Final answer:
Abnormal rocking of a prosthetic valve often indicates dehiscence, which is a detachment of the valve often caused by surgical failure or infection.
Step-by-step explanation:
Abnormal rocking motion of a prosthetic valve by two-dimensional echocardiography indicates prosthetic valve dehiscence. Prosthetic valve dehiscence is a condition where the valve becomes detached from its moorings, usually as a result of a failing surgical join or an infection such as endocarditis, leading to an abnormal motion observable via echocardiography.
This differs from vegetations which are patches of tissue-associated bacteria, or from stenosis which refers to valves becoming rigid, and thrombus which is a blood clot.