Arrhythmia-Induced Cardiomyopathy

Causal Effect of Atrial Fibrillation on Heart Failure Risk in East Asian Ancestry: A Bidirectional Mendelian Randomization Study Using Genome-wide Association Data

BACKGROUND

Atrial fibrillation (AF) and heart failure (HF) are prevalent cardiovascular conditions in East Asia, with a complex interrelationship. The directionality of the causal impact of AF on HF risk remains uncertain. This study employs Mendelian randomization (MR) to investigate the potential causal effect of AF on HF.

METHODS

Utilizing summary data from genome-wide association studies (GWAS) within the Medical Research Council Integrative Epidemiology Unit open GWAS database, we analyzed 8180 AF cases and 28 612 controls, alongside 9413 HF cases and 203 040 controls, all of East Asian descent. We conducted MR analysis using the inverse variance weighted (IVW) method, complemented by various sensitivity analyses, including bidirectional MR to assess causality in the reverse direction.

RESULTS

Genetically predicted AF was found to be causally associated with an increased risk of HF in East Asian populations (odds ratio = 1.14, 95% CI: 1.10-1.19, P <.001) as per the IVW method. These findings were consistent across multiple MR methods. Sensitivity analyses revealed no significant heterogeneity or pleiotropy. Notably, bidirectional MR analysis showed no causal effect of HF on the risk of developing AF.

CONCLUSIONS

The MR analysis supports a unidirectional causal relationship between AF and increased HF risk in East Asian individuals. The absence of a reverse causal effect reinforces the importance of maintaining sinus rhythm to mitigate HF risk. Further research is warranted to corroborate these findings and to explore their clinical implications in depth.

Role of POCUS in the Management of New-onset Tachyarrhythmia in the Setting of SARS-CoV-2: A Case Report

Introduction

SARS-CoV-2 infection is associated with myocardial inflammation, new onset cardiomyopathy, and arrhythmias. Here, we describe the utilization of POCUS and management of concurrent new onset atrial tachycardia and heart failure with reduced ejection fraction (HfrEF) in a patient with SARS-CoV-2 infection.

Presentation

An 80-year-old female with multiple medical problems presented with sudden onset of shortness of breath and cough. She tested positive for SARS-CoV-2. Initially, she was hypoxic on room air and her heart rhythm was sinus tachycardia. CT angiogram of the chest showed consolidation, pleural effusion, and absence of pulmonary embolism. Because of persistent tachycardia, repeat EKGs and POCUS were performed. Subsequent EKGs showed intermittent atrial tachycardia and sinus tachycardia. Initially, home beta blockers were continued on admission, and additional dosages were considered for rate control, but Cardiac POCUS revealed HfrEF and was subsequently confirmed by comprehensive cardiac echocardiogram, consistent with SARS-CoV-2 infection-related cardiomyopathy. Beta blockers were discontinued, and treatment with amiodarone and furosemide showed improvement in symptoms. The patient was discharged with oral amiodarone and supplemental oxygen. Additionally, once the patient's hemodynamics improved, oral carvedilol was also started as part of GDMT for HfrEF. Follow-up echocardiogram 4 months later showed recovery of systolic EF to 60%.

Conclusion

It is essential to consider new onset HFrEF in the evaluation and management of new onset tachyarrhythmias since IV fluids and AV nodal blocking agents can be harmful in decompensated HFrEF. With the advent of POCUS, HFrEF can be quickly identified, and therapy can be tailored to that diagnosis.

The Detrimental Effect of Pre-Treatment with Ivermectin on Myocardial Ischemia

INTRODUCTION

Ivermectin (IVM) is a broad-spectrum anti-parasitic agent with potential antibacterial, antiviral, and anti-cancer effects. There are limited studies on the effects of IVM on cardiovascular diseases, so the present study sought to determine the effects of pre-treatment with IVM on myocardial ischemia in both ex vivo and in vivo.

METHODS

In the ex vivo part, two groups of control and treated rats with IVM (0.2 mg/kg) were examined for cardiac function and arrhythmias by isolated heart perfusion. In the in vivo part, four groups, namely, control, IVM, Iso (MI), and Iso + IVM 0.2 mg/kg were used. Subcutaneous injection of isoproterenol (100 mg/kg/day) for 2 consecutive days was used for the induction of myocardial infarction (MI) in male Wistar rats. Then electrocardiogram, hemodynamic factors, cardiac hypertrophy, and malondialdehyde (MDA) levels were investigated.

RESULTS

The ex vivo results showed that administration of IVM induces cardiac arrhythmia and decreases the left ventricular maximal rate of pressure increase (contractility) and maximal rate of pressure decline (relaxation). The isoproterenol-induced MI model used as an in vivo model showed that cardiac hypertrophy were increased with no improvement in the hemodynamic and electrocardiogram pattern in the IVM-treated group in comparison to MI (Iso) group. However, the MDA level was lower in the IVM-treated group.

CONCLUSION

IVM pre-treatment demonstrates detrimental effects in cardiac ischemia through exacerbation of cardiac arrhythmia, myocardial dysfunction, and increased cardiac hypertrophy. Therefore, the use of IVM in ischemic heart patients should be done with great caution.

How arrhythmias weaken the ventricle: an often underestimated vicious cycle

Arrhythmia-induced cardiomyopathy (AIC) is classified as a form of dilated cardiomyopathy in which left ventricular systolic dysfunction (LVSD) is triggered by tachycardic or arrhythmic heart rates. On the one hand AIC can develop in patients without cardiac disease and on the other hand it can appear in patients with pre-existing LVSD, leading to a further reduction in left ventricular (LV) ejection fraction. A special aspect of AIC is the potential termination or partial reversibility of LVSD; thus, AIC is curatively treatable by the elimination of the underlying arrhythmia. Since arrhythmias are often seen merely as a consequence than as an underlying cause of LVSD, and due to the fact that the diagnosis of AIC can be made only after recovery of LV function, the prevalence of AIC is probably underestimated in clinical practice. Pathophysiologically, animal models have shown that continuous tachycardic pacing induces consecutive changes such as the occurrence of LVSD, increased filling pressures, LV dilatation, and decreased cardiac output. After termination of tachycardia, reversibility of the described pathologies can usually be observed. Studies in human ventricular myocardium have recently demonstrated that various cellular structural and functional mechanisms are activated even by normofrequent atrial fibrillation, which may help to explain the clinical AIC phenotype.

Effectiveness and safety of Linggui Zhugan decoction for the treatment of premature contraction in patients with coronary heart disease: A systematic review and meta-analysis

Objective

To evaluate the effectiveness and safety of Linggui Zhugan decoction (LZD) as an adjunct treatment of premature contraction in patients with coronary heart disease.

Methods

PubMed, Embase, Web of Science, ClinicalTrials.gov Cochrane Library, Chinese Knowledge Infrastructure, Wanfang database, Sino Med, and VIP database were searched from inception until July 2022. Two reviewers independently selected randomized controlled trials assessing the effectiveness of LZD combined with conventional antiarrhythmic drugs in treating premature contraction in patients with coronary heart disease compared to conventional antiarrhythmic drugs only. The clinical effectiveness was considered as the primary outcome, and the times of premature junctional beats in 24 h after treatment along with adverse reactions were considered secondary outcomes. The Cochrane risk of bias 2 tool was used for the risk of bias assessment. Meta-analysis was conducted using RevMan 5.4.1. and RStudio software.

Results

A total of 14 studies including 1,236 participants were included. The primary outcome indicated that, compared with antiarrhythmic drugs alone (especially β receptor blockers), the combination of LZD and conventional antiarrhythmic drugs resulted in higher clinical effectiveness (RR = 1.29, 95% CI: [1.22,1.36]) and lower number of premature junctional beats in 24 h (MD = -71.14, 95% CI: [-76.23, -66.06]) at end-of-intervention. The differences in adverse reactions (RR = 0.42, 95%CI: [0.15, 1.14], p = 0.09) were not significant. The risk of bias was marginally high among the studies. Funnel plot and Harbord's test (t = 1.63, p = 0.1346) indicated no existence of publication bias.

Conclusion

The current evidence shows that LZD can increase the effectiveness of conventional antiarrhythmic drugs for treating premature contraction in patients with coronary heart disease. However, the results should be interpreted with caution because of the high overall risk of bias. Future studies with appropriate randomization and double-blind methods are warranted to confirm these findings.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=296628], identifier [CRD42022296628].

E-cigarettes and their lone constituents induce cardiac arrhythmia and conduction defects in mice

E-cigarette use has surged, but the long-term health effects remain unknown. E-cigarette aerosols containing nicotine and acrolein, a combustion and e-cigarette byproduct, may impair cardiac electrophysiology through autonomic imbalance. Here we show in mouse electrocardiograms that acute inhalation of e-cigarette aerosols disturbs cardiac conduction, in part through parasympathetic modulation. We demonstrate that, similar to acrolein or combustible cigarette smoke, aerosols from e-cigarette solvents (vegetable glycerin and propylene glycol) induce bradycardia, bradyarrhythmias, and elevations in heart rate variability during inhalation exposure, with inverse post-exposure effects. These effects are slighter with tobacco- or menthol-flavored aerosols containing nicotine, and in female mice. Yet, menthol-flavored and PG aerosols also increase ventricular arrhythmias and augment early ventricular repolarization (J amplitude), while menthol uniquely alters atrial and atrioventricular conduction. Exposure to e-cigarette aerosols from vegetable glycerin and its byproduct, acrolein, diminish heart rate and early repolarization. The pro-arrhythmic effects of solvent aerosols on ventricular repolarization and heart rate variability depend partly on parasympathetic modulation, whereas ventricular arrhythmias positively associate with early repolarization dependent on the presence of nicotine. Our study indicates that chemical constituents of e-cigarettes could contribute to cardiac risk by provoking pro-arrhythmic changes and stimulating autonomic reflexes.

Arrhythmia-induced Cardiomyopathy: An Article Review

Arrhythmia is one of the significant reversible causes in patients with heart disease and left ventricular dysfunction. Tachycardia, atrial fibrillation, and premature ventricular contractions have indeed been related to arrhythmia-induced cardiomyopathy (CM), a reversible dilated CM. Effective arrhythmia suppression will entirely or partially recover ventricular function, lowering morbidity and mortality. However, the importance of arrhythmia-induced CM (ARiCM) is often underestimated in clinical practice because arrhythmia is often seen as a result rather than a cause of CM, leading in treatment delays and failure to increase the quality of life and better clinical outcomes. This article review aims to summarize the pathomechanisms, and a general approach to the management of ARiCM and its long-term outcomes. ARiCM can cause a variety of clinical signs, ranging from asymptomatic to severe heart failure symptoms. Electrocardiogram, 24 h Holter monitoring, echocardiography, and cardiac magnetic resonance are all recommended for diagnosis. More research is required to better understand the pathogenesis of ARiCM and to differentiate treatment alternatives to choose the ideal ARiCM management approach.

Tachycardiomyopathy entails a dysfunctional pattern of interrelated mitochondrial functions

Tachycardiomyopathy is characterised by reversible left ventricular dysfunction, provoked by rapid ventricular rate. While the knowledge of mitochondria advanced in most cardiomyopathies, mitochondrial functions await elucidation in tachycardiomyopathy. Pacemakers were implanted in 61 rabbits. Tachypacing was performed with 330 bpm for 10 days (n = 11, early left ventricular dysfunction) or with up to 380 bpm over 30 days (n = 24, tachycardiomyopathy, TCM). In n = 26, pacemakers remained inactive (SHAM). Left ventricular tissue was subjected to respirometry, metabolomics and acetylomics. Results were assessed for translational relevance using a human-based model: induced pluripotent stem cell derived cardiomyocytes underwent field stimulation for 7 days (TACH-iPSC-CM). TCM animals showed systolic dysfunction compared to SHAM (fractional shortening 37.8 ± 1.0% vs. 21.9 ± 1.2%, SHAM vs. TCM, p < 0.0001). Histology revealed cardiomyocyte hypertrophy (cross-sectional area 393.2 ± 14.5 µm² vs. 538.9 ± 23.8 µm², p < 0.001) without fibrosis. Mitochondria were shifted to the intercalated discs and enlarged. Mitochondrial membrane potential remained stable in TCM. The metabolite profiles of ELVD and TCM were characterised by profound depletion of tricarboxylic acid cycle intermediates. Redox balance was shifted towards a more oxidised state (ratio of reduced to oxidised nicotinamide adenine dinucleotide 10.5 ± 2.1 vs. 4.0 ± 0.8, p < 0.01). The mitochondrial acetylome remained largely unchanged. Neither TCM nor TACH-iPSC-CM showed relevantly increased levels of reactive oxygen species. Oxidative phosphorylation capacity of TCM decreased modestly in skinned fibres (168.9 ± 11.2 vs. 124.6 ± 11.45 pmol·O₂·s^-1·mg^-1 tissue, p < 0.05), but it did not in isolated mitochondria. The pattern of mitochondrial dysfunctions detected in two models of tachycardiomyopathy diverges from previously published characteristic signs of other heart failure aetiologies.

Exercise-Training Regulates Apolipoprotein B in Drosophila to Improve HFD-Mediated Cardiac Function Damage and Low Exercise Capacity

Apolipoprotein B plays an essential role in systemic lipid metabolism, and it is closely related to cardiovascular diseases. Exercise-training can regulate systemic lipid metabolism, improve heart function, and improve exercise capacity, but the molecular mechanisms involved are poorly understood. We used a Drosophila model to demonstrate that exercise-training regulates the expression of apoLpp (a homolog of apolipoprotein B) in cardiomyocytes, thereby resisting heart insufficiency and low exercise capacity caused by obesity. The apoLpp is an essential lipid carrier produced in the heart and fat body of Drosophila. In a Drosophila genetic screen, low expression of apoLpp reduced obesity and cardiac dysfunction induced by a high-fat diet (HFD). Cardiac-specific inhibition indicated that reducing apoLpp in the heart during HFD reduced the triglyceride content of the whole-body and reduced heart function damage caused by HFD. In exercise-trained flies, the result was similar to the knockdown effect of apoLpp. Therefore, the inhibition of apoLpp plays an important role in HFD-induced cardiac function impairment and low exercise capacity. Although the apoLpp knockdown of cardiomyocytes alleviated damage to heart function, it did not reduce the arrhythmia and low exercise capacity caused by HFD. Exercise-training can improve this condition more effectively, and the possible reason for this difference is that exercise-training regulates climbing ability in ways to promote metabolism. Exercise-training during HFD feeding can down-regulate the expression of apoLpp, reduce the whole-body TG levels, improve cardiac recovery, and improve exercise capacity. Exercise-training can downregulate the expression of apoLpp in cardiomyocytes to resist cardiac function damage and low exercise capacity caused by HFD. The results revealed the relationship between exercise-training and apoLpp and their essential roles in regulating heart function and climbing ability.

Pedigree analysis of atrial fibrillation in Irish wolfhounds supports a high heritability with a dominant mode of inheritance

Background

Atrial fibrillation (AF) is the most common arrhythmia in dogs. The Irish Wolfhound breed has a high prevalence of AF making them an ideal breed to investigate possible genetic contributions to this disease. The aim of this study was to perform a heritability analysis in North American Irish Wolfhounds using phenotype data from cardiac screenings performed between 2000 and 2019 in order to determine how much of this disease can be attributed to genetics compared to environmental causes. The second aim was to determine the disease mode of inheritance to help inform prevention and breeding practices.

Results

There were 327 Irish Wolfhounds diagnosed with AF and 136 Irish Wolfhounds over 8 years of age without AF. The estimated mean (95% confidence interval) heritability of AF in Irish Wolfhounds was 0.69 (0.50–0.86). The pedigree was consistent with a dominant mode of inheritance.

Conclusion

Results of this study indicate a strong genetic contribution to AF in Irish Wolfhounds and suggest that future research to identify causative genetic mutations is warranted.

Skeletal muscle alterations in tachycardia-induced heart failure are linked to deficient natriuretic peptide signalling and are attenuated by RAS-/NEP-inhibition

Background

Heart failure induced cachexia is highly prevalent. Insights into disease progression are lacking.

Methods

Early state of left ventricular dysfunction (ELVD) and symptomatic systolic heart failure (HF) were both induced in rabbits by tachypacing. Tissue of limb muscle (LM) was subjected to histologic assessment. For unbiased characterisation of early and late myopathy, a proteomic approach followed by computational pathway-analyses was performed and combined with pathway-focused gene expression analyses. Specimen of thoracic diaphragm (TD) served as control for inactivity-induced skeletal muscle alterations. In a subsequent study, inhibition of the renin-angiotensin-system and neprilysin (RAS-/NEP) was compared to placebo.

Results

HF was accompanied by loss of protein content (8.7±0.4% vs. 7.0±0.5%, mean±SEM, control vs. HF, p<0.01) and a slow-to-fast fibre type switch, establishing hallmarks of cachexia. In ELVD, the enzymatic set-up of LM and TD shifted to a catabolic state. A disturbed malate-aspartate shuttle went well with increased enzymes of glycolysis, forming the enzymatic basis for enforced anoxic energy regeneration. The histological findings and the pathway analysis of metabolic results drew the picture of suppressed PGC-1α signalling, linked to the natriuretic peptide system. In HF, natriuretic peptide signalling was desensitised, as confirmed by an increase in the ratio of serum BNP to tissue cGMP (57.0±18.6pg/ml/nM/ml vs. 165.8±16.76pg/ml/nM/ml, p<0.05) and a reduced expression of natriuretic peptide receptor-A. In HF, combined RAS-/NEP-inhibition prevented from loss in protein content (8.7±0.3% vs. 6.0±0.6% vs. 8.3±0.9%, Baseline vs. HF-Placebo vs. HF-RAS/NEP, p<0.05 Baseline vs. HF-Placebo, p = 0.7 Baseline vs. HF-RAS/NEP).

Conclusions

Tachypacing-induced heart failure entails a generalised myopathy, preceding systolic dysfunction. The characterisation of “pre-cachectic” state and its progression is feasible. Early enzymatic alterations of LM depict a catabolic state, rendering LM prone to futile substrate metabolism. A combined RAS-/NEP-inhibition ameliorates cardiac-induced myopathy independent of systolic function, which could be linked to stabilised natriuretic peptide/cGMP/PGC-1α signalling.

[The effect of angiotensin receptors and neprilysin inhibitors on myocardial remodeling in patients with chronic heart failure and atrial fibrillation]

AIM

To evaluate the effect of angiotensin-neprilysin receptor inhibitors on myocardial remodeling in patients with chronic heart failure and atrial fibrillation.

MATERIALS AND METHODS

We studied dynamics of the parameters of ultrasound structural and functional parameters of the left atrium and left ventricle of the heart was during 3-month therapy with sacubitryl-valsartan in a group of 15 patients with a combination of chronic heart failure due to dilated and paroxysmal paroxysmal forms of atrial fibrillation.

RESULTS

Showed a statistically significant positive effect of the use of angiotensin receptors and neprilysin inhibitors on the parameters of remodeling of the left atrium (according to transthoracic and transesophageal echocardiography), left ventricle, as well as levels of natriuretic peptides ANP and NT-pro-BNP.

CONCLUSION

The use of ARNI may be promising in terms of treatment and prevention of AF in patients with heart failure.

Catheter ablation of atrial fibrillation-A key role in heart failure therapy?

Atrial fibrillation (AF) and heart failure (HF) are epidemic cardiac diseases and are often detected in the same patient. Recent evidence suggests that this is not a mere coincidence but that the strategy of AF treatment may impact HF development. This review comprehensively summarizes current trial data on rhythm and rate control strategies in atrial fibrillation with a special focus on catheter ablation of AF in HF patients. For a long time, rate and rhythm control strategies for AF have been regarded as equal regarding long term mortality. Decision making has been based on the symptoms of patients. Current trials, however, show that the treatment strategy of AF and its effectiveness may significantly impact survival of HF patients. The benefits of rhythm control in HF patients may have been masked by side effects of antiarrhythmic drugs. If rhythm control, however, is achieved by catheter ablation, a reduction of HF related mortality can be observed. As catheter ablation of AF may reduce mortality in HF patients, AF ablation should be preferred over medical treatment in HF patients. In general, HF patients may profit most from rigorous AF treatment.

The detrimental potential of arrhythmia-induced cardiomyopathy

Here we discuss a case of arrhythmia‐induced cardiomyopathy (AIC) with consecutive severe multiple organ failure. In relation to this imposing case, we discuss the significance of this potentially underestimated cause of newly occurred left‐ventricular systolic dysfunction and concomitant arrhythmia. We further delineate the diagnostic algorithm and differential diagnoses of AIC.