ReviewThe Cardiac Malpositions
Section snippets
Cardiac position
The intrathoracic position of the heart as left sided, right sided, or midline (i.e., levocardia, dextrocardia, or mesocardia).
Cardiac malposition
An abnormal intrathoracic position of the heart.
Situs
Site or position.
Solitus
Normal or usual.
Situs solitus
Normal position (Figure 1).
Situs inversus
Mirror image (Figure 2).
Displacement
An abnormal cardiac position secondary to eventration of a hemidiaphragm, agenesis of a lung, or congenital complete absence of the pericardium.
Ectopia cordis
Location of the heart outside the thoracic cavity (Figure 3).
Chamber designations
Right and left, as in right and left atrium and right and left ventricle.
Great arterial designations
The ascending aorta and pulmonary trunk defined by their ventricle of origin and by their morphology.
Heterotaxy
From the Greek “heteros,” different, and “taxis,” arrangement. Loosely and poorly translated as “another arrangement” or “a different arrangement.” The internal thoracic organs and the abdominal organs exhibit abnormal left-right relations. The concept of bilateral right- and left-sidedness as it applies to the heart is a good mnemonic but is not supported by developmental or embryologic observations.
Isomerism
From the Greek “isos,” equal, and “meros,” part. The similarity of bilateral structures that are normally dissimilar, such as right and left bronchi and right and left lungs. Isomerism is not an erroneous concept, Van Praagh6 notwithstanding.
Right isomerism
Bilateral structures with morphologic right characteristics, such as bilateral morphologic right bronchi and bilateral trilobed lungs.
Left isomerism
Bilateral structures with morphologic left characteristics, such as bilateral morphologic left bronchi and bilateral bilobed lungs.
Asplenia
Congenital absence of the spleen.
Polysplenia
Multiple spleens, each of which is appreciably smaller than a normal-sized spleen.
Ventricular loop
The straight heart tube of the embryo forms the left ventricle of the definitive heart. Looping is the consequence of the addition of new material at the arterial pole of the developing heart.
D-loop
Rightward (d = “dextro”) bend.
L-loop
Leftward (l = “levo”) bend.
Concordant
From the Latin “concordare,” to agree. A loop that agrees with the visceroatrial situs.
Atrioventricular concordance
Connection of a morphologic right atrium to a morphologic right ventricle and a morphologic left atrium to a morphologic left ventricle.
Ventriculoarterial concordance
Connection of a morphologic right ventricle to a pulmonary trunk and a morphologic left ventricle to an aorta.
Discordant
From the Latin “dis,” apart. Inappropriate.
Transposition of the great arteries
Each great artery arises from an anatomically discordant ventricle, the aorta from a morphologic right ventricle, and the pulmonary trunk from a morphologic left ventricle.
Malposition of the great arteries
Abnormal spatial relations of the aorta and pulmonary trunk to each other. Each of the abnormally related great arteries arises above the anatomically correct ventricle. The definition applies more accurately to anatomically corrected malposition, because the great arteries are also malposed in double-outlet left or right ventricle, but they do not arise from concordant ventricles.
Inversion
Mirror imagery.
Atrioventricular discordance
A morphologic right atrium connects to a morphologic left ventricle, and a morphologic left atrium connects to a morphologic right ventricle.
Ventriculoarterial discordance
A morphologic right ventricle gives rise to the aorta, and a morphologic left ventricle gives rise to the pulmonary trunk.
Double discordance
Atrioventricular discordance together with ventriculoarterial discordance. The result is physiologically correct circulatory flow.
Systematic analysis
Sequential attention to the atria, atrioventricular valves, atrioventricular connections, ventricles, ventriculoarterial connections, great arteries, and position or malposition of the heart and abdominal viscera.
I shall first deal with normal cardiac and abdominal visceral positions, then with the 3 major cardiac malpositions.
The embryonic straight heart tube initially bends to the right (d-loop), then moves to the left until the ventricular portion occupies a normal left thoracic position.
Heterotaxy with right isomerism
Heterotaxy (from the Greek “heteros,” different, and “taxis,” arrangement) is loosely and poorly translated as “another arrangement” or “a different arrangement.” Isomerism (from the Greek “isos,” equal) refers to the similarity of bilateral structures that are normally morphologically asymmetric, such as right and left bronchi, right and left lungs, and right and left atrial appendages. There is strong concordance between a morphologic right bronchus, a trilobed right lung, and a morphologic
Heterotaxy with left isomerism
Heterotaxy with left isomerism is more prevalent in women39 and is characterized by bilateral morphologic left bronchi, bilateral morphologic bilobed lungs, bilateral morphologic left atrial appendages, bilateral superior vena cavae attached to bilateral morphologic left atria, an absent or atretic sinoatrial node, common atrium, common atrioventricular valve, atrioventricular septal defect, and partial anomalous pulmonary venous connection. The pulmonary veins can be connected in a symmetric
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