Inflammatory and Infiltrative Myocardial Diseases

Introduction to Inflammatory Myocardial Diseases

Inflammatory and infiltrative myocardial diseases represent distinct pathophysiologic categories that can overlap clinically, with inflammatory diseases primarily involving immune-mediated myocardial damage and infiltrative diseases characterized by abnormal substance deposition in the myocardium, according to the American College of Radiology 1, 2

Viral myocarditis is the most common inflammatory myocardial disease, caused by cardiotropic viruses including enteroviruses, adenoviruses, parvovirus B19, human herpesvirus 6, and SARS-CoV-2, as stated by the American College of Cardiology 3, 4, 5
SARS-CoV-2 has emerged as a major cause, with autopsy studies showing classic myocarditis in 7.2% of COVID-19 deaths and some form of cardiac inflammation in 47.8%, according to the American College of Cardiology 5
Protozoal myocarditis, particularly Chagas disease caused by Trypanosoma cruzi, affects 13% of the at-risk population in endemic areas, with one-third developing chronic heart disease, as reported by the American College of Radiology 6
Giant cell myocarditis is a rare, rapidly fatal autoimmune condition requiring aggressive multidrug immunosuppression, as this approach has shown improved survival, according to the American College of Cardiology 4, 5
Eosinophilic myocarditis (Loeffler endocarditis in nontropical regions) is part of hypereosinophilic syndrome (eosinophils >1,500/mm³ for >6 months), with cardiac involvement in 50% of patients, as stated by the American College of Radiology 1, 2

Cardiac amyloidosis (AL type or transthyretin-related ATTR type) results in myocardial and valvular thickening, presenting with heart failure or arrhythmia, according to the American College of Radiology 1, 2, 7
Anderson-Fabry disease causes glycosphingolipid accumulation in the myocardium, as reported by the American College of Radiology 1, 2, 7
Acute sarcoidosis presents with myocardial thickening in the early inflammatory phase, according to the American College of Radiology 1, 2
Danon disease is a lysosomal storage disorder causing myocardial hypertrophy, as stated by the American College of Radiology 1, 2, 7
Myocardial oxalosis presents with left ventricular thickening, heart block, and conduction abnormalities, according to the American College of Radiology 1, 2
Mucopolysaccharidoses has variable phenotypic expression with glycosaminoglycan accumulation, as reported by the American College of Radiology 1, 2, 7
Friedreich ataxia is characterized by mitochondrial iron accumulation, with cardiomyopathy in 63% of patients, according to the American College of Radiology 1, 2, 7

Patients with rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis are at increased risk for inflammatory myocarditis, as stated by the American College of Radiology 6
Scleroderma has particularly high cardiac involvement (80% at autopsy) and should be actively screened, according to the American College of Radiology 1, 2, 7
Systemic sarcoidosis patients require cardiac evaluation given 25% myocardial involvement rate, as reported by the American College of Radiology 1, 2
The American Heart Association recommends corticosteroids as first-line therapy for cardiac sarcoidosis, with alternative immunosuppressive agents for steroid-intolerant patients, according to the American Heart Association 4

Endomyocardial biopsy remains the gold standard for definitive diagnosis when life-threatening clinical course requires consideration of immunosuppression, as stated by the American College of Cardiology 4, 5
Cardiac MRI is a sensitive, non-invasive diagnostic tool that can confirm acute myocarditis and guide biopsy decisions, according to the American College of Cardiology 4