A young man with acute chest pain

CASE CONTINUED

The patient underwent cardiac MRI, which showed myocardial edema and patchy areas of late gadolinium enhancement, raising suspicion for myocarditis (Figure 2).

Causes of myocarditis are numerous (Table 1),^3,21,22 but viral and postinfectious etiologies remain the most common causes of acute myocarditis.²³

2. What is the most likely causative infectious agent?

,

• Parvovirus B19
• Coxsackievirus B
• Adenovirus species
• Human herpesvirus 6
• Staphylococcus aureus
• Corynebacterium diphtheria
• Trypanosoma cruzi
• Influenza H1/N1

INFECTIOUS CAUSES OF MYOCARDITIS

Coxsackievirus B was the agent most often linked to this condition from the 1950s through the 1990s. However, in the last 2 decades, adenovirus species and human herpesvirus 6 have been increasingly encountered, and recently, parvovirus B19 has been credited as the most common culprit,^11,23 at least in the Western world. In developing nations, T cruzi and C diphtheria are the most common offenders^.21

S aureus is a common cause of endocarditis, but it rarely plays a role in myocarditis. When it does, the myocarditis is often the sequela of profound bacteremia. This was much more common before antibiotics were invented.^24,25

Influenza H1/N1 is not among the most common causes of viral myocarditis, but it should be considered during flu season, given its ability to result in fulminant myocarditis.^3,26

TREATMENT FOR MYOCARDITIS

3. Which treatment is the most appropriate at this time?

• Intravenous immunoglobulin
• Interferon beta
• Acyclovir
• Prednisone
• Colchicine

Treatment for myocarditis depends on the cause but always includes supportive care to address the constellation of presenting symptoms. Standard therapies for tachy- or bradyarrhythmias, heart failure, and hemodynamic derangement should be started.

Supportive care

In patients with severe left ventricular dysfunction, an implantable cardiac electronic device, left ventricular assist device, or heart transplant may ultimately be needed. However, if possible these should be deferred for several months to determine response to treatment, since the myocardium can possibly recover.¹⁶

Diuretics, beta-blockers, angiotensin II receptor blockers, angiotensin-converting enzyme inhibitors, and aldosterone antagonists should be given as part of guideline-directed medical therapy for patients with heart failure and reduced ejection fraction.^3,27 However, whether and how the patient should be weaned from these agents after disease recovery are unknown.³

Intravenous immunoglobulin

Intravenous immunoglobulin in high doses has had mixed results. Its efficacy is well documented in children,²¹ but limited supportive data are available in adults.³ As such, recent ESC guidelines do not provide recommendations regarding its use in adults.³

Interferon beta

Interferon beta has shown promise in improving New York Heart Association class and left ventricular ejection fraction.³ This is attributed to its effects on eliminating adenoviral species and enteroviruses. Treatment of enteroviral organisms in particular has been associated with improved 10-year prognosis.³ Interferon beta also has in vitro data showing efficacy at diminishing apoptosis from parvovirus B19.²⁸

Nucleoside analogues

Empiric treatment with nucleoside analogues (acyclovir, ganciclovir, and valacyclovir) has been tried for patients in whom human herpesvirus is suspected as the causative organism, although with unconfirmed effects.³ Consultation with an infectious disease specialist is recommended before starting these agents, and biopsy is often needed beforehand.³

Immunosuppressive agents

Immunosuppressive agents such as prednisone, azathioprine, and cyclosporine can be used in cases of biopsy-proven disease with manifestations of severe heart failure, especially if biopsy results reveal sarcoidosis, giant cell myocarditis, or necrotizing eosinophilic myocarditis. Although the results were neutral in the Myocarditis Treatment Trial,²⁹ the cause of myocarditis in this trial was unknown. Therapy with such agents should be initiated after active infection is ruled out, which also would require a biopsy.

Colchicine

Mechanisms of chest pain in myocarditis include associated pericarditis and coronary artery vasospasm.^3,23 Our patient’s chest pain changed when he changed position, possibly indicating associated pericarditis. In myocarditis with accompanying pericarditis symptoms, colchicine (1–2 mg as an initial dose and then 0.6 mg daily for up to 3 months) can be helpful in alleviating symptoms.^21,30 Thus, starting this agent in a patient who presents with myocarditis in absence of heart failure, arrhythmias, or left ventricular dysfunction is prudent.

Colchicine is used mainly to address the pain associated with pericarditis. For patients who present with pericarditis without myocarditis, nonsteroidal anti-inflammatory drugs (NSAIDs) remain the first-line treatment, with the addition of colchicine leading to faster symptom resolution.³⁰ The benefit of colchicine for isolated myocarditis is not well established, with only limited data showing some clinical effects.³¹