What Is the Arrhythmic Substrate in Viral Myocarditis? Insights from Clinical and Animal Studies

Prevalence, Outcomes, and Predictors of Prolonged Corrected QT Interval in Hydroxychloroquine-Naïve Hospitalized COVID-19 Patients

The studies regarding prevalence, outcomes, and predictors of prolonged corrected QT (QTc) among COVID-19 patients not on QTc-prolonging medication are not available in the literature. In this retrospective cohort study, the QTc of 295 hospital-admitted COVID-19 patients was analyzed and its association with in-hospital mortality was determined. The QTc was prolonged in 14.6% (43/295) of the study population. Prolonged QTc was seen in patients with older age (P = 0.018), coronary artery disease (P = 0.001), congestive heart failure (P = 0.042), elevated N-terminal-pro-B-type natriuretic peptide (NT-ProBNP) (P < 0.0001), and on remdesivir (P = 0.046). No episode of torsades de pointes arrhythmia or any arrhythmic death was observed among patients with prolonged QTc. The mortality was significantly high in patients with prolonged QTc (P = 0.003). The multivariate logistic regression analysis showed coronary artery disease (odds ratio (OR): 4.153, 95% CI 1.37-14.86; P = 0.013), and NT-ProBNP (ng/L) (OR: 1.000, 95% CI 1.000-1.000; P = 0.007) as predictors of prolonged QTc. The prolonged QTc was associated with the worst in-hospital survival (p by log-rank 0.001). A significant independent association was observed between prolonged QTc and in-hospital mortality in multivariate cox-regression analysis (adjusted hazard ratio: 3.861; (95% CI 1.719-6.523), P < 0.0001). QTc was found to be a marker of underlying comorbidities among COVID-19 patients. Prolonged QTc in hospitalized COVID-19 patients was independently associated with in-hospital mortality.

Cardiovascular Manifestations of Long COVID: A Review

The acute phase of severe acute respiratory syndrome coronavirus 2 [coronavirus disease (COVID)] infection has many well-documented cardiovascular manifestations, however, the long-term sequelae are less understood. In this focused review, we explore the risk factors, character, and rates of cardiovascular events in patients with Long COVID, which is defined as symptoms occurring more than 4 weeks following initial infection. Research has identified increased rates of cerebrovascular disease, dysrhythmias, ischemic and inflammatory heart disease, cardiopulmonary symptoms, and thrombotic events among those with Long COVID, though the risk rates and potential mechanisms behind each cardiovascular event vary. Finally, we discuss the current gaps in the literature as well as how COVID compares to other viral infections when it comes to causing long-term cardiovascular sequelae.

The natural history of CVB3 myocarditis in C57BL/6J mice: an extended in-depth characterization

BACKGROUND AND AIMS

Viral infections are the leading cause of myocarditis. Besides acute cardiac complications, late-stage sequelae such as myocardial fibrosis may develop, importantly impacting the prognosis. Coxsackievirus B3 (CVB)-induced myocarditis in mice is the most commonly used translational model to study viral myocarditis and has provided the majority of our current understanding of the disease pathophysiology. Nevertheless, the late stages of disease, encompassing fibrogenesis and arrhythmogenesis, have been underappreciated in viral myocarditis research to date. The present study investigated the natural history of CVB-induced myocarditis in C57BL/6J mice, expanding the focus beyond the acute phase of disease. In addition, we studied the impact of sex and inoculation dose on the disease course.

METHODS AND RESULTS

C57BL/6J mice (12 weeks old; n=154) received a single intraperitoneal injection with CVB to induce viral myocarditis, or vehicle (PBS) as control. Male mice (n=92) were injected with 5 × 105 (regular dose) (RD) or 5 × 106 (high dose) (HD) plaque-forming units of CVB, whereas female mice received the RD only. Animals were sacrificed 1, 2, 4, 8, and 11 weeks after CVB or PBS injection. Virally inoculated mice developed viral disease with a temporary decline in general condition and weight loss, which was less pronounced in female animals (P<.001). In male CVB mice, premature mortality occurred between days 8 and 23 after inoculation (RD: 21%, HD: 20%), whereas all female animals survived. Over the course of disease, cardiac inflammation progressively subsided, with faster resolution in female mice. There were no substantial group differences in the composition of the inflammatory cell infiltrates: predominance of cytotoxic T cells at day 7 and 14, and a switch from arginase1-reactive macrophages to iNOS-reactive macrophages from day 7 to 14 were the main findings. There was concomitant development and maturation of different patterns of myocardial fibrosis, with enhanced fibrogenesis in male mice. Virus was almost completely cleared from the heart by day 14. Serum biomarkers of cardiac damage and cardiac expression of remodeling genes were temporarily elevated during the acute phase of disease. Cardiac CTGF gene upregulation was less prolonged in female CVB animals. In vivo electrophysiology studies at weeks 8 and 11 demonstrated that under baseline conditions (i.e. in the absence of proarrhythmogenic drugs), ventricular arrhythmias could only be induced in CVB animals. The cumulative arrhythmia burden throughout the entire stimulation protocol was not significantly different between CVB and control groups.

CONCLUSION

CVB inoculation in C57BL/6J mice represents a model of acute self-limiting viral myocarditis, with progression to different patterns of myocardial fibrosis. Sex, but not inoculation dose, seems to modulate the course of disease.

Cardiac Manifestations of Viral Infections, Including COVID-19: A Review

Viral infections have been linked to a variety of cardiac pathology, which may include acute myocarditis, dilated cardiomyopathy, heart failure, cardiogenic shock, pericarditis, acute coronary syndromes, and arrhythmias. We performed a systematic review of literature focusing on the cardiovascular effects of various viral infections, as well as providing an update on the current understanding of the pathophysiology of Coronavirus disease-2019 (COVID-19). Cardiac manifestations of viral illnesses are usually self-limiting, have variable clinical presentations, and require sufficient clinical suspicion for diagnosis and optimal management.

"When," "Where," and "How" of SARS-CoV-2 Infection Affects the Human Cardiovascular System: A Narrative Review

Coronavirus disease 2019 (COVID-19) is caused by the novel severe acute respiratory coronavirus-2 (SARS-CoV-2). Several explanations for the development of cardiovascular complications during and after acute COVID-19 infection have been hypothesized. The COVID-19 pandemic, caused by SARS-CoV-2, has emerged as one of the deadliest pandemics in modern history. The myocardial injury in COVID-19 patients has been associated with coronary spasm, microthrombi formation, plaque rupture, hypoxic injury, or cytokine storm, which have the same pathophysiology as the three clinical variants of Kounis syndrome. The angiotensin-converting enzyme 2 (ACE2), reninaldosterone system (RAAS), and kinin-kallikrein system are the main proposed mechanisms contributing to cardiovascular complications with the COVID-19 infection. ACE receptors can be found in the heart, blood vessels, endothelium, lungs, intestines, testes, neurons, and other human body parts. SARS-CoV-2 directly invades the endothelial cells with ACE2 receptors and constitutes the main pathway through which the virus enters the endothelial cells. This causes angiotensin II accumulation downregulation of the ACE2 receptors, resulting in prothrombotic effects, such as hemostatic imbalance via activation of the coagulation cascade, impaired fibrinolysis, thrombin generation, vasoconstriction, endothelial and platelet activation, and pro-inflammatory cytokine release. The KKS system typically causes vasodilation and regulates tissue repair, inflammation, cell proliferation, and platelet aggregation, but SARS-CoV-2 infection impairs such counterbalancing effects. This cascade results in cardiac arrhythmias, cardiac arrest, cardiomyopathy, cytokine storm, heart failure, ischemic myocardial injuries, microvascular disease, Kounis syndrome, prolonged COVID, myocardial fibrosis, myocarditis, new-onset hypertension, pericarditis, postural orthostatic tachycardia syndrome, pulmonary hypertension, stroke, Takotsubo syndrome, venous thromboembolism, and thrombocytopenia. In this narrative review, we describe and elucidate when, where, and how COVID-19 affects the human cardiovascular system in various parts of the human body that are vulnerable in every patient category, including children and athletes.

Cardiac Complications and COVID-19: A Review of Life-threatening Co-morbidities

The novel 2019 coronavirus disease (COVID-19) was first reported in the last days of December 2019 in Wuhan, China. The presence of certain co-morbidities, including cardiovascular diseases (CVDs), are the basis for worse outcomes in patients with COVID-19. Relevant English-language literature was searched and retrieved from the Google Scholar search engine and PubMed database up to 2023 using COVID-19, SARS-CoV-2, Heart failure, Myocardial infarction, and Arrhythmia and Cardiac complication as keywords. Increased hemodynamic load, ischemia-related dysfunction, ventricular remodeling, excessive neurohumoral stimulation, abnormal myocyte calcium cycling, and excessive or insufficient extracellular matrix proliferation are associated with heart failure (HF) in COVID-19 patients. Inflammatory reaction due to the excessive release of inflammatory cytokines, leads to myocardial infarction (MI) in these patients. The virus can induce heart arrhythmia through cardiac complications, hypoxia, decreased heart hemodynamics, and remarkable inflammatory markers. Moreover, studies have linked cardiac complications in COVID-19 with poor outcomes, extended hospitalization time, and increased mortality rate. Patients with COVID-19 and CVDs are at higher mortality risk and they should be given high priority when receiving the treatment and intensive care during hospitalization.

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.

Biological Modification of Arrhythmogenic Substrates by Cell-Free Therapeutics

Ventricular arrhythmias (VAs) represent a major cause of sudden cardiac death and afflict patients with heart failure from both ischaemic and non-ischaemic origins, and inherited cardiomyopathies. Current VA management, including anti-arrhythmic medications, autonomic modulation, implantable cardioverter-defibrillator implantation, and catheter ablation, remains suboptimal. Catheter ablation may even cause significant cardiomyocyte loss. Cell-based therapies and exosome treatment have been proposed as promising strategies to lessen cardiomyocyte death, modulate immune reaction, and reduce myocardial scarring, and, therefore, are potentially beneficial in treating VAs. In this review, we summarise the current cornerstones of VA management. We also discuss recent advances and ongoing evidence regarding cell-based and exosome therapy, with special attention to VA treatment.

Incidence of arrhythmias in COVID-19 patients with double mutant strain of SARS-CoV-2 virus: A tertiary care experience

Background: Our understanding of arrhythmias is minimal with SARS-CoV-2 virus and with the emergence of its double mutant, virtually nonexistent. Patients with the double mutant (B.1.617) SARS-CoV infection had more cardiac manifestations, including arrhythmias and sudden death, than with the traditional variant. Objective: To determine the incidence of arrhythmias in COVID-19 patients with double mutant strain of SARS-CoV-2 virus (B.1.617). Materials and methods: We describe a prospective observational study conducted in the Department of Medicine, United Institute of Medical Sciences, Prayagraj, Uttar Pradesh on patients admitted to the hospital during the period March 2021 to May 2021. Different type of arrhythmias were studied in the admitted patients. Results: Sinus bradycardia is the most common arrhythmia, followed by atrial fibrillation. Malignant arrhythmias, such as ventricular tachycardia/ventricular fibrillation and Torsades de pointes due to QT prolongation, were present in small number of patients with high mortality outcomes. Sinus tachycardia and high-grade AV blocks were also present in some of the patients. Conclusions: Current literature lacks studies on arrhythmias secondary to COVID-19 (double mutant) strain and its possible mechanisms. This makes it difficult to distinguish between arrhythmias secondary to COVID-19 (double mutant) infection due to hypoxemia, dyselectrolytemia, SIRS, comorbidities, and medications or direct viral effects on the cardiomyocytes.

Cardiovascular Complications of Viral Respiratory Infections and COVID-19

Viral respiratory infections (VRI) are the most prevalent type of infectious diseases and constitute one of the most common causes of contact with medical care. Regarding the pathophysiology of the cardiovascular system, VRI can not only exacerbate already existing chronic cardiovascular disease (such as coronary artery disease or heart failure) but also trigger new adverse events or complications (e.g., venous thromboembolism), the latter particularly in subjects with multimorbidity or disease-related immobilization. In the current paper, we provide a narrative review of diverse cardiovascular complications of VRI as well as summarize available data on the pathology of the circulatory system in the course of coronavirus disease 2019 (COVID-19).

Parameters Of Myocardial Electrical Instability In Patients After Myocardial Infarction Comorbid With A Novel Coronavirus Infection (COVID-19)

Objective — This article aims to assess parameters of myocardial electrical instability and arrhythmic events in patients after myocardial infarction (MI), with and without ST-segment elevation, comorbid/noncomorbid with a novel coronavirus infection (COVID-19) using a long-term electrocardiographic (ECG) monitoring. Methods — The study included 64 subjects: 25 (39%) patients with MI comorbid with COVID-19 (MI+C group) and 39 (61%) patients with MI noncomorbid with a novel coronavirus infection (MI group). The mean age of patients was 54.3±6.8 years. A long-term ECG monitoring for 97.4 (95% CI 77.9-115.2) hours was performed with Astrocard®-Telemetry system (Meditek JSC, Russia), starting from the 4th day of MI. Rhythm and conduction disorders, along with ischemic episodes were recorded; an analysis of ventricular late potentials, heart rate turbulence, and QT dispersion was carried out. Results — There were no differences in the frequency of delayed afterdepolarizations in MI and MI+C groups: 15-28% and 18-33% of patients, respectively. An analysis of turbulence parameters did not reveal statistically significant differences between the groups. Such arrhythmic events as frequent supraventricular extrasystole and life-threatening arrhythmias (ventricular extrasystole of grade 4A and higher sensu B. Lown and M. Wolf) were recorded significantly more often in the MI+C group than in the MI group: 48% vs. 20.5% (p=0.021) and 24% vs. 5.1% (p=0.026), respectively. Conclusion — The novel coronavirus infection (COVID-19) exacerbates myocardial electrophysiological heterogeneity in the acute cardiovascular event and is associated with an increase in clinically significant arrhythmic events.

Cardiac Evaluation in Children with Multisystem Inflammatory Syndrome Associated with SARS-CoV-2

Objectives

The heart is one of the organs frequently affected by the multisystem inflammatory syndrome in children (MIS-C), associated with severe acute respiratory syndrome coronavirus 2 infection. Cardiac involvement in patients with MIS-C was evaluated with physical examination findings, biochemical test, and cardiological imaging tests. We reported the degree of cardiac involvement in patients with MIS-C.

Methods

In this retrospective study, the complaints, physical examination, and cardiac findings of patients with MIS-C were evaluated.

Results

Sixteen patients (four males and 12 females) with MIS-C were included in the study. The median age was 6 (5-17) years. In patients, palpitations (6%), chest pain (12%), ECG changes (50%), valve insufficiency (50%), low ejection fraction (6%), coronary dilatation (6%), troponin (38%), and d-dimer (88%) elevation were detected. One patient died. Valve insufficiency persisted in 5 (31%) patients.

Conclusion

Severe cardiac involvement can be seen in MIS-C patients. Due to its serious effects on mortality and morbidity, cardiac involvement should be evaluated with cardiac imaging tools such as echocardiography and ECG in all MIS-C patients.

Clinical Management of New-Onset Atrial Fibrillation in COVID-19 Patients Referred to a Tertiary Cardiac Arrhythmia Center after Hospital Discharge

Background: Available reports on the post-discharge management of atrial fibrillation (AF) in COVID-19 patients are scarce. The aim of this case series was to describe the clinical outcomes of new-onset AF in COVID-19 patients referred to a tertiary cardiac arrhythmia center after hospital discharge. Methods: All consecutive patients referred to our center for an ambulatory evaluation from 18 May 2020 to 15 March 2022 were retrospectively screened. Patients were included in the current analysis if new-onset AF was diagnosed during hospitalization for COVID-19 and then referred to our clinic. Results: Among 946 patients, 23 (2.4%) were evaluated for new-onset AF during COVID-19. The mean age of the study cohort was 71.5 ± 8.1 years; 87.0% were male. Median time from COVID-19 discharge and the first ambulatory evaluation was 53 (41.5–127) days; median follow-up time was 175 (83–336) days. At the in-office evaluation, 14 (60.9%) patients were in sinus rhythm, and nine patients were in AF. In 13.0% of cases, oral anticoagulation was stopped according to CHADS-VASc. Eight patients in AF were scheduled for electrical cardioversion; one patient was rate-controlled. Four patients were treated with catheter ablation (CA) during follow-up. Two post-cardioversion AF recurrences were detected during follow-up, while no recurrences were diagnosed among patients who underwent CA. Conclusion: Our data suggest that AF may not be considered as a simple bystander of the in-hospital COVID-19 course. Management of new-onset AF in post-COVID-19 patients referred to our clinic did not significantly differ from our usual practice, both in terms of long-term oral anticoagulation and in terms of rhythm control strategy.

Effects of COVID-19 on Arrhythmia

The World Health Organization announced that COVID-19, with SARS-CoV-2 as its pathogen, had become a pandemic on 11 March 2020. Today, the global epidemic situation is still serious. With the development of research, cardiovascular injury in patients with COVID-19, such as arrhythmia, myocardial injury, and heart failure, is the second major symptom in addition to respiratory symptoms, and cardiovascular injury is related to the prognosis and mortality of patients. The incidence of arrhythmia in COVID-19 patients ranges from 10% to 20%. The potential mechanisms include viral infection-induced angiotensin-converting enzyme 2 expression change, myocarditis, cytokine storm, cardiac injury, electrophysiological effects, hypoxemia, myocardial strain, electrolyte abnormalities, intravascular volume imbalance, drug toxicities and interactions, and stress response caused by virus infection. COVID-19 complicated with arrhythmia needs to be accounted for and integrated in management. This article reviews the incidence, potential mechanisms, and related management measures of arrhythmia in COVID-19 patients.

COVID-19: The Impact on Cardiovascular System

SARS-CoV-2 has been circulating in population worldwide for the past year and a half, and thus a vast amount of scientific literature has been produced in order to study the biology of the virus and the pathophysiology of COVID-19, as well as to determine the best way to prevent infection, treat the patients and eliminate the virus. SARS-CoV-2 binding to the ACE2 receptor is the key initiator of COVID-19. The ability of SARS-CoV-2 to infect various types of cells requires special attention to be given to the cardiovascular system, as it is commonly affected. Thorough diagnostics and patient monitoring are beneficial in reducing the risk of cardiovascular morbidity and to ensure the most favorable outcomes for the infected patients, even after they are cured of the acute disease. The multidisciplinary nature of the fight against the COVID-19 pandemic requires careful consideration from the attending clinicians, in order to provide fast and reliable treatment to their patients in accordance with evidence-based medicine principles. In this narrative review, we reviewed the available literature on cardiovascular implications of COVID-19; both the acute and the chronic.

A Patient Infected with SARS-CoV-2 Presenting with Complete Heart Block

Complete heart block is a rare presentation in a patient with COVID-19 infection that may result when the virus enters the myocardial cell by the angiotensin-converting enzyme-2 receptor. Here, we report a case of forty-nine-year male with COVID-19 with complete heart block (CHB).

Role of the Renin-Angiotensin-Aldosterone and Kinin-Kallikrein Systems in the Cardiovascular Complications of COVID-19 and Long COVID

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the virus responsible for the COVID-19 pandemic. Patients may present as asymptomatic or demonstrate mild to severe and life-threatening symptoms. Although COVID-19 has a respiratory focus, there are major cardiovascular complications (CVCs) associated with infection. The reported CVCs include myocarditis, heart failure, arrhythmias, thromboembolism and blood pressure abnormalities. These occur, in part, because of dysregulation of the Renin-Angiotensin-Aldosterone System (RAAS) and Kinin-Kallikrein System (KKS). A major route by which SARS-CoV-2 gains cellular entry is via the docking of the viral spike (S) protein to the membrane-bound angiotensin converting enzyme 2 (ACE2). The roles of ACE2 within the cardiovascular and immune systems are vital to ensure homeostasis. The key routes for the development of CVCs and the recently described long COVID have been hypothesised as the direct consequences of the viral S protein/ACE2 axis, downregulation of ACE2 and the resulting damage inflicted by the immune response. Here, we review the impact of COVID-19 on the cardiovascular system, the mechanisms by which dysregulation of the RAAS and KKS can occur following virus infection and the future implications for pharmacological therapies.

A case of complete heart block in a COVID-19 infected patient

In the midst of the COVID-19 pandemic, we herein report the case of an elderly female with multiple comorbidities coming with typical symptoms of the viral infection in addition to the unusual presentation of bradycardia due to complete heart block requiring pacemaker placement. This may be a rare complication of the disease but one has to keep a high index of suspicion since this virus has an ability to affect multiple organ systems with many ways yet to be uncovered. .

Lone Atrial Flutter in Children and Adolescents: Is It Really "Lone"?

Atrial flutter (AFL) in children and adolescents beyond the neonatal period in the absence of any underlying myocardial disease ("lone AFL") is rare and data is limited. Our study aims to present clinical and electrophysiological data of presumed "lone AFL" in pediatric patients and discuss the role of endomyocardial biopsy (EMB) and further follow-up. Since July 2005, eight consecutive patients at a median age of 12.7 (range 10.4-16.7) years presenting with presumed "lone AFL" after negative non-invasive diagnostic work-up had electrophysiological study (EPS) and induction of cavotricuspid isthmus (CTI) conduction block by radiofrequency (RF) current application. In 6/8 patients EMB could be taken. Induction of CTI conduction block was achieved in all patients. Histopathological examination of EMB from the right ventricular septum exhibited myocarditis or cardiomyopathy in 4/6 patients, respectively. During follow-up, 4/8 patients had recurrent arrhythmia (AFL n = 2, wide QRS complex tachycardia n = 1, monomorphic premature ventricular contractions n = 1) after the ablation procedure. 3/4 patients with recurrent arrhythmia had pathological EMB results. The remaining patient with recurrent arrhythmia had a negative EMB but was diagnosed with Brugada syndrome during further follow-up. Taking together results of EMB and further clinical course, only 3/8 patients finally turned out to have true "lone AFL". Our study demonstrates that true "lone AFL" in children and adolescents is rare. EMB and clinical course revealed an underlying cardiac pathology in the majority of the individuals studied. EMB was very helpful in order to timely establish the diagnosis of myocarditis or cardiomyopathy.

Lethal Arrhythmia (Torsade de Pointes) in COVID-19: An Event Synergistically Induced by Viral Associated Cardiac Injury, Hyperinflammatory Response, and Treatment Drug?

Arrhythmias in patients with coronavirus disease 2019 (COVID-19) are prevalent and deserve special attention because they are associated with an increased risk of fatal outcome. The mechanism of arrhythmia in COVID-19 remains unclear. Here, we report our first case of confirmed COVID-19 with documented Torsade de Pointes (TdP). A 64-year-old woman, previously healthy, presented to our emergency department with progressive shortness of breath, dry cough, and 1 week of fever. She was treated with chloroquine phosphate, meropenem, and ciprofloxacin. After 5 days of admission, her condition deteriorated and she was admitted to the intensive care unit. The patient had two episodes of malignant arrhythmias within 24 hours. The former was TdP, and the latter was a fatal pulseless ventricular tachycardia that occured even after chloroquine was discontinued. There was evidence of cardiac injury shown by increased serum level of troponin I. We propose a synergistic concept of lethal arrhythmia due to direct severe acute respiratory syndrome coronavirus (SARS-CoV)-2-associated cardiac injury, hyperinflammatory response, and drug-induced arrhythmia.

COVID-19 et troubles du rythme

Lors de la pandémie due au virus SARS-CoV2 les troubles du rythme n’ont pas été au premier plan. Cependant, le virus semble atteindre de nombreux organes et le tropisme cardiaque est maintenant bien connu. Les connaissances dans ce domaine sont encore loin d’être exhaustives, mais plusieurs séries publiées concernant les patients atteints de la COVID-19 retrouvent une proportion significative de troubles du rythme, dont certains pouvant potentiellement mener à une issue fatale. Ces troubles du rythmes sont principalement supraventriculaires à type de fibrillation atriale (FA) ou flutter, mais également ventriculaire avec des tachycardies ventriculaires (TV) fibrillation ventriculaire (FV) et plus rarement torsades de pointe (TdP). Les causes en sont multiples, du fait de l’atteinte multiorgane du virus et des interactions médicamenteuses potentielles. Par ailleurs, la question de la surveillance de troubles du rythme pouvant émerger à moyen et long terme après une infection reste à explorer.

Infanticide vs. inherited cardiac arrhythmias

AIMS

In 2003, an Australian woman was convicted by a jury of smothering and killing her four children over a 10-year period. Each child died suddenly and unexpectedly during a sleep period, at ages ranging from 19 days to 18 months. In 2019 we were asked to investigate if a genetic cause could explain the children's deaths as part of an inquiry into the mother's convictions.

METHODS AND RESULTS

Whole genomes or exomes of the mother and her four children were sequenced. Functional analysis of a novel CALM2 variant was performed by measuring Ca2+-binding affinity, interaction with calcium channels and channel function. We found two children had a novel calmodulin variant (CALM2 G114R) that was inherited maternally. Three genes (CALM1-3) encode identical calmodulin proteins. A variant in the corresponding residue of CALM3 (G114W) was recently reported in a child who died suddenly at age 4 and a sibling who suffered a cardiac arrest at age 5. We show that CALM2 G114R impairs calmodulin's ability to bind calcium and regulate two pivotal calcium channels (CaV1.2 and RyR2) involved in cardiac excitation contraction coupling. The deleterious effects of G114R are similar to those produced by G114W and N98S, which are considered arrhythmogenic and cause sudden cardiac death in children.

CONCLUSION

A novel functional calmodulin variant (G114R) predicted to cause idiopathic ventricular fibrillation, catecholaminergic polymorphic ventricular tachycardia, or mild long QT syndrome was present in two children. A fatal arrhythmic event may have been triggered by their intercurrent infections. Thus, calmodulinopathy emerges as a reasonable explanation for a natural cause of their deaths.

Use of the new Lake Louise Criteria improves CMR detection of atypical forms of acute myocarditis

The purpose of our study was to compare diagnostic performance of old and new Lake Louise Criteria (oLLC and nLLC) among different clinical presentations: infarct-like (IL), cardiomyopathic (CM) and arrhythmic (AR). 102 patients with clinical suspicion of acute myocarditis underwent cardiac magnetic resonance (CMR) on a 1.5 T scanner. Protocol included cine-SSFP, T2-weighted STIR, T2 mapping, early and late gadolinium enhancement and T1 mapping acquired before and after gadolinium administration. The degree of agreement has been calculated with Cohen's K test. 42 patients also underwent endomyocardial biopsy (EMB). IL onset was present in 54/102 patients, CM in 28/102 and AR in 20/102. nLLC were positive in 58.3% of the patients, while oLLC in 37.9%, k = 0.57 (IC: 0.428-0.713). The degree of agreement between nLLC and oLLC was 0.49 (IC: 0.111-0.876) for AR onset (nLLC positive in 35% vs oLLC in 15%), 0.25 (IC: 0.035-0.459) for CM pattern (nLLC positive in 60.7% vs oLLC 17.9%) and 0.73 (IC: 0.543-0.912) for IL presentation (nLLC positive in 66.7% vs oLLC in 57.4%). Diagnostic accuracy was 75% for both nLLC and oLLC among IL onset, and 41.6% for oLLC vs 66.7% for nLLC, as regards CM clinical presentation. nLLC have improved diagnostic performance of CMR for the diagnosis of acute myocarditis, in particular for atypical clinical presentation.

Arrhythmias and COVID-19: A Review

Current understanding of the impact of coronavirus disease-2019 (COVID-19) on arrhythmias continues to evolve as new data emerge. Cardiac arrhythmias are more common in critically ill COVID-19 patients. The potential mechanisms that could result in arrhythmogenesis among COVID-19 patients include hypoxia caused by direct viral tissue involvement of lungs, myocarditis, abnormal host immune response, myocardial ischemia, myocardial strain, electrolyte derangements, intravascular volume imbalances, and drug sides effects. To manage these arrhythmias, it is imperative to increase the awareness of potential drug-drug interactions, to monitor QTc prolongation while receiving COVID therapy and provide special considerations for patients with inherited arrhythmia syndromes. It is also crucial to minimize exposure to COVID-19 infection by stratifying the need for intervention and using telemedicine. As COVID-19 infection continues to prevail with a potential for future surges, more data are required to better understand pathophysiology and to validate management strategies.

Incidence and impact of cardiac arrhythmias in coronavirus disease 2019 (COVID-19): A systematic review and meta-analysis

BACKGROUND

Studies have shown that cardiac arrhythmias may occur in up to 44% of patients with severe coronavirus disease 2019 (COVID-19) and has been associated with an increased risk of death. This systematic review and meta-analysis aimed to evaluate the incidence of cardiac arrhythmias in patients with COVID-19 and their implications on patient prognosis.

METHODS

We performed a systematic literature search from PubMed, SCOPUS, Europe PMC, Cochrane Central Databases, and Google Scholar + Preprint Servers. The primary endpoint of the study was poor outcomes including mortality, severe COVID-19, and the need for ICU care.

RESULTS

A total of 4 studies including 784 patients were analyzed. The incidence of arrhythmia in patients with COVID-19 was 19% (9-28%; I²: 91.45). Arrhythmia occurred in 48% (38-57%; I²: 48.08) of patients with poor outcome and 6% (1-12%; I²: 85.33%) of patients without poor outcome. Patients with COVID-19 experiencing arrhythmia had an increased risk of poor outcome (RR 7.96 [3.77, 16.81], p < 0.001; I²: 71.1%). The funnel-plot analysis showed an asymmetrical funnel plot with most of the studies on the right side of the effect estimate. The regression-based Egger's test showed indication of small-study effects (p = 0.001).

CONCLUSION

Cardiac arrhythmias were significantly associated with an increased risk of poor outcome in COVID-19. Arrhythmias were observed in 19% of patients with COVID-19 and in 48% of patients with COVID-19 and poor outcomes.

Arrhythmia in COVID-19

The current outbreak of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) also known as coronavirus disease 2019 (COVID-19) has quickly progressed to a global pandemic. There are well-documented cardiac complications of COVID-19 in patients with and without prior cardiovascular disease. The cardiac complications include myocarditis, heart failure, and acute coronary syndrome resulting from coronary artery thrombosis or SARS-CoV-2-related plaque ruptures. There is growing evidence showing that arrhythmias are also one of the major complications. Myocardial inflammation caused by viral infection leads to electrophysiological and structural remodeling as a possible mechanism for arrhythmia. This could also be the mechanism through which SARS-CoV-2 leads to different arrhythmias. In this review article, we discuss arrhythmia manifestations in COVID-19.

Seasonality of ventricular fibrillation at first myocardial infarction and association with viral exposure

AIMS

To investigate seasonality and association of increased enterovirus and influenza activity in the community with ventricular fibrillation (VF) risk during first ST-elevation myocardial infarction (STEMI).

METHODS

This study comprised all consecutive patients with first STEMI (n = 4,659; aged 18-80 years) admitted to the invasive catheterization laboratory between 2010-2016, at Copenhagen University Hospital, Rigshospitalet, covering eastern Denmark (2.6 million inhabitants, 45% of the Danish population). Hospital admission, prescription, and vital status data were assessed using Danish nationwide registries. We utilized monthly/weekly surveillance data for enterovirus and influenza from the Danish National Microbiology Database (2010-2016) that receives copies of laboratory tests from all Danish departments of clinical microbiology.

RESULTS

Of the 4,659 consecutively enrolled STEMI patients, 581 (12%) had VF before primary percutaneous coronary intervention. In a subset (n = 807), we found that VF patients experienced more generalized fatigue and flu-like symptoms within 7 days before STEMI compared with the patients without VF (OR 3.39, 95% CI 1.76-6.54). During the study period, 2,704 individuals were diagnosed with enterovirus and 19,742 with influenza. No significant association between enterovirus and VF (OR 1.00, 95% CI 0.99-1.02), influenza and VF (OR 1.00, 95% CI 1.00-1.00), or week number and VF (p-value 0.94 for enterovirus and 0.89 for influenza) was found.

CONCLUSION

We found no clear seasonality of VF during first STEMI. Even though VF patients had experienced more generalized fatigue and flu-like symptoms within 7 days before STEMI compared with patients without VF, no relationship was found between enterovirus or influenza exposure and occurrence of VF.

Sudden cardiac death in patients with myocarditis: Evaluation, risk stratification, and management

Myocarditis is a major cause of sudden cardiac death (SCD) and dilated cardiomyopathy (DCM) in young adults. Cardiac magnetic resonance is the established tool for the diagnosis of myocarditis, and late gadolinium enhancement detected on cardiac magnetic resonance imaging is the strongest independent predictor of SCD, all-cause mortality, and cardiac mortality. Several other factors have been associated with SCD or cardiac transplantation including New York Heart Association functional class III/IV, reduced left ventricular ejection fraction <35%, and right ventricular ejection fraction ≤45%. A fragmented QRS and a prolonged QTc interval on an electrocardiogram are predictors of VAs. The postulated mechanism of VA in acute myocarditis is ion channel dysfunction and inflammation that alter intracellular signaling, producing interstitial edema and fibrosis and thereby causing conduction abnormalities. VAs in chronic myocarditis are generally due to scar-mediated reentry. Treatment of myocarditis is tailored toward supportive care and symptomatic relief. The subset of patients who develop DCM should be treated with heart failure medications according to professional guideline recommendations. Indications for an implantable cardioverter-defibrillator are similar to those for nonischemic cardiomyopathy; however, an implantable cardioverter-defibrillator should be held in the acute phase of myocarditis to allow left ventricular ejection fraction recovery, and a wearable cardioverter-defibrillator may be beneficial for some patients. Antiarrhythmic medications are reserved for patients with symptomatic nonsustained or sustained VAs. Radiofrequency ablation appears to be an effective treatment option for VAs; however, more data on its safety and effectiveness are needed. This review addresses risk factors of SCD and VAs in patients with myocarditis with special emphasis on treatment and prevention of these outcomes.

miR‑217 and miR‑543 downregulation mitigates inflammatory response and myocardial injury in children with viral myocarditis by regulating the SIRT1/AMPK/NF‑κB signaling pathway

The aim of the present study was to investigate the expression levels and roles of microRNA (miR)‑217 and miR‑543 in viral myocarditis, and to examine their underlying mechanisms. Coxsackievirus B3 (CVB3) was used to establish in vivo and in vitro models of viral myocarditis. The levels of miR‑217 and miR‑543 were detected using reverse transcription‑quantitative PCR. The association between miR‑217 and miR‑543 and sirtuin‑1 (SIRT1) was predicted and confirmed by TargetScan and dual‑luciferase reporter assay. Cell viability was detected using Cell Counting Kit‑8 assay, and cell apoptosis was measured by analyzing the expression levels of Bcl‑2 and Bax, and by flow cytometry. In addition, the synthesis of various pro‑inflammatory factors was determined by ELISA. In addition, superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels were measured in cardiomyocytes following transfection and CVB infection. miR‑217 and miR‑543 were found to be highly expressed in the peripheral blood of pediatric patients with viral myocarditis, in the peripheral blood and myocardial tissues of viral myocarditis mice and in CVB3‑infected cardiomyocytes. SIRT1 was found to be a target of both miR‑217 and miR‑543, and SIRT1 expression level was downregulated in viral myocarditis. Further analysis indicated that the reduced cell viability, increased cell apoptosis, enhanced synthesis of inflammatory factors, increased MDA content and decreased SOD activity associated with myocarditis were significantly reversed after inhibition of miR‑217 or miR‑543. Importantly, the present results showed that all the effects of miR‑217 and miR‑543 inhibition on cardiomyocytes were significantly suppressed following SIRT1 knockdown. Collectively, the present data indicated that miR‑217 and miR‑543 were significantly upregulated in viral myocarditis, and downregulation of miR‑217 and miR‑543 attenuated CVB3 infection‑induced cardiomyocyte injury by targeting SIRT1. miR‑217 and miR‑543 may be potential therapeutic targets for developing novel viral myocarditis treatments in the future.

Effects of granulocyte colony‑stimulating factor on rabbit carotid and porcine heart models of chronic obliterative arterial disease

Previous studies suggest that granulocyte colony‑stimulating factor (G‑CSF) can promote bone marrow derived progenitor cells to mediate cardiovascular repair, potentially reversing mechanical dysfunction in chronic ischaemic heart disease and post myocardial infarction. Two models were used in the present study both using a surgical ameroid constrictor to induce arterial stenosis. The first model used the carotid artery of rabbits. They were divided into high fat diet (inducing atherosclerosis) or normal fat diet (control) groups. Each was subdivided into surgical exposure group without constrictor, ameroid constrictor receiving normal saline or receiving G‑CSF 15 µg/kg/day. Endothelial markers of endothelial nitric oxide synthase and endothelin 1 were increased by the use of ameroid constrictor in both atherosclerotic and non‑atherosclerotic mice, however were not further altered by G‑CSF. Scanning electron microscopy indicated that ameroid constrictor application altered endothelial morphology from an oval shape to a round shape and this was more prominent in the atherosclerotic compared with the non‑atherosclerotic group. G‑CSF injection increased the number of endothelial cells in all groups. The second model used the left coronary artery of pigs. They were equally divided into following groups, receiving normal saline (control), G‑CSF 2.5 µg/kg/day (low dose), 5 µg/kg/day (medium dose) and 10 µg/kg/day (high dose) for 5 days. G‑CSF at a low or high dose worsened intimal hyperplasia however at a medium dose improved it. In conclusion, G‑CSF had no effect in a rabbit carotid artery model of atherosclerosis. Its effects on the porcine heart were dose‑dependent; arterial disease worsened at a low or high dose, but improved at a medium dose.

Computational Identification of Ventricular Arrhythmia Risk in Pediatric Myocarditis

Children with myocarditis have increased risk of ventricular tachycardia (VT) due to myocardial inflammation and remodeling. There is currently no accepted method for VT risk stratification in this population. We hypothesized that personalized models developed from cardiac late gadolinium enhancement magnetic resonance imaging (LGE-MRI) could determine VT risk in patients with myocarditis using a previously-validated protocol. Personalized three-dimensional computational cardiac models were reconstructed from LGE-MRI scans of 12 patients diagnosed with myocarditis. Four patients with clinical VT and eight patients without VT were included in this retrospective analysis. In each model, we incorporated a personalized spatial distribution of fibrosis and myocardial fiber orientations. Then, VT inducibility was assessed in each model by pacing rapidly from 26 sites distributed throughout both ventricles. Sustained reentrant VT was induced from multiple pacing sites in all patients with clinical VT. In the eight patients without clinical VT, we were unable to induce sustained reentry in our simulations using rapid ventricular pacing. Application of our non-invasive approach in children with myocarditis has the potential to correctly identify those at risk for developing VT.

Ventricular arrhythmias and myocardial inflammation: Long-term follow-up of patients with suspected myocarditis

BACKGROUND

Inflammatory heart disease is known to be associated with ventricular arrhythmias (VA) and impaired ventricular function at presentation or during follow-up. We aimed to investigate the need for implanted cardioverter defibrillator (ICD) due to ventricular dysfunction and occurrence of VA during long-term follow-up in patients admitted with suspected myocarditis.

METHODS

Between 2000 and 2016, 191 patients (age 43 ± 13 years, 71% male, mean left ventricular ejection fraction (LVEF) 33 ± 15%) with clinically suspected myocarditis, who underwent endomyocardial biopsies (EMB), were prospectively enrolled and followed up in 6-months-intervals (median follow-up was 83 (49-156) months). The primary endpoint was deterioration of cardiac function (LVEF ≤ 35%) or occurrence of VA leading to ICD implantation.

RESULTS

According to EMB results, patients were stratified in three diagnostic groups: acute myocarditis (5%), chronic myocarditis (50%) and dilated cardiomyopathy (DCM) (45%). An ICD implantation was performed in 58 patients (30%, n = 38 for primary prevention). Besides LVEF at baseline, chronic myocardial inflammation was the only independent predictor of ICD implantation for primary prevention (hazard ratio 2.48 (95% confidence interval 1.02-5.5); p = 0.045). VA requiring ICD therapy occurred in 29 of 58 patients (50%) after a median of 14 (2-37) months without a significant difference between presence and absence of myocardial inflammation.

CONCLUSIONS

Nearly one third of patients with suspected myocarditis require an ICD due to impaired LVEF or occurrence of VA. Half of these patients experienced VA with adequate ICD therapy.

MicroRNA-381 protects myocardial cell function in children and mice with viral myocarditis via targeting cyclooxygenase-2 expression

The present study aimed to determine the expression of cyclooxygenase (COX)-2 and microRNA (miRNA/miR)-381 in the blood of children with viral myocarditis (VM), and investigate the association between COX-2 and miR-381 in the occurrence and development of the disease using a mouse model. A total of 26 children with VM (15 boys and 11 girls) were included in the present study. Peripheral blood was collected from all children. The mouse model of VM was constructed by coxsackievirus B3 (CVB3) infection. Peripheral blood and myocardial tissues were collected from all mice for analysis. Reverse transcription-quantitative polymerase chain reaction was used to determine the expression of COX-2 mRNA and miR-381 in serum and myocardial tissues. ELISA was used to measure the content of COX-2 protein in serum from humans and mice, and western blotting was employed to determine the expression of COX-2 protein in myocardial tissues from mice. Contents of creatine kinase (CK-MB) and lactate dehydrogenase (LDH) were evaluated using an automatic biochemical analyzer. A dual luciferase assay was conducted to identify interactions between COX-2 mRNA and miR-381. Children with VM had increased COX-2 levels and decreased miR-381 expression in peripheral blood, compared with those who had recovered from VM. CVB3 infection resulted in damage in the myocardium of mice, and elevated CK-MB and LDH contents. VM model mice exhibited increased COX-2 levels and decreased miR-381 expression in peripheral blood and myocardial tissues compared with normal mice. miR-381 binds to the 3'-untranslated seed regions of both human and mouse COX-2 mRNA to regulate their expression. The present study demonstrated that children with VM have decreased miR-381 expression and elevated COX-2 expression in peripheral blood. miR-381 may inhibit myocardial cell damage caused by CVB3 infection and protect myocardial cell function by targeting COX-2 expression.

When is myocarditis indeed the cause of death?

Attribution of death to myocarditis continues to be a controversial issue in forensic pathology, despite the existence of established histopathological criteria as well as complementary investigations. The aim of the study was two-fold: (a) to retrospectively analyse the data obtained from a series of clinical and forensic autopsies in order to assess the number of cases with death attributed to myocarditis, and (b) to reevaluate these cases in order to assess how properly the histopathological diagnosis of myocarditis conformed to established criteria and therefore how accurately these were used on the basis of all postmortem investigation findings to conclude the cause of death. 2474 clinical and forensic autopsies were taken into consideration. Myocarditis was recorded as the official, underlying cause of death in 48 cases. Of those, 8 cases were considered to accurately conform to the histopathological Dallas criteria for the presence of myocarditis and could therefore be classified as cases of fatal myocarditis. In 19 out of 48 cases, description of focal myocarditis was considered to accurately fulfill the histopathological Dallas criteria for the presence of myocarditis. However, data provided by histological analysis and virology testing result reevaluation allowed alternative causes of death to be speculated. In another 21 out of 48 cases, description of focal myocardial inflammation was considered to inaccurately meet the histopathological Dallas criteria for the presence of myocarditis. The findings of our own study appear to be in agreement with previous observations in similar study groups and highlight that since myocarditis may occur in association with many diseases, a great deal of evidence is required before settling on categorical conclusions.

Pancreatitis and myocarditis coexistence due to infection by Coxsackie B1 and B4 viruses

Myocarditis can be a rare late manifestation of acute pancreatitis caused by Coxsackie virus infection. Clinicians should be aware of potentially life-threatening myocarditis because immediate recognition and management are the cornerstones in achieving a better outcome.

Tachycardia-bradycardia syndrome: Electrophysiological mechanisms and future therapeutic approaches (Review)

Sick sinus syndrome (SSS) encompasses a group of disorders whereby the heart is unable to perform its pacemaker function, due to genetic and acquired causes. Tachycardia‑bradycardia syndrome (TBS) is a complication of SSS characterized by alternating tachycardia and bradycardia. Techniques such as genetic screening and molecular diagnostics together with the use of pre-clinical models have elucidated the electrophysiological mechanisms of this condition. Dysfunction of ion channels responsible for initiation or conduction of cardiac action potentials may underlie both bradycardia and tachycardia; bradycardia can also increase the risk of tachycardia, and vice versa. The mainstay treatment option for SSS is pacemaker implantation, an effective approach, but has disadvantages such as infection, limited battery life, dislodgement of leads and catheters to be permanently implanted in situ. Alternatives to electronic pacemakers are gene‑based bio‑artificial sinoatrial node and cell‑based bio‑artificial pacemakers, which are promising techniques whose long-term safety and efficacy need to be established. The aim of this article is to review the different ion channels involved in TBS, examine the three‑way relationship between ion channel dysfunction, tachycardia and bradycardia in TBS and to consider its current and future therapies.

The role of gap junctions in inflammatory and neoplastic disorders (Review)

Gap junctions are intercellular channels made of connexin proteins, mediating both electrical and biochemical signals between cells. The ability of gap junction proteins to regulate immune responses, cell proliferation, migration, apoptosis and carcinogenesis makes them attractive therapeutic targets for treating inflammatory and neoplastic disorders in different organ systems. Alterations in gap junction profile and expression levels are observed in hyperproliferative skin disorders, lymphatic vessel diseases, inflammatory lung diseases, liver injury and neoplastic disorders. It is now recognized that the therapeutic effects mediated by traditional pharmacological agents are dependent upon gap junction communication and may even act by influencing gap junction expression or function. Novel strategies for modulating the function or expression of connexins, such as the use of synthetic mimetic peptides and siRNA technology are considered.

Animal models of atherosclerosis

Atherosclerosis is a significant cause of morbidity and mortality globally. Many animal models have been developed to study atherosclerosis, and permit experimental conditions, diet and environmental risk factors to be carefully controlled. Pathophysiological changes can be produced using genetic or pharmacological means to study the harmful consequences of different interventions. Experiments using such models have elucidated its molecular and pathophysiological mechanisms, and provided platforms for pharmacological development. Different models have their own advantages and disadvantages, and can be used to answer different research questions. In the present review article, different species of atherosclerosis models are outlined, with discussions on the practicality of their use for experimentation.

Electrophysiological mechanisms of long and short QT syndromes

The QT interval on the human electrocardiogram is normally in the order of 450 ms, and reflects the summated durations of action potential (AP) depolarization and repolarization of ventricular myocytes. Both prolongation and shortening in the QT interval have been associated with ventricular tachy-arrhythmias, which predispose affected individuals to sudden cardiac death. In this article, the molecular determinants of the AP duration and the causes of long and short QT syndromes (LQTS and SQTS) are explored. This is followed by a review of the recent advances on their arrhythmogenic mechanisms involving reentry and/or triggered activity based on experiments conducted in mouse models. Established and novel clinical risk markers based on the QT interval for the prediction of arrhythmic risk and cardiovascular mortality are presented here. It is concluded by a discussion on strategies for the future rational design of anti-arrhythmic agents.

Mouse models of atherosclerosis: a historical perspective and recent advances

Atherosclerosis represents a significant cause of morbidity and mortality in both the developed and developing countries. Animal models of atherosclerosis have served as valuable tools for providing insights on its aetiology, pathophysiology and complications. They can be used for invasive interrogation of physiological function and provide a platform for testing the efficacy and safety of different pharmacological therapies. Compared to studies using human subjects, animal models have the advantages of being easier to manage, with controllable diet and environmental risk factors. Moreover, pathophysiological changes can be induced either genetically or pharmacologically to study the harmful effects of these interventions. There is no single ideal animal model, as different systems are suitable for different research objectives. A good understanding of the similarities and differences to humans enables effective extrapolation of data for translational application. In this article, we will examine the different mouse models for the study and elucidation of the pathophysiological mechanisms underlying atherosclerosis. We also review recent advances in the field, such as the role of oxidative stress in promoting endoplasmic reticulum stress, mitochondrial dysfunction and mitochondrial DNA damage, which can result in vascular inflammation and atherosclerosis. Finally, novel therapeutic approaches to reduce vascular damage caused by chronic inflammation using microRNA and nano-medicine technology, are discussed.

Coxsackievirus B3 Directly Induced Th17 Cell Differentiation by Inhibiting Nup98 Expression in Patients with Acute Viral Myocarditis

Th17 cells play a key role in the progression of coxsackievirus B3 (CVB3)-induced acute viral myocarditis (AVMC). However, the direct effect of virus on Th17 cell differentiation is still unknown. Recently, nucleoporin (Nup) 98 has been proved to be associated with lymphocyte differentiation. Therefore, we investigated whether Nup98 mediated Th17 cell differentiation in AVMC. In our study, patients with AVMC and healthy controls were recruited. The results showed that CVB3 could enter into the CD4⁺ T cells in AVMC patients and healthy controls. After transfecting purified CD4⁺ T cells with CVB3 in vitro, the Th17 cell frequency, IL-17 secretion, and RORγT synthesis were increased while the Nup98 levels were decreased. Furthermore, down-regulating Nup98 expression by siRNA-Nup98 in CD4⁺ T cells resulted in the elevated Th17 cell frequency and IL-17 secretion, along with enhanced levels of RORγT, dissociative p300/CBP, and acetylated Stat3. Up-regulation of Nup98 expression by pcDNA3.1-Nup98 showed the opposite effects. Our results suggested that CVB3 directly induced CD4⁺ T cell differentiation into Th17 cells by inhibiting Nup98 expression, representing a therapeutic target in AVMC.

Animal models for the study of primary and secondary hypertension in humans

Hypertension is a significant cause of morbidity and mortality worldwide. It is defined as systolic and diastolic blood pressures (SBP/DBP) >140 and 90 mmHg, respectively. Individuals with an SBP between 120 and 139, or DBP between 80 and 89 mmHg, are said to exhibit pre-hypertension. Hypertension can have primary or secondary causes. Primary or essential hypertension is a multifactorial disease caused by interacting environmental and polygenic factors. Secondary causes are renovascular hypertension, renal disease, endocrine disorders and other medical conditions. The aim of the present review article was to examine the different animal models that have been generated for studying the molecular and physiological mechanisms underlying hypertension. Their advantages, disadvantages and limitations will be discussed.

Gap junction inhibition by heptanol increases ventricular arrhythmogenicity by reducing conduction velocity without affecting repolarization properties or myocardial refractoriness in Langendorff-perfused mouse hearts

In the current study, arrhythmogenic effects of the gap junction inhibitor heptanol (0.05 mM) were examined in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricular epicardium during right ventricular pacing. Regular activity was observed both prior and subsequent to application of heptanol in all of the 12 hearts studied during 8 Hz pacing. By contrast, induced ventricular tachycardia (VT) was observed after heptanol treatment in 6/12 hearts using a S1S2 protocol (Fisher's exact test; P<0.05). The arrhythmogenic effects of heptanol were associated with increased activation latencies from 13.2±0.6 to 19.4±1.3 msec (analysis of variance; P<0.001) and reduced conduction velocities (CVs) from 0.23±0.01 to 0.16±0.01 msec (analysis of variance; P<0.001) in an absence of alterations in action potential durations (ADPs) at x=90% (38.0±1.0 vs. 38.3±1.8 msec), 70% (16.8±1.0 vs. 19.5±0.9 msec), 50% (9.2±0.8 vs. 10.1±0.6 msec) or 30% (4.8±0.5 vs. 6.3±0.6 msec) repolarization (APDx) or in effective refractory period (ERPs) (39.6±1.9 vs. 40.6±3.0 msec) (all P>0.05). Consequently, excitation wavelengths (λ; CV x ERP) were reduced from 9.1±0.6 to 6.5±0.6 mm (P<0.01), however critical intervals for re‑excitation (APD90 ‑ ERP) were unaltered (‑1.1±2.4 vs. ‑2.3±1.8 msec; P>0.05). Together, these observations demonstrate for the first time, to the best of our knowledge, that inhibition of gap junctions alone using a low heptanol concentration (0.05 mM) was able to reduce CV, which alone was sufficient to permit the induction of VT using premature stimulation by reducing λ, which therefore appears central in the determination of arrhythmic tendency.

Reactive Oxygen Species, Endoplasmic Reticulum Stress and Mitochondrial Dysfunction: The Link with Cardiac Arrhythmogenesis

BACKGROUND

Cardiac arrhythmias represent a significant problem globally, leading to cerebrovascular accidents, myocardial infarction, and sudden cardiac death. There is increasing evidence to suggest that increased oxidative stress from reactive oxygen species (ROS), which is elevated in conditions such as diabetes and hypertension, can lead to arrhythmogenesis.

METHOD

A literature review was undertaken to screen for articles that investigated the effects of ROS on cardiac ion channel function, remodeling and arrhythmogenesis.

RESULTS

Prolonged endoplasmic reticulum stress is observed in heart failure, leading to increased production of ROS. Mitochondrial ROS, which is elevated in diabetes and hypertension, can stimulate its own production in a positive feedback loop, termed ROS-induced ROS release. Together with activation of mitochondrial inner membrane anion channels, it leads to mitochondrial depolarization. Abnormal function of these organelles can then activate downstream signaling pathways, ultimately culminating in altered function or expression of cardiac ion channels responsible for generating the cardiac action potential (AP). Vascular and cardiac endothelial cells become dysfunctional, leading to altered paracrine signaling to influence the electrophysiology of adjacent cardiomyocytes. All of these changes can in turn produce abnormalities in AP repolarization or conduction, thereby increasing likelihood of triggered activity and reentry.

CONCLUSION

ROS plays a significant role in producing arrhythmic substrate. Therapeutic strategies targeting upstream events include production of a strong reducing environment or the use of pharmacological agents that target organelle-specific proteins and ion channels. These may relieve oxidative stress and in turn prevent arrhythmic complications in patients with diabetes, hypertension, and heart failure.