Congenital heart defects in the fetus and embryological classification: Cladistics and phylogeny

Abstract

Congenital heart defects (CHD) are a common cause of fetal death and termination of pregnancy for fetal anomaly (TPFA). No series with sufficient cohort, based on description of the anatomic phenotype of CHD discovered in fetal period, have been published until now. To phenotype all the fetal cardiac specimens of the M3 C collection, which counts more than 1500 hearts. A complete morphological examination of each specimen according to segmental analysis was performed by two observers (MH, LH). We determined the main CHD according to the 11 categories and 23 subcategories of the clinical and anatomical classification of CHD and we coded the associated lesions with IPCCC codes. These codes were recorded in a database including photographs for each heart. To date, we have analyzed 758 cardiac specimens. Among them, 77 were normal (10.2%). The most frequent groups of CHD were: anomalies of the ventricular outflow tracts (VOT, 34%), functionally univentricular hearts (FUV, 24%) and anomalies of atrioventricular junctions and valves (AAVJV, 15%). As an example of a phylogenetic analysis starting from a specific anomaly, a right aortic arch was most frequent in double outlet right ventricle with subaortic ventricular septal defect (VSD) (39%), tetralogy of Fallot group (24%) and outlet VSD (9%). It was almost absent in other anomalies of VOT and other CHD ( Fig. 1 ). These first results confirm the predominance of the anomalies of the VOT. The high rate of FUV and AAVJV underlines the selection bias related to the high number of TPFA for severe CHD or chromosomal abnormality. This anatomical phenotyping of the collection should allow us to identify rare associations of malformations and could change our current way of grouping some phenotypes together. This could help us, by integrating current embryological knowledge, to elaborate a cladistics analysis of CHD, starting from one part of the phenotype.