28
2 Right Atrium
The normal RA is an oval chamber that supports the filling of the RV and represents
a “passive conduit” to the RV in early diastole. It completes the diastole with an
active contraction, that contributes to 30% of RV cardiac output. During physical
exercise, there is a volume overload of the right chambers that involves also the
right atrium [ 9 ]. The strength exercise generate an acute pressure overload with only
transient increased of volume overload of RA, that normalize at rest. Instead, during
endurance exercise, the volume overload causes an acute increase of RA dimension
that persists also at rest in the athlete who perform endurance exercise at competi-
tive level for long term period. This different mechanism explains the difference of
the dimensions of RA in endurance athletes, often higher than in strength athletes.
Acute, transient RA (and RV) dilatation correlates with the release of cardiac mark-
ers of workload such as B-type natriuretic peptides [ 10 ] and cardiac troponin-I [ 17 ],
immediately after severe endurance exercise such as marathon running. Several
observational studies demonstrate a prevalence of RA dilatation that is independent
on age [ 30 ]. In a cohort of more than 1.300 elite athletes, it was observed a preva-
lence of RA ECG abnormalities (P-wave amplitude more than 2.5 mm in the infe-
rior leads) in 1.2% of endurance athletes and 0.5% in non-endurance athletes [ 31 ].
For echocardiographic evaluation of RA size, it is recommended to measure the RA
area, because this parameter is easier to obtain and seems more reliable rather than
the RA diameters or volume [ 32 , 33 ]. The American Society of Echocardiography
proposed a cut-off of 18 cm^2 for the RA dimension, but this value is derived from a
study of small dimension and is not indexed for age, BSA or gender [ 34 ].
The largest observational studied was realized by Ekkehard et al. [ 32 ]. They pro-spectively analyzed the RA dimensions of a population of 880 Caucasian healthy
subjects (composted of non athletes, strength and endurance athletes), with the aim
of defining the mean value and the cut-off of RA dimension. They measured the RA
area at the end of ventricular systole (when atrial chambers reach the maximum
size), by using a 2 dimensional echocardiography in four-chamber view.
It was observed that RA mean area was similar in non athletes (12.5 ± 2.0 cm^2 )and in strength athletes group (12.7 ± 1.6 cm^2 ), with a superior cut-off area for both
group of 15 cm^2. In endurance athletes the RA area was higher (15.4 ± 2.1 cm^2 ) with
a superior cut-off area of 18 cm^2. Data were also stratified for gender, age and
BSA. It was found that BSA is the second determinant of RA dimension, after the
type of sport. The gender also determine difference in the RA area, with higher
value in men (Fig. 2.1), even if this difference disappears when the values are
indexed for BSA (Table 2.2). It was hypothized that also the race would determine
differences on the RA dimension. At this purpose, Zaidi et al. compared the RA
dimension in a group of about 300 black athletes with a group of 375 white athletes
and any difference was found [ 35 ]. This indicates no need to obtain cut-off value of
RA stratified for race, but only for type of sports and BSA.
A. D’Andrea et al.