Acute rheumatic fever causes changes in the endocardium, myocardium, and epicardium. Chronic rheumatic heart disease is almost always caused by deformity of the heart valves, particularly the mitral and aortic valves.
Pathogenesis and key morphologic changes of acute RHD
Acute rheumatic carditis
Acute rheumatic carditis is marked by a peculiar form of granulomatous inflammation with so-called "Aschoff nodules" seen best in myocardium. These are centered in interstitium around vessels as shown here.Acute rheumatic carditis, microscopic
Aschoff nodule. Aschoff giant cell. Several appear here as large cells with two or more nuclei that have prominent nucleoli. Scattered inflammatory cells accompany them and can be mononuclears or occasionally neutrophils.Fibrinous pericarditis
Lt. The pericardium has been opened to reveal the surface of the heart. There are thin strands of fibrinous exudate that extend from the parietal to visceral pericardium.. This is typical for a fibrinous pericarditis. Rt. More florid example of fibrinous pericarditis.The epicardial surface of the heart shows a shaggy fibrinous exudate. This is another example of fibrinous pericarditis. This appearance has often been called a "bread and butter" pericarditis, but you would have to drop your buttered bread on the carpet to really get this effect. The fibrin often results in the finding on physical examination of a "friction rub" as the strands of fibrin on epicardium and pericardium rub against each other.
Fibrinous pericarditis
Acute rheumatic valvulitis
Small verrucous vegetations seen along the closure line of this mitral valve. These warty vegetations average only a few millimeters and form along the line of valve closure over areas of endocardial inflammation. The lower photo. display Acute rheumatic mitral valvulitis superimposed on chronic rheumatic heart disease. Small vegetations (verrucae) are visible along the line of closure of the mitral valve leaflet (arrows). Previous episodes of rheumatic valvulitis have caused fibrous thickening and fusion of the chordae tendineae.