RADIOLOGIC FINDINGS IN THE DEVELOPMENTAL COMPLEX OF PARACHUTE MITRAL VALVE, SUPRAVALVULAR RING OF LEFT ATRIUM, SUBAORTIC STENOSIS, AND COARCTATION OF AORTA.

Abstract

Aprevious report by Shone and associates (1) described a developmental cardiac complex characterized by the tendency to coexistence of 4 obstructive or potentially obstructive anomalies. These anomalies are a parachute mitral valve, supravalvular ring of the left atrium, subaortic stenosis, and aortic coarctation (Fig. 1). Eight cases which had come to autopsy formed the basis for that report (Table I). All 4 abnormalities were exhibited in Cases I, II, and III, although in Case III the parachute mitral valve was of the modified type. In the remainder, 2 or more of the anomalies coexisted and were considered to represent incomplete or partial forms of the fully developed complex. In some of the patients, as will be indicated, certain malformations not considered part of the complex were also en-countered. This report describes the radiologic features in the 4 cases which either represented or closely approximated the complete form of the complex (Cases I to IV of the earlier report). Definition of the Anomalies of the Complex Parachute mitral valve (P.M.V.) was characterized by the occurrence of but a single major papillary muscle to which all the mitral chordae tendineae converged. The basic structure of the mitral valve leaflets and commissures was normal. The chordae were often short and thick, and this, together with their convergent insertion, allowed little mobility of the leaflets (Figs. 1–3). The parachute analogy was suggested by the shape of the deformed valve: the leaflets resembling the canopy of a parachute, the chordae its shrouds, and the single papillary muscle the harness. Since the leaflets were held closely apposed, in effect a stenotic mitral valve was created. A few interchordal slit-like spaces were the only means of egress of blood from the left atrium into the left ventricle. In one instance (Case III) 2 papillary muscles, although present, were immediately adjacent to each other. This yielded the effect of a single papillary muscle, since the chordae converged to their papillary insertions. Supraoaloular ring oj the left atrium (S.V.R.) was characterized by a protrusion into the mitral valve inlet of a circumferential ridge of connective tissue, whi ch arises at the base of the atrial aspect of the mitral leaflets. Wh en full y developed, it acts as a st enosing, perforated diaphragm (Fig. 1). In other cases, it is not sufficiently developed to cause obstruction. Two types of subaortic stenosis (S.S.) were observed in our cases—the muscular and the membranous. In the muscular, there was localized protrusion of hypertrophied ventricular septal tissue into the outflow tract of the left ventricle (Fig. 1). The membranous type showed localized, circumferential endocardial thickening in the same region. In some instances, both types were present.