Congenital Abnormalities of the Pulmonic Valve

Semilunar valves: The normal semilunar valve has 3 equal-sized cusps or leaflets and 3 commissures between leaflets (A). Congenital abnormalities of the pulmonic valve are rare--21 in 3600 (0.58%) consecutive autopsies in one series--and include pulmonic stenosis and bicuspid and quadricuspid pulmonic valves [1]. Any developmental deformity predisposes the valve to remodeling because of abnormal hemodynamics of valve closure. Continued erosion and repair produce thickening and predispose to infection just as in acquired valvar disease. In a study of 360 congenitally malformed semilunar valves, 208 involved the pulmonic, and 108 involved the aortic valve (1.9:1). Age range was from 0 to 77 y with a mean of 8 y, and 90% were under age 16. Males outnumbered females 153:120 (1.3:1). None of the valves, however, resembled that seen in our patient [2].

A. Normal pulmonic valve. Note the thin, translucent valve cusps. The commissural junction of the cusps is normal.

Congenital lesion in this patient: A deformity similar to that found in our patient was described in inbred Syrian adult hamsters with a high incidence of abnormalities of the pulmonic valve. Of 206 abnormal valves, 21 showed a spectrum from tricuspid to quadricuspid: 9 were quadricuspid, 7 were tricuspid with a raphe (ridge) in the right pulmonary sinus (space behind the cusp) and fusion of the dorsal commissure (opposite the aortic valve), and 5 were tricuspid with a raphe in the right sinus. This last anomaly corresponds to that found in our patient. He had 3 normally-formed commissures and 3 equally proportioned cusps, but behind the right cusp was a shallow raphe that indicated a partially formed 4th commissure (B). This condition is thought to result from partial division of the right valve cushion very early in its development. The authors postulate that the abnormalities of the semilunar valves may be mediated during embryogenesis by cells of the neural crest that act separately on the aortic and pulmonic valves [3].

B. Although the vegetation (V) on the anterior cusp caused partial obliteration of the commissure between it and the right cusp, all commissures appeared to have been normally formed, and cusps were of the same size. A shallow raphe (R) that originated opposite the aortic commissure (diagram) was present at the base of the right cusp, and the commissure between right and left cusps (arrow), which should have been opposite the aortic commissure, was shifted slightly to the left. All the cusps were thickened. A vegetation (not shown) was also present on the left cusp at autopsy.

C. This diagram shows the aortic (AV) and pulmonic valve (PV) cusps and their commissures in this patient. The raphe in the right sinus originated opposite the commissure of the aortic valve, and the commissure between the right and left cusps was shifted to the left. R = right cusp, L = left cusp, A = anterior cusp

References

1. Koletsky S. Congenital bicuspid pulmonary valves. Arch Pathol 1941; 31:338-353.

2. Moore G, Hutchins G, Brito J, Kang H. Congenital malformations of the semilunar valves. Hum Pathol 1980; 11:367-372.

3.Fernández B, Fernández M, Durán A, López D, Martire A, Sans-Coma V. Anatomy and formation of congenital bicuspid and quadricuspid pulmonary valves in Syrian hamsters. Anat Rec 1998; 250:70-79.

Discussion

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