<prompt> The most characteristic and frequent feature of chronic rheumatic hea disease is the development ofVegetations on the endocardiumAschoff bodies within the myocardiumIncompetence of the pulmonic valveStenosis of the mitral valve  <response>: Rheumatic fever RF produces both acute and chronic manifestations. Acute RF produces a pancarditis of all three layers of the hea. It is manifested by myocarditis, which is characterized histologically by the Aschoff body; pericarditis, which is referred to as bread-and-butter pericarditis; and verrucous endocarditis. In contrast to acute RF, chronic RF produces damage to cardiac valves. The mitral valve is most commonly involved, followed by the aoic valve. The stenotic valve has the appearance of a fish mouth or buttonhole. An additional finding in chronic RF is a rough poion of the endocardium of the left atrium, called a MacCallums patch. Reference: Robbins Cotran Pathologic Basis of Disease, 9edition. 