What is a key pathological finding in rheumatic myocarditis?

A key pathological finding in rheumatic myocarditis is the presence of Aschoff bodies. These are characteristic granulomatous lesions that appear in the myocardium as a result of rheumatic fever, which is caused by an autoimmune response following a streptococcal infection. Aschoff bodies are composed of a collection of immune cells—predominantly lymphocytes and macrophages—and often contain multinucleated giant cells.

The formation of Aschoff bodies indicates an inflammatory response that disrupts normal heart tissue, leading to symptoms associated with rheumatic myocarditis, such as chest pain, arrhythmias, and heart failure. The identification of these bodies during histological examination is crucial in diagnosing rheumatic heart disease and determining the extent of myocarditis present.

The other options, while related to different cardiac conditions or findings, do not specifically relate to rheumatic myocarditis. Thickened vessel walls can be associated with hypertension or atherosclerosis; calcification of cardiac tissue may be seen in chronic heart conditions but is not specific for rheumatic myocarditis; and increased cardiac output is more of a physiological response than a pathological finding in this context. Thus, the presence of Aschoff bodies is a definitive pathological characteristic that highlights the inflammatory nature