Dissection and measurements
The hearts and the proximal parts of the main vessels were dissected
from each chest cavity in routine manner. Before being immersed in a
10% paraformaldehyde solution, the hearts were weighed using a 0.5 g
precision electronic laboratory scale (SATIS, BSA‐L Laboratory, Poland).
The right atrium was opened through an intercaval incision extending
from the orifice of the superior vena cava to the orifice of the
inferior vena cava.
The detailed morphology of each valve was examined. We identified,
labelled, and counted all the commissures and leaflets. A leaflet was
defined as a tissue fold located between two commissures. Using the
attitudinally correct terminology of human anatomy, we identified 4
leaflets: a superior, a septal, a mural and an inferior leaflet
(although the latter was only present in hearts with a 4-leaflet
configuration) (10,14). Commissures were defined as areas within the
valve located between two adjacent leaflets. They had a characteristic
arched appearance and were accompanied by a fan-shaped cord originating
from the respective papillary muscle (or septal band) located directly
below the commissure (10,15,16). We observed the following commissures:
the supero-septal commissure (found between the superior and the septal
leaflet); the supero-mural commissure (found between the superior and
the mural leaflet); the muro-septal commissure (found between the mural
and the septal leaflet in the 3-leaflet configuration); the
infero-septal commissure (found between the inferior and the septal
leaflet in the 4-leaflet configuration) and the infero-mural commissure
(found between the inferior and the mural leaflet in the 4-leaflet
configuration) (Figure 1) (10).
We measured the length of each leaflet and commissure bordering the
hinge line of the RAV annulus (Figure 1). The perimeter of the annulus
was calculated as the sum of the lengths of the leaflets and
commissures. Leaflet height was defined as the maximum distance from the
hinge line to the free edge (see Figure 1). To determine the spatial
position of the RAV, we described the location of the septal leaflet and
its adjacent commissures with respect to selected landmarks within the
right atrium. We measured the distance from the terminal crest (the
inferior isthmus of the right atrial appendage vestibule) to the
muro-septal commissure (in the 3-leaflet configuration) and from the
terminal crest to the infero-septal commissure in the 4-leaflet
configuration (see A). We also measured the distance from the center
point of the ostium of the coronary sinus to the center point of the
supero-septal and the muro-septal commissures (in hearts with a
3-leaflet configuration) or the infero-septal commissure (in hearts with
a 4-leaflet configuration) (see B and C). Lastly, we measured the
distance from the superior isthmus of the right atrial appendage
vestibule to the supero-septal commissure and to the supero-mural
commissure (see D and E) (Figure 1).
Linear measurements were obtained using 0.03-mm precision electronic
calipers (YATO, YT–7201, Poland). All measurements were performed by
two independent researchers to reduce human bias. If results obtained by
the two researchers differed by more than 10%, the sample was
reassessed. The mean of the two new measurements was calculated,
approximated to the tenth decimal place, and reported as the new final
value.