Final answer:
Acute mitral regurgitation in a young, healthy patient without history of MI may be caused by conditions such as infective endocarditis or valvular disorders such as mitral valve prolapse.
Step-by-step explanation:
In a young and otherwise healthy patient who has not had a myocardial infarction (MI), infective endocarditis or severe valvular disorders such as mitral valve prolapse could be suspected as the cause of acute mitral regurgitation. Mitral regurgitation is a common valve disorder and is often due to the malfunctioning of the valve which disrupts the flow of blood, leading to mitral insufficiency.
While rheumatic fever, a disease typically of childhood, is one common cause of valvular disorders, in young adults without a history of MI, other causes such as infective endocarditis should be considered.