Chronic Myocarditis Pathogenesis and Clinical Features

Primary Etiologic Mechanisms

The American College of Cardiology notes that viral persistence after acute infection is the most common pathway to chronic myocarditis in developed countries, with viral genomes detectable in myocardial tissue despite clearance of active viremia 2
Parvovirus B19 and human herpes virus 6 are the most frequently identified viruses in chronic cases in Western Europe, while enteroviruses (particularly Coxsackie B) remain important in North America 2
Coinfection with two or more viruses occurs in a substantial minority and may predispose to chronicity 2

Cardiac sarcoidosis frequently presents as chronic myocarditis and often affects the heart without clinical evidence of extracardiac disease 2
The American College of Cardiology recommends that giant cell myocarditis is an aggressive autoimmune disorder that, if untreated acutely, can transition to chronic disease requiring ongoing immunosuppression 2
Eosinophilic myocarditis is caused by hypersensitivity reactions, drug sensitivity, neoplasia, vasculitis, or hematologic disorders that create sustained eosinophilic infiltration 1, 5

Rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis cause chronic myocardial inflammation as part of systemic autoimmune processes 1, 5, 6
In rheumatoid arthritis, 46-55% of patients show focal late gadolinium enhancement on cardiac MRI, indicating chronic myocardial injury 1, 5
In systemic sclerosis, 17-53% demonstrate chronic myocardial involvement with fibrosis 1, 6

Chronic inflammation leads to progressive collagen deposition, with chronic myocarditis patients showing mean collagen volume fraction of 14% 5, 6
Late gadolinium enhancement is seen in up to 70% of patients with biopsy-proven chronic inflammation in the setting of heart failure 1, 5
This fibrosis represents irreversible myocardial damage from sustained inflammation 1

Chagas disease (Trypanosoma cruzi) is a major cause of chronic myocarditis in Central and South America, with one-third of seropositive individuals developing chronic cardiac disease 7, 2
HIV causes chronic cardiomyopathy in 8% of asymptomatic individuals through persistent viral effects 7