Microbes Implicated in Myocarditis

Slideshow

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  Myocarditis: Diagnosis and Etiology

  The diagnostic workup may include electrocardiogram, chest radiographs, MRI, blood analyses, echocardiogram and cardiac MRI, and endomyocardial biopsy (EMB). EMB is the gold standard for diagnosis of myocarditis.² Treatment depends on the underlying cause and is often targeted at the presenting symptoms. Patients typically receive standard heart failure treatment and additional therapies for associated arrhythmias or other cardiac abnormalities.

  
  

  Etiology is linked to a range of sources, including cardiotoxins such as ethanol and cocaine, hypersensitivity reactions to snake or insect bites or to agents such as lithium or sulfonamides, systemic disorders including Kawasaki disease, and infection with various pathogens.⁴ Here, we review a selection of microbes that have been implicated in infective myocarditis.

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  Borrelia burgdorferi

  Borrelia burgdorferi is a tick-borne spirochete that results in Lyme disease. Symptoms include headache, fever, fatigue, and achy muscles and joints.⁵ Lyme carditis develops in an estimated 4% to10% of patients with Lyme disease, many of whom also have conduction abnormalities and perimyocarditis (90% and 60%, respectively).¹⁴ In cases of suspected Lyme carditis, ECG should be conducted to identify or exclude atrioventricular conduction block, with continuous monitoring indicated for patients with syncope or a PQ interval >300 ms. Full reversal of the conduction disorders occurs within 6 weeks in the vast majority of cases and prognosis is excellent with appropriate antibiotic treatment.¹⁴

  
  

  Photo Credit: CDC/ Claudia Molins

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  Myocarditis: Introduction

  Myocarditis is an inflammatory disorder that can lead to dilated cardiomyopathy (DCM) and heart failure.¹ Myocarditis has been observed in up to 42% of sudden death cases² in individuals aged 35 years or younger, 46% of children with DCM, and up to 16% of adults with unexplained nonischemic DCM.³

  
  

  According to the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases, “In patients presenting with mild symptoms and minimal ventricular dysfunction, myocarditis often resolves spontaneously without specific treatment. However, in up to 30% of cases, biopsy-proven myocarditis can progress to DCM and is associated with a poor prognosis.”³

  
  

  Photo Credit: Astrid & Hanns-Frieder Michler/Science Source

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  Parvovirus B19

  Parvovirus B19, the virus that causes fifth disease, is a common cause of myocarditis. It is typically transmitted by exposure to respiratory droplets from infected individuals.⁵ Like many of the viral pathogens associated with myocarditis, parvovirus B19 can also be detected in the hearts of healthy people, limiting the diagnostic value of serologic testing for viral detection in this context.⁶ Symptoms of infection, including rash — “slapped cheek” syndrome in children and more widespread rash in teens and young adults — appear approximately 1 week following exposure to parvovirus B19.

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  Human Herpes 6 Virus

  Human herpes 6 virus (HHV-6) is a highly prevalent betaherpesvirus that was discovered in 1986. It is related to human cytomegalovirus (HCMV) and is composed of 2 distinct species: HHV-6A and HHV-6B.⁷ Exposure occurs by the age of 13 months in most people. HHV-6 has been cited as the potential cause of roughly 20% of emergency department visits for fever in infants.⁵ Fever and rash are symptoms of viral shedding. In addition to myocarditis, HHV-6 has also been linked with roseola infantum, encephalitis, hepatitis, multiple sclerosis, fibromyalgia, and chronic fatigue syndrome.⁵

  
  

  Photo Credit: Phanie/Tumor Cell Lab

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  Coxsackie B Virus

  Coxsackie B virus (CBV) is a type of enterovirus with symptoms including fever, fatigue, and chest pain. CBV has been noted in 25% to 40% of infants and young adolescents with acute myocarditis and DCM.⁸ Symptoms usually appear 2 weeks after infection.⁹ As with many enteroviruses, transmission occurs through the fecal-oral route or by direct contact with mucosal secretions. Research findings have demonstrated that myocarditis and heart failure caused by CBV may be facilitated by dystrophin mutations.²

  
  

  Photo Credit: CDC/Dr Fred Murphy; Sylvia Whitfield

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  Corynebacterium diptheriae

  Corynebacterium diptheriae has been linked with myocarditis in 10% to 25% of individuals infected with diptheria and myocarditis and causes an estimated 50% to 60% of deaths resulting from diptheria.¹⁰ Although the estimated mortality rate associated with diphtheria myocarditis is high (60%),¹⁰ research suggests that patients who survive the disease fully recover.¹¹ “The principal manifestations of diphtheritic myocarditis are dilated cardiomyopathy and a variety of types of dysrhythmia and conduction disturbances. If complete heart block develops, the prognosis is almost always death,” according to a 2002 study involving children and adolescents with diphtheric myocarditis and complete heart block.¹¹ However, the authors found that insertion of a temporary pacemaker reduced the mortality rate from 100% to 74% in this patient group.

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  Staphylococcus aureus

  Staphylococcus aureus is a rare cause of myocarditis and typically affects immunocompromised patients with sepsis. S aureus myocarditis usually occurs with endocarditis and may result in the formation of abscesses on the heart valves and muscle.⁵ “As with viral myocarditis, this disease can present with signs and symptoms of acute myocardial infarction, complicating the diagnosis,” wrote the authors of a 2008 case study.¹²

  
  

  “Much of the available data on bacterial myocarditis [were] collected before the development of many modern diagnostic tests and before antibiotics [thus] the appropriate workup, diagnosis and treatment remain unclear.”¹² A case report published in 2018 described a 44-year-old man with rheumatoid arthritis taking methotrexate who was diagnosed with S aureus myocarditis (and associated left ventricular apical thrombus) after having septic shock.¹³ Complete recovery was achieved with a 12-week course of antibiotics and anticoagulation.

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  Ehrlichia chaffeensis and Babesia microti

  Ehrlichia chaffeensis and Babesia microti, the causative agents of human monocytic ehrlichiosis and babesiosis, respectively, are additional tick-borne parasites that are rare causes of myocarditis. In most reported cases of ehrlichial myocarditis, complete recovery occurred after doxycycline treatment.^5,15

  
  

  Photo Credit: Medical Images RM / Johan Bakken

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  Babesia microti (Continued)

  As with the other tick-borne parasites, patients infected with B microti may experience symptoms such as fever, muscle pain, fatigue, and headache, although approximately 25% of adults and 50% of children infected with babesial infection do not exhibit symptoms.⁵ Babesiosis may be treated with antibiotics, such as clindamycin/quinine combination therapy, or blood exchanges in severe cases.¹⁶ Some patients have coinfection involving multiple tick-borne parasites, which has been implicated in increased disease severity, although findings have been mixed overall.

  
  

  Photo Credit: CDC/ Dr. George Healy