Fulminant myocarditis in adults: a narrative review

Fulminant Influenza Myocarditis Requiring Extracorporeal Membrane Oxygenation (ECMO) Support

Viral infections may lead to myocarditis, which is inflammation of the myocardium. This inflammation, when severe enough, can result in left ventricular dysfunction and potentially reduce the left ventricular ejection fraction (LVEF). In rare cases, the effects of this inflammation lead to hemodynamic changes that can be life-threatening. We discuss a case of a 38-year-old female recently diagnosed with influenza A (H3 subtype) who presented to our institution's emergency department for evaluation after an episode of syncope, as well as intermittent chest pressure and dyspnea on exertion. Initial vitals displayed a heart rate of 87 bpm and blood pressure of 105/66 mmHg. The physical examination demonstrated a regular rhythm, no lower extremity edema, and lungs that were clear to auscultation. She was found to have an elevated pro-B-type natriuretic peptide level of 6152 pg/mL and a positive influenza A polymerase chain reaction (PCR) test. A transthoracic echocardiogram (TTE) was obtained and demonstrated globally reduced left ventricular systolic function with an estimated ejection fraction of 28%, as well as reduced right ventricular systolic function. Over the next six hours, the patient became progressively tachycardic and hypotensive, with a heart rate of 135 bpm and a blood pressure measured at 46/28 mmHg. She was initially admitted to the cardiovascular ICU and started on dobutamine and vasopressin. Pulmonary artery catheterization was completed for better evaluation of cardiogenic shock, and it demonstrated a severely reduced cardiac index of 0.9 L/min/m2. Due to concerns of worsening cardiogenic shock and impending circulatory collapse, mechanical circulatory support was initiated via veno-arterial extracorporeal membrane oxygenation (VA-ECMO), and she was admitted to the cardiothoracic surgery ICU. Several days later, a biventricular assist device (BiVAD) was implanted with the goal of discontinuing ECMO as a bridge to transplant. Shortly afterwards, a repeat echocardiogram demonstrated a normalized left and right ventricular systolic function, and the BiVAD was removed. Ten days after the initiation of ECMO, it was able to be discontinued, and the patient was decannulated. The patient was discharged home in stable condition. This case exemplifies how fulminant myocarditis (FM) can have positive outcomes, even in critically ill patients, when the timing of intervention is early and aggressive.

Myocarditis: Diagnostic Modalities and Treatment Options

Myocarditis is an underdiagnosed condition that affects people of all ages. It can be asymptomatic or present with a variety of symptoms. The etiology of myocarditis is broad and can be infectious, autoimmune, or toxin-induced. The diagnosis of myocarditis can be challenging at times due to varied clinical features that sometimes overlap with other cardiac conditions. It is essential to have a high index of suspicion and use appropriate diagnostic methods for timely detection. In this review, we discuss establishing the diagnosis of acute myocarditis with initial workup to gold standard noninvasive cardiac magnetic resonance imaging methods and the use of invasive techniques such as endomyocardial biopsy. Furthermore, we discuss the treatment options, including novel approaches based on the severity of the symptoms and the specific etiologies of myocarditis.

Acute Fulminant Myocarditis Secondary to Coxsackie B Virus

Fulminant myocarditis is a severe form of acute myocarditis, characterized by complications such as hemodynamic compromise, often requiring advanced mechanical support. It can occur as a result of infection, toxin exposure, or autoimmune processes. This is a case of a 53-year-old male with no past medical history who presented with one week of fever, shortness of breath, and upper respiratory symptoms and subsequently developed fulminant myocarditis, characterized by severe left ventricular dysfunction and cardiogenic shock requiring both inotropic and advanced mechanical support. Initial serological diagnostics were negative for a viral etiology; however, repeat testing, prompted by continued high clinical suspicion, subsequently yielded a positive Coxsackie B viral titer. The diagnosis of myocarditis was further supported by the specific distribution of late gadolinium enhancement (LGE) on cardiac MRI. We describe the nuanced management approach, including heart failure guideline-directed medical therapy (GDMT), high-dose steroids, and intravenous immunoglobulins. Additionally, we highlight the role of noninvasive diagnostics and the challenges in targeted management of fulminant myocarditis.

Pyruvate kinase M2 sustains cardiac mitochondrial quality surveillance in septic cardiomyopathy by regulating prohibitin 2 abundance via S91 phosphorylation

The endogenous mitochondrial quality control (MQC) system serves to protect mitochondria against cellular stressors. Although mitochondrial dysfunction contributes to cardiac damage during many pathological conditions, the regulatory signals influencing MQC disruption during septic cardiomyopathy (SC) remain unclear. This study aimed to investigate the involvement of pyruvate kinase M2 (PKM2) and prohibitin 2 (PHB2) interaction followed by MQC impairment in the pathogenesis of SC. We utilized LPS-induced SC models in PKM2 transgenic (PKM2TG) mice, PHB2S91D-knockin mice, and PKM2-overexpressing HL-1 cardiomyocytes. After LPS-induced SC, cardiac PKM2 expression was significantly downregulated in wild-type mice, whereas PKM2 overexpression in vivo sustained heart function, suppressed myocardial inflammation, and attenuated cardiomyocyte death. PKM2 overexpression relieved sepsis-related mitochondrial damage via MQC normalization, evidenced by balanced mitochondrial fission/fusion, activated mitophagy, restored mitochondrial biogenesis, and inhibited mitochondrial unfolded protein response. Docking simulations, co-IP, and domain deletion mutant protein transfection experiments showed that PKM2 phosphorylates PHB2 at Ser91, preventing LPS-mediated PHB2 degradation. Additionally, the A domain of PKM2 and the PHB domain of PHB2 are required for PKM2-PHB2 binding and PHB2 phosphorylation. After LPS exposure, expression of a phosphorylation-defective PHB2S91A mutant negated the protective effects of PKM2 overexpression. Moreover, knockin mice expressing a phosphorylation-mimetic PHB2S91D mutant showed improved heart function, reduced inflammation, and preserved mitochondrial function following sepsis induction. Abundant PKM2 expression is a prerequisite to sustain PKM2-PHB2 interaction which is a key element for preservation of PHB2 phosphorylation and MQC, presenting novel interventive targets for the treatment of septic cardiomyopathy.

The Epidemiology of COVID-19 Vaccine-Induced Myocarditis

Background

In December 2019, the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) led to the COVID-19 pandemic, with millions of deaths worldwide. Vaccine breakthroughs in late 2020 resulted in the authorization of COVID-19 vaccines. While these vaccines have demonstrated efficacy, evidence from vaccine safety monitoring systems around the globe supported a causal association between COVID-19 vaccines, in particular those using mRNA technology, i.e., Moderna's mRNA-1273 and Pfizer-BioNTech's BNT162b2, and myocarditis.

Objective

This paper aims to investigate the epidemiology of mRNA COVID-19 vaccine-induced myocarditis, including age, ethnicity, and gender associations with these vaccines. It also discusses the immunopathophysiological mechanisms of mRNA COVID-19 vaccine-associated myocarditis and outlines principles of diagnosis, clinical presentation, and management.

Methods

A literature review was conducted using PubMed, Embase, and Queen Mary University of London Library Services databases. Search terms included "myocarditis," "coronavirus disease 2019," "SARS-CoV-2," "mRNA Covid-19 vaccines," "Covid vaccine-associated myocarditis," "epidemiology," "potential mechanisms," "myocarditis diagnosis," and "myocarditis management."

Results

While the definite mechanism of mRNA COVID-19 vaccine-associated myocarditis remains ambiguous, potential mechanisms include molecular mimicry of spike proteins and activation of the adaptive immune response with dysregulated cytokine expression. Male predominance in COVID-19 vaccine-induced myocarditis may be attributed to sex hormones, variations in inflammatory reactions, coagulation states based on gender, and female-specific protective factors. Moreover, an analysis of diagnostic and management strategies reveals a lack of consensus on acute patient presentation management.

Conclusion

In contrast to viral infections that stand as the predominant etiological factor for myocarditis with more severe consequences, the mRNA COVID-19 vaccination elicits a mild and self-limiting manifestation of the condition. There is currently insufficient evidence to confirm the definite underlying mechanism of COVID-19 vaccine-associated myocarditis. Further research is needed to develop preventive and therapeutic solutions in this context.

Clinical Application of Extracorporeal Membrane Oxygenation in the Treatment of Fulminant Myocarditis

Fulminant myocarditis (FM) is a rare but serious clinical syndrome which can be characterized by the rapid deterioration of cardiac function, with cardiogenic shock (CS) and arrhythmic electrical storms being common presentations, often requiring adjunctive support with mechanical circulatory devices. With the development of mechanical circulatory support (MCS) devices, there are now more and more studies investigating the application of MCS in FM patients, and the use of extracorporeal membrane oxygenation (ECMO) to treat FM has shown good survival rates. This review elucidates the treatment of FM, and the application and clinical outcomes associated with ECMO intervention.

Advances in myocarditis management in the light of the latest research and recent guidelines of the European Society of Cardiology

Myocarditis remains an unknown disease with varying clinical manifestations, often leading to heart failure. The latest 2021 and 2022 guidelines of the European Society of Cardiology (ESC) are the first official European documents updating knowledge on the diagnosis and treatment of myocarditis since the 2013 ESC expert consensus statement. These guidelines and new studies allow standardization and improvements to the management of myocarditis. In this review, we discuss the most important aspects of myocarditis diagnosis, therapies and follow-up based on current knowledge.

Dual-specificity phosphatase 1 interacts with prohibitin 2 to improve mitochondrial quality control against type-3 cardiorenal syndrome

Type-3 cardiorenal syndrome (CRS-3) is acute kidney injury followed by cardiac injury/dysfunction. Mitochondrial injury may impair myocardial function during CRS-3. Since dual-specificity phosphatase 1 (DUSP1) and prohibitin 2 (PHB2) both promote cardiac mitochondrial quality control, we assessed whether these proteins were dysregulated during CRS-3-related cardiac depression. We found that DUSP1 was downregulated in heart tissues from a mouse model of CRS-3. DUSP1 transgenic (DUSP1Tg) mice were protected from CRS-3-induced myocardial damage, as evidenced by their improved heart function and myocardial structure. CRS-3 induced the inflammatory response, oxidative stress and mitochondrial dysfunction in wild-type hearts, but not in DUSP1Tg hearts. DUSP1 overexpression normalized cardiac mitochondrial quality control during CRS-3 by suppressing mitochondrial fission, restoring mitochondrial fusion, re-activating mitophagy and augmenting mitochondrial biogenesis. We found that DUSP1 sustained cardiac mitochondrial quality control by binding directly to PHB2 and maintaining PHB2 phosphorylation, while CRS-3 disrupted this physiological interaction. Transgenic knock-in mice carrying the Phb2S91D variant were less susceptible to cardiac depression upon CRS-3, due to a reduced inflammatory response, suppressed oxidative stress and improved mitochondrial quality control in their heart tissues. Thus, CRS-3-induced myocardial dysfunction can be attributed to reduced DUSP1 expression and disrupted DUSP1/PHB2 binding, leading to defective cardiac mitochondrial quality control.

Altered Gut Microbiota as a Potential Risk Factor for Coronary Artery Disease in Diabetes: A Two-Sample Bi-Directional Mendelian Randomization Study

The current body of research points to a notable correlation between an imbalance in gut microbiota and the development of type 2 diabetes mellitus (T2D) as well as its consequential ailment, coronary artery disease (CAD). The complexities underlying the association, especially in the context of diabetic coronary artery disease (DCAD), are not yet fully understood, and the causal links require further clarification. In this study, a bidirectional Mendelian randomization (MR) methodology was utilized to explore the causal relationships between gut microbiota, T2D, and CAD. By analyzing data from the DIAGRAM, GERA, UKB, FHS, and mibioGen cohorts and examining GWAS databases, we sought to uncover genetic variants linked to T2D, CAD, and variations in gut microbiota and metabolites, aiming to shed light on the potential mechanisms connecting gut microbiota with DCAD. Our investigation uncovered a marked causal link between the presence of Oxalobacter formigenes and an increased incidence of both T2D and CAD. Specifically, a ten-unit genetic predisposition towards T2D was found to be associated with a 6.1% higher probability of an increase in the Oxalobacteraceae family's presence (β = 0.061, 95% CI = 0.002-0.119). In a parallel finding, an augmented presence of Oxalobacter was related to an 8.2% heightened genetic likelihood of CAD (β = 0.082, 95% CI = 0.026-0.137). This evidence indicates a critical pathway by which T2D can potentially raise the risk of CAD via alterations in gut microbiota. Additionally, our analyses reveal a connection between CAD risk and Methanobacteria, thus providing fresh perspectives on the roles of TMAO and carnitine in the etiology of CAD. The data also suggest a direct causal relationship between increased levels of certain metabolites - proline, lysophosphatidylcholine, asparagine, and salicylurate - and the prevalence of both T2D and CAD. Sensitivity assessments reinforce the notion that changes in Oxalobacter formigenes could pose a risk for DCAD. There is also evidence to suggest that DCAD may, in turn, affect the gut microbiota's makeup. Notably, a surge in serum TMAO levels in individuals with CAD, coinciding with a reduced presence of methanogens, has been identified as a potentially significant factor for future examination.

METTL3 boosts mitochondrial fission and induces cardiac fibrosis after ischemia/reperfusion injury

METTL3, an RNA methyltransferase enzyme, exerts therapeutic effects on various cardiovascular diseases. Myocardial ischemia-reperfusion injury (MIRI) and subsequently cardiac fibrosis is linked to acute cardiomyocyte death or dysfunction induced by mitochondrial damage, particularly mitochondrial fission. Our research aims to elucidate the potential mechanisms underlying the therapeutic actions of METTL3 in MIRI, with focus on mitochondrial fission. When compared with Mettl3flox mice subjected to MIRI, Mettl3 cardiomyocyte knockout (Mettl3Cko) mice have reduced infarct size, decreased serum levels of myocardial injury-related factors, limited cardiac fibrosis, and preserved myocardial ultrastructure and contractile/relaxation capacity. The cardioprotective actions of Mettl3 knockout were associated with reduced inflammatory responses, decreased myocardial neutrophil infiltration, and suppression of cardiomyocyte death. Through signaling pathway validation experiments and assays in cultured HL-1 cardiomyocytes exposed to hypoxia/reoxygenation, we confirmed that Mettl3 deficiency interfere with DNA-PKcs phosphorylation, thereby blocking the downstream activation of Fis1 and preventing pathological mitochondrial fission. In conclusion, this study confirms that inhibition of METTL3 can alleviate myocardial cardiac fibrosis inflammation and prevent cardiomyocyte death under reperfusion injury conditions by disrupting DNA-PKcs/Fis1-dependent mitochondrial fission, ultimately improving cardiac function. These findings suggest new approaches for clinical intervention in patients with MIRI.

Involvement of mitochondrial dynamics and mitophagy in diabetic endothelial dysfunction and cardiac microvascular injury

Endothelial cells (ECs), found in the innermost layer of blood vessels, are crucial for maintaining the structure and function of coronary microcirculation. Dysregulated coronary microcirculation poses a fundamental challenge in diabetes-related myocardial microvascular injury, impacting myocardial blood perfusion, thrombogenesis, and inflammation. Extensive research aims to understand the mechanistic connection and functional relationship between cardiac EC dysfunction and the development, diagnosis, and treatment of diabetes-related myocardial microvascular injury. Despite the low mitochondrial content in ECs, mitochondria act as sensors of environmental and cellular stress, influencing EC viability, structure, and function. Mitochondrial dynamics and mitophagy play a vital role in orchestrating mitochondrial responses to various stressors by regulating morphology, localization, and degradation. Impaired mitochondrial dynamics or reduced mitophagy is associated with EC dysfunction, serving as a potential molecular basis and promising therapeutic target for diabetes-related myocardial microvascular injury. This review introduces newly recognized mechanisms of damaged coronary microvasculature in diabetes-related microvascular injury and provides updated insights into the molecular aspects of mitochondrial dynamics and mitophagy. Additionally, novel targeted therapeutic approaches against diabetes-related microvascular injury or endothelial dysfunction, focusing on mitochondrial fission and mitophagy in endothelial cells, are summarized.

Pgam5-mediated PHB2 dephosphorylation contributes to endotoxemia-induced myocardial dysfunction by inhibiting mitophagy and the mitochondrial unfolded protein response

Numerous mitochondrial abnormalities are reported to result from excessive inflammation during endotoxemia. Prohibitin 2 (PHB2) and phosphoglycerate mutase 5 (Pgam5) have been associated with altered mitochondrial homeostasis in several cardiovascular diseases; however, their role in endotoxemia-related myocardial dysfunction has not been explored. Our experiments were aimed to evaluate the potential contribution of Pgam5 and PHB2 to endotoxemia-induced mitochondrial dysfunction in cardiomyocytes, with a focus on two endogenous protective programs that sustain mitochondrial integrity, namely mitophagy and the mitochondrial unfolded protein response (UPRmt). We found that PHB2 transgenic mice are resistant to endotoxemia-mediated myocardial depression and mitochondrial damage. Our assays indicated that PHB2 overexpression activates mitophagy and the UPRmt, which maintains mitochondrial metabolism, prevents oxidative stress injury, and enhances cardiomyocyte viability. Molecular analyses further showed that Pgam5 binds to and dephosphorylates PHB2, resulting in cytosolic translocation of mitochondrial PHB2. Silencing of Pgam5 or transfection of a phosphorylated PHB2 mutant in mouse HL-1 cardiomyocytes prevented the loss of mitochondrially-localized PHB2 and activated mitophagy and UPRmt in the presence of LPS. Notably, cardiomyocyte-specific deletion of Pgam5 in vivo attenuated LPS-mediated myocardial dysfunction and preserved cardiomyocyte viability. These findings suggest that Pgam5/PHB2 signaling and mitophagy/UPRmt are potential targets for the treatment of endotoxemia-related cardiac dysfunction.

A case of fulminant myocarditis with full recovery after a 38-h sustained asystole

Key Clinical Message

Even if cardiac rhythm deteriorated to asystole in the clinical course of fulminant myocarditis, cardiac function may recover, and the patient may be discharged without brain damage, if circulation could be maintained by appropriate mechanical cardiac supports.

Abstract

A 69-year-old man was diagnosed with fulminant myocarditis with circulatory collapse. His cardiac rhythm deteriorated to asystole on the second day; however, circulatory status was maintained through extracorporeal membrane oxygenation and intra-aortic balloon pumping. After 38 h-lasting asystole, his heart resumed beating. He was discharged without neurological deficits on Day 25.

The role of temporary mechanical circulatory support in de novo heart failure syndromes with cardiogenic shock: A contemporary review

Cardiogenic shock (CS) is a complex clinical syndrome with a high mortality rate. It can occur to due to multiple etiologies of cardiovascular disease and is phenotypically heterogeneous. Acute myocardial infarction-related CS (AMI-CS) has historically been the most prevalent cause, and thus, research and guidance have focused primarily on this. Recent data suggest that the burden of non-ischemic CS is increasing in the population of patents requiring intensive care admission. There is, however, a paucity of data and guidelines to inform the management of these patients who fall into two broad groups: those with existing heart failure and CS and those with no known history of heart failure who present with "de novo" CS. The use of temporary mechanical circulatory support (MCS) has expanded across all etiologies, despite its high cost, resource intensity, complication rates, and lack of high-quality outcome data. Herein, we discuss the currently available evidence on the role of MCS in the management of patients with de novo CS to include fulminant myocarditis, right ventricular (RV) failure, Takotsubo syndrome, post-partum cardiomyopathy, and CS due to valve lesions and other cardiomyopathies.