Abnormal pulmonary and aortic semilunar valves in embryos

Abstract

Abstract Four kinds of abnormal pulmonary and three kinds of abnormal semilunar valves are described from pig and human embryos of an age equivalent to the first human trimester. The pulmonary valves include bicuspid forms resulting from the absence of an anterior cusp, from the fusion of left and anterior cusps and from the fusion of left and right cusps; also dome‐shaped valves. The aortic valves include bicuspid forms resulting from the absence of the non‐coronary cusp and from the fusion of right and left cusps. All are discussed in the light of accompanying heart anomalies and a re‐examination of normal cusp development. Embryonic abnormal pulmonary valves are generally linked with early stages of Fallot's tetralogy. They are caused by an arrest in heart development and the changed hemodynamic conditions that result from it. Embryonic abnormal aortic valves are caused by an arrest in heart development and an abnormal degree of coarctation of the aorta. The evidence from embryos supports the general belief that abnormal pulmonary cusps of all ages, when not caused by infection, are of congenital origin. Some aortic abnormal valves are also of congenital origin, but are hard to distinguish from similar ones produced after birth by postnatal coarctation.