What does an endocardial biopsy show in myocarditis?

In myocarditis, an endocardial biopsy typically reveals myocardial tissue necrosis and an infiltration of lymphocytes. This is significant because the histopathological findings are indicative of the inflammatory process that characterizes myocarditis, which is often caused by viral infections or autoimmune conditions.

The presence of lymphocytes suggests an inflammatory response, which is central to the pathophysiology of myocarditis. The necrosis of myocardial tissue signifies damage to the heart muscle itself, contributing to the symptoms of the disease. The infiltration of these immune cells indicates that the body is actively responding to an insult, which could be a viral agent or another trigger.

Other findings, such as myocardial hypertrophy or fibrosis, are more indicative of chronic issues or conditions like hypertensive heart disease or chronic heart failure rather than the acute inflammatory process seen in myocarditis. Additionally, while infective endocarditis might involve the endocardial surface and lead to seeding of bacteria, it is a separate condition with distinct pathological features and is not characterized by the same inflammatory response observed in myocarditis. Thus, the correct answer focuses on the key pathological hallmark of myocarditis found during an endocardial biopsy.