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ARTICLE
Morphology of Papillary Muscles: An Observational Study
in Cadaveric Adult Human Hearts
Running Title:An anatomical study of papillary muscles of heart
Mamatha Hosapatna, Anne D Souza, Aswin Das M, Supriya, Vrinda Hari Ankolekar, Antony Sylvan D
Souza
Department of Anatomy, Kasturba Medical College, Manipal University, India.
Corresponding author Dr. Vrinda H. Ankolekar
E-mail: [email protected]
Abstract
Introduction: The papillary muscles (PM) play an important role in ventricular contraction. The variability
in the number, shape and location of papillary muscle of the right and the left ventricle is important for the
surgeon in reparative procedures, papillary muscle dysfunction, mitral valve replacement and use of mitral
valve homograft for mitral/tricuspid replacement. Materials and Methods: The study was conducted using
15 formalin fixed adult human hearts procured from the Department of Anatomy, Kasturba Medical
College, Manipal. The presence, number, shapes, length, number of additional heads of the papillary
muscles were observed. The presence of moderator band (MB) was noted and its level of attachment to the
anterior PM was observed. Results: Double anterior and posterior PM were also found in few cases. The
mean length of PM in the left ventricle was longer than that in the right ventricle which was statistically
significant. In the right ventricle cone shaped PM was observed in the majority of the cases whereas flat
topped PM was observed in 2 cases. In the left ventricle all the PM were cone shaped. In majority of the
cases (N=13) the MB was attached to the lower 3rd of the PM whereas in one case each it was attached to
the upper 3rd and to the middle 3rd respectively. Conclusion: The morphology and morphometry of the
papillary muscles of both ventricles and moderator band were studied to help the surgeons during surgical
procedures conducted for correction of their defects.
Keywords: Papillary muscle, moderator band, morphology, chordae tendineae
Introduction
The papillary muscles (PM) play an important role in ventricular contraction by drawing atrioventricular
valve annulus toward the apex, and prevent ventricular blood from passing back into the atria (1, 2).
Anterior papillary muscle (APM) of the right ventricle is largest, posterior or inferior papillary muscle
(PPM) is frequently bifid or trifid. Septal papillary muscle (SPM) is small. All the major papillary muscles
supply chordae to the adjacent component of the cusp they support. The two papillary muscles of the left
ventricle supporting the cusps of mitral valve also vary in length and breadth and may be bifid. The papillary
muscle and their chordae regulate the closure of the AV valve during systole. The moderator band (MB),
also known as septomarginal trabeculae extends from the right side of the ventricular septum to the base of
anterior papillary muscle. It conveys the right branch of the atrio ventricular bundle and is presumed to
prevent the over distention of the right ventricle. The moderator band, or other large trabeculations, is the
major obstacle for the repair of apical ventricular septal defects (3).
The relevance of chordo papillary variations in rheumatic heart disease, reparative procedures, papillary
muscle dysfunction, mitral valve prolapse, mitral valve replacement and use of mitral valve homograft for
mitral/tricuspid replacement have been discussed in previous studies (4-6). In particular, the variability in
the number, shape and location of papillary muscle of the right ventricle has been studied (7, 8). Congenital
variations are known to be potential candidates for mechanical trauma leading to tricuspid valve lesions (9,
10).
Damage to valves or papillary muscles may occur after a trauma, negatively affecting valve functions and
creating losses in the functional capacity of the body. Anatomic variations of the right atrioventricular valve
may occur in association with other congenital anomalies and syndromes. Also the number, length and
shape of the papillary muscles are variable. This can be of clinical significance since the papillary muscles
play an important role in the contraction of the right ventricle and in the closure of the tricuspid valve so as
to prevent ventricular blood from passing back into the right atrium (11). Anatomical studies on
morphology of papillary muscle of heart are rare. For this reason, the morphology and morphometry of the
papillary muscles of both ventricles and moderator band were studied to help the surgeons during surgical
procedures conducted for correction of their defects.
Material and methods
The study was conducted using 15 formalin fixed adult human hearts procured from the Department of
Anatomy, Kasturba Medical College, Manipal. The ventricles were opened using incisions along the
anterior wall to expose the interior. The presence, number and shape of the PM were observed. The length
of the PM was measured from the tip to the basal attachment (figure 1). The number of additional heads
was also noted. The shape at the tip was classified as conical or flattened. The presence of MB was noted
and its level of attachment to the anterior PM was observed. The attachment was classified as to the upper,
middle or lower 3rd.
Results
The study was done on 15 adult human hearts for the morphology of papillary muscles. Double APM and
PPM were also found in few cases, the frequency distribution of which is shown in graph 1. The chordae
tendineae from the septal leaflet of tricuspid valve were attached directly to the ventricular wall whereas in
5 hearts single SPM was found. The mean and standard deviations of the lengths of PM is shown in table
1. The mean length of PM in the left ventricle was longer than that in the right ventricle which was
statistically significant (p=0.04). In the right ventricle cone shaped PM were observed in the majority of the
cases (N=13) whereas flat topped PM was observed in 2 cases. In the left ventricle all the PM were cone
shaped.
The PM were also observed for the presence of multiple heads (figure 2). The frequency distribution of
specimens having bifid PM is shown in graph 2. The bifid PM was more commonly observed in the left
ventricle. The MB was observed for its attachment to the anterior PM. In majority of the cases it was
attached to the lower 3rd of the PM (N=13) (figure 3) whereas in one case each it was attached to the upper
3rd and to the middle 3rd respectively.
Discussion
According to Aktas et al the papillary muscles were conical projections of the ventricular muscle the apices
which afforded attachment to the chordae tendineae. Although the papillary muscle presented great
variability in number, with a minimum of 2 and a maximum of 9 papillary muscle in the right ventricle
there were usually 3 papillary muscles, anterior (APM) posterior (PPM) and SPM in the right ventricle that
corresponded nominally to the leaflets of the tricuspid valve (12). In our study the number of heart
specimens having double APM in right and left ventricle was 3 and 2 specimens, double PPM in right and
left ventricle was in 8 and 6 specimens respectively. Study conducted by Aktas et al found a single APM
in 80.5% of the cases (161 cases) and a double APM in 19.5% (39 cases). A double APM was found
associated with the lack of SPM in 4 cases (2.5%) and with the presence of a muscular bridge connecting
the two heads (12). According to Victor et al the papillary muscles of the mitral valve were studied in 100
human autopsy hearts collected at random. The anterolateral papillary support had 1 belly in 67 hearts, 2 in
27, 3 in 4, 4 in 1, and 5 in 1 heart. Likewise, the posteromedial papillary support had 1 muscle belly in 50
hearts, 2 in 36, 3 in 11, and 4 in 3 hearts (13). In the study conducted by Aktas et al the single papillary
muscles were either conical, mamillated, flat topped, grooved, stepped, wavy, arched, sloped or saucerized
(12). Victor et al classified the single papillary muscles according to the shape as conical, mammillated,
flat topped, grooved, stepped, wavy, arched, sloped or saucerized (13). In our study cone shaped PM were
observed in the majority of the cases (N=13) whereas flat topped PM was observed in 2 cases in the right
ventricle. In the left ventricle all the PM were cone shaped. According to Aktas et al a single APM was
found with a length ranging between 11.45 and 45.3 mm (mean 20), and this was greater than that of a
double one ranging between 7.2 and 25.15 mm (mean 15) (12). In our study the mean length of APM was
1.3±0.4 cm and 1.63±0.5 cm on right and left side respectively. The mean length of PPM was 0.98±0.4 cm
and 2.14±0.6 cm on right and left side respectively. The mean length of SPM was 0.55±0.2 cm and on right
side. The double headed APM (N: 39) was associated with the presence of at least one SPM in 32 hearts,
82.1% and were distributed as follows: 12 hearts presented one SPM (30.8%), 9 presented 2 SPM (23.1%),
6 presented 3 SPM (15.4%) and 5 presented 4 SPM (12.8%). The double headed APM was not associated
with the existence of the SPM in 7 hearts (17.9%) (12). In our study the double headed APM was observed
in 4 and 6 specimens on the right and left side respectively. The double headed PPM was observed in 4 and
9 specimens on the right and left side respectively. According to F. Bojsen-moller et al the right bundle
branch of the conducting system in 19 pig hearts was traced through part of the interventricular septum and
through the moderator band as far as the base of the anterior papillary muscle (13). In our study the
moderator band was observed for its attachment to the anterior APM. In majority of the cases it was attached
to the lower 3rd of the APM (N=13) whereas in one case it was attached to the upper 3rd and in other it
was attached to the middle third. The morphology of moderator band might help in understanding and
surgical corrections of the defects pertaining to interventricular septum.
In conclusion, the morphology and morphometry of the papillary muscles of both ventricles and
moderator band were studied to help the surgeons during surgical procedures conducted for correction of
their defects.
References
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absence of the anterolateral papillary muscle. Ann Thorac Surg2001; 72: 1386-87.
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cords causing congenital tricuspid regurgitation: improved understanding of tricuspid valvar dysplasia in
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3. Peter L Williams: Grays Anatomy, 39th edition, Churchill Living stone. 2005, 967-72.
4.Hetzer R, Drews T, Siniawski H, Komoda T, Hofmeister J, Wenig Y. Preservation of papillary muscles
and chordae during mitral valve replacement: possibilities and limitations. J Heart Valve Dis 1995; 4
(Suppl 2): 115-23
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prenatal and neonatal life. J Am Coll Cardiol 1991; 17:1161-67.
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42: 23-26
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papillary muscle of the tricuspid valve in a case of blunt chest trauma. Thorac Cardiovasc Surg 1993; 41:
325-27.
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traumatic tricuspid regurgitation. J Heart Valve Dis 2001; 10: 276-78.
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12. Ekin O. Aktas, MD, Figen Govsa, MD, Aytac Kocak, MD, Bahar Boydak, MD, Ismail C, Yavuz,
MD. Variations in the papillary muscles of normal tricuspid valve and their clinical relevance in
medicolegal autopsies. Saudi Med J 2004 25 (9): 1176-85
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moderator band (septomarginal trabecula), J. Anat. (1971), 108, 3, pp. 387-95
Table 1: Mean and standard deviations of the length of papillary muscles
Length in cm (N=15)
Right
Left
APM
1.3±0.4
1.63±0.5
PPM
0.98±0.4
2.14±0.6
SPM
0.55±0.2
-
APM- Anterior papillary muscle, PPM- Posterior papillary muscle, SPM- Septal papillary muscle.
Graph 1: Frequency distribution of specimens having double papillary muscles.
9
Number of specimens
8
7
6
5
4
3
2
1
0
APM
PPM
APM
PPM
Right ventricle
LeftPosterior
ventriclepapillary muscle
APM- Anterior
papillary muscle, PPMGraph 2: Frequency distribution of specimens having bifid papillary muscles.
10
9
Number of specimens
8
7
6
5
4
3
2
1
0
APM
PPM
APM
PPM
Rightpapillary
ventriclemuscle, PPM- Posterior
Left ventricle
APM- Anterior
papillary muscle
Figure 1: Interior of right ventricle showing the papillary muscles
APM- Anterior papillary muscle, PPM- Posterior papillary muscle, L- Length of papillary muscle
Figure 2: Interior of the right ventricle showing the bifid PPM (1a) and bifid APM (1b)
PPM- Posterior papillary muscle, APM- Anterior papillary muscle
Figure 3: Interior of right ventricle showing the moderator band attached to the lower 1/3rd of the anterior
papillary muscle.
APM- Anterior papillary muscle, MB- Moderator band