous balloon mitral valvuloplasty (PBMV) by real time three-dimensional echocardiography (RT3DE).

METHODS

Thirty patients with rheumatic MS who underwent PBMV and 30 controls were enrolled. RT3DE was used to measure LA volume and function, the standard deviation of time to the minimal systolic volume divided into 16 segments, 12 segments, or 6 segments (Tmsv 16-SD, Tmsv 12-SD, Tmsv 6-SD), and the maximum differences (Tmsv 16-Dif, 12-Dif, 6-Dif) in RT3DE derived values in MS patients before and 2 days after PBMV were obtained and compared with those of normal controls. The associations between the LA asynchrony and heart volume, function, mitral valve area (MVA), maximum mitral valve gradient (MVGmax ), mean mitral valve gradient (MVGmean), and mean LA pressure (MLAP) were investigated.

RESULTS

Left atrium asynchrony indexes were significantly larger, and LA function parameters were significantly lower in the MS group than in the controls (P < 0.05 for all). Of all the LA asynchrony indexes, LA Tmsv16-SD was most significantly correlated with the LA volume and function parameters, MVGmax , MVGmean , and MLAP (P < 0.05 for all). LA asynchrony indexes and LA volume significantly deceased, and LA function significantly increased post-PBMV (P < 0.05).

CONCLUSION

Real time three-dimensional echocardiography is a reliable and reproducible method to quantify LA function and asynchrony. RT3DE revealed a significant, early improvement in LA function and asynchrony in MS patients after PBMV.

Tissue velocity imaging-based atrial fibrillatory cycle length and wall motion for predicting atrial structural remodeling in patients undergoing catheter ablation

BACKGROUND

Atrial fibrillation (AF) causes atrial electrical and structural remodeling, which are linked to recurrence of AF after ablation. Atrial fibrillatory cycle length (AFCL) and AF wall motion velocity (AFW-V) obtained by tissue velocity imaging (TVI) might characterize such atrial electrical and structural remodeling. The purpose of this study was to assess the clinical and electrophysiologic correlates of these parameters and their relation to ablation outcomes.

METHODS AND RESULTS

The study group comprised 80 patients who underwent transthoracic echocardiography followed by AF ablation. Atrial TVI traces were used to determine AFCL-tvi and AFW-V-tvi at the left atrial septal wall. AFCL that was measured from intracardiac electrograms correlated well with AFCL-tvi (R=0.6094; P=0.0002). AFW-V-tvi was significantly lower and AFCL-tvi was significantly shorter in patients with non-paroxysmal AF than in those with paroxysmal AF (1.63±0.76 cm/s vs. 2.85±1.00 cm/s, respectively, P<0.0001; and 118.2±23.0 ms vs. 145.0±35.0 ms, respectively, P=0.0001). These findings held true for patients with and without post-ablation recurrence. Upon multivariate analysis, a reduced AFW-V-tvi remained the strongest predictor of post-ablation recurrence (hazard ratio for +1-cm/s change, 0.573; 95% confidence interval, 0.337-0.930; P=0.0234).

CONCLUSIONS

TVI of atrial fibrillatory wall motion might enhance the non-invasive characterization of atrial remodeling in patients with AF and thus be used for predicting AF recurrence after ablation.

A novel finding of the atrial substrate properties and long-term results of catheter ablation in chronic atrial fibrillation patients with left atrial spontaneous echo contrast

BACKGROUND

The atrial substrate in chronic atrial fibrillation (AF) patients with a left atrial spontaneous echo contrast (LASEC) has not been previously reported. The aim of this study was to investigate the atrial substrate properties and long-term follow-up results in the patients who received catheter ablation of chronic AF.

METHODS

Of 36 consecutive patients with chronic AF who received a stepwise ablation approach, 18 patients with an LASEC (group I) were compared with 18 age-gender-left atrial volume matched patients without an LASEC (group II). The atrial substrate properties including the weighted peak-to-peak voltage, total activation time during sinus rhythm (SR), dominant frequency (DF), and complex fractionated electrograms (CFEs) during AF in the bi-atria were evaluated.

RESULT

The left atrial weighted bipolar peak-to-peak voltage (1.0 ± 0.6 vs 1.6 ± 0.7 mV, P = 0.04), total activation time (119 ± 20 vs 103 ± 13 ms, P < 0.001) and DF (7.3 ± 1.3 vs 6.6 ± 0.7 Hz, P < 0.001) differed between group I and group II, respectively. Those parameters did not differ in the right atrium. The bi-atrial CFEs (left atrium: 89 ± 24 vs 92 ± 25, P = 0.8; right atrium: 92 ± 25 vs 102 ± 3, P = 0.9) did not differ between group I and group II, respectively. After a mean follow-up of 30 ± 13 month, there were significant differences in the antiarrhythmic drugs (1.1 ± 0.3 vs 0.7 ± 0.5, P = 0.02) needed after ablation, and recurrence as persistent AF (92% vs 50%, P = 0.03) between group I and group II, respectively. After multiple procedures, there were more group II patients that remained in SR, when compared with group I (78% vs 44%, P = 0.04).

CONCLUSION

There was a poorer atrial substrate, lesser SR maintenance after catheter ablation and need for more antiarrhythmic drugs in the chronic AF patients with an LASEC when compared with those without an LASEC.

Impact of circulating monocyte CD36 level on atrial fibrillation and subsequent catheter ablation

BACKGROUND

Inflammation, an important mechanism in the pathogenesis of atrial fibrillation (AF), can be regulated by CD36 in monocytes.

OBJECTIVE

The purpose of this study was to test the hypothesis that CD36 in monocytes contributes to the pathogenesis of AF.

METHODS

A prospective study that enrolled 87 patients with AF and 70 without AF was conducted.

RESULTS

Compared to patients without AF, patients with AF had monocytes with a lower level of CD36 protein, which correlated with left atrial diameter, left atrial emptying fraction, and left atrial mean voltage. In AF patients after catheter ablation, Kaplan-Meier analysis showed that the sinus rhythm maintenance rate was higher in patients with high CD36 levels. Low CD36 level was an independent predictor of recurrence. After successful ablation, the CD36 level increased by 57%, reaching that of control patients. CD36 level was not correlated with the level of high-sensitivity C-reactive protein. Analysis of mRNA levels from a buffy coat revealed that AF patients had lower CD36 and interleukin-10 levels and higher peroxisome proliferator-activated receptor-γ and tumor necrosis factor-α levels, with CD36 level positively correlated with interleukin-10 level but inversely correlated with peroxisome proliferator-activated receptor-γ and tumor necrosis factor-α levels.

CONCLUSION

Low CD36 levels in circulating monocytes were associated with AF occurrence and predicted recurrence after catheter ablation. The link between CD36 and AF identified a novel AF-related inflammatory pathway.