The Eisenmenger malformation: a morphologic study

Transpositions of the great arteries versus aortic dextropositions. A review of some embryogenetic and morphological aspects

This review examines and discusses the morphology and embryology of two main groups of conotruncal cardiac malformations: (a) transposition of the great arteries (complete transposition and incomplete/partial transposition namely double outlet right ventricle), and (b) aortic dextroposition defects (tetralogy of Fallot and Eisenmenger malformation). In both groups, persistent truncus arteriosus was included because maldevelopment of the neural crest cell supply to the outflow tract, contributing to the production of the persistent truncus arteriosus, is shared by both groups of malformations. The potentially important role of the proximal conal cushions in the rotatory sequence of the conotruncus is emphasized. Most importantly, this study emphasizes the differentiation between the double-outlet right ventricle, which is a partial or incomplete transposition of the great arteries, and the Eisenmenger malformation, which is an aortic dextroposition. Special emphasis is also given to the leftward shift of the conoventricular junction, which covers an important morphogenetic role in both aortic dextropositions and transposition defects as well as in normal development, and whose molecular genetic regulation seems to remain unclear at present. Emphasis is placed on the distinct and overlapping roles of Tbx1 and Pitx2 transcription factors in modulating the development of the cardiac outflow tract.

Systematic Approach to Malalignment Type Ventricular Septal Defects

Various congenital heart diseases are associated with malalignment of a part of the ventricular septum. Most commonly, the outlet septum is malaligned toward the right or left ventricle. Less commonly, the whole or a major part of the ventricular septum is malaligned in relation to the atrial septal plane. Although the pathological conditions associated with ventricular septal malalignment have been well recognized, the descriptions are often confusing and sometimes incorrect. In this pictorial essay, we introduce our systematic approach to the assessment of malalignment type ventricular septal defects with typical case examples. The systematic approach comprises description of the essential features of malalignment, including the following: (1) the malaligned part of the ventricular septum, (2) the reference structure, (3) the mechanism of malalignment, (4) the direction of malalignment, and (5) the severity of malalignment.

Secundum Atrial Septal Defect With Early Presentation of Eisenmenger Syndrome and Right-Heart Failure: A Rare Case Report and Literature Review

Eisenmenger syndrome, the most advanced form of pulmonary arterial hypertension (PAH), poses a considerable risk to the survival and quality of life of patients. It is more commonly seen in large intra-cardiac defects like ventricular septal defects (VSD) or patent ductus arteriosus (PDA), and rarely in atrial septal defects (ASD). Early diagnosis is the single most important step in the definitive management of the condition; otherwise, only conservative treatment can be offered. In this report, we present the case of a 20-year-old female patient diagnosed with Eisenmenger syndrome secondary to a large secundum ASD. The patient responded well to medical treatment.

Assessing the criteria for definition of perimembranous ventricular septal defects in light of the search for consensus

Background

Discussions continue as to whether ventricular septal defects are best categorized according to their right ventricular geography or their borders. This is especially true when considering the perimembranous defect. Our aim, therefore, was to establish the phenotypic feature of the perimembranous defect, and to establish the ease of distinguishing its geographical variants.

Methods and results

We assessed unrepaired isolated perimembranous ventricular defects from six historic archives, subcategorizing them using the ICD-11 coding system. We identified 365 defects, of which 94 (26%) were deemed to open centrally, 168 (46%) to open to the outlet, and 84 (23%) to the inlet of the right ventricle, with 19 (5%) being confluent. In all hearts, the unifying phenotypic feature was fibrous continuity between the leaflets of the mitral and tricuspid valves. This was often directly between the valves, but in all instances incorporated continuity through the atrioventricular portion of the membranous septum. In contrast, we observed fibrous continuity between the leaflets of the tricuspid and aortic valves in only 298 (82%) of the specimens. When found, discontinuity most commonly was seen in the outlet and central defects. There were no discrepancies between evaluators in distinguishing the borders, but there was occasional disagreement in determining the right ventricular geography of the defect.

Conclusions

The unifying feature of perimembranous defects, rather than being aortic-to-tricuspid valvar fibrous continuity, is fibrous continuity between the leaflets of the atrioventricular valves. While right ventricular geography is important in classification, it is the borders which are more objectively defined.

Development and Morphology of the Ventricular Outflow Tracts

It is customary, at the current time, to consider many, if not most, of the lesions involving the ventricular outflow tract in terms of conotruncal malformations. This reflects the introduction, in the early 1940s, of the terms conus and truncus to describe the components of the developing outflow tract. The definitive outflow tracts in the postnatal heart, however, possess three, rather than two, components. These are the intrapericardial arterial trunks, the arterial roots, and the subvalvar ventricular outflow tracts. Congenital lesions afflicting the arterial roots, however, are not currently considered to be conotruncal malformations. This suggests a lack of logic in the description of cardiac development and its use as a means of categorizing congenital malformations. It is our belief that the developing outflow tract, like the postnatal outflow tracts, can readily be described in tripartite fashion, with its distal, intermediate, and proximal components forming the primordiums of the postnatal parts. In this review, we present evidence obtained from developing mice and human hearts to substantiate this notion. We show that the outflow tract, initially with a common lumen, is divided into its aortic and pulmonary components by a combination of an aortopulmonary septum derived from the dorsal wall of the aortic sac and outflow tract cushions that spiral through its intermediate and proximal components. These embryonic septal structures, however, subsequently lose their septal functions as the outflow tracts develop their own discrete walls. We then compare the developmental findings with the anatomic arrangements seen postnatally in the normal human heart. We show how correlations with the embryologic findings permit logical analysis of the congenital lesions involving the outflow tracts.

Correlating the morphological features of tetralogy of Fallot and the Eisenmenger malformation

We studied a series of 43 autopsied cases of tetralogy of Fallot, assessing the mode of insertion of the outlet septum relative to the limbs of the septomarginal trabeculation, and compared the findings in retrospective fashion with our previous observations of a group of hearts with the so-called Eisenmenger malformation. In the majority of hearts with tetralogy of Fallot, the outlet septum inserted frontally relative to the septomarginal trabeculation, but in a minority of cases the outlet septum inserted in lateral fashion, as had been observed in all our hearts studied with the Eisenmenger malformation. The different modes of insertion were found to correlate, first, with the axis of anatomical aortic rightward rotation, coincident with the commissure between the right coronary and the left coronary leaflets of the aortic valve. The different modes of insertion of the outlet septum also correlated with the level of attachment of the arterial valvar leaflets on its subpulmonary and subaortic surfaces; concomitantly, correlation was found between the length of the subpulmonary infundibulum and the length of the muscular outlet septum itself. In the majority of hearts showing tetralogy of Fallot, the elongated infundibulum was also uniformly narrow, but in a minority the infundibulum was well expanded, obstructed only at its mouth, but widening at the valvar level. In all the hearts with the Eisenmenger malformation, in contrast, the unobstructed infundibulum was well expanded. The morphological findings of the present study show unequivocally that tetralogy of Fallot and Eisenmenger malformation are two phenotypically different congenital cardiac anomalies.