In the complex
myriad of possible anomalies, some of the most difficult to determine
are those involving abnormalities of atrial situs. Mention of atrial
situs is made only to point out that any complex malposition of
the atria may occur.
Four possible atrial arrangements are encountered in congenital
heart disease: the normal arrangement of the right atrium and left
atrium (situs solitus), the direct opposite to the normal where
the right atrium is on the left and the left atrium on the right
(situs inversus), bilateral right atria (right atrial isomerism
associated with the asplenia syndrome) or bilateral left atria (left
atrial isomerism associated with the polysplenia syndrome). For
the purposes of this volume, we shall assume atrial situs to be
normal in all patients. The reader is referred to more detailed
texts for determination of this important facet of evaluating complex
congenital heart disease.
2004