Deformities secondary to rheumatic endocarditis most often affect the:

The correct answer is A. mitral valve.

Rheumatic endocarditis, a complication of acute rheumatic fever (ARF), most commonly affects the mitral valve, leading to:

– Mitral stenosis (narrowing of the valve opening)
– Mitral regurgitation (leaking of the valve)
– Mixed mitral valve disease (combination of stenosis and regurgitation)