Mechanical Properties and Composition of the Basal Leaﬂet-Annulus
Region of the Tricuspid Valve
Department of Mechanical Engineering, Texas Tech University, 2703 7th street, PO Box 41021, Lubbock, TX 79409-1021,
Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA; and
Research Center of Fluid
Machinery Engineering & Technology, Jiangsu University, Zhenjiang 212013, Jiangsu, People’s Republic of China
(Received 9 August 2017; accepted 19 February 2018; published online 26 February 2018)
Associate Editor Ajit P. Yoganathan oversaw the review of this article.
Abstract—The Tricuspid valve (TV) annulus is a transition
structure from the leaﬂets to the myocardium, with 3
different annulus segments corresponding to the TV leaﬂets,
which includes both basal leaﬂets and bordering myocar-
dium. The objective of this study was to understand TV
annulus mechanical properties and correlate it to the
biological composition. The uniaxial testing of the annulus
segments from ten porcine TVs was performed to measure
Young’s modulus (E) and extensibility (e
). Western blotting
and histology were executed. The septal annulus E value
(208.7 ± 67.2 kPa) was statistically greater (p < 0.01) than
that of the anterior (92.0 ± 66.8 kPa) and the posterior
annulus segment (136.8 ± 56.9 kPa) (p < 0.05), respectively.
among the 3 segments were equivalent (p values < 0.05).
Western blotting and histology indicated that collagen was
greatest along the septal annulus segment, which is correlated
to E values. Collagen ﬁbers from the leaﬂets inserted into the
myocardium and faded out. Collagen content explains
greater E and suture strength in the surgical annulus repair
and larger resistance to annulus dilation in the septal annulus
as compared with other segments. This study elucidates new
knowledge of mechanical properties of the basal leaﬂet-
annulus region of the TV annulus, which can be useful for
future TV repair techniques.
Keywords—Tricuspid valve (TV), Young’s modulus (E),
), Collagen I, Collagen III, Annulus segment,
The tricuspid valve (TV) consists of septal, poste-
rior, and anterior leaﬂets, 3 papillary muscles, annulus,
and chordae tendineae. All of these components of the
TV help in coordinating blood ﬂow from the right
atrium to the right ventricle.
The normal TV annulus
has a distinct 3D saddle-shape and is dilated and ﬂat-
tened due to right ventricle dilation.
As a result,
the TV annulus becomes more circular in structure.
The annulus area is one of the leading predictors of
The mechanical proper-
ties and biological composition of the annulus may
help understand annulus dilation. The TV annulus is a
transition structure from leaﬂets to the myocardium
and can be viewed as a composite of multiple protein
and non-protein components. Histology and micro-
scopic studies of the TV annulus indicate that it is a
composite annulus structure with a deﬁned
ﬁbrous/collagenous tissue in the septal annulus and
main muscle bundles in the anterior and posterior
annulus regions, respectively.
The leaﬂets of the TV
are similar in composition to other heart valves and are
composed of glycosaminoglycans (GAGs), proteogly-
cans (PGs), elastin, and collagen ﬁbers.
leaﬂets to the myocardium, collagen ﬁbers are inter-
twined along the TV annulus and contribute to its
There are two main types of collagen, collagen I and
III, that are abundant in both the myocardium and
leaﬂets; which are responsible for tensile strength and
Collagen I is the primary
tensile strength protein associated with supporting the
most signiﬁcant force under tension.
is mainly related to providing a general lattice for the
heart tissue structures, which has been shown to be a
malleable protein structure.
Both collagen I
and III are critical structural components of the TV
annulus. For the mitral valve annulus, denser collagen
content and higher Young’s modulus (E) was seen
along the anterior annulus segment in comparison to
Address correspondence to Zhaoming He, Department of
Mechanical Engineering, Texas Tech University, 2703 7th street, PO
Box 41021, Lubbock, TX 79409-1021, USA. Electronic mail:
Cardiovascular Engineering and Technology, Vol. 9, No. 2, June 2018 (
2018) pp. 217–225
2018 Biomedical Engineering Society