Many physicians
dealing with adults find congenital heart disease extremely complex.
The terms and classifications used over the years by pediatric cardiologists
may be largely to blame. Most previous nomenclature systems are
largely based upon embryology. Thus, such terms as L-loop and D-loop
were common and generally confused most individuals. In this unit,
a simple descriptive nomenclature, known as the sequential segmental
approach, introduced during the 1980's is employed. It avoids terms
derived from embryology and, where possible, uses simple and uncomplicated
descriptions. Its major goal is to convey information simply and
accurately without regard to how the lesions came to be.
The Sequential Segmental Approach
This newer nomenclature approach has remarkably simplified the
classification of congenital heart disease. It is based on following
the blood flow into the heart (systemic venous and pulmonary venous),
through the heart (the atrioventricular valves and ventricles)
and then out the great vessels (semilunar valves and great vessels).
This nomenclature system is extraordinarily helpful to those conducting
echocardiographic examinations as it forms a systematic guide
for verification that all the pertinent chambers and valves and
their relationships have been documented. The system is dependent
on a few words that are very important in describing the various
lesions:
Connection refers to the sequence of anatomic structures.
Normally, the right atrium is connected to the right ventricle
by means of the tricuspid valve. The right ventricle is then connected
to the pulmonary artery by means of the pulmonic valve. Therefore,
there are atrioventricular connections and ventriculo-great arterial
connections.
Concordance describes the relationship between the various
chambers, valves, and great vessels. In the normal heart all the
connections and relationships in the anatomic sequence are concordant.
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| Fig. 2 |
Discordance describes abnormal relationships between the
various chambers and great vessels. For example, when the right
atrium leads into the morphologic left ventricle and the left atrium
into the morphologic right ventricle, the atrioventricular relationships
are discordant, as seen in Fig. 2. Likewise, the atrioventricular
relationships may be concordant (normal) but the ventriculo-great
arterial relationships may be discordant where the aorta rises from
the right ventricle and the pulmonary artery from the left ventricle.
Known formerly as transposition of the great vessels, these abnormal
relationships would now be termed ventriculo-great arterial discordance
as seen in the right panel of Fig. 2.
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| Fig. 3 |
Absent or imperforate connections - Valves normally form
the connections between chambers. There are atrioventricular connections
that lead from the right atrium to right ventricle or left atrium
to vessels. When connections are not present, the term absent
connection is used. Thus, when the tricuspid valve is absent,
an absent right atrioventricular connection may not be totally absent,
only severely malformed and does not allow blood to pass antegradely.
In this setting the term imperforate connection may be used,
also seen in Fig. 3.
Commitment further describes possible abnormalities of flow
through valves into ventricles and great vessels. For example, in
a patient with tetralogy of Fallot, the atria, atrioventricular
valves, and ventricles are positioned normally, and concordant.
Since the aorta overrides a ventricular septal defect the aorta
is doubly committed to both ventricles. Likewise, in cases where
there is only one ventricle (univentricular heart), both atrioventricular
valves are usually doubly committed to the single ventricle.
Ambiguous is used when precise identification of a ventricle
or other structure cannot be made. For example, in a univentricular
heart with a doubly committed atrioventricular connection it may
not be possible to always identify clearly whether it is the right
or left ventricle. Thus, the single ventricle would be ambiguous.
Inlet refers to anomalies of the structures and flow into
the ventricle.
Outlet refers to anomalies of the structures and flow out
of the ventricles into the great vessels.
2004