The parachute-like asymmetric mitral valve and its two papillary muscles

The morphologic features of parachute-like asymmetric mitral valves are described to discriminate this anomaly from parachute mitral valves.

Mitral valves with unifocal attachment of chords have been called "parachute valves," independent of the number of papillary muscles. Therefore the anomaly involving two papillary muscles has not received separate attention.

The gross anatomy of 29 mitral valves with focalized attachment of chords was studied.

In 28 of the autopsy specimens asymmetric mitral valves with two papillary muscles were present, and one of the muscles was elongated, located higher in the left ventricle with its tip reaching to the anulus, and attached at both its base and lateral side to the left ventricular wall. The valve leaflets could be directly attached to this abnormal muscle that received few chords or, in three hearts, no chords at all, resulting in an oblique and eccentric orifice. Because of the focalized attachment of chords to one of the two papillary muscles, we call this malformation "parachute-like asymmetric mitral valve," We found only one "true parachute mitral valve," that is, one having a single papillary muscle that received all chords.

The morphologic features of asymmetric mitral valves are essentially different from those of true parachute valves. A distinction between these two anomalies will contribute to recognition by the pediatric cardiologist and surgeon.