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Vestigial bands in the left ventricle
Vijaya M. Nayalc,
MS,
Solomon Victor, FRCP
The Heart Institute, Madras, India Background: Echocardiography has rekindled interest in the nature of the left ventricular bands. Aims: Our intention was to document the incidence, course and size of the left ventricular bands in human hearts and to consider the reasons for the existence of the bands. Methods: One hundred normal human hearts were collected at raadom and analysed following autopsy. The left ventricles were opened, bkecting the mural leaflet and carrying the incision up to the apex without dividing any bands crossing the lumen. Results: Left ventricular bands were seen in 55 hearts. A single band was seen in 26 hearts, and multiple bands were seen in 29. When multiple, the bands varied from 2 to 6. Rand length varied from 5 mm to 49 mm, and width from 0.5 mm to 5 mm. Forty-eight bands were tendinous and 60 muscular. One hundred bands originated from the septum of which 64 terminated in the anterior wall, 26 in the lateral wall, 2 in the papillary muscle, 6 in the apex and 2 in the septmn. One band originated and terminated in the anterior wall, and 7 bands comted the anterior wall to the lateral wall. Conclusions: Left ventricular bands occur in normal hearts and vary widely in size, number and location, each heart beii unique. They are phylogenic vestigial remnants of the pathway for the transmission of impulses from the left bundle of His across the lumen of the left ventricle, as seen prominently in bovine hearts. (Asia Pacific Heart J 1997;6(2):121-123) Introduction Variations in the incidence, size, origin and termination of the fibromuscular structures traversing the left ventricular cavity encountered in a study of 100 human autopsy hearts are reported. Papillary muscles and interpapillary connections are excluded.
Table 1. Size of the bands. Dimensions
Number of bands
Length (mm) o-4 5-9
lo- 19 20 - 29 30 - 39 40 - 49
Material and Methods One hundred human autopsy hearts collected at random following autopsy were studied. Age and sex of the deceased were not known. The left ventricle was opened by an incision passing through the middle of the mural leaflet, between the anterolateral and posteromedial chordopapillary support and extended downwards towards the left ventricular apex, ensuring that no fibromuscular bands, excepting interpapillary connections, were divided. All fibromuscular structures other than chordopapillary support and interpapillary connections, which were traversing the lumen of the left ventricle, were analysed.
20 45 20 22
1
Width (mm) 0.5 - 0.9 1.0 - 2.9
16 51 26
3.0 - 4.9
5.0 and above
9
and 7 bands connected the anterior wall to the lateral wall. Their length and width are listed in the table. Discussion This study confirms
the high incidence
of left
ventricular bands crossing the lumen of the left ventricle.’ The incidence of detection of these bands
Results Left ventricular bands were seen in 55 hearts (Table 1). A single band was seen in 26 hearts. Two bands were present in 15 hearts, 3 bands in 8, 4 bands in 4 and 6 bands in 2. Thus, 29 hearts had 2 or more bands. Sixty bands were muscular (Fig. 1) and 48 tendinous. One hundred bands originated from the septum of which 64 terminated in the anterior wall, 26 in the lateral wall, 2 in a papillary muscle, 6 in the apex and 2 in the septum. One band originated and terminated in the anterior wall,
during echocardiography has varied from 0.4 2 to 71%.3
The wide variations in the width, length, and direction of these bands should be borne in mind while imaging the left ventricle.*+3
Diastolic flutter of longitudinal bands has been noted in aortic regurgitation.1 Goebel and Schneider (as quoted by Brenner 1) identified bands in the angiocardiogram. These bands can occur in otherwise normal hearts or coincidentally in association with various congenital or
121
Asia Pacific
Heart J 1997;6(2) Vestigial
Nayak, Victor bands in the left ventricle
Fig. 1. An unusually stout muscular left ventricular band in a human heart, extending from the upper third of the interventicular septum to the baseof the anterolateral papillary muscle.
acquired heart diseases.i.4.5 They could produce a murmur when they become taut due to dilatation of the ventricle,6 especially if they are transverse.’ Oscillation of the band has been documented during echocardiography.’ These bands are possibly related to the evolution of the atrioventricular conducting tissue. Pathways exist in the hearts of invertebrates between the atria and ventricles for conduction of impulses and passage of autonomous nerves.7 In the vertebrates, there is progressive sophistication of these pathways for atrioventricular conduction.7 When the right and left ventricular chambers develop as independent chambers in mammals, the 2 divisions of the bundle of His use bands in either ventricle to reach the papillary muscles across the lumen. The right bundle uses the so-called moderator band as a scaffold and reaches the anterior papillary muscle. Similarly the left bundle sends offshoots across the lumen of the left ventricle through intraluminal bands to reach and activate the papillary muscles. The need for the transluminal passage of the conducting tissue may be related to the sequence of the contraction of the papillary muscles in relation to the rest of the ventricular musculature. Perhaps the papillary muscles need to contract first to tense the chordopapillary support in preparation for the ventricular systole. In the mammals such as the ox and buffalo, the left
ventricular bands are prominent, inverted Y-shaped and consistently carry conducting tissue.8 Gerlis et al s detected left ventricular bands in 42 sheep, 20 horses, 24 cats, 12 dogs, in 23 out of 25 oxen, and in 31 out of 36 pigs. The pattern of the bands was found to vary between species but was fairly constant within each species. Details of the pattern were not described. We find wide variations within the species, such as ox, buffalo, sheep, goat, horse, elephant, rhinoceros and pig in our preliminary studies. It would be of interest to correlate these variations with histopathological and electrophysiological studies. It is interesting that these conducting bands have been inappropriately labelled as ‘moderator bands’ both in the right 9 and left lo ventricles. Leonardo da Vinci, credited with the first drawing of the right ventricular band, also drew left ventricular bands.9 In humans the papillary muscles of the mitrali%ricuspidi2 valves and the moderator band 13 of the right ventricle exhibit countless variations and are as unique as finger prints. When the moderator band is absent or too thin, the right bundle would take alternate routes. Likewise the pattern of left ventricular bands is also unique in each human heart. Obviously these bands are not crucial for conducting the left bundle tissue, since the bands were absent in 45 hearts. When present they may be muscular, tendinous and carry blood vessels. Some of
122
Asia Pacific
Heart J 1997;6(2) Vestigial
these bands may contain Purkinje fibres.4 No wonder these bands have been referred to as telegraph wires.5 Such bands may be responsible, especially when thick and stretched, for premature ventricular contractions and ventricular arrhythmia.3 Or stretched nonconducting bands could disturb Purkinje fibres around their ventricular attachment.3 The bands have also been incriminated in preexcitation.5 Kudoh et al 4 have recorded rate dependent ventricular tachycardia. They postulated that exercise induced tachycardia might decrease tension on the bands and abort the arrhythmia.4 With advances in electrophysiology and imaging, interventional techniques for division of arrhythmogenic bands are likely to be introduced. Some bands may spontaneously rupture. Darazs et al I4 point out the risk of rupturing these bands during catheterisation with potential risk of embolism, conduction disturbance and infective endocarditis. Atypical chest pain, distortion and hour-glass constriction of the left ventricle have been attributed to these bands.14 Darazs et al 14attribute left ventricular bands to the same process leading to the formation of trabeculae cameae and chordae in the left ventricle. In the light of comparative cardiac morphology,7 the left ventricular bands are best considered as vestiges of the bands carrying the left bundle prominent in mammals, especially the bovine species. Obviously with increasing sophistication of the Purkinje system in humans, these bands have become functionally redundant.
Nayak, Victor bands in the left ventricle
References 1.
2.
3.
4. 5.
6. 7. 8.
9. 10. 11.
12. 13. 14.
Subscription
Brenner JI, Baker K, Ringel RE, Berman MA. Echocardiographic evidence of left ventricular bands in infants and children. J Am Co11 Cardiol 1984;3:1515-20. Sethuraman KR, Sriram R, Balachandar J. Left ventricular false tendons: echocardiographic incidence in India and clinical importance. Int J Cardiol 1984;6:385-7. Suwa M, Hirota Y, Kaku K, Yoneda Y, Nakayama A, Kawamura K, Doi K. Prevalence of the coexistence of left ventricular false tendons and premature ventricular complexes in apparently healthy subjects: a prospective study in the general population. J Am Co11 Cardiol 1988;12:910-4. Kudoh Y, Hiraga Y, Iimura 0. Benign ventricular tachycardia in systemic sarcoidosis. Japan Ciic J 1988;52:385-9. Gerlis LM, Wright HM, Wilson N, Erzengin F, Dickinson DF. Ventricular bands - a normal anatomical feature. Br Heart J 1984;52:641-7. Roberts WC. Anomalous left ventricular band - an unemphasized cause of a precordial musical murmur. Am J Cardiol 1969;23:735-8. Robb JS. Comparative basic cardiology. New York: Grune & Stratton, Inc, 1965:349-452. Getty R. Heart and blood vessels. In: Sisson and Grossman. The Anatomy of the domestic animals. 5th ed. Philadelphia: WB Saunders Co, 1975;2: 164-75. Giorgio de Santillana. Leonardo da Vinci. Novara: Grange Books, 1996:369,377,401. Turner W. Another heart with moderator band in the left ventricle. J Anat Physiol 1876; 30: 568-9. Victor S, Nayak VM. Variations in the papillary muscles of the normal mitral valve and their surgical relevance. J Card Surg 1995;10:597-607. Victor S, Nayak VM. The tricuspid valve is bicuspid. J Heart Valve Dis 1994;3:27-36. Ravindran P, Victor S. The moderator band. Indian J Thorac Cardiovasc Surg 1982;1:15-21. Darazs B, Taylor HR, van Gelder AL. The relevance of left ventricular bands. South Afr Med J 1988;74:68-71
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MS,
Solomon Victor, FRCP
The Heart Institute, Madras, India Background: Echocardiography has rekindled interest in the nature of the left ventricular bands. Aims: Our intention was to document the incidence, course and size of the left ventricular bands in human hearts and to consider the reasons for the existence of the bands. Methods: One hundred normal human hearts were collected at raadom and analysed following autopsy. The left ventricles were opened, bkecting the mural leaflet and carrying the incision up to the apex without dividing any bands crossing the lumen. Results: Left ventricular bands were seen in 55 hearts. A single band was seen in 26 hearts, and multiple bands were seen in 29. When multiple, the bands varied from 2 to 6. Rand length varied from 5 mm to 49 mm, and width from 0.5 mm to 5 mm. Forty-eight bands were tendinous and 60 muscular. One hundred bands originated from the septum of which 64 terminated in the anterior wall, 26 in the lateral wall, 2 in the papillary muscle, 6 in the apex and 2 in the septmn. One band originated and terminated in the anterior wall, and 7 bands comted the anterior wall to the lateral wall. Conclusions: Left ventricular bands occur in normal hearts and vary widely in size, number and location, each heart beii unique. They are phylogenic vestigial remnants of the pathway for the transmission of impulses from the left bundle of His across the lumen of the left ventricle, as seen prominently in bovine hearts. (Asia Pacific Heart J 1997;6(2):121-123) Introduction Variations in the incidence, size, origin and termination of the fibromuscular structures traversing the left ventricular cavity encountered in a study of 100 human autopsy hearts are reported. Papillary muscles and interpapillary connections are excluded.
Table 1. Size of the bands. Dimensions
Number of bands
Length (mm) o-4 5-9
lo- 19 20 - 29 30 - 39 40 - 49
Material and Methods One hundred human autopsy hearts collected at random following autopsy were studied. Age and sex of the deceased were not known. The left ventricle was opened by an incision passing through the middle of the mural leaflet, between the anterolateral and posteromedial chordopapillary support and extended downwards towards the left ventricular apex, ensuring that no fibromuscular bands, excepting interpapillary connections, were divided. All fibromuscular structures other than chordopapillary support and interpapillary connections, which were traversing the lumen of the left ventricle, were analysed.
20 45 20 22
1
Width (mm) 0.5 - 0.9 1.0 - 2.9
16 51 26
3.0 - 4.9
5.0 and above
9
and 7 bands connected the anterior wall to the lateral wall. Their length and width are listed in the table. Discussion This study confirms
the high incidence
of left
ventricular bands crossing the lumen of the left ventricle.’ The incidence of detection of these bands
Results Left ventricular bands were seen in 55 hearts (Table 1). A single band was seen in 26 hearts. Two bands were present in 15 hearts, 3 bands in 8, 4 bands in 4 and 6 bands in 2. Thus, 29 hearts had 2 or more bands. Sixty bands were muscular (Fig. 1) and 48 tendinous. One hundred bands originated from the septum of which 64 terminated in the anterior wall, 26 in the lateral wall, 2 in a papillary muscle, 6 in the apex and 2 in the septum. One band originated and terminated in the anterior wall,
during echocardiography has varied from 0.4 2 to 71%.3
The wide variations in the width, length, and direction of these bands should be borne in mind while imaging the left ventricle.*+3
Diastolic flutter of longitudinal bands has been noted in aortic regurgitation.1 Goebel and Schneider (as quoted by Brenner 1) identified bands in the angiocardiogram. These bands can occur in otherwise normal hearts or coincidentally in association with various congenital or
121
Asia Pacific
Heart J 1997;6(2) Vestigial
Nayak, Victor bands in the left ventricle
Fig. 1. An unusually stout muscular left ventricular band in a human heart, extending from the upper third of the interventicular septum to the baseof the anterolateral papillary muscle.
acquired heart diseases.i.4.5 They could produce a murmur when they become taut due to dilatation of the ventricle,6 especially if they are transverse.’ Oscillation of the band has been documented during echocardiography.’ These bands are possibly related to the evolution of the atrioventricular conducting tissue. Pathways exist in the hearts of invertebrates between the atria and ventricles for conduction of impulses and passage of autonomous nerves.7 In the vertebrates, there is progressive sophistication of these pathways for atrioventricular conduction.7 When the right and left ventricular chambers develop as independent chambers in mammals, the 2 divisions of the bundle of His use bands in either ventricle to reach the papillary muscles across the lumen. The right bundle uses the so-called moderator band as a scaffold and reaches the anterior papillary muscle. Similarly the left bundle sends offshoots across the lumen of the left ventricle through intraluminal bands to reach and activate the papillary muscles. The need for the transluminal passage of the conducting tissue may be related to the sequence of the contraction of the papillary muscles in relation to the rest of the ventricular musculature. Perhaps the papillary muscles need to contract first to tense the chordopapillary support in preparation for the ventricular systole. In the mammals such as the ox and buffalo, the left
ventricular bands are prominent, inverted Y-shaped and consistently carry conducting tissue.8 Gerlis et al s detected left ventricular bands in 42 sheep, 20 horses, 24 cats, 12 dogs, in 23 out of 25 oxen, and in 31 out of 36 pigs. The pattern of the bands was found to vary between species but was fairly constant within each species. Details of the pattern were not described. We find wide variations within the species, such as ox, buffalo, sheep, goat, horse, elephant, rhinoceros and pig in our preliminary studies. It would be of interest to correlate these variations with histopathological and electrophysiological studies. It is interesting that these conducting bands have been inappropriately labelled as ‘moderator bands’ both in the right 9 and left lo ventricles. Leonardo da Vinci, credited with the first drawing of the right ventricular band, also drew left ventricular bands.9 In humans the papillary muscles of the mitrali%ricuspidi2 valves and the moderator band 13 of the right ventricle exhibit countless variations and are as unique as finger prints. When the moderator band is absent or too thin, the right bundle would take alternate routes. Likewise the pattern of left ventricular bands is also unique in each human heart. Obviously these bands are not crucial for conducting the left bundle tissue, since the bands were absent in 45 hearts. When present they may be muscular, tendinous and carry blood vessels. Some of
122
Asia Pacific
Heart J 1997;6(2) Vestigial
these bands may contain Purkinje fibres.4 No wonder these bands have been referred to as telegraph wires.5 Such bands may be responsible, especially when thick and stretched, for premature ventricular contractions and ventricular arrhythmia.3 Or stretched nonconducting bands could disturb Purkinje fibres around their ventricular attachment.3 The bands have also been incriminated in preexcitation.5 Kudoh et al 4 have recorded rate dependent ventricular tachycardia. They postulated that exercise induced tachycardia might decrease tension on the bands and abort the arrhythmia.4 With advances in electrophysiology and imaging, interventional techniques for division of arrhythmogenic bands are likely to be introduced. Some bands may spontaneously rupture. Darazs et al I4 point out the risk of rupturing these bands during catheterisation with potential risk of embolism, conduction disturbance and infective endocarditis. Atypical chest pain, distortion and hour-glass constriction of the left ventricle have been attributed to these bands.14 Darazs et al 14attribute left ventricular bands to the same process leading to the formation of trabeculae cameae and chordae in the left ventricle. In the light of comparative cardiac morphology,7 the left ventricular bands are best considered as vestiges of the bands carrying the left bundle prominent in mammals, especially the bovine species. Obviously with increasing sophistication of the Purkinje system in humans, these bands have become functionally redundant.
Nayak, Victor bands in the left ventricle
References 1.
2.
3.
4. 5.
6. 7. 8.
9. 10. 11.
12. 13. 14.
Subscription
Brenner JI, Baker K, Ringel RE, Berman MA. Echocardiographic evidence of left ventricular bands in infants and children. J Am Co11 Cardiol 1984;3:1515-20. Sethuraman KR, Sriram R, Balachandar J. Left ventricular false tendons: echocardiographic incidence in India and clinical importance. Int J Cardiol 1984;6:385-7. Suwa M, Hirota Y, Kaku K, Yoneda Y, Nakayama A, Kawamura K, Doi K. Prevalence of the coexistence of left ventricular false tendons and premature ventricular complexes in apparently healthy subjects: a prospective study in the general population. J Am Co11 Cardiol 1988;12:910-4. Kudoh Y, Hiraga Y, Iimura 0. Benign ventricular tachycardia in systemic sarcoidosis. Japan Ciic J 1988;52:385-9. Gerlis LM, Wright HM, Wilson N, Erzengin F, Dickinson DF. Ventricular bands - a normal anatomical feature. Br Heart J 1984;52:641-7. Roberts WC. Anomalous left ventricular band - an unemphasized cause of a precordial musical murmur. Am J Cardiol 1969;23:735-8. Robb JS. Comparative basic cardiology. New York: Grune & Stratton, Inc, 1965:349-452. Getty R. Heart and blood vessels. In: Sisson and Grossman. The Anatomy of the domestic animals. 5th ed. Philadelphia: WB Saunders Co, 1975;2: 164-75. Giorgio de Santillana. Leonardo da Vinci. Novara: Grange Books, 1996:369,377,401. Turner W. Another heart with moderator band in the left ventricle. J Anat Physiol 1876; 30: 568-9. Victor S, Nayak VM. Variations in the papillary muscles of the normal mitral valve and their surgical relevance. J Card Surg 1995;10:597-607. Victor S, Nayak VM. The tricuspid valve is bicuspid. J Heart Valve Dis 1994;3:27-36. Ravindran P, Victor S. The moderator band. Indian J Thorac Cardiovasc Surg 1982;1:15-21. Darazs B, Taylor HR, van Gelder AL. The relevance of left ventricular bands. South Afr Med J 1988;74:68-71
Fmu
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to: The Asia Pacific Heart PO Box 348, Prahran, Victoria, 3181 Aushalii
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Pacific
q
Heart
VISA
Journal)
0
is automaticalb of Cardiac
sent and
. ... .. .. .. .. . .. .. .. . ... .. .. .. .. .. ... . ... .. .. .. .. .. ... .. .. . . .. .. .. ... .. .. .. .. .. .. .. .. .. ... .. .. . .. .. .. ... . .. ... .. .. .. .. .. . . .. .. . .._
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Signature.. Expiry
123
. .. .. .. . ... .. .. . .. .. ... . .. . ... . . .. .. .. . . .. . . .. .. .. .. . Date ..,.........................................................