Influenza Myocarditis: A Literature Review

A Narrative Review of Key Risk Factors for Severe Illness Following SARS-CoV-2, Influenza Virus, and Respiratory Syncytial Virus Infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, and respiratory syncytial virus (RSV) are highly infectious respiratory viruses that affect people of all ages and are typically associated with mild symptoms and few complications in immunocompetent individuals. However, the risk of severe outcomes (e.g., hospitalization and death) following infection with these respiratory viruses is higher in certain populations, including older adults and individuals of certain race/ethnic and sociodemographic groups. Additionally, immunocompromising conditions and pre-existing comorbidities, including underlying cardiovascular (e.g., congestive heart failure) and respiratory diseases (e.g., chronic obstructive pulmonary disease), diabetes, chronic kidney disease, and obesity, are key factors that predispose individuals to SARS-CoV-2-, influenza-, and RSV-related severe outcomes. Increased risk for severe outcomes associated with advancing age and comorbidities is compounded by residence in long-term care facilities due to the enhanced spread of respiratory infections in congregate living environments. In this narrative review, risk factors associated with severe outcomes following infection with SARS-CoV-2, influenza, and RSV in adult populations are explored. Additionally, distinct clinical outcomes based on underlying comorbidities following infection are discussed in the context of high-risk populations. Factors unique to each virus that underpin distinct risk profiles are described and suggest the potential for tailored surveillance and healthcare approaches to target and ultimately mitigate SARS-CoV-2-, influenza-, and RSV-associated disease burden in vulnerable populations. Mutual risk factors for severe outcomes are also highlighted; these similarities indicate that cohesive risk reduction strategies may also be feasible, particularly since vaccines are available for each of these respiratory viruses. Ultimately, a more thorough understanding of the risk factors that predispose individuals to develop SARS-CoV-2-, influenza-, and RSV-related severe outcomes may improve risk reduction strategies, inform healthcare policy, and contribute to the expansion and refinement of existing surveillance approaches to ultimately mitigate disease burden in vulnerable populations.

Latest developments in early diagnosis and specific treatment of severe influenza infection

Influenza pandemics are unpredictable recurrent events with global health, economic, and social consequences. The objective of this review is to provide an update on the latest developments in early diagnosis and specific treatment of the disease and its complications, particularly with regard to respiratory organ failure. Despite advances in treatment, the rate of mortality in the intensive care unit remains approximately 30%. Therefore, early identification of potentially severe viral pneumonia is extremely important to optimize treatment in these patients. The pathogenesis of influenza virus infection depends on viral virulence and host response. Thus, in some patients, it is associated with an excessive systemic response mediated by an authentic cytokine storm. This process leads to severe primary pneumonia and acute respiratory distress syndrome. Initial prognostication in the emergency department based on comorbidities, vital signs, and biomarkers (e.g., procalcitonin, ferritin, human leukocyte antigen-DR, mid-regional proadrenomedullin, and lactate) is important. Identification of these biomarkers on admission may facilitate clinical decision-making to determine early admission to the hospital or the intensive care unit. These decisions are reached considering pathophysiological circumstances that are associated with a poor prognosis (e.g., bacterial co-infection, hyperinflammation, immune paralysis, severe endothelial damage, organ dysfunction, and septic shock). Moreover, early implementation is important to increase treatment efficacy. Based on a limited level of evidence, all current guidelines recommend using oseltamivir in this setting. The possibility of drug resistance should also be considered. Alternative options include other antiviral drugs and combination therapies with monoclonal antibodies. Importantly, it is not recommended to use corticosteroids in the initial treatment of these patients. Furthermore, the implementation of supportive measures for respiratory failure is essential. Current recommendations are limited, heterogeneous, and not regularly updated. Early intubation and mechanical ventilation is the basic treatment for patients with severe respiratory failure. Prone ventilation should be promptly performed in patients with acute respiratory distress syndrome, while early tracheostomy should be considered in case of planned prolonged mechanical ventilation. Clinical trials on antiviral treatment and respiratory support measures specifically for these patients, as well as specific recommendations for different at-risk populations, are necessary to improve outcomes.

The Influence of Diagnoses of Specific Viral Infections on In-Hospital Mortality, Length of Stay and Cost in Patients Admitted to Hospital with a Diagnosis of Myocarditis: An Analysis of the National Inpatient Sample

Background

The influence of different viral infections in patients with myocarditis is unknown. Myocarditis is an inflammatory disease of heart muscle that is commonly caused by viruses. The impact of different viral infections in patients with myocarditis is unknown.

Methods

We conducted a retrospective cohort study using data between 2016-2020 in the National Inpatient Sample in the USA to evaluate admissions with myocarditis and concomitant viral infection. The outcomes of in-hospital mortality, length of stay (LoS), and cost, among patients hospitalized for myocarditis was evaluated.

Results

A total of 27,050 hospital admissions for myocarditis were included and 6750 (25.0%) had a co-diagnosis of viral infection. Patients with myocarditis and viral infection had significantly higher mortality compared to those without viral infection (23.6% vs. 4.4%, p < 0.001). Viral infection was associated with increased in-hospital mortality (odds ratio (OR) 2.03, 95% CI 1.51 to 2.73, p < 0.001), greater median LoS (7 vs. 3 days, p < 0.001) and median hospitalization cost ($21,445 vs. $11,596, p < 0.001), compared to patients without viral infection. The rate of death was greatest for patients with a diagnosis of coronavirus disease 2019 (COVID-19), viral pneumonia and herpes zoster, respiratory syncytial virus, chronic hepatitis, and influenza which was 36.0%, 34.3%, 27.3%, 21.4%, 20.0%, and 14.5%, respectively.

Conclusions

In conclusion, the diagnosis of viral infection is present in one in four patients hospitalized with myocarditis and is correlated with greater mortality, LoS, and in-hospital cost.

A Comparison of COVID-19 and Influenza-Associated Myocarditis: A Nationwide Study in the United States

We aimed to compare the characteristics and outcomes of adult patients hospitalized with myocarditis and either concomitant COVID-19 or influenza, and elucidate clinical predictors associated with adverse outcomes in both groups. The study used the National Inpatient Sample (NIS) from 2019 to 2020 to identify 27,725 adult myocarditis hospitalizations, of which 5,840 had concomitant COVID-19 and 1,045 had concomitant influenza. After propensity score matching, the in-hospital mortality from myocarditis was significantly higher in COVID-19 compared to influenza. Patients with myocarditis and COVID-19 were more likely to have cardiovascular comorbidities and be older than those with influenza-associated myocarditis. Predictors of mortality were also different in both groups.

Multisystem Inflammatory Syndrome Causing Mixed Cardiogenic Shock in a 34-Year-Old With Influenza A

Multisystem inflammatory syndrome in adults (MIS-A) is a sequela of COVID-19 and can cause mixed cardiogenic and vasodilatory shock. We present the case of a 34-year-old female who presented with mixed cardiogenic and vasodilatory shock and was found to be influenza A positive while also meeting criteria for MIS-A. She responded well to treatment with steroids and intravenous immunoglobulin (IVIG).

Influenza Vaccination for Cardiovascular Prevention: Further Insights from the IAMI Trial and an Updated Meta-analysis

PURPOSE OF REVIEW

Influenza infection is a significant, well-established cause of cardiovascular disease (CVD) and CV mortality. Influenza vaccination has been shown to reduce major adverse cardiovascular events (MACE) and CV mortality. Therefore, major society guidelines have given a strong recommendation for its use in patients with established CVD or high risk for CVD. Nevertheless, influenza vaccination remains underutilized. Historically, influenza vaccination is administered to stable outpatients. Until recently, the safety and efficacy of influenza vaccination among patients with acute myocardial infarction (MI) had not been established.

RECENT FINDINGS

The recently published Influenza Vaccination after Myocardial Infarction (IAMI) trial showed that influenza vaccination within 72 h of hospitalization for MI led to a significant 28% reduction in MACE and a 41% reduction in CV mortality, without any excess in serious adverse events. Additionally, we newly performed an updated meta-analysis of randomized clinical trials (RCTs) including IAMI and the recent Influenza Vaccine to Prevent Adverse Vascular Events (IVVE) trial. In pooled analysis of 8 RCTs with a total of 14,420 patients, influenza vaccine, as compared with control/placebo, was associated with significantly lower risk of MACE at follow-up [RR 0.75 (95%CI 0.57-0.97), I2 56%]. The recent IAMI trial showed that influenza vaccination in patients with recent MI is safe and efficacious at reducing CV morbidity and mortality. Our updated meta-analysis confirms a 25% reduction in MACE. The influenza vaccine should be strongly encouraged in all patients with CVD and incorporated as an essential facet of post-MI care and secondary CVD prevention.

Fulminant Influenza a Myocarditis Complicated by Transient Ventricular Wall Thickening and Cardiac Tamponade

Myocarditis is an infrequent complication of influenza infection that is most often diagnosed clinically in the setting of confirmed influenza infection and elevated cardiac enzymes. Pericarditis can also occur in cases of influenza myocarditis and may require pericardiocentesis for tamponade. Patients with fulminant myocarditis have cardiogenic shock; however, echocardiographic findings may be subtle, showing a preserved ejection fraction and diffuse left ventricular wall thickening (compared to baseline) due to inflammatory edema. Recognizing these echocardiographic findings in the appropriate clinical setting facilitates the early recognition of fulminant myocarditis. Therefore, we report a case of fulminant influenza A myocarditis in healthy 37-year-old women complicated by transient left ventricular wall thickening and tamponade, highlighting the importance of early diagnosis and supportive management for a successful outcome.

Influenza Myopericarditis and Pericarditis: A Literature Review

Myopericarditis is a rare complication of influenza infection. The presentation may range from mild and frequently unrecognized, to fulminant and potentially complicated by cardiogenic and/or obstructive shock (tamponade), which is associated with high mortality. We performed a review of literature on all influenza pericarditis and myopericarditis cases according to PRISMA guidelines using the PubMed search engine of the Medline database. Seventy-five cases of influenza myopericarditis and isolated pericarditis were identified from 1951 to 2021. Influenza A was reported twice as often as influenza B; however, influenza type did not correlate with outcome. Men and elderly patients were more likely to have isolated pericarditis, while women and younger patients were more likely to have myopericarditis. All included patients had pericardial effusion, while 36% had tamponade. Tamponade was more common in those with isolated pericarditis (41.2%) than myopericarditis (13.8%). Cardiogenic shock was more common in patients with myopericarditis (64%), with an overall mortality rate of 14.7%. Nearly 88% of the recovered patients remained without long-term complications reported. Conclusion: Influenza A appears a more common cause of pericarditis and myopericarditis. Isolated pericarditis was more commonly associated with tamponade but without reported deaths, whereas myopericarditis was more commonly associated with cardiogenic shock and death (19%).

Influenza A, Influenza B, and SARS-CoV-2 Similarities and Differences – A Focus on Diagnosis

In late December 2019, the first cases of viral pneumonia caused by an unidentified pathogen were reported in China. Two years later, SARS-CoV-2 was responsible for almost 450 million cases, claiming more than 6 million lives. The COVID-19 pandemic strained the limits of healthcare systems all across the world. Identifying viral RNA through real-time reverse transcription-polymerase chain reaction remains the gold standard in diagnosing SARS-CoV-2 infection. However, equipment cost, availability, and the need for trained personnel limited testing capacity. Through an unprecedented research effort, new diagnostic techniques such as rapid diagnostic testing, isothermal amplification techniques, and next-generation sequencing were developed, enabling accurate and accessible diagnosis. Influenza viruses are responsible for seasonal outbreaks infecting up to a quarter of the human population worldwide. Influenza and SARS-CoV-2 present with flu-like symptoms, making the differential diagnosis challenging solely on clinical presentation. Healthcare systems are likely to be faced with overlapping SARS-CoV-2 and Influenza outbreaks. This review aims to present the similarities and differences of both infections while focusing on the diagnosis. We discuss the clinical presentation of Influenza and SARS-CoV-2 and techniques available for diagnosis. Furthermore, we summarize available data regarding the multiplex diagnostic assay of both viral infections.