Practical approach for atrial cardiomyopathy characterization in patients with atrial fibrillation

Atrial fibrillation (AF) causes progressive structural and electrical changes in the atria that can be summarized within the general concept of atrial remodeling. In parallel, other clinical characteristics and comorbidities may also affect atrial tissue properties and make the atria susceptible to AF initiation and its long-term persistence. Overall, pathological atrial changes lead to atrial cardiomyopathy with important implications for rhythm control. Although there is general agreement on the role of the atrial substrate for successful rhythm control in AF, the current classification oversimplifies clinical management. The classification uses temporal criteria and does not establish a well-defined strategy to characterize the individual-specific degree of atrial cardiomyopathy. Better characterization of atrial cardiomyopathy may improve the decision-making process on the most appropriate therapeutic option. We review current scientific evidence and propose a practical characterization of the atrial substrate based on 3 evaluation steps starting with a clinical evaluation (step 1), then assess outpatient complementary data (step 2), and finally include information from advanced diagnostic tools (step 3). The information from each of the steps or a combination thereof can be used to classify AF patients in 4 stages of atrial cardiomyopathy, which we also use to estimate the success on effective rhythm control.

Association between left atrial low-voltage area and induction and recurrence of macroreentrant atrial tachycardia in pulmonary vein isolation for atrial fibrillation

BACKGROUND

The relationship between induction and recurrence due to atrial tachycardia (AT) and left atrial (LA) matrix progression after atrial fibrillation (AF) ablation remains unclear.

METHODS

One hundred fifty-two consecutive patients with paroxysmal and persistent AF who underwent pulmonary vein isolation (PVI) and cavo-tricuspid isthmus (CTI) ablation and achieved sinus rhythm before the procedure were classified into three groups according to the AT pattern induced after the procedure: group N (non-induced), F (focal pattern), and M (macroreentrant pattern) in 3D mapping.

RESULTS

The total rate of AT induction was 19.7% (30/152) in groups F (n = 13) and M (n = 17). Patients in group M were older than those in groups N and F, with higher CHADS2/CHA2DS2-VASc values, left atrial enlargement, and low-voltage area (LVA) size of LA. The receiver operating characteristic curve determined that the cut-off LVA for macroreentrant AT induction was 8.8 cm2 (area under the curve [AUC]: 0.86, 95% confidence interval [CI]: 0.75-0.97). The recurrence of AT at 36 months in group N was 4.1% (5/122), and at the second ablation, all patients had macroreentrant AT. Patients with AT recurrence in group N had a wide LVA at the first ablation, and the cut-off LVA for AT recurrence was 6.5 cm2 (AUC 0.94, 95%CI 0.88-0.99). Adjusted multivariate analysis showed that only LVA size was associated with the recurrence of macroreentrant AT (odds ratio 1.21, 95%CI 1.04-1.51).

CONCLUSIONS

It is important to develop a therapeutic strategy based on the LVA size to suppress the recurrence of AT in these patients.

Atrial electrical remodeling and function after transcatheter aortic valve replacement in patients with aortic stenosis

To examine reverse atrial electrical remodeling in patients with aortic stenosis (AS) after trans-catheter aortic valve replacement (TAVR). In 65 consecutive patients with severe AS (83 ± 4 years, 47 (72.3%) females), we analyzed ECG records for the P wave duration (PWD) in lead II and P-terminal force (PTFV1) in V1, and measured cardiac dimensions and function by echocardiography (ECHO) following TAVR. Biomarkers were measured to assess myocardial injury by TAVR. TAVR was successfully performed without major complications: the aortic valve area increased from 0.62 ± 0.14 cm2 to 1.52 ± 0.24cm2, and the trans-aortic pressure gradient decreased from 58.4 ± 15.9 mmHg to 15.0 ± 19.6 mmHg. PWD and PTFV increased immediately after TAVR and returned to the pre-TAVR levels on the next day. Then, the PWD declined toward 6 months after TAVR non-significantly in all patients, but significantly in 25 patients with baseline PWD ≥ 130 ms (P = 0.039). PTFV1 showed no long-term change. Improvement was observed in the ejection fraction, all thickness of the left ventricle and in the left atrial dimensions on ECHO. After recovery from transient aggravation by TAVR procedure, PWD reversed slowly, and the change was significant in those with baseline PWD ≥ 130 ms while change in PTFV1 was not significant at 6 months of follow-up. ECHO showed a reversal of remodeling in the left ventricle and in the left atrial dimension after TAVR.

[Catheter ablation of atrial fibrillation : Evidence and current techniques]

Atrial fibrillation (AF) is the most frequent cardiac arrhythmia with increasing clinical and healthcare economic relevance. A timely treatment prevents or slows the remodelling process of the atrial and ventricular myocardium initiated by AF, emphasizing its relevance especially in heart failure patients. Catheter ablation for the treatment of AF is safe and effective. The three ablation techniques currently used are comparable in terms of success rates but differ in terms of risk profile and the type of lesion formation.

TRPV2 inhibitor tranilast prevents atrial fibrillation in rat models of pulmonary hypertension

Atrial fibrillation (AF) is common in pulmonary hypertension (PH), whereas the mechanisms and treatments remain to be explored. TRPV2 regulates the structure and function of the cardiovascular system; however, little attention has been given to its role in AF. This study was to determine whether TRPV2 was involved in PH-induced AF and the effects of TRPV2 inhibitor tranilast on AF in rat models of PH. Monocrotaline (MCT) and SU5416/hypoxia (SuHx)-induced PH models were performed to detect atrial electrophysiological parameters. Daily tranilast (a TRPV2 inhibitor) or saline was given starting 1 day before PH establishment. PH increased the susceptibility to AF, with TRPV2 up-regulated in the right atria. Compared to PH rats, tranilast reduced AF inducibility and the prolongations of ERP and APD; mitigated cardiopulmonary remodeling and the increases in P-wave duration and P-R interval; partially reversed the down-regulation of ion channels such as Cav1.2, Nav1.5, Kv4.3, Kv4.2, Kv1.5, Kir2.1, Kir3.1, Kir3.4 as well as connexin (Cx) 40 and Cx43; improved right atrial (RA) fibrosis, enlargement, and myocardial hypertrophy; decreased the accumulation of inflammatory cells; down-regulated inflammatory indicators such as TNF-α, IL-1β, CXCL1, and CXCL2; and inhibited the activation of the PI3K-AKT-NF-κB signaling pathway. Our results reveal that TRPV2 participates in PH-induced AF, and TRPV2 inhibitor tranilast prevents PH-induced RA remodeling. TRPV2 might be a promising target for PH-induced AF.

Study of ECG-derived atrial fibrillatory rate for prediction of the outcome of cardioversion of short duration atrial fibrillation (CASAF)

AIMS

The present study aimed at testing the hypothesis that atrial fibrillatory rate (AFR) is predictive of sinus rhythm maintenance after electrical cardioversion.

METHODS AND RESULTS

The study comprised 32 patients admitted for cardioversion of atrial fibrillation of short duration (mean duration 3.8 ± 7.7 days). AFR was estimated using frequency power spectrum analysis of QRST-cancelled ECG. At six-weeks follow-up 22% of the patients had relapsed to AF. The pre-cardioversion mean AFR of those was 332 ± 64 fpm compared to 378 ± 59 fpm among patients maintaining sinus rhythm (p = 0.12).

CONCLUSION

AFR was not predictive of sinus rhythm maintenance in patients of short duration AF undergoing cardioversion. This is in stark contrast with the earlier reported findings.

CLINICAL TRIAL REGISTRATION

NCT02112318 (http://www.

CLINICALTRIALS

gov).

Left atrial sphericity in relation to atrial strain and strain rate in atrial fibrillation patients

PURPOSE

Left atrial (LA) sphericity is a novel, geometry-based parameter that has been used to visualize and quantify LA geometrical remodeling in patients with atrial fibrillation (AF). This study examined the association between LA sphericity, and LA longitudinal strain and strain rate measured by feature-tracking in AF patients.

METHODS

128 AF patients who underwent cardiovascular magnetic resonance (CMR) imaging in sinus rhythm prior to their pulmonary vein isolation (PVI) procedure were retrospectively analyzed. LA sphericity was calculated by segmenting the LA (excluding the pulmonary veins and the LA appendage) on a 3D contrast enhanced MR angiogram and comparing the resulting shape with a perfect sphere. LA global reservoir strain, conduit strain, contractile strain and corresponding strain rates were derived from cine images using feature-tracking. For statistical analysis, Pearson correlations, multivariable logistic regression analysis, and Student t-tests were used.

RESULTS

Patients with a spherical LA (dichotomized by the median value) had a lower reservoir strain and conduit strain compared to patients with a non-spherical LA (-15.4 ± 4.2% vs. -17.1 ± 3.5%, P = 0.02 and - 8.2 ± 3.0% vs. -9.5 ± 2.6%, P = 0.01, respectively). LA strain rate during early ventricular diastole was also different between both groups (-0.7 ± 0.3s- 1 vs. -0.9 ± 0.3s- 1, P = 0.001). In contrast, no difference was found for LA contractile strain (-7.2 ± 2.6% vs. -7.6 ± 2.2%, P = 0.30).

CONCLUSIONS

LA passive strain is significantly impaired in AF patients with a spherical LA, though this relation was not independent from LA volume.

P-wave duration as a marker of atrial remodeling in patients referred to ablation for atrial fibrillation: A new stratification tool emerging?

Ablation of atrial fibrillation is one of the most widely applied invasive procedures in cardiovascular medicine, and populations with atrial fibrillation continuously rise. Recurrence rates are, however, consistently high, even in patients without severe comorbidities. Robust stratification algorithms to distinguish patients suitable for ablation are generally lacking. This is a fact caused by the inability to incorporate evidence of atrial remodeling and fibrosis, e.g., atrial remodeling, in the decision pathways. Cardiac magnetic resonance is a powerful tool in identifying fibrosis; however, it is costly and not routinely used. Electrocardiography has been generally underutilized in clinical practice during pre-ablative screening. One of the characteristics of the electrocardiogram that can give us valuable data depicting the existence and the extent of atrial remodeling and fibrosis is the duration of the P-wave. Currently, many studies support the implementation of P-wave duration in the routine practice of patient evaluation as a surrogate marker of existing atrial remodeling, that in turn predicts recurrence after ablation of atrial fibrillation. Further research is guaranteed to establish this electrocardiographic characteristic in our stratification quiver.

Asymmetric remodeling between the left and right atria in patients with advanced interatrial block and atrial fibrillation

BACKGROUND

Advanced interatrial block (A-IAB) on electrocardiography (ECG) represents the conduction delay between the left and right atria. We investigated the association of A-IAB with left and right atrial (LA/RA) remodeling in patients with atrial fibrillation (AF).

METHODS

We enrolled 74 patients who underwent ECG, cardiac computed tomography (CCT), and echocardiography during sinus rhythm before catheter ablation of AF. A-IAB was defined as P-wave duration ≥120 ms with a biphasic morphology in leads III and aVF or notched morphology in lead II. We compared the maximum and minimum LA/RA volume indices (max and min LAV/RAVI), LA/RA expansion index (LAEI/RAEI), and total, passive, and active LA/RA emptying fraction (LAEF/RAEF) between patients with and without A-IAB.

RESULTS

Of the 74 patients (mean age, 64.3 ± 9.6 years), 35 (47%) showed A-IAB. Patients with A-IAB had a significantly higher likelihood of hypertension and left ventricular diastolic dysfunction than those without. Patients with A-IAB had significantly larger max (69.2 [60.7-79.7]mL/m2 vs. 60.9 [50.4-68.3]mL/m2, P < 0.01) and min (44.0 [37.2-52.1]mL/m2 vs. 34.1 [29.2-43.5]mL/m2, P < 0.01) LAVI than those without. The max and min RAVI were not significantly different between groups. LAEI (55.1 [48.2-78.5]% vs. 72.1 [57.8-84.8]%, P < 0.05), total LAEF (35.5 [32.5-44.0]% vs. 41.9 [36.6-45.9]%, P < 0.05), and passive LAEF (12.2 [10.0-14.4]% vs. 15.5 [11.2-19.6]%, P < 0.05) were significantly lower in patients with A-IAB than without.

CONCLUSIONS

A-IAB was associated with LA, but not RA enlargement, in patients with AF. A-IAB may indicate LA functional remodeling in the reservoir and conduit phases.

Disordered gut microbiota promotes atrial fibrillation by aggravated conduction disturbance and unbalanced linoleic acid/SIRT1 signaling

Emerging evidence suggests an association of dysbiotic gut microbiota (GM) with atrial fibrillation (AF). The current study aimed to determine whether aberrant GM promotes AF development. A fecal microbiota transplantation (FMT) mouse model demonstrated that dysbiotic GM is sufficient to enhance AF susceptibility assessed by transesophageal burst pacing. Compared with recipients transplanted with GM obtained from healthy subjects (FMT-CH), the prolonged P wave duration and an enlarging tendency for the left atrium were detected in recipients transplanted with AF GM (FMT-AF). Meanwhile, the disrupted localizations of connexin 43 and N-cadherin and increased expression levels of phospho-CaMKII and phospho-RyR2, were observed in the atrium of FMT-AF, which indicated aggravated electrical remodeling caused by the altered gut flora. Specifically, exacerbated fibrosis disarray, collagen deposition, α-SMA expression, and inflammation in the atrium were also confirmed to be transmissible by the GM. Furthermore, deteriorated intestinal epithelial barrier and intestinal permeability, accompanied by disturbing metabolomic features in both feces and plasma, especially decreased linoleic acid (LA), were identified in FMT-AF mice. Subsequently, the anti-inflammatory role of LA among the imbalanced SIRT1 signaling discovered in the atrium of FMT-AF was confirmed in mouse HL-1 cells treated with LPS/nigericin, LA, and SIRT1 knockdown. This study provides preliminary insights into the causal role of aberrant GM in the pathophysiology of AF, suggesting the GM-intestinal barrier-atrium axis might participate in the vulnerable substrates for AF development, and the GM could be utilized as an environmental target in AF management.

Characterization of atrial and ventricular remodeling in an improved minimally invasive mouse model of transverse aortic constriction

Introduction

Heart failure (HF) is the leading cause of death worldwide. Most large and small animal disease models of HF are based on surgical procedures. A common surgical technique to induce HF is transverse aortic constriction (TAC), which induces pressure overload. The conventional TAC (cTAC) procedure is a highly invasive surgery that is associated with severe inflammation and excessive perioperative deaths.

Aim

To establish an improved, minimally invasive TAC (mTAC) procedure that does not require thoracotomy.

Methods and results

Following anesthesia, mice were intubated, and a small incision was made at the neck and chest. After cutting the sternum about 4 mm, the aortic arch was approached without opening the pleural cavity. A suture was placed between the brachiocephalic artery and the left common carotid artery. This model was associated with low perioperative mortality and a highly reproducible constriction evidenced by an increased right-to-left carotid blood flow velocity ratio in mTAC mice (5.9 ± 0.2) vs. sham controls (1.2 ± 0.1; P < 0.001). mTAC mice exhibited progressive cardiac remodeling during the 8 weeks post-TAC, resulting in reduced left ventricular (LV) contractility, increased LV end-systolic diameter, left atrial enlargement and diastolic dysfunction, and an increased heart weight to tibia length ratio (mTAC: 15.0 ± 0.8 vs. sham: 10.1 ± 0.6; P < 0.01).

Conclusion

Our data show that the mTAC procedure yields a highly reproducible phenotype consisting of LV contractile dysfunction and enlargement, combined with left atrial enlargement and diastolic dysfunction.

Potential impact of the findings

This model may be used to test the molecular mechanisms underlying atrial remodeling associated with HF development or to evaluate therapeutic strategies to treat these conditions.

Sacubitril/valsartan reduces susceptibility to atrial fibrillation by improving atrial remodeling in spontaneously hypertensive rats

AIM

Sacubitril/valsartan (Sac/Val, LCZ696), the world's first angiotensin receptor-neprilysin inhibitor (ARNi), has been widely used in the treatment of heart failure. However, the use of Sac/Val in the treatment of atrial fibrillation (AF), especially AF with hypertension, has been less reported. We investigated the effect of Sac/Val on atrial remodeling and hypertension-related AF.

METHODS

The AF induction rate and electrophysiological characteristics of spontaneously hypertensive rats (SHRs) treated with Sac/Val or Val were detected by rapid atrial pacing and electrical mapping/optical mapping. The whole-cell patch-clamp and western blot were used to observe electrical/structural remodeling of atrial myocytes/tissue of rats and atrium-derived HL-1 cells cultured under 40 mmHg in vitro.

RESULTS

Sac/Val was superior to Val in reducing blood pressure, myocardial hypertrophy and susceptibility of AF in SHRs. The shorten action potentials duration (APD), decreased L type calcium channel current (I_Ca,L) and Cav1.2, increased ultrarapid delayed rectified potassium current (I_kur) and Kv1.5 in atrial myocytes/tissue of SHRs could be better improved by Sac/Val, as well as the levels of atrial fibrosis. While the protein expression of angiotensin-converting enzyme-1 (ACE-1), angiotensin, angiotensin II type I AT1 receptor (AT1R) and neprilysin (NEP) were increased, which could be more effective ameliorated by Sac/Val than Val. Furthermore, Val + Sacubitrilat (LBQ657) (an active NEP inhibitor) was also superior to LBQ657 or Val in improving the electrical and structural remodeling of HL-1 cells through inhibiting NEP.

CONCLUSION

Sac/Val can improve atrial structural and electrical remodeling induced by hypertension and reduce the AF susceptibility by inhibiting RAS and NEP. The above effects of Sac/Val were superior to Val alone.

Left atrial strain is associated with arrhythmia recurrence after atrial fibrillation ablation: Cardiac magnetic resonance rapid strain vs. feature tracking strain

PURPOSE

The present study assesses different left atrial (LA) strain approaches in relation to atrial fibrillation (AF) recurrence after ablation and compares LA feature tracking (FT) strain to novel rapid LA strain approaches in AF patients.

METHODS

This retrospective single-center study comprised of 110 prospectively recruited AF patients who underwent cardiac magnetic resonance (CMR) imaging in sinus rhythm prior to their first pulmonary vein isolation ablation. LA rapid strain (long axis strain and atrioventricular (AV)-junction strain), LA FT strain, and LA volumes were derived from 2-chamber and 4-chamber cine images. AF recurrence was followed up for 12 months using either 12‑lead ECGs or rhythm Holter monitoring.

RESULTS

Arrhythmia recurrence was observed in 39 patients (36%) after the 90-day blanking period, occurring at a median of 181 (122-286) days. LA long axis strain, AV-junction strain, and FT strain were all more impaired in patients with AF recurrence compared to patients without AF recurrence (long axis strain: P < 0.01; AV-junction strain: P < 0.001; FT strain: P < 0.01, respectively). Area under the curve (AUC) values for LA remodeling parameters in association with AF recurrence were 0.68 for long axis strain, 0.68 for AV-junction strain, 0.66 for FT strain, 0.66 for LA volume index. Phasic FT LA strain demonstrated that contractile strain had the highest AUC (0.70).

CONCLUSION

Both LA rapid strain and LA FT strain are associated with arrhythmia recurrence after ablation in AF patients. LA rapid strain can be a convenient and reproducible alternative for LA FT strain to assess LA function in clinical practice.

Does conduction heterogeneity determine the supervulnerable period after atrial fibrillation?

Atrial fibrillation (AF) resumes within 90 s in 27% of patients after sinus rhythm (SR) restoration. The aim of this study is to compare conduction heterogeneity during the supervulnerable period immediately after electrical cardioversion (ECV) with long-term SR in patients with AF. Epicardial mapping of both atria was performed during SR and premature atrial extrasystoles in patients in the ECV (N = 17, age: 73 ± 7 years) and control group (N = 17, age: 71 ± 6 years). Inter-electrode conduction times were used to identify areas of conduction delay (CD) (conduction times 7-11 ms) and conduction block (CB) (conduction times ≥ 12 ms). For all atrial regions, prevalences and length of longest CB and continuous CDCB lines, magnitude of conduction disorders, conduction velocity, biatrial activation time, and voltages did not differ between the ECV and control group during both SR and premature atrial extrasystoles (p ≥ 0.05). Hence, our data suggest that there may be no difference in biatrial conduction characteristics between the supervulnerable period after ECV and long-term SR in AF patients. The supervulnerable period after AF termination is not determined by conduction heterogeneity during SR and PACs. It is unknown to what extent intra-atrial conduction is impaired during the supervulnerable period immediately after ECV and whether different right and left atrial regions are equally affected. This high-resolution epicardial mapping study (upper left panel) of both atria shows that during SR the prevalences and length of longest CB and cCDCB lines (upper middle panel), magnitude of conduction disorders, CV and TAT (lower left panel), and voltages did not differ between the ECV and control group. Likewise, these parameters were comparable during PACs between the ECV and control group (lower left panel). †Non-normally distributed. cm/s = centimeters per second; mm = millimeter; ms = millisecond; AF = atrial fibrillation; AT = activation time; BB = Bachmann's bundle; cCDCB = continuous lines of conduction delay and block; CB = conduction block; CD = conduction delay; CT = conduction time; CV = conduction velocity; ECV = electrical cardioversion; LA = left atrium; LAT = local activation times; PAC = premature atrial complexes; PVA = pulmonary vein area; RA = right atrium; SR = sinus rhythm; TAT = total activation time.

Cardiac remodeling after tricuspid valve repair in Ebstein's anomaly: a magnetic resonance study

OBJECTIVES

We aimed to evaluate immediate and midterm cardiac remodeling after surgery by cardiac magnetic resonance (CMR) in Ebstein's anomaly (EA), and also to investigate preoperative predictors of right ventricular (RV) normalization.

METHODS

We retrospectively analyzed CMR parameters of the whole heart in adult patients with EA before surgery, at discharge and follow-up.

RESULTS

A total of 26 patients were included and performed CMR at 7 days (interquartile range, 3-13 days) before surgery. Immediate postoperative CMR was finished at discharge (median: 8 [7-9] days; n = 18) and follow-up CMR at 187 days (interquartile range, 167-356 days; n = 17). RV and right atrial (RA) volumes promptly decreased immediately after surgery and at follow-up (all p < 0.05). RV ejection fraction decreased significantly at discharge (p < 0.05) but recovered at follow-up (p = 0.18). However, RV global longitudinal strain and RA reservoir strain were significantly impaired immediately and midterm after surgery (all p < 0.05). Indexed left ventricular (LV) end-diastolic volume, stroke volume, as well as global longitudinal strain increased from preoperative to follow-up (all p < 0.05). Patients who achieved normalization of RV volumes after surgery had smaller severity index and RV and RA volumes and higher LV ejection fraction and RA reservoir strain at baseline than patients without RV normalization (all p < 0.05).

CONCLUSIONS

Reverse biventricular remodeling took place in EA after tricuspid valve surgery. Tricuspid valve reconstruction should be performed before deterioration of RV volume overload and LV function to achieve reverse RV remodeling. Key Points • After removing the volume load of tricuspid regurgitation in Ebstein's anomaly, reverse remodeling was detected by CMR in both left and right heart at midterm follow-up. • Tricuspid valve reconstruction should be performed before deterioration of RV volume overload and LV function to achieve reverse RV remodeling.

Atrial Cardiomyopathy with Impaired Functional Reserve in Patients with Paroxysmal Atrial Fibrillation

BACKGROUND

Impaired atrial functional reserve during exercise may represent an early stage of atrial cardiomyopathy. To test this hypothesis, the authors evaluated left atrial (LA) and left ventricular (LV) function reserve during exercise in patients with paroxysmal atrial fibrillation (PAF).

METHODS

Sixty-one patients with PAF undergoing radiofrequency catheter ablation and 38 healthy control subjects were prospectively enrolled. LV global longitudinal strain and LA reservoir strain (RS) were measured at rest and during supine bicycle exercise. To identify the early stage of atrial cardiomyopathy without LA structural remodeling, patients with PAF were divided into two groups according to LA volume index (LAVI): atrial fibrillation (AF) group 1 (LAVI ≥ 34 mL/m²) and AF group 2 (LAVI < 34 mL/m²).

RESULTS

LV ejection fraction and global longitudinal strain did not differ between patients with AF and control subjects. LAVI and LA RS did not differ between AF group 2 and control subjects. During exercise, LV global longitudinal strain improved in all groups. Increases in LA RS were attenuated in both AF groups, which also exhibited lower LA functional reserve index than the control subjects. Although resting LA RS was similar between AF group 2 and control subjects, LA functional reserve index was significantly lower in AF group 2. LA functional reserve index was associated with risk for AF recurrence (hazard ratio, 0.852; 95% CI, 0.736-0.988).

CONCLUSIONS

Atrial cardiomyopathy can be anticipated by impaired LA functional reserve during exercise in patients with AF, even in those with normal-sized left atria. Atrial cardiomyopathy occurs independently of changes in LV function and is associated with the recurrence of AF in patients with PAF after radiofrequency catheter ablation.

Atrial fibrillation: Epigenetic aspects and role of sodium-glucose cotransporter 2 inhibitors

Atrial fibrillation (AF) is the most frequent arrhythmia and is associated with substantial morbidity and mortality. Pathophysiological aspects consist in the activation of pro-fibrotic signaling and Ca²⁺ handling abnormalities at atrial level. Structural and electrical remodeling creates a substrate for AF by triggering conduction abnormalities and cardiac arrhythmias. The care of AF patients focuses predominantly on anticoagulation, symptoms control and the management of risk factors and comorbidities. The goal of AF therapy points to restore sinus rhythm, re-establish atrioventricular synchrony and improve atrial contribution to the stroke volume. New layer of information to better comprehend AF pathophysiology, and identify targets for novel pharmacological interventions consists of the epigenetic phenomena including, among others, DNA methylation, histone modifications and noncoding RNAs. Moreover, the benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in diabetic and non-diabetic patients at cardiovascular risk as well as emerging evidence on the ability of SGLT2i to modify epigenetic signature in cardiovascular diseases provide a solid background to investigate a possible role of this drug class in the onset and progression of AF. In this review, following a summary of pathophysiology and management, epigenetic mechanisms in AF and the potential of sodium-glucose SGLT2i in AF patients are discussed.

Inhibition of ferroptosis by icariin treatment attenuates excessive ethanol consumption-induced atrial remodeling and susceptibility to atrial fibrillation, role of SIRT1

Ferroptosis contributes to the pathogenesis of atrial fibrillation (AF), although the mechanisms are still largely uncovered. The current study was designed to explore the pharmacological effects of icariin against ethanol-induced atrial remodeling, if any, and the mechanisms involved with a focus on SIRT1 signaling. Excessive ethanol-treated animals were administered with Ferrostatin-1, Erastin or icariin to evaluate the potential effects of icariin or ferroptosis. Then, the underling mechanisms was further explored in the in vitro experiments using HL-1 atrial myocytes. Excessive ethanol administration caused significant atrial damage as evidenced by increased susceptibility to AF, altered atrial conduction pattern, atrial enlargement, and enhanced fibrotic markers. These detrimental effects were reversed by Ferrostatin-1 or icariin treatment, while Erastin co-administration markedly abolished the beneficial actions conferred by icariin. Mechanistically, ethanol-treated atria exhibited markedly up-regulated pro-ferroptotic protein (PTGS2, ACSL4, P53) and suppressed anti-ferroptotic molecules (GPX4, FTH1). Icariin treatment inhibited ethanol-induced atrial ferroptosis by reducing atrial mitochondrial damage, ROS accumulation and iron overload. Interestingly, the in vivo and in vitro data showed that icariin activated atrial SIRT1-Nrf-2-HO-1 signaling pathway, while EX527 not only reversed these effects, but also abolished the therapeutic effects of icariin. Moreover, the stimulatory effects on GPX4, SLC7A11 and the suppressive effects on ACSL4, P53 conferred by icariin were blunted by EX527 treatment. These data demonstrate that ferroptosis plays a causative role in the pathogenesis of ethanol-induced atrial remodeling and susceptibility to AF. Icariin protects against atrial damage by inhibiting ferroptosis via SIRT1 signaling. Its role as a prophylactic/therapeutic drug deserves further clinical study.

Multimodality imaging assessment of the Biatrial remodeling of the burden of atrial high-rate episodes in patients with cardiac implanted electronic devices

AIMS

The underlying mechanisms of atrial remodeling in cardiac implanted electronic device(CIED)-detected atrial high-rate episodes(AHRE) remains to be elucidated.

METHODS

A cardiac computed tomography and a strain echocardiography were performed to delineate the structural and functional characteristics of both atria. Biatrial volumes, emptying fraction(EF) and peak atrial longitudinal/contractile strain(PALS/PACS) were evaluated. All AHRE were analyzed.

RESULTS

A total of 80 CIED patients with AHRE were categorized by AHRE duration into 3 groups: Group 1: <6 min(n = 42), Group 2: 6 min ∼ 6 h(n = 23), and Group 3: >6 h(n = 15). Left atrial(LA) maximal volume(V_max), atrial precontraction volume(V_apc), minimal volume(V_min), LAEF, and PALS/PACS were all increasingly worsened among the patients in the 3 groups (p value for trend <0.05). Compared to Group 1, Group 2 had decreased LA PALS/PACS. There was no significant difference in LA volume or EF between Group 1 and 2. Group 3 had enlarged biatrial volumes (LAV_max: 57.1(SD 16.0) vs. 45.4(SD 9.2) mL/m², p = 0.002; LAV_min: 42.6(SD 18.2) vs. 28.2(SD 7.2) mL/m², p < 0.001), impaired total LAEF (28.0(SD 13.7) vs. 38.2(SD 7.7)%, p = 0.004) and reduced PALS/PACS compared to Group 1. Atrial remodeling in those with AHRE >6 h had increased LA volumes, impaired LAEF and reduced PALS/PACS compared to those with AHRE <6 h.

CONCLUSION

Functional remodeling of the atria manifested after AHRE >6 min. Increased biatrial volumes and decreased LA reservoir and pump function occurred when AHRE were > 6 h. These LA structural and functional may be considered surrogate imaging markers for stroke risk assessment in patients with CHA₂DS₂-VASc ≥2 and AHRE.

Diminished α7 nicotinic acetylcholine receptor (α7nAChR) rescues amyloid-β induced atrial remodeling by oxi-CaMKII/MAPK/AP-1 axis-mediated mitochondrial oxidative stress

The potential coexistence of Alzheimer's disease (AD) and atrial fibrillation (AF) is increasingly common as aging-related diseases. However, little is known about mechanisms responsible for atrial remodeling in AD pathogenesis. α7 nicotinic acetylcholine receptors (α7nAChR) has been shown to have profound effects on mitochondrial oxidative stress in both organ diseases. Here, we investigate the role of α7nAChR in mediating the effects of amyloid-β (Aβ) in cultured mouse atrial cardiomyocytes (HL-1 cells) and AD model mice (APP/PS1). In vitro, apoptosis, oxidative stress and mitochondrial dysfunction induced by Aβ long-term (72h) in HL-1 cells were prevented by α-Bungarotoxin(α-BTX), an antagonist of α7nAChR. This cardioprotective effect was due to reinstating Ca²⁺ mishandling by decreasing the activation of CaMKII and MAPK signaling pathway, especially the oxidation of CaMKII (oxi-CaMKII). In vivo studies demonstrated that targeting knockdown of α7nAChR in cardiomyocytes could ameliorate AF progression in late-stage (12 months) APP/PS1 mice. Moreover, α7nAChR deficiency in cardiomyocytes attenuated APP/PS1-mutant induced atrial remodeling characterized by reducing fibrosis, atrial dilation, conduction dysfunction, and inflammatory mediator activities via suppressing oxi-CaMKII/MAPK/AP-1. Taken together, our findings suggest that diminished α7nAChR could rescue Aβ-induced atrial remodeling through oxi-CaMKII/MAPK/AP-1-mediated mitochondrial oxidative stress in atrial cells and AD mice.

Correlation between Serum Myosin Light Chain 4 Levels and Recurrence after Radiofrequency Ablation in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia that is harmful to human health. This study aims to explore the relationship between myosin light chain 4 (MYL4) and AF recurrence after radiofrequency ablation (RFA). Patients with AF (n = 85) were enrolled, and healthy subjects (n = 90) with normal sinus rhythm and no previous history of AF were selected as controls. The serum levels of MYL4, transforming growth factor (TGF) -β1, and procollagen type-I C-terminal propeptide (PICP) were determined. The correlation between MYL4 and atrial fibrosis remodeling indicators (TGF-β1/PICP) and left atrial diameter (LAD) was analyzed. The influence of MYL4 on AF recurrence after RFA was evaluated, and the independent correlation between them was assessed. Patients with AF and the controls showed no significant differences in age, gender, body mass index, systolic blood pressure, diastolic blood pressure, left ventricular ejection fraction, triglycerides, total cholesterol, high-density lipoprotein, low-density lipoprotein, white blood cell count, neutrophil/lymphocyte ratio, brain natriuretic peptide, and history of smoking, drinking, hypertension, and diabetes (P > 0.05), but with increased LAD in patients with AF (P < 0.01). Serum MYL4 level was reduced in patients with AF (0.6 ± 0.2) compared with that of controls (0.1 ± 0.6) (P < 0.01), and it was negatively correlated with TGF-β1, PICP, and LAD (r = -0.2389, P < 0.05; r = -0.5174, P < 0.01; r = -0.3191; P < 0.01). Low levels of MYL4 increased the risk of AF recurrence after RFA (χ² = 16.64; P < 0.0001). A low MYL4 level in patients with AF showed a poorer prognosis. Serum MYL4 level and AF type were independent risk factors affecting AF recurrence after RFA.

A novel therapeutic strategy for alleviating atrial remodeling by targeting exosomal miRNAs in atrial fibrillation

Atrial fibrillation (AF) is one of the most frequent cardiac arrhythmias, and atrial remodeling is related to the progression of AF. Although several therapeutic approaches have been presented in recent years, the continuously increasing mortality rate suggests that more advanced strategies for treatment are urgently needed. Exosomes regulate pathological processes through intercellular communication mediated by microribonucleic acid (miRNA) in various cardiovascular diseases (CVDs). Exosomal miRNAs associated with signaling pathways have added more complexity to an already complex direct cell-to-cell interaction. Exosome delivery of miRNAs is involved in cardiac regeneration and cardiac protection. Recent studies have found that exosomes play a critical role in the diagnosis and treatment of cardiac fibrosis. By improving exosome stability and modifying surface epitopes, specific pharmaceutical agents can be supplied to improve tropism and targeting to cells and tissues in vivo. Exosomes harboring miRNAs may have clinical utility in cell-free therapeutic approaches and may serve as prognostic and diagnostic biomarkers for AF. Currently, limitations challenge pharmaceutic design, therapeutic utility and in vivo targeted delivery to patients. The aim of this article is to review the developmental features of AF associated with exosomal miRNAs and relate them to underlying mechanisms.

Clinical utility of left atrial strain in predicting atrial fibrillation recurrence after catheter ablation: An up-to-date review

Rhythm control is the core part of the integrated management of atrial fibrillation (AF), especially in the early stages. Despite advances in catheter ablation (CA), the recurrence rate of AF after CA remains high. As a result, stratification and early management of AF recurrence after CA are critical. Currently, predictors of recurrence of AF after CA are mostly based on dysfunction caused by structural remodeling, apart from traditional risk factors. Atrial strain is a recently developed important parameter for detecting the deformability of atrial myocardium during the cardiac cycle prior to atrial remodeling. Although there is only preliminary evidence, atrial strain is still a promising parameter in predicting the recurrence of AF after CA at an early stage. This review focuses on the evaluation of atrial strain, the current applications of atrial strain in assessing atrial function, and predicting the recurrence of AF after CA. We summarize the contents related as follows: (1) CA for rhythm control in AF; (2) Evaluation methods of atrial strain; (3) Atrial strain in the remodeling and reverse remodeling of AF; and (4) Clinical applications of atrial strain in predicting the recurrence of AF after CA. Although there is accumulating evidence on the role of decreased atrial strain in the early prediction of AF recurrence, atrial strain is limited in clinical practice for lacking exact cut-off values and difficulty in distinguishing specific function phases of the atrium. More research is needed in the future to add strength to the early prediction value of atrial strain in AF recurrences.

Commensal microbe-derived SCFA alleviates atrial fibrillation via GPR43/NLRP3 signaling

Rationale: Dysbiotic gut microbiota (GM) and NLRP3 inflammasome are proarrhythmic factors in atrial fibrillation (AF). Herein, whether short-chain fatty acid (SCFA) produced from GM fermentation of dietary fiber serving as invisible mediators is yet unclear. Thus, the current study aimed to determine whether SCFA alleviated from NLRP3 signaling-mediated atrial remodeling protects AF development. Methods: First, a cross-sectional study based on the GC-MS metabolomics was performed to explore the association between fecal SCFA levels and AF traits in a cohort consisted of 48 individuals. Then, a well-established mice model fed diet deficient or enriched in dietary fiber was established to elucidate the pathophysiological role of SCFA involved in AF susceptibility, atrial remodeling, and G-protein-coupled receptor 43 (GPR43)/NLRP3 signaling. Finally, the effects of SCFA were verified on HL-1 cells. Results: Fecal SCFA levels were remarkably reduced in AF patients with a declining trend from paroxysmal to persistent AF. Prolonged P wave duration based on surface ECG and increased left atrial diameter gained from echocardiography was identified in low-fiber diet mice but lost in SCFA-supplemented group. Lack of dietary fiber enhanced susceptibility to AF under burst pacing, whereas SCFA might exert a protective effect. The supplementation of SCFA prevented dietary fiber deficiency-upregulated phosphorylation of calmodulin-dependent protein kinase II and ryanodine receptor 2, the disarray fibrosis, collagen expression, and NLRP3 inflammasome activation in atrial tissue. Finally, the AF protective roles of SCFA were identified through GPR43 mediated deactivation of NLRP3 by GPR43 knockdown in HL-1 cells. Conclusions: SCFA derived from dietary fiber fermentation by gut commensals alleviates AF development via GPR43/NLRP3 signaling.

Left atrioventricular coupling index in hypertrophic cardiomyopathy and risk of new-onset atrial fibrillation

BACKGROUNDS

This study aimed to investigate the association between left atrioventricular coupling index (LACI) and the occurrence of atrial fibrillation (AF) in patients with hypertrophic cardiomyopathy (HCM).

METHODS

A total of 373 patients with HCM and no history of AF were evaluated by transthoracic echocardiography. LACI was defined by the ratio of left atrial (LA) end-diastolic volume divided by left ventricular (LV) end-diastolic volume. The cut-off value for LACI (≥40%) to identify LA-LV uncoupling was chosen based on the risk excess of new-onset AF described with a spline curve analysis.

RESULTS

The median LACI was 37.5% (IQR: 24.4-56.7) and LA-LV uncoupling (LACI ≥40%) was observed in 171 (45.8%) patients. During a median follow-up of 11 (IQR 7-15) years, 118 (31.6%) subjects developed new-onset AF. The cumulative event-free survival at 10 years was 53% for patients with LA-LV uncoupling versus 94% for patients without LA-LV uncoupling (p < 0.001). Multivariable Cox regression analyses performed separately for each LA parameter showed an independent association between new-onset AF and LACI (hazard ratio [HR], 1.021; 95% CI, 1.017-1.026), LA maximum volume indexed (HR, 1.028; 95% CI, 1.017-1.039), LA minimum volume indexed (HR, 1.047; 95% CI, 1.037-1.060) and LA emptying fraction (HR, 0.967; 95% CI, 0.959-0.977, all p < 0.001). The inclusion of LACI in the multivariate model provided a larger improvement in the risk stratification for new-onset AF, as compared to conventional LA parameters.

CONCLUSION

In patients with HCM, LACI was more predictive of the occurrence of new-onset AF than conventional LA parameters.

Prednisone Ameliorates Atrial Inflammation and Fibrosis in Atrial Tachypacing Dogs

Atrial inflammation and fibrosis have long been considered culprits in the development of atrial fibrillation (AF). Prior clinical studies showed that corticosteroid therapy is beneficial in patients with AF. Here we sought to determine whether prednisone treatment prevents atrial tachypacing (ATP) induced atrial fibrosis.Dogs were randomized into the sham, ATP, ATP + low-dose prednisone (ALP), and ATP + high-dose prednisone (AHP) groups. After 6 days of recovery from surgery, dogs were subjected to ATP at 400 beats per minute for 4 weeks while being treated with prednisone (15 or 40 mg/day) or a placebo. Pacemakers were not activated in the sham group.Compared with the ATP group, the expression of collagen I, collagen III, α-smooth muscle actin, transforming growth factor-β1 and connective tissue growth factor were significantly reduced in the ALP and AHP groups. Fluorescence assays showed that reactive oxygen species formation in the right atrium was suppressed in the ALP and AHP groups compared with the ATP group. The protein level of NADPH oxidase 2 was reduced in the ALP and AHP groups' versus ATP group, while NOX4 and NOX5 were unchanged. ATP-induced downregulation of BH4 and eNOS uncoupling in the atria was partially restored in the prednisone-treated groups.Our study demonstrated that atrial fibrosis induced by ATP were suppressed by prednisone. Low-dose prednisone was also effective in suppressing the development of atrial fibrosis.

Renal denervation reduces atrial remodeling in hypertensive rats with metabolic syndrome

Atrial fibrillation (AF) is highly prevalent in hypertensive patients with metabolic syndrome and is related to inflammation and activation of the sympathoadrenergic system. The multi-ligand Receptor-for-Advanced-Glycation-End-products (RAGE) activates inflammation-associated tissue remodeling and is regulated by the sympathetic nervous system. Its counterpart, soluble RAGE (sRAGE), serves as anti-inflammatory decoy receptor with protective properties. We investigated the effect of sympathetic modulation by renal denervation (RDN) on atrial remodeling, RAGE/sRAGE and RAGE ligands in metabolic syndrome. RDN was performed in spontaneously hypertensive obese rats (SHRob) with metabolic syndrome compared with lean spontaneously hypertensive rats (SHR) and with normotensive non-obese control rats. Blood pressure and heart rate were measured by telemetry. The animals were killed 12 weeks after RDN. Left atrial (LA) and right atrial (RA) remodeling was assessed by histological analysis and collagen types. Sympathetic innervation was measured by tyrosine hydroxylase staining of atrial nerve fibers, RAGE/sRAGE, RAGE ligands, cytokine expressions and inflammatory infiltrates were analyzed by Western blot and immunofluorescence staining. LA sympathetic nerve fiber density was higher in SHRob (+44%) versus controls and reduced after RDN (-64% versus SHRob). RAGE was increased (+718%) and sRAGE decreased (- 62%) in SHRob as compared with controls. RDN reduced RAGE expression (- 61% versus SHRob), significantly increased sRAGE levels (+162%) and induced a significant decrease in RAGE ligand levels in SHRob (- 57% CML and - 51% HMGB1) with reduced pro-inflammatory NFkB activation (- 96%), IL-6 production (- 55%) and reduced inflammatory infiltrates. This led to a reduction in atrial fibrosis (- 33%), collagen type I content (- 72%), accompanied by reduced LA myocyte hypertrophy (- 21%). Transfection experiments on H9C2 cardiomyoblasts demonstrated that RAGE is directly involved in fibrosis formation by influencing cellular production of collagen type I. In conclusion, suppression of renal sympathetic nerve activity by RDN prevents atrial remodeling in metabolic syndrome by reducing atrial sympathetic innervation and by modulating RAGE/sRAGE balance and reducing pro-inflammatory and pro-fibrotic RAGE ligands, which provides a potential therapeutic mechanism to reduce the development of AF.

Cardiac and vascular features of arterial and venous primary antiphospholipid syndrome. The multicenter ATHERO-APS study

BACKGROUND

Patients with primary antiphospholipid syndrome (PAPS) may suffer from venous and/or arterial thrombosis, but studies addressing eventual clinical and laboratory features that may discriminate between arterial thromboembolism (ATE) from venous thromboembolism (VTE) have been poorly addressed.

METHODS

Cross sectional comparison of baseline characteristics of 100 patients enrolled in the multi center ATHERO-APS cohort study; patients with previous ATE and VTE were compared with regards to clinical and biochemical variables as well as to echocardiographic features and ankle-brachial index (ABI) measured at enrolment.

RESULTS

Mean age of patients was 51 years, 72 were women. 60 patients suffered VTE and 40 ATE. Compared to VTE, ATE patients displayed a higher prevalence of hypertension (43.3% vs. 65%, p = 0.034) and diabetes (3.3% vs. 17.5%, p = 0.015). Mean concentration of inflammation and complement activation markers were similar between the two groups as well as autoantibodies titres; mean D-dimer concentration was greater in VTE patients (184 ng/ml vs. 347 ng/ml; p = 0.024) whereas mean platelet count was greater in ATE patients (263 × 10⁹/L vs 216 × 10⁹/L, p = 0.044). By multivariable logistic regression analysis, adjusted for age, sex, hypertension and diabetes, ABI ≤ 0.9 (OR: 3.4; p = 0.041) and left atrial enlargement (OR: 3.5; p = 0.035) were associated with a history of ATE. ATE patients had a higher prevalence of ABI <0.9 (32.5% vs 10% p = 0.005) than VTE patients. At logistic regression analysis, IgG aCL >120 GPL U/ml was associated with an ABI ≤0.9 (OR: 5; p = 0.023) after adjustment for age and sex.

CONCLUSION

Clinical, laboratory and cardiovascular variables distinguish arterial from venous APS patients, amongst which the ABI and left atrial enlargement. Implications for these two distinct clinical phenotypes of APS patients need further investigation.

Left Atrial Remodeling and Cerebrovascular Disease Assessed by Magnetic Resonance Imaging in Continuously Monitored Patients

BACKGROUND

Atrial remodeling is associated with future atrial fibrillation (AF) and stroke. AF has been associated with cognitive impairment and cerebral white matter lesions. We wished to investigate the possible direct association between atrial remodeling and cerebrovascular disease in patients with and without AF documented by implantable loop recorder (ILR).

METHODS

Cardiac and cerebral magnetic resonance imaging were acquired in a cross-sectional study, including participants ≥70 years of age with stroke risk factors without known AF. Cerebrovascular disease was visually rated using the Fazekas scale and number of lacunar strokes. Left atrial (LA) and ventricular volumes and function were analyzed. Associations between atrial remodeling and cerebrovascular disease were assessed with logistic regression models. The analyses were stratified according to sinus rhythm or any AF during 3 months of continuous ILR monitoring to account for subclinical AF.

RESULTS

Of 200 participants investigated, 87% had a Fazekas score ≥1 and 45% had ≥1 lacunar infarct. Within 3 months of ILR monitoring, AF was detected in 28 (14%) participants. For participants with sinus rhythm (n = 172), lower LA passive emptying fraction was associated with Fazekas score after multivariable adjustment (OR [95% CI]: 0.51 [0.27; 0.86] p = 0.02), and increased LA maximum (OR [95% CI]: 1.38 [1.07; 1.82] p = 0.01) and minimum volumes (OR [95% CI]: 1.48 [1.03; 2.17] p = 0.04) were associated with lacunar infarcts. There were no significant associations in patients with AF.

CONCLUSION

In AF-free patients, as documented by ILR monitoring, we found an independent association between LA passive emptying fraction and Fazekas score and between atrial volumes and lacunar infarcts.

Impaired left atrial reservoir and conduit strain in patients with atrial fibrillation and extensive left atrial fibrosis

BACKGROUND

Atrial fibrillation (AF) is associated with profound structural and functional changes in the atria. In the present study, we investigated the association between left atrial (LA) phasic function and the extent of LA fibrosis using advanced cardiovascular magnetic resonance (CMR) imaging techniques, including 3-dimensional (3D) late gadolinium enhancement (LGE) and feature tracking.

METHODS

Patients with paroxysmal and persistent AF (n = 105) underwent CMR in sinus rhythm. LA global reservoir strain, conduit strain and contractile strain were derived from cine CMR images using CMR feature tracking. The extent of LA fibrosis was assessed from 3D LGE images. Healthy subjects underwent CMR and served as controls (n = 19).

RESULTS

Significantly lower LA reservoir strain, conduit strain and contractile strain were found in AF patients, as compared to healthy controls (- 15.9 ± 3.8% vs. - 21.1 ± 3.6% P < 0.001, - 8.7 ± 2.7% vs. - 12.6 ± 2.5% P < 0.001 and - 7.2 ± 2.3% vs. - 8.6 ± 2.2% P = 0.02, respectively). Patients with a high degree of LA fibrosis (dichotomized by the median value) had lower reservoir strain and conduit strain compared to patients with a low degree of LA fibrosis (- 15.0 ± 3.9% vs. - 16.9 ± 3.3%, P = 0.02 and - 7.9 ± 2.7% vs. - 9.5 ± 2.6%, P = 0.01, respectively). In contrast, no difference was found for LA contractile strain (- 7.1 ± 2.4% vs. - 7.4 ± 2.3%, P = 0.55).

CONCLUSIONS

Impaired LA reservoir and conduit strain are present in AF patients with extensive atrial fibrosis. Future studies are needed to examine the biologic nature of this association and possible therapeutic implications.

miR-425-5p is negatively associated with atrial fibrosis and promotes atrial remodeling by targeting CREB1 in atrial fibrillation

BACKGROUND

Progression of atrial fibrosis is vital for atrial remodeling in atrial fibrillation (AF). The main objective of the present study was to explore the association between miR-425-5p and atrial fibrosis as well as the resultant impact on atrial remodeling in AF.

METHODS

Firstly, miRNAs sequencing and quantitative real-time polymerase chain reaction was used to screen and verify the miRNAs expression level in plasma and atrial tissue in AF patients. The left atrial fibrosis was evaluated with the left atrial low voltage area by using left atrial voltage matrix mapping. Cell counting kit-8 was used to detect fibroblasts proliferation. The AF mouse model was established using acetylcholine-CaCl2 injection for 7 days. Target gene prediction software, luciferase assay, and western blotting were employed to confirm the direct targets of miR-425-5p.

RESULTS

Firstly, we demonstrated that miR-425-5p was downregulated in plasma and atrial tissue among the patients who suffered from AF. We then confirmed that the plasma's miR-425-5p level was negatively correlated with left atrial fibrosis in persistent AF, and catheter ablation could restore the decreased plasma miR-425-5p. Besides, receiver operating characteristic curve analysis revealed the miR-425-5p not only could differentiate AF from healthy control wit area under the curve (AUC) 0.921, but also discriminated persistent AF from paroxysmal AF with AUC 0.888. Furthermore, downregulation of miR-425-5p could promote atrial remodeling, and overexpression of miR-425-p could improve atrial remodeling and decrease susceptibility to atrial fibrillation. Finally, CREB1 was verified to be a direct target for miR-425-5p.

CONCLUSIONS

Our findings suggested that miR-425-5p could serve as novel atrial fibrosis biomarker and contributed to atrial remodeling in AF.

Association of atrial arrhythmias with thrombospondin-1 in patients with acute myocardial infarction

OBJECTIVES

Atrial remodeling is the main developmental cause of atrial arrhythmias (AA), which may induce atrial fibrillation, atrial flutter, atrial tachycardia, and frequent premature atrial beats in acute myocardial infarction (AMI) patients. Thrombospondin-1 (TSP-1) has been shown to play an important role in inflammatory and fibrotic processes, but its role in atrial arrhythmias is not well described. The purpose of this study was to investigate the role of TSP-1 in AMI patients with atrial arrhythmias.

METHODS

A total of 219 patients with AMI who underwent percutaneous coronary intervention and with no previous arrhythmias were included. TSP-1 were analyzed in plasma samples. Patients were classified into 2 groups, namely, with and without AA during the acute phase of MI. Continuous electrocardiographic monitoring was used for AA diagnosis in hospital.

RESULTS

Twenty-four patients developed AA. Patients with AA had higher TSP-1 levels (29.01 ± 25.87 μg/mL vs 18.36 ± 10.89 μg/mL, p < 0.001) than those without AA. AA patients also tended to be elderly (65.25 ± 9.98 years vs 57.47 ± 10.78 years, p < 0.001), had higher Hs-CRP (39.74 ± 43.50 mg/L vs 12.22 ± 19.25 mg/L, p < 0.001) and worse heart function. TSP-1 (OR 1.033; 95% CI 1.003-1.065, p = 0.034), Hs-CRP (OR 1.023; 95% CI 1.006-1.041, p = 0.008), age (OR 1.067; 95% CI 1.004-1.135, p = 0.038) and LVDd (OR 1.142; 95% CI 1.018-1.282, p = 0.024) emerged as independent risk factors for AA in AMI patients.

CONCLUSION

TSP-1 is a potential novel indicator of atrial arrhythmias during AMI.

Effect of intensive blood pressure lowering on left atrial remodeling in the SPRINT

Upstream therapy of atrial remodeling may decrease atrial fibrillation and associated thromboembolism. We examined the impact of intensive BP lowering on ECG-defined left atrial abnormalities in the SPRINT. SPRINT was a randomized clinical trial comparing outcomes when a systolic BP of <120 mmHg (standard treatment) was the target. We included SPRINT participants without baseline atrial fibrillation who had a technically interpretable baseline ECG and at least one follow-up ECG. The primary outcome was incident left atrial abnormality, defined as P-wave terminal force in V₁ (PTFV₁) > 4000 μV × ms. Secondary outcomes were regression of the left atrial abnormality and the change in PTFV₁ from baseline across follow-up ECGs. Cox regression was used to examine the associations between treatment assignment and incident left atrial abnormality and its regression. We used linear mixed models to examine the changes in PTFV₁. Of 9361 SPRINT participants, 7738 qualified for this analysis, of whom 5544 did not have baseline left atrial abnormalities. Intensive BP management was not associated with incident left atrial abnormality (HR, 0.96; 95% CI, 0.87-1.07) or regression of the baseline left atrial abnormality (HR, 1.09; 95% CI, 0.98-1.21). The change in PTFV₁ from baseline through follow-up did not differ significantly between treatment groups (difference in μV × ms per year, 6; 95% CI, -67 to 79). Thus, among patients in a randomized clinical trial, we found no difference in the progression or regression of ECG-defined left atrial abnormalities with intensive BP management compared to standard BP management.

Extracellular matrix remodeling precedes atrial fibrillation: Results of the PREDICT-AF trial

BACKGROUND

To which extent atrial remodeling occurs before atrial fibrillation (AF) is unknown.

OBJECTIVE

The PREventive left atrial appenDage resection for the predICtion of fuTure Atrial Fibrillation (PREDICT-AF) study investigated such subclinical remodeling, which may be used for risk stratification and AF prevention.

METHODS

Patients (N = 150) without a history of AF with a CHA₂DS₂-VASc score of ≥2 at an increased risk of developing AF were included. The left atrial appendage was excised and blood samples were collected during elective cardiothoracic surgery for biomarker discovery. Participants were followed for 2 years with Holter monitoring to determine any atrial tachyarrhythmia after a 50-day blanking period.

RESULTS

Eighteen patients (12%) developed incident AF, which was associated with increased tissue gene expression of collagen I (COL1A1), collagen III (COL3A1), and collagen VIII (COL8A2), tenascin-C (TNC), thrombospondin-2 (THBS2), and biglycan (BGN). Furthermore, the fibroblast activating endothelin-1 (EDN1) and sodium voltage-gated channel β subunit 2 (SCN2B) were associated with incident AF whereas the Kir2.1 channel (KCNJ2) tended to downregulate. The plasma levels of COL8A2 and TNC correlated with tissue expression and predicted incident AF. A gene panel including tissue KCNJ2, COL1A1, COL8A2, and EDN1 outperformed clinical prediction models in discriminating incident AF.

CONCLUSION

The PREDICT-AF study demonstrates that atrial remodeling occurs long before incident AF and implies future potential for early patient identification and therapies to prevent AF (ClinicalTrials.gov identifier NCT03130985).

Exercising immune cells: The immunomodulatory role of exercise on atrial fibrillation

Exercise training is generally beneficial for cardiovascular health, improving stroke volume, cardiac output, and aerobic capacity. Despite these benefits, some evidence indicates that endurance training may increase the risk of atrial fibrillation (AF), particularly in highly trained individuals. Among multiple mechanisms, autonomic tone changes and atrial remodeling have been proposed as main contributors for exercise-induced AF. However, the contribution of local and systemic immunity is poorly understood in the development of atrial arrhythmogenic substrates. Here we aim to update the field of immunomodulation in the context of exercise and AF by compiling and reconciling the most recent evidence from preclinical and human studies and rationalize the applicability of "lone" AF terminology in athletes.

The Association of Cardio-Ankle Vascular Index (CAVI) with Biatrial Remodeling in Atrial Fibrillation

AIM

Arterial stiffness results in elevated left ventricular filling pressure and can promote atrial remodeling due to chronic pressure overload. However, the impact of arterial stiffness on the process of atrial remodeling in association with atrial fibrillation (AF) has not been fully evaluated.

METHODS

We enrolled 237 consecutive patients diagnosed with AF who had undergone ablation; data from 213 patients were analyzed. Cardio-ankle vascular index (CAVI) was used as a marker of arterial stiffness. The left atrial (LA) and right atrial (RA) volumes were determined by computed tomography imaging; atrial conduction and voltage amplitude were evaluated using a three-dimensional electromapping system used to guide the ablation procedure.

RESULT

In univariate analysis, CAVI significantly correlated with atrial structural and electrical remodeling (LA volume index, r=0.297, P=0.001; RA volume index, r=0.252, P=0.004; LA conduction velocity, r=0.254, P= 0.003; LA mean voltage, r=-0.343, P=0.001, RA mean voltage; r=-0.245, P=0.015). Multivariate regression analysis revealed that CAVI and plasma levels of N-terminal B-type natriuretic peptide were independent determinants of LA and RA remodeling, respectively. On the other hand, age and LA conduction velocity were independent variables with respect to CAVI. Age-adjusted CAVI was highest in long-standing persistent AF when compared with measures of persistent or paroxysmal AF.

CONCLUSION

CAVI was closely associated with biatrial remodeling in patients diagnosed with AF. These results suggest that arterial stiffness may play a significant role with respect to disease progression.

Tachypacing-induced CREB/CD44 signaling contributes to the suppression of L-type calcium channel expression and the development of atrial remodeling

BACKGROUND

Atrial fibrillation (AF), a common arrhythmia in clinics, is characterized as downregulation of L-type calcium channel (LTCC) and shortening of atrial action potential duration (APD). Our prior studies have shown the association of CD44 with AF genesis.

OBJECTIVE

The purpose of this study was to explore the potential role of CD44 and its related signaling in tachypacing-induced downregulation of LTCC.

METHODS AND RESULTS

In vitro, tachypacing in atrium-derived myocytes (HL-1 cell line) induced activation (phosphorylation) of cyclic adenosine monophosphate response element-binding protein (CREB). Furthermore, tachypacing promoted an association between CREB and CD44 in HL-1 myocytes, which was documented in atrial tissues from patients with AF. Deletion and mutational analysis of the LTCC promoter along with chromatin immunoprecipitation revealed that cyclic adenosine monophosphate response element is essential for tachypacing-inhibited LTCC transcription. Tachypacing also hindered the binding of p-CREB to the promoter of LTCC. Blockade of CREB/CD44 signaling in HL-1 cells attenuated tachypacing-triggered downregulation of LTCC and shortening of APD. Atrial myocytes isolated from CD44^-/- mice exhibited higher LTCC current and longer APD than did those from wild-type mice. Ex vivo, tachypacing caused less activation of CREB in CD44^-/- mice than in wild-type mice. In vivo, burst atrial pacing stimulated less inducibility of AF in CREB inhibitor-treated mice than in controls.

CONCLUSION

Tachypacing-induced CREB/CD44 signaling contributes to the suppression of LTCC, which provides valuable information about the pathogenesis of atrial modeling and AF.

A fast and reproducible method to estimate left atrial volume using cardiac computed tomography

PURPOSE

The purpose of this study was to do better than the simple maximal axial area (MArea_ax) and to validate simple, fast and robust orthogonal methods for determining the left atrium volume (LAV) with cardiac CT (CCT).

MATERIAL AND METHODS

A total of 60 patients who underwent CTT were retrospectively included. There were 30 men and 30 women with a mean age of 59±12 (SD) years (range: 27-80 years), using four methods to assess LAV beyond the MArea_ax: two orthogonal methods requiring the measurements of axial, coronal and sagittal planes of 3 diameters LAV_3diam or 3 area LAV_3Areas; Area-length biplane method LAV_biplane; and volumetric method LAV_volumetric using a semi-automated tool that served as the reference standard. The orthogonal methods were applied on contrast-enhanced (IV+) and unenhanced (IV-) CCT images. Comparisons were performed using Pearson correlation test (r) and Bland-Altman analysis. Inter- and intra-observer variability were assessed using intraclass correlation coefficient (ICC) with a two-way mixed-effects model.

RESULTS

On IV+ CCT, LAV_biplane, LAV3diam_-IV+, LAV_3Areas-IV+ underestimated LAV (-15±1.99mL; -21±1.37mL; -15±1.98mL; all P<0.001). LAV_3diam-IV+, LAV3_Areas-IV+ better correlated with reference standard (r=0.97 and 0.98) than LAV_biplane (r=0.79) as well as MArea_ax (r=0.90). Estimating LAV on IV- further showed high correlation against the reference (r=0.93 and 0.95 for LAV3diam_-IV- and LAV_3Areass-IV-, respectively). Intra- and inter-observer ICC increased from LAV_volumetric (2.43% and 3.09%); LAV_3Areas-IV+ (3.04 and 3.30%); LAV_3Areas-IV-(3.34 and 4.23%), LAV3diam_-IV+ (3.36 and 5.11%); LAV3diam_-IV- (5.16 and 6.90%); to LAV_biplane (9.65 and 10.28%).

CONCLUSIONS

Better than MArea_ax, orthogonal methods using either diameter or surface are fast and reproducible methods to assess LAV on CCT when performed with or without intravenous administration of contrast material.

Implications of Inflammation and Fibrosis in Atrial Fibrillation Pathophysiology

Inflammation and fibrosis have been implicated in the pathophysiology of atrial fibrillation. Atrial fibrosis causes conduction disturbances and is a central component of atrial remodeling in atrial fibrillation. Cardiac fibroblasts, the cells responsible for fibrosis formation, are activated by inflammatory mediators and growth factors associated with systemic inflammatory conditions. Thus, inflammation contributes to atrial fibrosis; the complex interplay of these maladaptive components creates a vicious cycle of atrial remodeling progression, maintaining atrial fibrillation and increasing thrombogenicity. This review provides up-to-date knowledge regarding inflammation and fibrosis in atrial fibrillation pathophysiology and their potential as therapeutic targets.

Association of low-voltage areas with the regional wall deformation and the left atrial shape in patients with atrial fibrillation: A proof of concept study

Background

Left atrium (LA) remodeling is associated with atrial fibrillation (AF) and reduced success after AF ablation, but its relation with low-voltage areas (LVA) is not known. This study aimed to evaluate the relation between regional LA changes and LVAs in AF patients.

Methods

Pre-interventional CT data of patients (n = 24) with LA-LVA (<0.5 mV) in voltage mapping after AF ablation were analyzed (Surgery Explorer, QuantMD LLC). To quantify asymmetry (ASI = LA-A/LAV) a cutting plane parallel to the rear wall and along the pulmonary veins divided the LA-volume (LAV) into anterior (LA-A) and posterior parts. To quantify sphericity (LAS = 1-R/S), a patient-specific best-fit LA sphere was created. The average radius (R) and the mean deviation (S) from this sphere were calculated. The average local deviation (D) was measured for the roof, posterior, septum, inferior septum, inferior-posterior and lateral walls.

Results

The roof, posterior and septal regions had negative local deviations. There was a correlation between roof and septum (r = 0.42, p = 0.04), lateral and inferior-posterior (r = 0.48, p = 0.02) as well as posterior and inferior-septal deviations (r = −0.41, p = 0.046). ASI correlated with septum deformation (r = −0.43, p = 0.04). LAS correlated with dilatation (LAV, r = 0.49, p = 0.02), roof (r = 0.52, p = 0.009) and posterior deformation (r = −0.56, p = 0.005). Extended LVA correlated with local deformation of all LA walls, except the roof and the septum. LVA association with LAV, ASI and LAS did not reach statistical significance.

Conclusion

Extended LVA correlates with local wall deformations better than other remodeling surrogates. Therefore, their calculation could help predict LVA presence and deserve further evaluation in clinical studies.

Activation of NADPH oxidase mediates mitochondrial oxidative stress and atrial remodeling in diabetic rabbits

AIMS

The mechanisms of atrial fibrillation (AF) in diabetes mellitus (DM) involve a complex interplay between increased oxidative stress, mitochondrial dysfunction and atrial remodeling. In this study, we examined the effects of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation on mitochondrial oxidative stress and atrial remodeling in a rabbit model of diabetes mellitus (DM).

MAIN METHODS

Healthy rabbits were selected and randomly divided into control, diabetic and apocynin administration group. Parameters of echocardiography, atrial electrophysiology, oxidative stress and mitochondrial function were compared between the different groups.

KEY FINDINGS

Compared to the control group, the DM group showed higher activity of NADPH oxidase, increased oxidative stress, larger left atrial diameter, a reduction in atrial mean conduction velocity. These findings were associated with increased interstitial fibrosis of the atria and higher atrial fibrillation (AF) inducibility. Moreover, atrial ultrastructure and mitochondrial function such as the mitochondrial respiratory control rate (RCR) were impaired. NADPH oxidase inhibition using the pharmacological agent apocynin improved these changes.

SIGNIFICANCE

NADPH oxidase activity plays an important role in mitochondrial oxidative stress, which is associated with AF inducibility by promoting adverse atrial remodeling. The NADPH oxidase inhibitor apocynin can prevent these pathological changes and may be a potential drug for AF treatment.

Dual SGLT-1 and SGLT-2 inhibition improves left atrial dysfunction in HFpEF

BACKGROUND

Sodium-glucose linked transporter type 2 (SGLT-2) inhibition has been shown to reduce cardiovascular mortality in heart failure independently of glycemic control and prevents the onset of atrial arrhythmias, a common co-morbidity in heart failure with preserved ejection fraction (HFpEF). The mechanism behind these effects is not fully understood, and it remains unclear if they could be further enhanced by additional SGLT-1 inhibition. We investigated the effects of chronic treatment with the dual SGLT-1&2 inhibitor sotagliflozin on left atrial (LA) remodeling and cellular arrhythmogenesis (i.e. atrial cardiomyopathy) in a metabolic syndrome-related rat model of HFpEF.

METHODS

17 week-old ZSF-1 obese rats, a metabolic syndrome-related model of HFpEF, and wild type rats (Wistar Kyoto), were fed 30 mg/kg/d sotagliflozin for 6 weeks. At 23 weeks, LA were imaged in-vivo by echocardiography. In-vitro, Ca2+ transients (CaT; electrically stimulated, caffeine-induced) and spontaneous Ca2+ release were recorded by ratiometric microscopy using Ca2+-sensitive fluorescent dyes (Fura-2) during various experimental protocols. Mitochondrial structure (dye: Mitotracker), Ca2+ buffer capacity (dye: Rhod-2), mitochondrial depolarization (dye: TMRE) and production of reactive oxygen species (dye: H2DCF) were visualized by confocal microscopy. Statistical analysis was performed with 2-way analysis of variance followed by post-hoc Bonferroni and student's t-test, as applicable.

RESULTS

Sotagliflozin ameliorated LA enlargement in HFpEF in-vivo. In-vitro, LA cardiomyocytes in HFpEF showed an increased incidence and amplitude of arrhythmic spontaneous Ca2+ release events (SCaEs). Sotagliflozin significantly reduced the magnitude of SCaEs, while their frequency was unaffected. Sotagliflozin lowered diastolic [Ca2+] of CaT at baseline and in response to glucose influx, possibly related to a ~ 50% increase of sodium sodium-calcium exchanger (NCX) forward-mode activity. Sotagliflozin prevented mitochondrial swelling and enhanced mitochondrial Ca2+ buffer capacity in HFpEF. Sotagliflozin improved mitochondrial fission and reactive oxygen species (ROS) production during glucose starvation and averted Ca2+ accumulation upon glycolytic inhibition.

CONCLUSION

The SGLT-1&2 inhibitor sotagliflozin ameliorated LA remodeling in metabolic HFpEF. It also improved distinct features of Ca2+-mediated cellular arrhythmogenesis in-vitro (i.e. magnitude of SCaEs, mitochondrial Ca2+ buffer capacity, diastolic Ca2+ accumulation, NCX activity). The safety and efficacy of combined SGLT-1&2 inhibition for the treatment and/or prevention of atrial cardiomyopathy associated arrhythmias should be further evaluated in clinical trials.

Atrial matrix remodeling in atrial fibrillation patients with aortic stenosis

BACKGROUND

This study aimed to evaluate atrium extracellular matrix remodeling in atrial fibrillation (AF) patients with severe aortic stenosis, through histological fibrosis quantification and extracellular matrix gene expression analysis, as well as serum quantification of selected protein targets.

METHODS

A posthoc analysis of a prospective study was performed in a cohort of aortic stenosis patients. Between 2014 and 2019, 56 patients with severe aortic stenosis submitted to aortic valve replacement surgery in a tertiary hospital were selected.

RESULTS

Fibrosis was significantly increased in the AF group when compared to sinus rhythm (SR) patients (p = 0.024). Moreover, cardiomyocyte area was significantly higher in AF patients versus SR patients (p = 0.008). Conversely, collagen III gene expression was increased in AF patients (p = 0.038). TIMP1 was less expressed in the atria of AF patients. MMP16/TIMP4 ratio was significantly decreased in AF patients (p = 0.006). TIMP1 (p = 0.004) and TIMP2 (p = 0.012) were significantly increased in the serum of AF patients. Aortic valve maximum (p = 0.0159) and mean (p = 0.031) gradients demonstrated a negative association with serum TIMP1.

CONCLUSIONS

Atrial fibrillation patients with severe aortic stenosis present increased atrial fibrosis and collagen type III synthesis, with extracellular matrix remodelling demonstrated by a decrease in the MMP16/TIMP4 ratio, along with an increased serum TIMP1 and TIMP2 proteins.

MicroRNAs: New contributors to mechano-electric coupling and atrial fibrillation

Atrial fibrillation (AF) is a multifactorial disease, which often occurs in the presence of underlying cardiac abnormalities and is supported by electrophysiological and structural alterations, generally referred to as atrial remodeling. Abnormal substrates are commonly encountered in various conditions that predispose to AF, such as hypertension, heart failure, obesity, and sleep apnea, in which atrial stretch plays a key mechanistic role. Emerging evidence suggests a role for microRNAs (small non-coding RNAs) in the pathogenesis of AF, where they can act as post-transcriptional regulators of the genes involved in atrial remodeling. This review summarizes the experimental and clinical evidence that supports the role of microRNAs in the modulation of atrial electrical and structural remodeling with a focus on overload-induced atrial alterations, and discusses the potential contribution of microRNAs to mechano-electrical coupling and AF.

Electrical and structural remodeling contribute to atrial fibrillation in type 2 diabetic db/db mice

BACKGROUND

Atrial fibrillation (AF) is highly prevalent in diabetes mellitus (DM), yet the basis for this finding is poorly understood. Type 2 DM may be associated with unique patterns of atrial electrical and structural remodeling; however, this has not been investigated in detail.

OBJECTIVE

The purpose of this study was to investigate AF susceptibility and atrial electrical and structural remodeling in type 2 diabetic db/db mice.

METHODS

AF susceptibility and atrial function were assessed in male and female db/db mice and age-matched wildtype littermates. Electrophysiological studies were conducted in vivo using intracardiac electrophysiology and programmed stimulation. Atrial electrophysiology was also investigated in isolated atrial preparations using high-resolution optical mapping and in isolated atrial myocytes using patch-clamping. Molecular biology studies were performed using quantitative polymerase chain reaction and western blotting. Atrial fibrosis was assessed using histology.

RESULTS

db/db mice were highly susceptible to AF in association with reduced atrial conduction velocity, action potential duration prolongation, and increased heterogeneity in repolarization in left and right atria. In db/db mice, atrial K⁺ currents, including the transient outward current (I_to) and the ultrarapid delayed rectifier current (I_Kur), were reduced. The reduction in I_to occurred in association with reductions in Kcnd2 mRNA expression and K_V4.2 protein levels. The reduction in I_Kur was not related to gene or protein expression changes. Interstitial atrial fibrosis was increased in db/db mice.

CONCLUSION

Our study demonstrates that increased susceptibility to AF in db/db mice occurs in association with impaired electrical conduction as well as electrical and structural remodeling of the atria.

Left ventricular response after cardiac resynchronization therapy is related to early left atrial volume reduction

BACKGROUND/AIMS

The current study aimed to elucidate a time-course change in left atrial volume after cardiac resynchronization therapy (CRT) and to verify factors associated with left atrial volume reduction (LAVR) and its prognostic implications.

METHODS

The records of 97 patients were retrospectively reviewed after CRT. Echocardiographic data were analyzed at baseline before CRT, at early follow-up (FU) (≤ 1 year, median 6 months), and at late FU (median 30 months). Left ventricular volume response (LVVR) was defined as 15% reduction in left ventricular (LV) end-systolic volume (ESV). LAVR was classified into two groups by the median value at early FU: LAVR (≥ 7.5%) and no LAVR (< 7.5%).

RESULTS

LV ESV index continuously decreased from baseline to early FU and from early FU to late FU (106.1 ± 47.4 mL/m2 vs. 87.6 ± 51.6 mL/m2 vs. 72.5 ± 57.1 mL/m2). LA volume index decreased from baseline to early FU, but there were no reductions thereafter (51.8 ± 21.9 mL/m2 vs. 45.1 ± 19.6 mL/m2 vs. 44.9 ± 23.0 mL/m2). The only echocardiographic factor associated with LAVR was change in E velocity (odds ratio [OR], 1.04; p = 0.002). Early LAVR (OR, 10.05; p = 0.002) was an independent predictor for late LVVR.

CONCLUSION

LAVR was related to reduction in E velocity, suggesting its relation with optimization of LV filling pressure. Early LAVR was a predictor for LVVR to CRT in long-term FU.

Upstream Therapy for Atrial Fibrillation Prevention: The Role of Sacubitril/Valsartan

The therapy or prevention of atrial fibrillation (AF) is defined as upstream therapy when conducted with the use of drugs, e.g., angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor antagonists, statins, and omega-3 fatty acids, not included in the classes of antiarrhythmic drugs recognized by the Vaughan Williams classification. In our review, we illustrate the rational bases of upstream AF therapy, which encompasses drugs having the property to reduce hemodynamic congestion and cardiac overload, as in the case of ACEIs or angiotensin receptor blockers, as well as drugs able to prevent atrial fibrosis or reduce oxidative stress, such as statins or omega-3 fatty acids, respectively. In this review, randomized controlled trials (RCTs) conducted with the abovementioned drugs are examined. Really, these RCTs have generated mixed results. In the context of the prevention and therapy of AF, our experience is then presented, relating to a patient with heart failure and reduced left ventricular ejection fraction, with a history of relapsing episodes of paroxysmal AF. In this patient, administration of sacubitril/valsartan at appropriate doses allowed recovery of the sinus rhythm. Therefore this case testifies how the upstream therapy of AF might have good results when conducted with sacubitril/valsartan. Thus, RCTs with adequate statistical power are warranted in order to confirm the preliminary encouraging result of our case report, and validate a useful role of sacubitril/valsartan as an upstream therapy of AF.

Attenuation of atrial remodeling by aliskiren via affecting oxidative stress, inflammation and PI3K/Akt signaling pathway

INTRODUCTION

Atrial fibrillation (AF) is the most common type of arrhythmia. Atrial remodeling is a major factor to the AF substrate. The purpose of the study is to explore whether aliskiren (ALS) has a cardioprotective effect and its potential molecular mechanisms on atrial remodeling.

METHODS

In acute experiments, dogs were randomly assigned to Sham, Paced and Paced+aliskiren (10 mg kg^-1) (Paced+ALS) groups, with 7 dogs in each group. Rapid atrial pacing (RAP) was maintained at 600 bpm for 2 h for paced and Paced+ALS groups and atrial effective refractory periods (AERPs), inducibility of AF (AFi) and average duration time (ADT) were measured. In chronic experiments, there were 5 groups: Sham, Sham+ALS, Paced, Paced+ALS and Paced+ALS+PI3K antagonist wortmannin (WM) (70 μg kg^-1 day^-1). RAP at 500 beats/min was maintained for 2 weeks. Inflammation and oxidative stress indicators were measured by ELISA assay, echocardiogram and pathology were used to assess atrial structural remodeling, phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/Akt) signaling pathways were studied by RT-PCR and western blotting to evaluate whether the cardioprotective effect of ALS works through PI3K/Akt signaling pathway.

RESULTS

The electrophysiological changes were observed after 2-h pacing. The AERP shortened with increased AFi and ADT, which was attenuated by ALS (P < 0.05). After pacing for 2 weeks, oxidative stress and inflammation markers in the Paced group were significantly higher than those in the Sham group (P < 0.01) and were reduced by ALS treatment (P < 0.01). The reduced level of antioxidant enzymes caused by RAP was also found to be elevated in ALS-treated group (P < 0.01). The results of pathology and echocardiography showed that RAP can cause atrial enlargement, fibrosis (P < 0.01), and were attenuated in ALS treatment group. The PI3K/Akt signaling pathway were downregulated induced by RAP. ALS could upregulate the PI3K/Akt pathway expression (P < 0.05). Furthermore, the cardioprotective effects in structural remodeling of ALS were suppressed by WM.

CONCLUSIONS

ALS may offer cardioprotection in RAP-induced atrial remodeling, which may partly be ascribed to its anti-inflammatory and anti-oxidative stress action and the regulation of PI3K/Akt signaling pathway.

Microtubule polymerization state and clathrin-dependent internalization regulate dynamics of cardiac potassium channel: Microtubule and clathrin control of KV1.5 channel

Ion channel trafficking powerfully influences cardiac electrical activity as it regulates the number of available channels at the plasma membrane. Studies have largely focused on identifying the molecular determinants of the trafficking of the atria-specific K_V1.5 channel, the molecular basis of the ultra-rapid delayed rectifier current I_Kur. Besides, regulated K_V1.5 channel recycling upon changes in homeostatic state and mechanical constraints in native cardiomyocytes has been well documented. Here, using cutting-edge imaging in live myocytes, we investigated the dynamics of this channel in the plasma membrane. We demonstrate that the clathrin pathway is a major regulator of the functional expression of K_V1.5 channels in atrial myocytes, with the microtubule network as the prominent organizer of K_V1.5 transport within the membrane. Both clathrin blockade and microtubule disruption result in channel clusterization with reduced membrane mobility and internalization, whereas disassembly of the actin cytoskeleton does not. Mobile K_V1.5 channels are associated with the microtubule plus-end tracking protein EB1 whereas static K_V1.5 clusters are associated with stable acetylated microtubules. In human biopsies from patients in atrial fibrillation associated with atrial remodeling, drastic modifications in the trafficking balance occurs together with alteration in microtubule polymerization state resulting in modest reduced endocytosis and increased recycling. Consequently, hallmark of atrial K_V1.5 dynamics within the membrane is clathrin- and microtubule- dependent. During atrial remodeling, predominance of anterograde trafficking activity over retrograde trafficking could result in accumulation ok K_V1.5 channels in the plasma membrane.