Abnormal pulmonary and aortic semilunar valves in embryos

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 a n arrest in heart development and the changed hemodynamic conditions that result from it. Embryonic abnormal aortic valves are caused by a n 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.Many abnormal semilunar valves thought to be congenital have been reported from the hearts of infants and older persons. Abnormal pulmonary valves may be bicuspid, or dome-shaped; they may have extra cusps or no cusps at all. Abnormal aortic valves fall into the same categories, except that there seems to be no record of a complete absence of aortic cusps.Pulmonary bicuspid valves in infants and older persons occur so often with a patent interventricular foramen and other signs of arrested heart development that a congenital origin may always be suspected (Koletsky, '41a). The comprehensive surveys of Dilg (1883) and of all later writers attest this. Just which cusp is defective in bicuspid pulmonary valves is not always clear, thanks to confusing terminology and lack of critical detail. Bicuspid pulmonary valves may result from a simple absence of the anterior cusp ( fig. I ) , or from a fusion of the anterior cusp with either the right or left cusps; a fusion of the right and left cusps is the least frequent anomaly. Dome-shaped pulmonary valves are often found with isolated pulmonary stenosis (Friedberg, '56). Some quadricuspid valves appear in hearts with other congenital anomalies ( Kissin, '36).Campeau et al. ('61) cite 15 cases of complete absence of pulmonary cusps linked with Fallot's tetralogy and presumably congenital in origin.Authorities differ over the congenital origin of aortic bicuspid valves, especially of those in older persons (Gross, '37; Koletsky, '41b). Bicuspid aortic valves are very often combined with coarctation (Reifenstein e t al., '47). Since the coronary arteries label the right and left cusps, the cusps involved are easily recognized. All agree that bicuspid valves from a fusion of the two coronary cusps is the most frequent an...

Absent aortic and pulmonary valves: Investigation of three fetal cases with cystic hygroma and review of the literature

“…The observation of hypoplasia of the left heart in many AAV cases gave rise to the idea that the pathogenesis of AAV might be similar to that of APV with tricuspid stenosis or atresia [6]. Abnormal development of early cardiogenesis and hemodynamic change is thought to interfere with the formation of the semilunar valve [1,48]. Hypoplasia of the right heart, however, was not apparent in many cases of APV.…”

Epidemiologic and Genetic Studies of Congenital Heart Disease in the Dog

“…Isolated defects of the pulmonary valve such as pulmonic stenosis and fusion of the right and left cusps may also be the result of abnormal development of the conus ridges, since the right and left pulmonary valve cusps are derived from these structures (25). Fusion of the right and left pulmonary cusps has been described in a pig embryo with tetralogy of Fallot by Shaner (27), and attributed to abnormal development of the aorticopulmonary septum (actually, truncoconal septum by the terminology of Kramer [25]). …”

New Concepts in the Development and Malformation of the Arterial Valves

“…Although many of these suggestions were made decades before developmental molecular genetics existed, these potential mechanisms remain and there is evidence for each of them as potential mechanisms for BAV in the literature today. Numerous mechanisms to explain development of BAV have been proposed ( Figure 6A) over the last century [122][123][124][125][126][127]. These include excessive cushion/leaflet fusion, failure to form the main cushions, abnormal outflow tract septation, and the absence of one of the leaflet primordia, primarily the ICVS that will form the non-coronary leaflet.…”

“…Moreover, in cases of BPV, the majority also had BAV without raphe, suggesting that whatever process causes bicuspid valves without raphe, it affects both valves at the same time [ 139 ]. However, it should be remembered that a raphe might be present initially and then disappear later, particularly if the fusion event occurred very early in development [ 125 ]. When the complete absence of a leaflet is considered, the non-coronary leaflet is usually suggested to be the missing one [ 20 , 62 , 63 , 140 ].…”