The Significance of Ventricular Topology in the Analysis of Congenitally Malformed Hearts

Figures

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  Figure 1. Hearts with the “classical” variant of tricuspid atresia serve to show that “alignments” cannot always be considered to represent the same feature as ‘connections”. As shown in panel (A), the right atrium is aligned with the incomplete right ventricle. As shown in panel (B), however, the essential feature of the classical variant of tricuspid atresia is the absence of the right atrioventricular connection.

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  Figure 2. The images show the ventricular loop as seen in a developing murine embryo 10.5 days subsequent to fertilisation. Panel (A) shows the frontal section through the loop, while panel (B), taken obliquely, reveals that at this early stage, the right atrium has no direct connection with the developing right ventricle.

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  Figure 3. The images are from a developing mouse embryo at embryonic day 11.5. Panel (A) is a four-chamber section, showing that, by expansion of the atrioventricular canal, the right ventricle has achieved its own inlet. Panel (B) is a long axis section, showing that both arterial trunks still arise from the right ventricle. It can also be seen, however, that because of the formation of the inlet, it is now possible to recognise that the right ventricle shows right-handed topology.

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  Figure 4. The images show the essence of the patterns of ventricular topology as seen in postnatal hearts. Panel (A) shows a normal right ventricle, which accepts on its septal surface only the palmar surface of the right hand when the thumb is placed in the inlet, with the fingers extending into the outlet. Panel (B) shows the left-sided morphologically right ventricle from a heart with congenitally corrected transposition. This right ventricle accepts only the palmar surface of the left hand.

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  Figure 5. The images show a rare example of segmental disharmony. Panel (A) shows the left-sided morphologically right ventricle, which is connected through the tricuspid valve to the right-sided morphologically right atrium; in other words, there are concordant atrioventricular connections. There is also a double outlet from the right ventricle. Panel (B) shows that, despite the concordant atrioventricular connections, there is left-handed ventricular topology. This is segmental disharmony.

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  Figure 6. The images show a heart with usual atrial arrangement, concordant atrioventricular connections, with twisting of the atrioventricular connections, as shown in panel (A), producing the “cross-cross” arrangement (white arrows with red borders). As shown in panel (B), despite the rotation of the heart produced by the twisting, the right ventricle still shows right-handed topology, as expected for hearts with usual atrial arrangement and concordant atrioventricular connections.

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  Figure 7. The heart shows an example of transposition with left-sided aorta. This is “l-transposition”, but the heart is not congenitally corrected. There are concordant atrioventricular and discordant ventriculo-arterial connections. This is an example of disharmony between the ventricular and arterial segments of the heart.

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  Figure 8. Both of the hearts shown have double inlet left ventricle with incomplete right ventricle and concordant ventriculo-arterial connections. The heart shown in panel (A) is a classical “Holmes heart”. The inference can be made that there is a right-handed topology since the incomplete right ventricle is anterior and right-sided relative to the dominant left ventricle. In the heart shown in panel (B), the incomplete ventricle is anterior and left-sided. This permits the inference to be made that, during development, there had been leftward ventricular looping. Hence, the incomplete right ventricle can be considered to show left-handed topology. It could, however, be shifted to a right-sided position simply by rotating the heart.