Genesis of diastolic sounds in mitral incompetence.

A third heart sound, followed by a diminuendo diastolic murmur, is generally accepted as characteristic of all but the most trivial grades of mitral incompetence. The genesis of these physical signs has remained controversial despite many human and animal studies. There are two main schools of thought concerning the origin ofthese sounds. The first or "extravalvar" school originated in Potain's treatise on gallop sounds (Potain, 1876). He attributed the origin of the third heart sound to vibration of the ventricular walls resulting from a sudden distension due to the entry of a large volume of blood. Several other authors have subsequently, wholly or partially, supported this view (Wolferth and Margolies, 1933; Orias and Braun-Menendez, 1939; Smith, 1944; Kuo et al., 1957). The second or "valvar" school hold that the third sound is related to the anatomical arrangement of the mitral valve curtains, chordae, and papillary muscles. During the rapid inflow of blood into the ventricles at the start of diastole, the left ventricular cavity is suddenly elongated. This exerts traction on the chordae tendineae which, because of their insertion, pull the mitral cusps into the path of the inflowing blood and cause a transient obstruction of the mitral orifice. This partial reclosure of the mitral valve results in the production of these physical signs (Hirschfelder, 1907; Gibson, 1907; Thayer, 1909; Lewis and Dock, 1938; Dock, 1945; Brady and Taubman, 1950; Dock, Grandell, and Taubman, 1955; Fleming, 1969). The object of this report is to describe a unique situation in the human heart, namely massive mitral incompetence without cusps or chordae tendineae being present, which occurs in mitral incompetence around a prosthetic valve. This situation permits a separation of " valvar" and " extravalvar" elements in the genesis of these sounds. Investigation of this state by phonocardiography and recording the left ventricular apical movements provides convincing evidence that the mitral valve apparatus is