Cardiomyocyte Remodeling in Atrial Fibrillation and Hibernating Myocardium: Shared Pathophysiologic Traits Identify Novel Treatment Strategies?

Echocardiographic correlates of MRI imaging markers of cerebral small-vessel disease in patients with atrial-fibrillation-related ischemic stroke

Background and objectives

Atrial fibrillation (AF) has been linked to dementia risk, partly explained by cerebral small vessel disease (CSVD). Since AF and cardiovascular comorbidities were associated with cardiac dysfunction, we aimed to determine the association between echocardiographic parameters and neuroimaging markers of CSVD in patients with AF-related ischemic stroke.

Methods

This cross-sectional study enrolled patients with AF-related ischemic stroke from March 2013 to December 2019 who underwent transthoracic echocardiography and brain 3T MRI, including T1, T2, Flair, and SWI imaging sequences. We assessed the presence of lacunes and cerebellar microbleeds (CMBs), the severity of white matter hyperintensity (WMH) scored by the Fazekas scale (0-6), and the severity of enlarged perivascular spaces (EPVS) in basal ganglia (BG) and centrum semiovale (CSO) classified into three categories (0-10, 10-25, and >25). CSVD burden was rated on a 0-to-4 ordinal scale. Generalized linear regression analysis and post hoc comparisons with Bonferroni correction were performed to assess the association between various echocardiographic parameters and these lesions, adjusted for demographics and potential confounders.

Results

119 patients (68.38 ± 12.692 years; male 45.4 %) were included for analysis, of whom 55 (46.2%) had lacunes, 40 (33.6%) had CMBs, and median severity for WMH, BG-EPVS, CSO-EPVS, and CSVD burden were 2 (IQR: 1-3), 1 (IQR: 1-2), 1 (IQR: 0-1), and 1 (IQR: 1-2) respectively. In multivariable, fully adjusted models, left ventricular posterior wall thickness (LVPW) was associated with a higher risk of lacunes (RR 1.899, 95% CI: 1.342-2.686) and CSVD burden (RR = 2.081, 95%CI: 1.562-2.070). Right atrial diameter (RAD) was associated with greater CSO-EPVS (RR = 2.243, 95%CI: 1.234-4.075). No echocardiographic parameters were revealed to be associated with CMBs and WMH.

Conclusion

In patients with AF-related ischemic stroke, LVPW is associated with a higher risk of lacunes and CSVD burden, while RAD was associated with greater CSO-EPVS. Larger studies are required to determine these associations and to elucidate if these associations can help facilitate cognitive evaluation and brain MRI screening.

The relationship between coronary microvascular dysfunction, atrial fibrillation and heart failure with preserved ejection fraction

OBJECTIVE

Coronary microvascular dysfunction (CMD) is a new frontier in cardiovascular disease and an important contributor to myocardial ischemia. A high prevalence of CMD is shown in heart failure, however, the cause-and-effect relationship between CMD and atrial fibrillation (AF) is unknown. We hypothesize that CMD is associated with AF and increases susceptibility to the co-existence of AF and heart failure with preserved ejection fraction (HFpEF).

METHODS

Our study examined the relationship between CMD, AF, and HFpEF in all patients who underwent invasive coronary physiology studies for assessment of chest pain or dyspnea. CMD was defined as impaired coronary flow reserve (CFR) without obstructive coronary disease.

RESULTS

A total of 80 patients (mean age 60±12 years, 68.8% female, median follow up of 2.2 years) were studied. Patients with AF (61%) or HFpEF (62%), or both (71%) were more likely to have CMD than those patients without these conditions. Of the patients with AF and abnormal CFR, 91% had HFpEF. CMD was a predictor of AF with concomitant HFpEF (OR 4.38, P=0.02). Our clinical outcome analysis demonstrated that patients with CMD, AF or HFpEF had lower survival free of HF hospitalization than those patients without (P<0.05). AF (OR 5.5, P=0.02), diabetes, older age, female gender, and higher heart rate were predictors of CMD.

CONCLUSION

CMD is highly prevalent in patients with AF with or without HFpEF. CMD is associated with poor clinical outcomes and the co-existence of AF and HFpEF. Understanding of the association between CMD and AF is important for developing an effective treatment strategy and the risk stratification for the prevention of AF in patients with CMD and vice versa.

Echinacoside reverses myocardial remodeling and improves heart function via regulating SIRT1/FOXO3a/MnSOD axis in HF rats induced by isoproterenol

Myocardial remodelling is important pathological basis of HF, mitochondrial oxidative stress is a promoter to myocardial hypertrophy, fibrosis and apoptosis. ECH is the major active component of a traditional Chinese medicine Cistanches Herba, plenty of studies indicate it possesses a strong antioxidant capacity in nerve cells and tumour, it inhibits mitochondrial oxidative stress, protects mitochondrial function, but the specific mechanism is unclear. SIRT1/FOXO3a/MnSOD is an important antioxidant axis, study finds that ECH binds covalently to SIRT1 as a ligand and up-regulates the expression of SIRT1 in brain cells. We hypothesizes that ECH may reverse myocardial remodelling and improve heart function of HF via regulating SIRT1/FOXO3a/MnSOD signalling axis and inhibit mitochondrial oxidative stress in cardiomyocytes. Here, we firstly induce cellular model of oxidative stress by ISO with AC-16 cells and pre-treat with ECH, the level of mitochondrial ROS, mtDNA oxidative injury, MMP, carbonylated protein, lipid peroxidation, intracellular ROS and apoptosis are detected, confirm the effect of ECH in mitochondrial oxidative stress and function in vitro. Then, we establish a HF rat model induced by ISO and pre-treat with ECH. Indexes of heart function, myocardial remodelling, mitochondrial oxidative stress and function, expression of SIRT1/FOXO3a/MnSOD signalling axis are measured, the data indicate that ECH improves heart function, inhibits myocardial hypertrophy, fibrosis and apoptosis, increases the expression of SIRT1/FOXO3a/MnSOD signalling axis, reduces the mitochondrial oxidative damages, protects mitochondrial function. We conclude that ECH reverses myocardial remodelling and improves cardiac function via up-regulating SIRT1/FOXO3a/MnSOD axis and inhibiting mitochondrial oxidative stress in HF rats.

Elevated Plasma Levels of Circulating Extracellular miR-320a-3p in Patients with Paroxysmal Atrial Fibrillation

The potential of extracellular circulating microRNAs (miRNAs) as non-invasive biomarkers of atrial fibrillation (AF) has been confirmed by a number of recent studies. However, the current data for some miRNAs are controversial and inconsistent, probably due to pre-analytical and methodological differences. In this work, we attempted to fulfill the basic pre-analytical requirements provided for circulating miRNA studies for application to paroxysmal atrial fibrillation (PAF) research. We used quantitative PCR (qPCR) to determine the relative plasma levels of circulating miRNAs expressed in the heart or associated with atrial remodeling or fibrillation with reported altered plasma/serum levels in AF: miR-146a-5p, miR-150-5p, miR-19a-3p, miR-21-5p, miR-29b-3p, miR-320a-3p, miR-328-3p, miR-375-3p, and miR-409-3p. First, in a cohort of 90 adult outpatient clinic patients, we found that the plasma level of miR-320a-3p was elevated in PAF patients compared to healthy controls and hypertensive patients without AF. We further analyzed the impact of medication therapies on miRNA relative levels and found elevated miR-320a-3p levels in patients receiving angiotensin-converting-enzyme inhibitors (ACEI) therapy. Additionally, we found that miR-320a-3p, miR-21-5p, and miR-146a-5p plasma levels positively correlated with the CHA₂DS₂-Vasc score and were elevated in subjects with CHA₂DS₂-Vasc ≥ 2. Our results indicate that, amongst the analyzed miRNAs, miR-320a-3p may be considered as a potential PAF circulating plasma biomarker, leading to speculation as to whether this miRNA is a marker of platelet state change due to ACEI therapy.

Pro-Arrhythmic Signaling of Thyroid Hormones and Its Relevance in Subclinical Hyperthyroidism

A perennial task is to prevent the occurrence and/or recurrence of most frequent or life-threatening cardiac arrhythmias such as atrial fibrillation (AF) and ventricular fibrillation (VF). VF may be lethal in cases without an implantable cardioverter defibrillator or with failure of this device. Incidences of AF, even the asymptomatic ones, jeopardize the patient's life due to its complication, notably the high risk of embolic stroke. Therefore, there has been a growing interest in subclinical AF screening and searching for novel electrophysiological and molecular markers. Considering the worldwide increase in cases of thyroid dysfunction and diseases, including thyroid carcinoma, we aimed to explore the implication of thyroid hormones in pro-arrhythmic signaling in the pathophysiological setting. The present review provides updated information about the impact of altered thyroid status on both the occurrence and recurrence of cardiac arrhythmias, predominantly AF. Moreover, it emphasizes the importance of both thyroid status monitoring and AF screening in the general population, as well as in patients with thyroid dysfunction and malignancies. Real-world data on early AF identification in relation to thyroid function are scarce. Even though symptomatic AF is rare in patients with thyroid malignancies, who are under thyroid suppressive therapy, clinicians should be aware of potential interaction with asymptomatic AF. It may prevent adverse consequences and improve the quality of life. This issue may be challenging for an updated registry of AF in clinical practice. Thyroid hormones should be considered a biomarker for cardiac arrhythmias screening and their tailored management because of their multifaceted cellular actions.

Heat shock protein inducer GGA*-59 reverses contractile and structural remodeling via restoration of the microtubule network in experimental Atrial Fibrillation

BACKGROUND

Atrial Fibrillation (AF) is the most common progressive tachyarrhythmia. AF progression is driven by abnormalities in electrical impulse formation and contractile function due to structural remodeling of cardiac tissue. Previous reports indicate that structural remodeling is rooted in derailment of protein homeostasis (proteostasis). Heat shock proteins (HSPs) play a critical role in facilitating proteostasis. Hence, the HSP-inducing compound geranylgeranylacetone (GGA) and its derivatives protect against proteostasis derailment in experimental models for AF. Whether these compounds also accelerate reversibility from structural remodeling in tachypaced cardiomyocytes is unknown.

OBJECTIVE

To investigate whether the potent HSP inducer GGA*-59 restores structural remodeling and contractile dysfunction in tachypaced cardiomyocytes and explore the underlying mechanisms.

MATERIALS AND RESULTS

HL-1 cardiomyocytes post-treated with GGA*-59 or recombinant HSPB1 (rcHSPB1) revealed increased levels of HSPB1 expression and accelerated recovery from tachypacing (TP)-induced calcium transient (CaT) loss compared to non-treated cardiomyocytes. In addition, protein levels of the microtubule protein (acetylated) α-tubulin, and contractile proteins cardiac troponin I (cTnI) and troponin T (cTnT) were reduced after TP and significantly recovered by GGA*-59 or rcHSPB1 post-treatment. The mRNA levels of α-tubulin encoding genes, but not cardiac troponin genes, were reduced upon TP and during recovery, but significantly enhanced by GGA*-59 and rcHSPB1 post-treatment. In addition, TP increased calpain activity, which remained increased during recovery and GGA*-59 post-treatment. However, HDAC6 activity, which deacetylates α-tubulin resulting in microtubule disruption, was significantly increased after TP and during recovery, but normalized to control levels by GGA*-59 or rcHSPB1 post-treatment in HL-1 cardiomyocytes.

CONCLUSIONS

Our results imply that the HSP inducer GGA*-59 and recombinant HSPB1 accelerate recovery from TP-induced structural remodeling and contractile dysfunction in HL-1 cardiomyocytes. GGA*-59 increases HSPB1 levels, represses HDAC6 activity and restores contractile protein and microtubule levels after TP, indicating that HSP-induction is an interesting target to accelerate recovery from AF-induced remodeling.

Sarcopenia, frailty, cognitive impairment and mortality in elderly patients with non-valvular atrial fibrillation

OBJECTIVES

To determine the prevalence of sarcopenia, frailty and cognitive impairment in elderly patients with nonvalvular atrial fibrillation (NVAF) and the factors' influence on survival.

METHODS

Prospective, multicentre cohort study of patients older than 75 years with NVAF hospitalised in internal medicine departments in Spain. For each patient, we recorded the creatinine, haemoglobin and platelet levels, the scores on the CHA2DS2-VASc and HAS-BLED scales and Charlson index, as well as the use of oral anticoagulants. We measured sarcopenia with the SARC-F scale, frailty with the FRAIL scale and cognitive impairment with the Short Portable Mental State Questionnaire. We also conducted a 1-year follow-up.

RESULTS

The study included 596 patients with NVAF, with a mean age of 84.9 (SD: 5.2) years. Of these, 295 (49.5%) presented sarcopenia, 305 (51.2%) presented frailty, and 251 (42.1%) presented cognitive impairment. At the end of 1year, 226 (37.9%) patients had died. Mortality was greater for the patients with sarcopenia, frailty and cognitive impairment. In the multivariate analysis, sarcopenia (HR: 1.775; 95%CI: 1.270-2.481), age, comorbidity and a history of peripheral embolism were associated with increased mortality, and the use of oral anticoagulants at discharge (HR: 0.415; 95%CI: 0.307-0.560) was associated with lower mortality.

CONCLUSIONS

Sarcopenia, frailty and cognitive impairment are very common in elderly patients with NVAF and are frequently associated. Sarcopenia was associated with increased mortality.

Tβ4 Increases Neovascularization and Cardiac Function in Chronic Myocardial Ischemia of Normo- and Hypercholesterolemic Pigs

Translations of new therapeutic options for cardiovascular disease from animal studies into a clinical setting have been hampered, in part by an improper reflection of a relevant patient population in animal models. In this study, we investigated the impact of thymosin β4 (Tβ4), which promotes collateralization and capillarization, during hypercholesterolemia, a known risk factor of coronary artery disease. Initial in vitro results highlighted an improved endothelial cell function upon Tβ4 treatment under control conditions and during hypercholesterolemic stress (scratch area [pixels]: oxidized low-density lipoprotein [oxLDL], 191,924 ± 7,717; and oxLDL + Tβ4, 105,621 ± 11,245). To mimic the common risk factor of hypercholesterolemia in vivo, pigs on regular (NC) or high-fat (HC) diet underwent chronic myocardial ischemia followed by recombinant adeno-associated virus (rAAV)-mediated transduction of Tβ4 or LacZ as a control. We show that Tβ4 overexpression improves capillarization and collateralization (collaterals: NC + rAAV.LacZ, 2.1 ± 0.5; NC + rAAV.Tβ4, 6.7 ± 0.5; HC + rAAV.LacZ, 3.0 ± 0.3; and HC + rAAV.Tβ4, 6.0 ± 0.4), ultimately leading to an improved myocardial function in both diet groups (ejection fraction [EF] at day 56 [%]: NC + rAAV.LacZ, 26 ± 1.1; NC + rAAV.Tβ4, 45 ± 1.5; HC + rAAV.LacZ, 26 ± 2.5; and HC + rAAV.Tβ4, 41 ± 2.6). These results demonstrate the potency of Tβ4 in a patient-relevant large animal model of chronic myocardial ischemia.

Mechanisms of Cardiac Repair and Regeneration

Cardiovascular regenerative therapies are pursued on both basic and translational levels. Although efficacy and value of cell therapy for myocardial regeneration can be debated, there is a consensus that profound deficits in mechanistic understanding limit advances, optimization, and implementation. In collaboration with the TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes), this review overviews several pivotal aspects of biological processes impinging on cardiac maintenance, repair, and regeneration. The goal of summarizing current mechanistic understanding is to prompt innovative directions for fundamental studies delineating cellular reparative and regenerative processes. Empowering myocardial regenerative interventions, whether dependent on endogenous processes or exogenously delivered repair agents, ultimately depends on mastering mechanisms and novel strategies that take advantage of rather than being limited by inherent myocardial biology.

Label-free Imaging of Myocardial Remodeling in Atrial Fibrillation Using Nonlinear Optical Microscopy: A Feasibility Study

Atrial fibrillation, characterized by rapid disorganized electrical activation of myocardium, is caused by and accompanied by remodeling of myocardial tissue. We applied nonlinear optical microscopy (NLOM) to visualize typical myocardial features and atrial fibrillation effects in order to test anon-destructive imaging technology that in principle can be applied in vivo.Coherent anti-Stokes Raman scattering, endogenous two-photon excited fluorescence, and second harmonic generation were used to inspect unstained human atrial myocardium from three patients who underwent surgical Cox-MAZE procedure with amputation of left atrial appendage. Using NLOM techniques, we collected detailrich pictures of unstained tissue that enable comprehensive characterization of myocardial characteristics like myocyte structure, collagen and lipofuscin deposition, intercalating disc width, and fatty degradation. Development of in vivo application of the NLOM technique may represent a revolutionary approach in characterizing atrial fibrillation associated myocardial remodeling with important implications for therapy individualization and monitoring.

Atrial Arrhythmias and Electroanatomical Remodeling in Patients With Left Ventricular Assist Devices

BACKGROUND

The incidence, predictors, and impact of atrial arrhythmias along with left atrial structural changes in patients with left ventricular assist devices (LVADs) remain undetermined.

METHODS AND RESULTS

All patients who underwent LVAD implantation from 2008 to 2015 at the University of Chicago Medical Center were included. Electronic medical records, electrocardiograms, echocardiograms, and cardiac electrical device interrogations were reviewed. The association of arrhythmias and clinical covariates with survival was evaluated by Kaplan-Meier and Cox proportional hazards analyses. A total of 331 patients were followed for a median of 330 days (range 0-2306 days). Mean age was 57.8±12.8 years, 256 participants (77.3%) were male, mean left ventricular ejection fraction was 20±6.6%, and 124 (37.5%) had ischemic cardiomyopathy. Atrial arrhythmias (53.8%) were highly prevalent and frequently coexisted before LVAD implantation: atrial fibrillation (AF) in 45.9%, atrial flutter in 13.9%, atrial tachycardia in 6.9%, and atrioventricular nodal reentrant tachycardia in 1.2%. New-onset AF was documented in 14 patients (7.8% of patients without prior AF) after the first 30 days with an LVAD. Increasing age, renal insufficiency, and lung disease were predictors of new-onset AF after LVAD implantation. Of patients with paroxysmal AF, 43% had no further AF after LVAD. Left atrial size and volume index improved with LVAD (P<0.005). History of persistent AF, atrial tachycardia, ventricular arrhythmia, coronary artery bypass, and low albumin were associated with decreased survival.

CONCLUSIONS

Atrial arrhythmias are significantly prevalent in patients who require LVAD and are associated with increased mortality; however, LVADs induce favorable atrial structural and electrical remodeling.

Functional Role and Mechanism of microRNA-28b in Atrial Myocyte in a Persistent Atrial Fibrillation Rat Model

Background

Persistent atrial fibrillation has been indicated to be related with microRNA-28b. However, the exact role of microRNA-28b in persistent atrial fibrillation needs to be further elucidated. Therefore, this study aimed to establish a rat model of persistent atrial fibrillation to investigate the level of microRNA-28b in atrial myocytes and to explore the molecular mechanism involved.

Material/Methods

A persistent atrial fibrillation model was established in rats by using chronic rapid atrial pacing induction. The size of the heart was measured by ultrasonic method. The expression of microRNA-28b in left atrial myocytes was quantified by RT-PCR. Cardiomyocytes were isolated and cultured to detect cell proliferation and apoptosis by MTT and flow cytometry, respectively. The specific inhibitor of ERK signaling pathway, PD98059, was used to further illustrate the role of ERK signaling pathway in the modulation of cardiomyocytes in persistent atrial fibrillation.

Results

MicroRNA-28b was up-regulated in the experimental rat model with persistent atrial fibrillation. The proliferation of cardiomyocytes was significantly inhibited with potentiated apoptosis. Blockage of the ERK pathway suppressed the microRNA-28b expression and inhibited cell apoptosis.

Conclusions

microRNA-28b-induced growth inhibition and cell apoptosis of atrial myocytes was observed in the rat model with persistent atrial fibrillation, via activation of the ERK signaling pathway.