Abdullah N. M, Hazza M. A, Mohamed A. K. Q. Ventricular False Tendons in Human Hearts ,An Autopsy Study of the Incidence ,Morphology ,Histology and Distribution in Basrah City;12(4).

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Manuscript received on :13-04-2019
Manuscript accepted on :29-12-2019
Published online on: 28-12-2019

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Nawal  Mustafa Abdullah^1*, Mazin Abed Hazza² and Abdul Kareem Qasim Mohamed³

¹Department of Human Anatomy, Basrah Medical College, University of Basrah , Iraq

²Department medicine /cardiology, Basrah Medical College, University of Basrah, Iraq

³Department Pathology and Forensic medicine / Basrah  Medical College, University of Basrah, Iraq

Corresponding Author E-mail: nawal.abdullah@uobasrah.edu.iq

DOI : https://dx.doi.org/10.13005/bpj/1848

Abstract

The left ventricular false tendons (LVFTs ) are fibrous or fibromuscular bands crossing the left ventricle in human hearts ,they arise  mainly from the ventricular septum to the free wall or to a papillary muscle .They are  considered as normal anatomical variant with    different  numbers, location and type. LVFTs  had been associated with many clinical  studies and discussions  regarding  their function . Literatures were reviewed and their  incidence ,morphology , histology and clinical correlation  were discussed .This study was intended to evaluate the existence   LVFTs   in  Basrah city  , and to compare the findings with other  data verified in literatures. A prospective autopsy  study of  the prevalence  and  morphology   of LVFTs in 215 cadaveric human hearts was performed  to estimate  the number ,types and location .of these bands .10 out of 215 samples were undergo routine histopathological processing to obtain 4 micrometer thickness slides stained  with hematoxylin and eosin and  examined for histological characteristics  . LVFTs of varying number, types  and different attachment  were recorded  in 62 (  28.8% ) of 215 adult human cadaveric hearts studied. A complete morphologic assessments  were done. No significant  differences was found  regarding age or gender. , Majority  of LVFTs are single ,  commonly between  the  ventricular septum  and  papillary muscle .Fibrous  and fibro muscular type is predominant . In our community false tendons are frequent  anatomic variants of normal human LV which may be identified at routine examination  and should not be mistaken as pathologic structures such as flail chordae tendineae or thrombi,  further radiological and clinical  studies are suggested  to ensure their role and function .

Keywords

ventricular false tendons; incidence; morphology

Left ventricular false tendons (LVFTs) are isolated cordlike  filaments of tissue  that traverse  the cavity of  the  left ventricle , they are attached to  the ventricular septum ,  extending from the septum to the free wall  ,or from the septum to the papillary muscle , from a papillary muscle to the free wall ,or  between papillary muscles  ^{1,2 .} These bands  are not found at all  human hearts and considered within normal anatomical variations . Many identify  them  as intra cavity radiations of bundle of His  ^3,4. They are first reported by Turner at 1893 who incidentally found  these fascinating structures  at  autopsy  ⁵, Later, a series of morphological  studies have widely  explored the anatomic criteria  of them  in several mammalian species ^6-9

LVFTs  have various   numbers, length and thickness, they could be  single , multiple or branched , small multiple filaments  at the junction of the septum with the free wall  were considered an  apical network  ^10,11. Most of these tendons  were fibrous, or  fibro muscular and sometimes they contain conducting  fibers   ^12,13  The incidence  of FTs in human has been rising with technical improvements,. The LVFTs  nowadays become a common finding especially with the submission of ultrasound diagnostic instruments  primarily with the use of routine 2-dimensional echocardiography recommended in human patients for     different  cardiac conditions. Nishimura  supplied  the first paper using echocardiography to demonstrate LVFTs in 1981  ¹⁴.

Prior to the introduction of cardiac ultrasound, FTs in humans were identified at autopsy The earliest morphological studies recorded  rates of 0.5% whereas recent  investigations have achieved up to 78% in human and  95% of animal hearts .Other articles describe a range in 40-60% of examined hearts ¹⁵ .In a pathology study by Grzybiak et al  , the prevalence was about 40% and it was similar across all age groups.¹⁶  Loukas et al  reported  the prevalence in a series of 200 gross pathology specimens to 62%… The results reported in  literatures varied widely mainly because of the different methodologies and study designs ,age , race varieties, additional heart abnormalities and new equipment’s  used  .The embryogenetic origin of FTs was not fully elucidated , the most probable mechanism believed to involve displacement of conducting fibers into the LV lumen. In microscopic studies, the false bands  consist of fibrous tissue, cardiomyocytes, blood vessels; they may also contain conducting fibers pertaining to the left branch of the His bundle ^17,18

LVFTs are considered by many  as  benign anatomical variants  . Recent    morphologic studies have focused on the clinical importance of these bands ,several studies have indicated that they might have a pathophysiologic role in ventricular geometric anomalies. Increased prevalence of innocent precordial murmur and ventricular arrhythmias in humans, giant inverse T waves and left ventricular hypertrophy evident on resting electrocardiograms  and pre-excitation mitral regurgitation  considered to have   possible relationship with  these bands   ^19-26. No previous studies on LVFTs   in local participant of Basrah city  was done before .

Aim

The present study  directed to describe   the prevalence and characteristics of LVFs as normal anatomical variant and to estimate a prognostic significance of  these structures  and their role in clinical cardiac manifestations .

Materials and Methods

Anatomical  study

The present work was enrolled during the period extended from March 2018 –  December    2018  at  forensic medicine department in  Basrah with full  ethical approval obtained . Two hundred  fifteen   human hearts were examined  from cadavers for actual prevalence of LVFTs  . The age ranged from 18-71yrs, gender distribution  were 151 men (70.2%)  /  64 women (29.8%) . Children , individuals   below 18 years and those with  obvious  heart  problems were excluded .

The normal hearts were cleaned of surrounding tissue and left ventricular chamber was opened. A scalpel incision on the lateral wall of left ventricle was made  to visualize the interior and FTs. The number and  location of these tendons were examined  and  identified as isolated fibrous or fibromuscular bands  crossing the left ventricular cavity with no attachment to the atrioventricular valve ,they extend from a papillary muscle to the septum, or from a papillary muscle to the free wall, between papillary muscles, or from the septum to the free wall. The location of each band was described according to their  points of attachment . The number was recorded  as  single ,multiple or branched and the type  of the band  like   fibrous , fibromuscular or muscular is  described .

Histological study 

Visible false tendons  from 10 of total 215 dissected hearts were examined   for histopathological examination  , 2-3 mm thickness tissue samples were  preserved  in 10% NBF and embedded in paraffin blocks .Sections of 4 micrometer thickness were stained with hematoxylin-eosin stain and examined under light microscope. A microphotographs at 10, 20, and 40 by using Elica camera were  obtained  .Data were collected, tabulated and statistically analyzed by  a quantitative morphological assessment  using  ( version 21 ,SPSS,INC., Chicago ,Illinois ,USA ) and Pearson Chi-square   test for qualitative data verification . P≤ 0.05 was considered  statistically significant at  all tests

Results

Morphological study

Data  collected  for 10  months with  total 215 human hearts.  Age ranged  from 18-71yrs   with mean age 36  years  ± 14.9 . Male to female  ratio was 2.4 : 1 . LVFTs found    in   62  ( 28.8%) out of 215  hearts . ( Table  1 and  Diagram 1) .

Table 1 :  LVFTs  percentage according to total number

Diagram 1: LVFTs   percentage   Click here to View figure

Regarding gender   ,no of positive cases in male  was 39 ( 25.8%)  out of 151 male and in  female was  23 ( 35.9%) out of 64 female , Male to female ratio was 2.4 / 1 . No significant  difference was detected between M\F.(P value  n.s (Table 2 and Diagram 2  ).

Table 2 : Male to Female ratio and % of positive LVFTs

P value = n.s.

Diagram 2 : LVFTs  distribution according to gender     Click here to View figure

Regarding number  of bands ; the majority were single ( 53.2% )  followed by multiple bands ( 29.% ) . Multiple branching  bands are less  common with only 17.7%  . A  significant difference found   between number  of bands  with significant p v( 0.000  ) (Table 3 ,Diagram  3 and Figure  1a, b, & c )

Results showed that false tendons    were located  frequently between  papillary muscle and the ventricular  septum ,P-S (41.9%) ,followed by  FTs between ventricular septum and the free wall  S-F type  ( 24.2%) . Many  attachments  are combined and  connect  more than one point like  papillary muscle to a papillary  muscle to the septum  PP-PS  (8.1%) ,or false tendons  from papillary muscle to ventricular septum , to the free wall or to a papillary muscle PS-,P-F,P-P, ( 6.5%) .few no  include false tendons  between papillary muscle to the septum to the free wall P-S,P-F( 1.6%) .Significant p-value (0.000) was detected(Table3,Diagram 4&Fig 2 a &b) .

This study  found  that the commonest   type  was the  fibrous  ( 66.1%) , followed by fibro muscular type ( 33.9%)   while muscular type  was uncommon . Significant P value was detected    (0.000 ) (Table 3 ,Diagram 5 & Figure 3 a , b) .

Table 3: % of  LVFTs  regarding No of bands ,site and  type

Diagram 3: LVFTs in relation to number .   Click here to View figure

Figure 1: Number of bands . a Single. b  Multiple  & c  Multiple-branched .   Click here to View figure

Diagram 4: LVFTs according to site.   Click here to View figure

Figure 2: A, LVFs from papillary muscle to the septum(P-S) .B from papillary muscle to  a papillary muscle (P-P)  and P value ˂ 0.05   Click here to View figure

Diagram 5: LVFTs and type of bands   Click here to View figure

Figure 3:  LVFTs ,a- Fibrous type, b- Fibromuscular type.   Click here to View figure

Histopathological study

The histological examination  showed cardiac  muscle tissue in different proportions ,cardiomyeocytes, ,conductive and connective tissue fibers   , and  abundant blood vessels  . The fibromuscular type showed muscular  and fibrous tissue  crossed  by small branches of coronary arteries.   ( Fig 4 , a, b, c , & d)

Figure 4: (a) and (b) Cardiac muscle fibers (10x & 40x) .  (c)  and  (d) Blood vessels with connective &conductive  tissue (40x).   Click here to View figure

Discussion 

Various different terms have been used to describe left ventricular bands, these include; aberrant left ventricular chordae or anomalous, left ventricular chordate tendinae or tendinal cords, false chordae,  false tendons,  muscular strands,    anomalous left ventricular bands, moderator bands and septomarginal trabeculae  ^{2, 15, 26-29}.

The high incidence of LVFTs  have raised questions  about their possible role in the malfunctioning of the heart. Many  morphologic studies indicate that there could  be a relationship between their existence and physiologic heart problems  such as heart murmurs, arrhythmias or premature ventricular complexes. False tendons can be associated also  with ventricular septal defects, a bicuspid aortic valve and coarctation of the aorta ^30,31  , their functional significance remain largely unexplored till the establishment of the echocardiography which focus on these structures. From embryological point of view these ventricular bands have no obvious embryology ,it may be considered as  an extension of the cardiac conduction system into the left ventricular cavity, It was found that many of these bands bear some similarity to chordae tendinae of mitral valve with similar mode of embryological origin ,the difference is they are not connected to the papillary muscles ³²  . From developmental point of view these  tendons were thought to have been derived from the inner muscle layer of the primitive heart ³³ ;such a relation usually need more detailed morphological and clinical studies with more attention  for these normal variants recently. In some of these tendons , few conductive tissue components found to be connected to the branch of bundle of His ,which support the idea of their role in the heart arrhythmias ^17,26.

Previous studies found that both pathological and echocardiographic studies have controversy about their prevalence, morphology and clinical significance . The current study is the first to be done in Basrah city and demonstrates a lower incidence of LVFTs  ( 28.8%)  and this differ s from what Luetmer et al reported,he found that  FTs exist  in 55% of normal humans, while   Gerlis et al. found them in 46%. These investigators also reported that most of the bands extended between the papillary muscles and the interventricular septum., another study found left ventricular bands in 47% of the 28 human hearts examined, located primarily between the interventricular septum and free wall ³⁴ . In the present study the results demonstrate no significant difference between male and female while there is a significant difference found regarding the number of these bands ; majority are single, located mainly between the septum to the papillary muscle or between the septum to the free wall and usually composed of fibrous bands , this agrees with most studies done on LVFTs which emphasize on their anatomical bases . the differences detected in morphologic studies in humans could be  due to differences  in  the thickness criteria of these bands or may could be due to race  or methodology used ^{35, 36}  , the most probable mechanism is believed to involve displacement of conducting fibers into the LV lumen ,they are considered  to be a part of the conduction system that causes excess tension in the Purkinje fibers in the septum, thus irritating arrhythmia ^37,38

Histopathological examination showed that  FTs are mainly formed of cardiac muscle fibers , connective and conducting tissues, thick bands are composed of thickened endocardium with myocardial tissues that have all the features attributable to myogenic conducting tissues identical to that seen in the bundle of His . It is not clearly known whether these bands are functionally different although some studies correlate their presence with implication in cardiac arrhythmias^, Because of the presence of muscular and conductive tissues ,it can be assumed that their contraction may effect electrophysiologic changes , this may explain their usual existence in subjects with innocent cardiac murmurs compared with normal subjects, However, such causation need further expanded clinical studies to achieve a clear understanding of a relationship between the morphology of left ventricular bands and the clinical presentation.

Conclusion

This study provided suggestions that:

LVFTs In Basrah population can be identified at all age groups and both genders . Majority were found between   interventricular septum and papillary muscles with single appearance mostly and frequently as fibrous type .

LVFTs are common anatomical variants ,their prevalence is evaluated and compared with that reported in many published data of different populations .

Knowledge of the morphology and existence of these bands  may be helpful to link them  with  cardiac murmurs and arrhythmias , beside it may minimize difficulties and critical points which are faced  while  introducing devices in the left ventricular catheterization.

Acknowledgements

Authors are grateful  to forensic medicine department staff for their help

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