From the Guidelines
Myocarditis is primarily caused by viral infections, with enteroviruses, adenoviruses, and herpesviruses being the most common culprits, as well as other causes such as bacterial infections, autoimmune disorders, and certain medications. The causes of myocarditis can be diverse and vary regionally, with viral infections being the most commonly identified causes in North America and Western Europe 1. Other causes of myocarditis include:
- Bacterial infections, such as those caused by Staphylococcus, Streptococcus, and Borrelia burgdorferi (Lyme disease)
- Autoimmune disorders, such as lupus and rheumatoid arthritis
- Certain medications, particularly some antibiotics, anti-seizure drugs, and cancer treatments like doxorubicin
- Environmental toxins, such as heavy metals and recreational drugs (cocaine, methamphetamine)
- Radiation therapy directed near the heart
- In some cases, myocarditis occurs without an identifiable cause, termed idiopathic myocarditis.
The underlying mechanism typically involves either direct damage to heart cells by the infectious agent or an abnormal immune response where the body's defense system attacks cardiac tissue, leading to inflammation, reduced heart function, and potentially long-term damage if not properly treated 1.
Some of the key points to consider when evaluating the causes of myocarditis include:
- The role of viral infections, such as enteroviruses and adenoviruses, in the development of myocarditis
- The importance of considering regional variations in the causes of myocarditis
- The potential for other causes, such as bacterial infections and autoimmune disorders, to contribute to the development of myocarditis
- The need to avoid certain medications and environmental toxins that can trigger myocarditis
- The importance of proper diagnosis and treatment to prevent long-term damage and reduce the risk of complications.
It is essential to note that the most recent and highest quality study, which is 1, provides the most up-to-date information on the causes of myocarditis, and the diagnosis and treatment of myocarditis should be guided by the latest evidence-based recommendations.
From the Research
Causes of Myocarditis
The causes of myocarditis can be varied and include:
- Viral infections, such as influenza A, COVID-19, Coxsackievirus, and other viruses 2, 3, 4, 5
- Bacterial infections, such as diphtheria 4
- Autoimmune etiologies 3
- Rheumatic carditis 4
- Trypanosoma cruzi 4
- Lyme disease 6
- Chagas disease 6
- Vaccine-associated myocarditis, although this is extremely rare 3
Infectious Causes
Viral infections are a common cause of myocarditis, with cases described as early as the influenza pandemic of 1917 2. The current COVID-19 pandemic has also been associated with an increased risk of myocarditis 2, 3, 5. Other viral infections, such as Coxsackievirus, have also been implicated in the development of myocarditis 5.
Non-Infectious Causes
Non-infectious causes of myocarditis can include autoimmune disorders and other conditions 3. The exact cause of myocarditis can be difficult to determine, and further diagnostic workup may be warranted in some cases 5.