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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 1, January/February 2019
AFRICA
3
Right-sided hearts
C Greig, DG Buys, SC Brown
The discovery of a right-sided heart (RSH) can result in a
very simple to an extremely complex work-up that may require
multiple investigations and interventions. As associated lesions
are very common and sometimes multifaceted, it is essential
for any clinician to recognise this and target investigations
towards a comprehensive diagnosis. This is very important as the
ultimate prognosis will depend on the complexity of the cardiac
lesion and associated abnormalities.
1,2
The outcome may range
from incidental RSH as the only finding, to early morbidity
and mortality in more complex cases. For these reasons, early
identification of this condition is important.
The incidence of RSH is reported as low, ranging from 0.4 to
0.8 per 10 000 pregnancies. The prevalence of true dextrocardia is
described as 1/12 000 pregnancies.
1,3,4
Common to most statistics
in Africa, the reported incidence of RSH is lacking. As RSH is
relatively uncommon, understanding the possible complexity and
incidence in Africa remains important.
The classification of RSH may be puzzling due to multiple
conflicting views and terminologies. The terminology used
includes: dextrocardia, dextroversion, dextroposistion and
mirror-image dextrocardia. Since the early 1960s there have
been many reviews and updates to the different classifications.
Simplifying the approach and describing structures as they are
found may avoid these difficulties. The most simple and logical
way to classify RSH would be to make use of the sequential
segmental approach, which includes cardiac position within the
thorax, abnormalities of atrial and visceral situs, and associated
cardiac abnormalities (ACA).
2,3
We suggest a logical approach to patients with RSH,
starting with confirmation of the cardiac malposition and
then proceeding to rule out any extra-cardiac causes for this
malposition, such as hypoplastic/collapsed lung, large pleural
effusion and intra-thoracic mass. The next step will be to
establish atrial and visceral situs, caval position and connections.
Once atrial situs is determined, this should be followed by an
assessment of atrioventricular (AV) connections and AV valve
morphology, including commitment and chordal insertion. This
follows ventricular situs and morphology, and their relationship
with the great arteries as well as their extra-cardiac course
(including aortic arch location, branching pattern and other arch
abnormalities).
Cardiac position is divided into levocardia (left sided),
mesocardia (midline) and dextrocardia (right sided) irrespective
of the base–apex orientation. When evaluating patients with
cardiac malposition, it is important that the sonographer
maintains left–right conventions and not be tempted to make
the images look familiar.
3
RSH can then be subdivided into:
•
dextroposition: base–apex orientation to the left and caused
by extra-cardiac processes
•
dextroversion: atrial situs solitus and ventricular inversion
•
true dextrocardia: base–apex orientation to the right and
caused by intrinsic defect of the normal lateralisation process.
The relationship between the cardiac position and situs is
important to establish. Situs is primarily determined by the atria.
Further investigation into the visceral situs (tracheobronchial
tree and abdominal organs) is also necessary.
3
This is usually
most important in cases of true dextrocardia. Situs is classified
as:
•
situs solitus: morphological right atrium to the right of
morphological left atrium
•
situs inversus: mirror image of situs solitus and most common
in cases of true dextrocardia; both atrial and visceral involve-
ment is known as situs inversus totalis
•
situs ambiguous: difficult to accurately determine situs.
Situs ambiguous has a very low prevalence (1/20 000 pregnancies)
and is usually associated with complex cardiac anatomy and
requires further investigation into the heterotaxy syndromes.
Heterotaxia is also referred to as isomerism of the atrial
appendages and is defined as abnormal arrangement of the
abdominal and thoracic organs, caused by disruption of the
left–right axis orientation during early embryonic development.
Heterotaxia syndromes can be associated with considerable
morbidity and mortality.
1,3
Isomerism is defined as:
•
left isomerism: both atria morphologically left, multiple
spleens, midline liver and two-lobed lungs
•
right isomerism: both atria morphologically right, absent
spleen, midline liver and three-lobed lungs.
In all instances, associated cardiac abnormalities should be
excluded. These are most commonly found in true dextrocardia
with situs solitus and in all cases of situs ambiguous.
Associated syndromes to consider with RSH include:
CHARGE (coloboma, heart defects, choanal atresia, growth
retardation, genital hypoplasia and ear abnormalities), and
scimitar and Kartagener syndromes. Scimitar syndrome includes
the combination of dextroposition, hypoplastic right pulmonary
artery, anomalous pulmonary venous drainage of the right
pulmonary veins and sub-diaphragmatic collaterals from the
aorta to the right lung. Kartagener syndrome comprises a triad
of sinusitis, situs inversus and bronchiectasis.
3
The more complex
the ACAs and visceral abnormalities, the more likely the patient
will require percutaneous and/or surgical intervention.
Department of Paediatric Cardiology, University of the Free
State, Bloemfontein, South Africa
C Greig, MMed (Paed), Cert cardiology
DG Buys, MMed, Cert cardiology, DCH (SA),
buysdg@ufs.ac.zaSC Brown, DMed, FCPaed, DCH
Editorial