Subvalvar congenital mitral stenosis.

The recent rapid development of cardiac surgery now demands accurate diagnosis of the rarer types of congenital heart disease; the exact anatomy of congenital valve stenosis, for example, must be determined. The occurrence of valvar, subvalvar, and supravalvar forms of either aortic or pulmonary stenosis is well known. With respect to congenital mitral stenosis, a rarer cardiac anomaly, we are now beginning to distinguish the valvar type, of which we have previously reported two examples (Varela de Seijas et al., 1960), and the supravalvar form (Rogers et al., 1955; Johnson and Dodd, 1957; Manubens, Krovetz, and Adams 1960): this latter is to be distinguished from cor triatriatum in which an aberrant septum divides the left atrium into two different chambers, whereas in supramitral stenosis a fibrous stenosing ring is placed immediately above the valve. More recently, Shone et al. (1963) have defined a developmental complex comprising four successive obstructions to left heart flow: supravalvular mitral ring, "parachute" submitral anomaly, subaortic stenosis, and coarctation of the aorta; all or only some of these four being present in each of the eight cases they reported. The so-called "parachute" mitral valve was present in half. The term "parachute" is used by these authors by analogy with a parachute whose canopy is represented by the valve leaflets, its strings by the chordw, and its harness by the papillary muscle. The fused leaflets and chordm converge on a single papillary muscle and the subvalvar obstruction is formed by the small orifices between the chorde and papillary muscle. In rarer cases subvalvar mitral obstruction can be due to the existence of fibrous bands, or abnormal, shortened, and fused chords tendinee (Daoud et al., 1963). In this connexion Moller et al. (1964), studying cases of congenital endocardial fibroelastosis, either "primary" or "secondary" (i.e.