Infectious myocarditis is caused by pathogens that directly invade the myocardium or trigger a harmful immune response. The severity of the clinical picture depends on both the aggressiveness of the pathogen and the host's immune response.
Viral myocarditis is the most common form and often presents after a systemic viral infection. The viruses involved are:
Distinctive feature: many viral forms present an initial flu-like syndrome, followed by cardiac symptoms such as chest pain, palpitations, or dyspnea.
Bacterial myocarditis mainly arises from bacteremia with cardiac dissemination of the pathogen. The most frequently involved organisms include:
Distinctive feature: bacterial myocarditis is more frequently suppurative, with a risk of microabscess formation or localized fibrosis.
A rare form, typically associated with immunosuppression. The main etiologies include:
Distinctive feature: often associated with multiorgan involvement and signs of septic embolization.
Occurs predominantly in endemic areas or immunocompromised patients. The main cause is:
Distinctive feature: the chronic form may result in apical ventricular aneurysms and AV conduction disturbances.
Non-infectious myocarditis results from immunological or toxic reactions. Myocardial injury is predominantly mediated by inflammation rather than by direct pathogen invasion.
This form is characterized by eosinophilic myocardial infiltration, detectable through endomyocardial biopsy. It may result from various conditions:
Distinctive feature: may present with acute heart failure and systemic manifestations such as rash and marked eosinophilia.
Caused by exposure to cardiotoxic substances with variable mechanisms of injury. The main causes include:
Distinctive feature: toxic myocarditis may present with dose-dependent cardiac injury or idiosyncratic reactions, often with parallel systemic involvement (hepatotoxicity, neurotoxicity).
A diagnosis of exclusion, when no specific cause is identified. Some forms may have an as yet unidentified autoimmune basis.
Distinctive feature: may present with rapidly progressive ventricular dysfunction and partial response to steroids.
Myocarditis can lead to cardiovascular complications of varying severity. The main ones include:
| Type of Myocarditis | Etiology | Distinctive Features | Typical Clinical Manifestations | Complications |
|---|---|---|---|---|
| Viral | Coxsackievirus, Parvovirus B19, Adenovirus, SARS-CoV-2 | Fever, initial flu-like syndrome | Chest pain, dyspnea, palpitations | Heart failure, arrhythmias |
| Bacterial | Staphylococcus aureus, Borrelia burgdorferi (Lyme), TB | Frequently suppurative, microabscesses | High fever, septic shock, signs of systemic infection | Septic shock, AV blocks |
| Fungal | Candida spp., Aspergillus spp. | Associated with immunosuppression | Signs of sepsis, septic embolization | Systemic emboli, endocarditis |
| Parasitic | Trypanosoma cruzi (Chagas) | Chronic evolution with fibrosis | AV conduction disturbances, ventricular aneurysms | Dilated cardiomyopathy |
| Eosinophilic | Drugs, hypereosinophilic syndrome | Eosinophilic infiltrates, skin rash | Acute heart failure | Myocardial fibrosis |
| Toxic | Drugs (chemotherapeutic agents, immunotherapies), drugs of abuse, alcohol | Dose-dependent myocardial injury | Ventricular dysfunction, arrhythmias | Irreversible heart failure |
| Idiopathic | Unknown (likely autoimmune basis) | Diagnosis of exclusion | Ventricular dysfunction, variable progression | Dilated cardiomyopathy |
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