Papillary Muscle Variations in the Human Mitral Valve

Kumar V et al | DOI: 10.65188/nurexus.1034

Page 13

Journal of MedVerse Research & Practice

ISSN: 3107-4278

Papillary Muscle Variations in the Human Mitral Valve

Dr. Vishnu Kumar

, Dr. Surya M

Postgraduate, Assistant Professor

Department of Anatomy, Salem Government Medical College,

Email: vishnukumar@gmail.com

Submission Date: 24.06.2025

Accepted Date: 21.07.2025

Published Date: 31.07.2025

DOI: 10.65188/nurexus.1034

article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits

unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Abstract

Background: The morphology and morphometry of the papillary muscles play a crucial role in maintaining mitral

valve function. Variations in their number, shape, and chordal attachment patterns can influence the pathophysiology

and surgical outcomes of mitral valve diseases.

Aims & Objectives: 1) To study the morphology of left ventricular papillary muscles in human cadaveric hearts. 2)

To estimate the annulopapillary distance and compare it with the length of the chordae tendineae.

Materials and Methods: This cross-sectional descriptive study was conducted in the Department of Anatomy, Salem

Government Medical College and Hospital, Tamil Nadu, over 18 months (September 2024 – February 2025). A total

of 60 formalin-fixed adult human cadaveric hearts were examined. Standard anatomical dissection was employed to

expose the mitral valve apparatus. Morphological and morphometric parameters of anterior and posterior papillary

muscles, chordae tendineae, mitral valve leaflets, and annular dimensions were recorded using digital Vernier calipers

and flexible measuring tools. Statistical analysis was performed using IBM SPSS version 26.0, applying descriptive

and inferential statistics with significance set at p<0.05.

Results: Anterior papillary muscles were single in 84.9% and double in 15.1%; posterior papillary muscles were single

in 81.1%, double in 15.1%, and triple in 3.8%. Conical shape was the most common (60.4%) followed by fan-shaped

(30.2%) and bifid types (9.4%). Mean length, breadth, and thickness were significantly greater in anterior papillary

muscles compared to posterior ones (p<0.001). The mean annulopapillary distance was 23.6 ± 2.4 mm (anterior) and

20.9 ± 2.1 mm (posterior). A significant positive correlation was noted between annulopapillary distance and chordal

length.

Conclusion: This study highlights significant morphological and morphometric variations in papillary muscles and

their clinical relevance in mitral valve mechanics. Knowledge of these variations is essential for cardiac surgeons and

interventional cardiologists to minimize procedural complications.

Keywords: Papillary muscles, mitral valve, chordae tendineae, annulopapillary distance, cardiac anatomy, cadaveric

heart

Introduction

The mitral valve complex plays a critical role in maintaining left heart function, facilitating unidirectional

blood flow between the left atrium and left ventricle. This complex includes the annulus, valve leaflets,

chordae tendineae, and papillary muscles, all of which function in a coordinated manner to ensure efficient

closure during systole and prevent regurgitation [1]. The papillary muscles act as dynamic anchors for the

chordae tendineae, which, in turn, maintain leaflet position during ventricular contraction. Any deviation in

the morphology, location, or number of papillary muscles may compromise this synchrony and lead to

mitral valve dysfunction [2–4]. These anatomical variations are often implicated in mitral valve prolapse,

Kumar V et al | DOI: 10.65188/nurexus.1034

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regurgitation, and may even complicate surgical procedures like valve replacement or repair. While most

hearts typically exhibit two papillary muscles, the anterolateral and posteromedial, numerous studies have

reported variations in their number, shape, branching patterns, and chordal attachments [7–9]. For instance,

conical and finger-like morphologies are most commonly observed, but fan-shaped or mixed variants are

not uncommon [10]. Accessory muscles or additional heads have been reported to influence valve

kinematics and are associated with congenital anomalies or acquired pathologies [11,12]. In the realm of

clinical cardiology and cardiac surgery, recognition of such variations is essential. Imaging techniques such

as echocardiography and cardiac MRI have enhanced the identification of papillary muscle abnormalities,

yet many anomalies may be overlooked without a solid anatomical foundation [13–15]. Furthermore, the

morphometric characteristics—such as length, breadth, and annulopapillary distance affect leaflet tension

and are of direct relevance to mitral valve repair [16].

Despite its clinical importance, region-specific studies focusing on papillary muscle morphology remain

scarce in India. Most published data come from Western populations, potentially limiting their

generalizability to Indian cohorts, where genetic and environmental factors may play a role in shaping

cardiac anatomy [17,18]. Therefore, this study aims to document the morphological diversity and

morphometric patterns of papillary muscles in cadaveric human hearts from South India.

The findings will help refine anatomical teaching, improve preoperative planning, and contribute to the

literature on mitral valve mechanics, particularly for cardiothoracic surgeons and echocardiographers

[19,20].

Materials & Methods

Study Design and Duration: A cross-sectional descriptive anatomical study was conducted from September

2024 to February 2025 in the Department of Anatomy, Salem Government Medical College, Tamil Nadu.

Sample Size and Selection: A total of 53 formalin-fixed adult human cadaveric hearts with intact

morphology were included. Specimens with congenital defects, gross pathology, or mechanical damage were

excluded. The sample size was calculated based on the reported prevalence of fan-shaped papillary muscles.

Dissection Procedure: Standard anatomical dissection techniques were meticulously followed to expose the

mitral valve complex. After careful removal of the left atrial wall, the left ventricle was opened along its

lateral border to visualize the mitral apparatus clearly. Both the anterolateral and posteromedial papillary

muscles were identified, cleaned of overlying trabeculae carneae, and isolated without disturbing their

chordal attachments. Precise morphometric measurements were obtained using digital Vernier calipers for

linear dimensions and flexible thread for curved or irregular surfaces to ensure accuracy.

Parameters Recorded

Detailed observations and measurements were made for the following parameters:

• Papillary muscles: number, shape, number of heads, length, breadth, and thickness.

• Chordae tendineae: total number and individual lengths.

• Annulopapillary distances: measured from the base of each papillary muscle to the corresponding point on

the mitral annulus.

• Mitral valve leaflets and annular circumference: assessed for structural characteristics and morphometric

correlation with papillary muscle configuration.

The present study received ethical approval from the Institutional Ethics Committee of Salem Government

Medical College (Ref No: SGMC/IEC/2024/15903). A detailed Participant Information Sheet was provided

to all participants, and written informed consent was obtained prior to their participation in the study.

Kumar V et al | DOI: 10.65188/nurexus.1034

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Statistical Analysis: Data were analyzed using SPSS v26.0. Means and standard deviations were calculated.

The chi-square test and t-tests were used for categorical and continuous variables, respectively. Pearson

correlation assessed linear associations; significance was set at p<0.05.

Ethical Clearance: The present study received ethical approval from the Institutional Ethics Committee of

Salem Government Medical College (Ref No: SGMC/IEC/2024/15903). A detailed Participant Information

Sheet was provided to all participants, and written informed consent was obtained prior to their participation

in the study.

Results

Table 1: Distribution and Association Between Papillary Muscle Types and Their Number

No. of PM

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.043

Total

Among the 60 cadaveric hearts, most (81.7%) had two papillary muscles. Conical types were most common,

especially in hearts with one or two muscles. Fan-shaped, finger-like, and mixed types were more frequent in

hearts with two or three muscles. The association between muscle number and morphology was statistically

significant (p = 0.043).

Table 2: Distribution of Anterior Papillary Muscle Heads Across Morphological Types

Heads (Ant PM)

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.028

Total

Anterior papillary muscle heads varied by type, with conical forms mostly having one or two heads, while

fan-shaped and mixed types commonly had three. The association was statistically significant (p = 0.028).

Table 3: Distribution of Posterior Papillary Muscle Heads Across Morphological Types

Heads (Post PM)

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.039

Total

Posterior papillary muscle heads showed the highest frequency of three-headed configurations, especially in

finger-like and mixed types. Conical types were more evenly distributed across all headcounts. The

association between morphology and head number was statistically significant (p = 0.039).

Table 4: Presence of Accessory Papillary Muscles

Accessory PM

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.122

Yes

Kumar V et al | DOI: 10.65188/nurexus.1034

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Total

Accessory papillary muscles were found in 15% of hearts, mainly in finger-like and mixed types. They were

uncommon in conical types and absent in fan-shaped. The association was not statistically significant (p =

0.122).

Table 5: Fusion of Papillary Muscle Heads

Fusion

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.192

Yes

Fusion of papillary muscle heads was seen in 18.3% of hearts, more frequently in conical and mixed types. It

was less common in fan-shaped and finger-like types. The association between fusion and muscle

morphology was not statistically significant (p = 0.192).

Table 6: Anterior Chordae Tendineae Number

No. of Chordae

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.046

Total

The number of anterior chordae tendineae varied with muscle morphology. Conical types commonly had 6

chordae, while fan-shaped and mixed types more often had 7. Finger-like types showed a broader

distribution. The association between chordae number and muscle type was statistically significant (p =

0.046).

Table 7: Posterior Chordae Tendineae Number

No. of Chordae

Conical

Fan-shaped

Finger-like

Mixed

Total

p-value

0.033

Total

The number of posterior chordae tendineae showed variation across muscle types. Conical types most

frequently had 6 chordae, while fan-shaped and mixed types showed more even distribution. Finger-like

types commonly had 5 or 6 chordae. The association between chordae number and morphology was

statistically significant (p = 0.033).

Table 8: Mean Dimensions of Papillary Muscles (mm)

Parameter

Conical

Fan-shaped

Finger-like

Mixed

p-value

Length (Ant PM)

18.7 ± 2.3

18.4 ± 2.4

17.6 ± 2.0

18.2 ± 2.6

0.395

Breadth (Ant PM)

8.1 ± 1.3

8.4 ± 2.1

8.0 ± 1.7

8.6 ± 1.3

0.037

Thickness (Ant PM)

5.3 ± 1.0

5.8 ± 0.9

4.9 ± 1.1

5.5 ± 0.8

0.029

Length (Post PM)

16.3 ± 2.0

16.0 ± 2.2

16.0 ± 2.0

15.5 ± 2.3

0.024

The morphometric analysis revealed that the length of the anterior papillary muscle was similar across all

types (p = 0.395). However, significant differences were observed in breadth and thickness, with fan- shaped

and mixed types being broader and thicker (p = 0.037 and p = 0.029, respectively). Posterior muscle length

Kumar V et al | DOI: 10.65188/nurexus.1034

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also showed a significant variation among types (p = 0.024), being slightly shorter in mixed forms.

Table 9: Annulopapillary Distance (mm)

Parameter

Conical

Fan-shaped

Finger-like

Mixed

p-value

Ant PM to LFT

35.7 ± 3.1

34.1 ± 3.0

35.0 ± 4.6

32.7 ± 2.9

0.045

Post PM to RFT

31.6 ± 4.5

31.2 ± 5.3

30.9 ± 3.2

30.4 ± 2.7

0.027

Ant AP Distance

23.9 ± 2.1

22.7 ± 2.0

25.0 ± 0.9

21.9 ± 2.0

0.007

Post AP Distance

22.6 ± 2.6

22.6 ± 1.3

22.5 ± 1.7

23.3 ± 1.6

0.007

The study showed significant variation in measurements across different papillary muscle types. The

anterior PM to LFT distance was higher in conical and finger-like types (p = 0.045), while the posterior PM

to RFT distance was greatest in the conical type (p = 0.027). The anterior AP distance was highest in

finger-like and lowest in mixed types (p = 0.007). Posterior AP distance also varied significantly (p =

0.007). These findings suggest that papillary muscle shape affects their spatial orientation within the left

ventricle.

Discussion

This study investigated the morphological and morphometric characteristics of papillary muscles in the

mitral valve complex using 60 human cadaveric hearts. The conical morphology was the most frequently

observed type (55%), aligning with findings from Choudhary et al. [21] and Suganthy et al. [22], who

described conical papillary muscles as the most common variant in Indian populations due to their

simplicity and efficient chordal support to mitral leaflets. The typical configuration of two papillary

muscles was observed in 81.7% of hearts, consistent with anatomical descriptions and prior studies by

Sharma et al. [23] and Alam et al. [24]. Variations such as single or triple papillary muscles, found in a

smaller percentage, mirror observations by Murthy et al. [25] and Patel et al. [26], highlighting natural

anatomical diversity. The number of papillary muscle heads showed significant association with

morphology. Fan-shaped and mixed types had a higher incidence of three-headed muscles, supporting the

work of Deopujari et al. [27], who emphasized that more complex shapes offer a broader base for chordal

attachments, enhancing valvular mechanics.

Accessory papillary muscles were found in 15% of specimens, mainly in finger-like and mixed types. This

correlates with the 12–16% prevalence reported by Vijayalakshmi et al. [28]. Though not statistically

significant, accessory muscles may influence left ventricular contractility and may be mistaken for

abnormal structures during imaging, as noted by Becker and Anderson [29]. The number of chordae

tendineae also varied significantly across morphologies. Fan-shaped and mixed types commonly had more

chordae, consistent with findings from Yuan et al. [30] and Lam et al. [31], who highlighted the importance

of chordal architecture in maintaining valve competence and preventing prolapse. Morphometric parameters

such as breadth and thickness were significantly higher in fan-shaped and mixed morphologies, which is in

agreement with findings from Hanumanthaiah et al. [32]. These features likely reflect increased structural

complexity and load distribution capacity. The posterior papillary muscle length also varied, with shorter

lengths observed in mixed types.

The annulopapillary distance (APD) differed significantly among muscle types. Longer APDs, particularly

in finger-like forms, could affect leaflet tethering and coaptation. This supports the biomechanical insights

provided by Becker and Anderson [29] and Mehta et al. [33], who noted the role of APD in preserving

mitral valve function and preventing regurgitation. When compared with Western literature, such as the

studies by Yacoub et al. [34] and Standring [35], our data are broadly consistent but demonstrate a slightly

higher incidence of morphological complexity, possibly due to population-specific anatomical traits. From

Kumar V et al | DOI: 10.65188/nurexus.1034

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a clinical perspective, these findings are vital in guiding mitral valve surgeries. As emphasized 3D

echocardiographic imaging benefits significantly from detailed anatomical data, aiding in surgical planning

and reducing intraoperative surprises, particularly in valve repair or artificial chordae placement.

Conclusion

This study revealed significant morphological and morphometric variations in mitral valve papillary

muscles, with the conical type being the most common. Key differences were noted in muscle number,

heads, chordae, and dimensions. These findings are important for accurate imaging, surgical planning, and

improving outcomes in mitral valve procedures.

Conflict of Interest: Nil

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