First-degree atrioventricular block: a cause of false malfunction of a mitral disc-valve prosthesis. Case report.

Malfunction of a prosthetic mitral disc valve was clinically suspected on the basis of absent valve closing sound and an early opening click in a patient with first-degree atrioventricular (A-V) block. Premature closure and opening of the prosthetic valve was demonstrated by echocardiography. All abnormal auscultatory, phonocardiographic, and echocardiographic findings disappeared promptly upon spontaneous restoration of normal A-V conduction. The possible hemodynamic mechanism is discussed, and attention is drawn to this conduction abnormality as a cause of erroneous diagnosis of prosthetic mitral valve malfunction.