From the Guidelines
Acute viral myocarditis is primarily caused by viral infections, with the most common pathogens being enteroviruses, adenoviruses, parvovirus B19, and human herpesvirus 6, as reported in the most recent study 1. The etiology of acute viral myocarditis involves direct viral invasion and damage to heart muscle cells, triggering an inflammatory immune response that can cause additional myocardial injury.
- The pathophysiology involves both direct viral cytotoxicity and the body's immune response to the infection, with the virus entering cardiomyocytes through specific receptors, replicating within the cells, and causing direct cellular damage.
- This triggers an inflammatory immune response involving cytokines, natural killer cells, macrophages, and T lymphocytes, which while attempting to clear the infection, can cause additional myocardial injury.
- In some cases, molecular mimicry may occur where the immune system attacks cardiac tissues that share structural similarities with viral antigens, leading to autoimmune myocarditis.
- Risk factors include recent viral illness, compromised immune function, and genetic predisposition, as noted in studies 1. The severity of acute viral myocarditis ranges from subclinical disease to fulminant myocarditis with cardiogenic shock, and in some patients, it may progress to dilated cardiomyopathy and chronic heart failure, highlighting the importance of prompt diagnosis and treatment, as emphasized in the 2022 ACC expert consensus decision pathway 1.
- The diagnosis of myocarditis should be based on clinical presentation, electrocardiographic, echocardiographic, and biomarker findings, with cardiac magnetic resonance (CMR) imaging becoming a sensitive, non-invasive test for confirmation of acute myocarditis, as recommended in the European Heart Journal 1.
- Management of acute viral myocarditis involves supportive care, including rest, hydration, and monitoring for complications, as well as guideline-directed medical therapy for heart failure, as outlined in the Circulation journal 1.
- In cases of fulminant myocarditis, mechanical circulatory support and advanced therapies may be necessary, as noted in the European Heart Journal 1 and the Journal of the American College of Cardiology 1.
From the Research
Etiology of Acute Viral Myocarditis
The etiology of acute viral myocarditis is attributed to viral infections, with various studies identifying specific viral pathogens as the most common causes.
- Viral infection is the most common etiology of acute myocarditis, as stated in 2.
- The most frequently identified viruses in endomyocardial biopsies are parvovirus B19 and adenoviruses, according to 2.
- Coxsackievirus B is also a common cause of viral myocarditis, with the exact mechanism of damage to myocytes unknown but likely involving immune-mediated and direct viral cytotoxicity, as mentioned in 3.
- Other viruses, such as human herpes virus 6, have also been identified as potential causes of acute myocarditis, as noted in 4.
Pathogenesis of Acute Viral Myocarditis
The pathogenesis of acute viral myocarditis involves direct viral myocardial damage as well as autoimmune reactions against cardiac epitopes.
- The pathogenesis includes direct viral myocardial damage as well as autoimmune reaction against cardiac epitopes, as stated in 2.
- The mechanisms involved in viral invasion of the organism and the triggering of excessive inflammatory responses, resulting in different types of cell death, are complex and not fully understood, as discussed in 5.
- Immune-mediated and direct viral cytotoxicity are likely mechanisms of coxsackievirus B-induced damage to myocytes, as mentioned in 3.
- The pathogenesis of myocarditis can lead to infectious dilated cardiomyopathy, a disease frequently requiring cardiac transplantation, as noted in 6.