An uncommon case of isolated parachute-like asymmetric mitral valve in an adult.

A 31-year-old asymptomatic male was referred to hospital for an examination of right bundle brunch block. Both, transthoracic and transesophageal echocardiography revealed normal left ventricular function, and two different-sized papillary muscles; the anterolateral muscle was more pronounced, with almost major chordae tendineae inserted into this dominant muscle, whereas the immature, flat posteromedial papillary muscle had very short chordae tendineae and was located higher in the left ventricle, inserted directly into the mitral annulus. The mitral valve orifice was eccentrically located at the lateral side, but no significant mitral stenosis or regurgitation was observed. No other congenital heart anomalies were identified. Thus, the final diagnosis was isolated parachute-like asymmetric mitral valve (PLAMV), without any other congenital heart anomalies. The patient was followed up closely with periodic echocardiographic examinations. Parachute mitral valve is a rare congenital cardiac defect characterized by focalized attachment of the chordae tendineae of both leaflets to a single papillary muscle. In contrast to true parachute mitral valve, PLAMV has two separate papillary muscles, one of which is more pronounced and into which all chordae are inserted. PLAMV was highly associated with other congenital heart anomalies, and the involved dominant muscle was most frequently a posteromedial papillary muscle. Isolated PLAMV in an adult is even more rare, while the presence of an immature posteromedial papillary muscle--as in the present case--is extremely rare.