Left atrial enlargement or left atrial dilation refers to enlargement of the
left atrium of the heart, and is a form of cardiomegaly.
Causes In the general population, obesity
appears to be the most important risk factor for LAE. LAE has been found to be
correlated to body size, independent of obesity, meaning that LAE is more common
in people with a naturally large body size. Also, a study found that LAE can
occur as a consequence of atrial fibrillation, although another study
found that AF by itself does not cause LAE. The latter study also showed that
the persistent type of AF was associated with LAE, but the number of years that a
subject had AF was not. Obstructive sleep apnea may be a cause
of LAE in some cases. When an OSA event occurs, there is an attempt to breathe
with an obstructed airway and the pressure inside the chest is suddenly
lowered. The negative intrathoracic pressure may cause the left atrium to
expand and stretch its walls during each OSA event. Over time, the repetitive
stretching of the left atrium may result in a persistent left atrial enlargement.
Clinical implications Although other factors may contribute,
left atrium size has been found to be a predictor of mortality due to both
cardiovascular issues as well as all-cause mortality. Current research
suggests that left atrium size as measured by an echo-cardiograph may have
prognostic implications for preclinical cardiovascular disease. However, studies
that have found LAE to be a predictor for mortality recognize the need for
more standardized left atrium measurements than those found in an
echo-cardiogram. Diagnosis
LAE is suggested by an electrocardiogram that has a pronounced notch in the P
wave. However, if there is atrial fibrillation, a P wave would not be
present. In any case, LAE can be diagnosed and measured using an
echocardiogram. Characterizing the size of the left
atrium according to its volume is preferred over a single linear dimension
since enlargement can be different for different directions. For example,
because of the smaller distance in the thoracic cavity between the sternum and
spine, compared to the other directions, there is less room for enlargement of
the left atrium along the anteroposterior axis. By approximating
the shape of the left atrium as an ellipsoid, its volume can be calculated
from measurements of its dimensions along three perpendicular directions.
Indexing the left atrial volume to body surface area is recommended by the
American Society of Echocardiography and the European Association of
Echocardiography. The values for volume/BSA in the following table are
the ones that are the best validated and are the same for both men and women.
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