Muscular Band Research Articles

Histological examination of the chaetognathan morphological structure in the region of a supposed trunk-tail septum

A histological examination was conducted based on sections done in series in transverse and longitudinal directions of Aidanosagitta macilenta (Sagittidae, Chaetognatha) in a region which includes the anterior parts of the testes and the posterior part of the ovaries. We found that, in mature individuals (the 4th stage of maturation), the anterior parts of the testes are located in front of the posterior part of the ovaries. The anterior parts of the testes have a ventral position adjoining the ventral muscular bands. The ovaries are located more dorsally than the testes at the level of lateral fi elds. A transverse trunk-tail septum between testes and ovaries was not revealed. These data support an idea that a structure which was earlier treated as a tail-trunk septum is actually the anterior edges of the testes. Both longitudinal coelomic cavities continue into the tail region without any transverse septa. The paired tail cavities as can be seen from their composition and functions represent the testes consisting of a peripheral compact portion with undifferentiated germ cells and a space where the maturation of cells occurs. The tail is distinguished anatomically as a post-anal portion of the body but it is not a true segment as it is not separated from a trunk part of the body by the trunk-tail septum. The body of Chaetognatha consists of two true parts (segments). A mesenterial septum divides the body longitudinally-symmetrically from a trunk-head septum down only to the caudal end of the gut. In the tail region there is a medial septum formed by the medial walls of testes. Gonads in both females and males do not have any duct connecting them with a gut cavity. The ovaries and the testes are covered by a coelomic lining and a duct between the ovaries and the testes is absent.

Repaired tetralogy of Fallot in the adult: monitoring and management

Tetralogy of Fallot (ToF) is the most common cyanotic congenital heart disease (CHD). The history of surgical treatment of ToF is closely linked with the origins of cardiac surgery. Before...

Aneurysm of the right ventricular outflow tract after surgical repair of Tetralogy of Fallot: three-dimensional computed tomography findings

A 31-year-old man was admitted for catheter ablation of ventricular tachycardia (VT). He had undergone a surgical repair of Tetralogy of Fallot (TOF) at 6 years, including ventricular septal defect closure, right ventricular outflow tract (RVOT) widening by excision of muscular bands, and application of an autologous pericardial patch (28 × 30mm). A 12-lead surface electrocardiogram showed …

The Myocardial Band

Francisco (Paco) Torrent-Guasp, a Spanish cardiologist working in De'nia, Alicante, discovered that the complex structure of the ventricular myocardium is due to a double-loop helical orientation of a single muscular band that extends from the pulmonary artery to the aorta, with a 180-degree twist in its middle part. He predicted the twist-untwist motion of the ventricles and suggested that this is due to agonist-antagonist mechanics of the ventricular band segments.

Substrates for intra-atrial and interatrial conduction in the atrial septum: Anatomical study on 84 human hearts

Technical developments in the management of atrial arrhythmias revived interest into the detailed knowledge of atrial anatomy. The atrial septum (AS), known for its complex structure, has been particularly difficult to study, and our knowledge of the muscular bundles providing routes for intra-atrial and interatrial conduction within the AS remains limited. The purpose of this study was to describe myocardial arrangement within the AS and adjacent parts of atrial walls for delineation of possible substrates for interatrial and intra-atrial conduction. Human heart specimens from 84 postmortem studies were studied using conventional morphometric assessment, blunt dissection, and light microscopy of serial histological sections of AS. Interatrial muscular connections are present anteriorly, posteriorly between right pulmonary veins, and inferiorly between the coronary sinus and the right inferior pulmonary vein. The inferior connections can be more prominent than the Bachmann bundle. Atrial musculature in the fossa ovalis consists of muscular bands isolated by fatty tissue from the endocardium of the right and left atrium. They are arranged along the anterior-posterior axis and have connections with left atrial myocardium. Myocardial fascicles in the posterior-inferior and superior portions of the muscular rim of fossa ovalis originate on the right atrial side and can be traced toward the atrioventricular node. The general myocardial arrangement in the AS and adjacent regions of atrial walls are important for understanding propagation of atrial activation for selection of the optimal treatment strategy.

From Vision to Mission in Myocardial Restoration

What do myocardial restoration and hyperspace theory have in common? The usual perception of tissue engineering, the fl edgling new science, is of an art in 3 dimensions aimed at the reproduction of natural tissue in terms of structure and function. However, in the case of the heart, more than 3 dimensions need to be realized: the 4 th is the heart rhythm, and the 5 th is the contractile action and mechanics. Any ambitious attempt to manufacture cardiac muscle will have to address some unique issues if the product is to be one of high fi delity to nature. In the following, some important aspects of myocardial restoration will be discussed. Some 10 years ago, aspiring tissue engineers and heart surgeons such as us, stood up and stated that Homo sapiens would be producing the fi rst bioartifi cial left heart chamber within the decade. Unfortunately this prediction has proven premature, if not naive. This is for obvious reasons. First, the heart is a highly asymmetric organ. The architecture of the diverse portions of the heart differs from site to site. The left ventricle is built differently from the right, and fulfi lls its function on a different scale. Furthermore, the form of the heart is not that of a simple sphere. Would it be so, then the maximal possible ejection fraction would not exceed 15%. The heart comprises a helix of uniquely arranged muscular bands (Torrent-Guasp bands), overlaying each other at an angle of approximately 60°. 1 During systole, the heart functions as a vortex, thereby exploiting the maximal power possible from the muscular elements. These unique properties have not even been addressed so far by tissue engineering. All constructs without exception have been built in a symmetric fashion. With the available technology, it may be possible to produce a 3-dimensional graft that is shaped with 3 overlying layers and can be excited to twist as a vortex, but the idea has not been approached systematically so far. What has been achieved in the recent past is a mixture of collagen scaffolds and cells, and some 2-dimensional mechanical training of the constructs. 2

Accessory muscles in the lower part of the anterior compartment of the arm that may entrap neurovascular elements

The aim of this study was to evaluate the incidence of abnormal muscular bands of the anterior compartment of the arm that may compress the median, the ulnar, and the medial antebrachial cutaneous nerve as well as the brachial artery and vein, thus causing entrapment at and above the elbow. A total of 56 adult cadavers were studied during routine dissections that occurred in our laboratory. In the 112 upper limbs studied, we found three variant muscles of the flexor compartment of the arm (2.68%) entrapping nerves and vessels. The first muscle was emerging from the tendon of long head of biceps brachii and coracobrachialis muscle insertion. The second muscle inserted partially into the belly of biceps brachii and should be considered as a supernumenary head of biceps brachii. The third muscle, in fact, represents an accessory fascicle of the brachialis muscle that is an embryonic remnant of that muscle. A number of structures cross anterior to the median, ulnar, and medial antebrachial cutaneous nerve as well as the brachial artery and vein. Compression of nerves and vessels may be caused by additional muscular bundles that pass anterior to these structures. These additional muscular bundles arise either from the brachialis, coracobrachialis, or biceps brachii muscle. Such variations have clinical implications and should be considered in patients, with a high median or ulnar or medial antebrachial cutaneous nerve paralysis with symptoms of lower brachial artery or brachial vein compression.

An Association of Persistent Left Superior Vena Cava with Cribriform Secundum Atrial Septal Defect and A Long Muscular Band in The Right Atrium

We describe a case of an association of persistent left superior vena cava with cribriform secundum atrial septal defect and a long muscular band in the right atrium.

Ebstein's Anomaly: anatomo-echocardiographic correlation.

ObjectiveThe aim of this investigation is to demonstrate that in Ebstein's Anomaly (EA) the right ventricle (RV) is affected in its three portions and to establish an anatomoechocardiographic correlation between the anatomic features and the equivalent echocardiographic images.MethodsThirty hearts with EA were studied. The alterations of each portions of the RV were described. Fifty adult patients with this anomaly were studied by echocardiography.ResultsAnatomy: All hearts had atrial situs solitus, 27 had concordant atrioventricular connection and 3 discordant, of these 2 had transposition of the great arteries (TGA) and one double outlet right ventricle (DORV). The degree of tricuspid valve (TV) displacement showed a spectrum from I to III. The inlet of the RV was markedly thin in 27. The trabecular portion had multiples muscular bands in all. The outlet portion was dilated in 20 and stenotic in 5. In 25 atrial septal defects were found. Echocardiography: All patients had atrial situs solitus, 42 with concordant atrioventricular connection and 8 with discordant, of these last patients 5 had TGA and 3 DORV. The degree of TV displacement varied from I to III. The inlet of RV was markedly thin in 42. The trabecular portion had muscular bands in 45. The outlet portion was dilated in 31 and stenotic in 11. In 30 atrial septal defects were found.ConclusionThe EA affects the whole RV and the anatomoechocardiographic correlation provides an appropriate understanding of echocardiographic images in terms of a precise diagnosis, therapeutic decisions and prognosis.

Left ventricular noncompaction and mid-caviter narrowing associated with Ebstein's anomaly: Three-dimensional transthoracic echocardiographic image

An 50 year-old asymptomatic female was admitted to preoperative cardiovascular evaluation for noncardiac surgery. Two-dimensional transthoracic echocardiography demonstrated that left ventricular dimensions and ejection fraction were normal. The mitral valve was normal both in morphology and function. The attached margin of septal and anterior leaflet of the tricuspid valve was apically displaced. But right ventricle and right atrium dimensions were normal, and Doppler interrogation showed a slight tricuspid regurgitation. Two and three-dimensional transthoracic echocardiography showed prominent numerous trabeculations in the left ventricular apex. Colour flow Doppler studies confirmed the presence of blood flow within the trabeculations. Multi-plane three-dimensional transthoracic echocardiography showed a muscular band leading to left ventricular mid-caviter narrowing. Pulse wave Doppler echocardiography demonstrated that no intraventricular gradient existed. Ventricular noncompaction associated with Ebstein's malformation has been reported. But left ventricular noncompaction and mid-caviter narrowing associated with Ebstein's anomaly have not been reported so far.

Sustained monomorphic ventricular tachycardia associated with unrepaired double-chambered right ventricle

Double-chambered right ventricle (DCRV) is a congenital anomaly characterized by the division of the ventricular cavity into two chambers separated by an abnormal hypertrophied muscular band or by severe hypertrophy of the muscle wall. Two adult patients with a diagnosis of DCRV presented sustained monomorphic ventricular tachycardia. In both cases, the clinical tachycardia was induced with programmed stimulation. After surgically resecting, the muscular band tachycardia could no longer be induced in the patient who underwent follow-up electrophysiological study. The outcome was favourable; there was no clinical recurrence of ventricular tachycardia in the two patients at 48 and 36 months, respectively.

Structure/function interface with sequential shortening of basal and apical components of the myocardial band

To study the sequential shortening of Torrent-Guasp's 'rope-heart model' of the muscular band, and analyze the structure-function relationship of basal loop wrapping the outer right and left ventricles, around the inner helical apical loop containing reciprocal descending and ascending spiral segments. In 24 pigs (27-82 kg), temporal shortening by sonomicrometer crystals was recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. The predominant shortening sequence proceeded from right to left in basal loop, then down the descending and up the ascending apical loop segments. In muscle surrounded by the basal loop, epicardial muscle predominantly shortened before endocardial muscle. Crystal location defined underlying contractile trajectory; transverse in basal versus oblique in apical loop, subendocardial in descending and subepicardial in ascending segments. Mean shortening fraction average 18+/-3%, with endocardial exceeding epicardial shortening by 5+/-1%. Ascending segment crystal displacement followed descending shortening by 82+/-23 ms, and finished 92+/-33 ms after descending shortening stops, causing active systolic shortening to suction venous return; isovolumetric relaxation was absent. Shortening sequence followed the rope-like myocardial band model to contradict traditional thinking. Epicardial muscle shortened before endocardial papillary muscle despite early endocardial activation, and suction filling follows active systolic unopposed ascending segment shortening during the 'isovolumetric relaxation' phase.

Morphological and functional evidences of the helical heart from non-invasive cardiac imaging☆

The non-invasive study of cardiac mechanics has been improved after the recent introduction of advanced magnetic resonance and echocardiographic imaging techniques. Tagged and diffusion-sensitive cardiac magnetic resonance allows the study of myocardial torsion dynamics as well as the anatomical disposition of myocardial fibers. Local myocardial strain and synchronicity of myocardial contraction can also be determined with Doppler tissue imaging (DTI) echocardiography. Published results with these techniques demonstrate a mechanical behavior that is a consequence of a myocardial helical fiber orientation and strongly support the evidence of the double-loop single muscular band model described by Torrent-Guasp.

The sequence of regional ventricular motion

The chronology of electrical events that mechanically activate the myocardium has been described as initiating at the level of the septum, spreading to the apex, then to the bodies of both ventricles and eventually to the base of the heart (apex-to base activation). It has recently been suggested that the myocardium is a single muscular band that conforms a double-loop helicoid. Contraction of the myocardium would follow the trajectory of the muscular fibers that originate at the pulmonary artery towards the body of the left ventricle and to the aorta (base-to apex contraction). This would explain the movements of the base of the heart and the twisting motion of the ventricles seen at magnetic resonance studies. Temporal Fourier analysis of equilibrium radionucleide angiocardiography, by studying the topography of the regional myocardial mechanical displacement corresponding to the wave front of electro-mechanical activation, provides information on the sequence of regional ventricular contraction was used in 29 normal individuals to observe the sequence of myocardial motion. Analysis disclosed that the base of the heart first moves (right then left ventricle) and mechanical movement later descends to involve the apex and the septum. These findings are in concordance with the proposed activation of the helical myocardium and open the way to more complex studies. Although electrical activation of the myocardium (QRS complex) follows a septum-apex-body-base of the left ventricle sequence, mechanical activation follows a base-to-apex sequence. This is likely to be related to anisotropic propagation of the electromechanical stimulus throughout the myocardial band once the electrical stimulus has been delivered at the base of the heart.

Double chambered right ventricle

Two patients, a 31-year-old man and a 29-year-old man, were admitted to our hospital for further evaluation of heart murmur and exertional dyspnoea. In addition to abnormalities on their chest radiographs and electrocardiograms suggestive of right ventricular overload, two-dimensional Doppler echocardiography revealed enlarged right atrium with severe tricuspid regurgitation, aberrant muscular bands of the right ventricle but no definitive left ventricular abnormality in the patients. MRI clearly demonstrated anomalous muscle bundles that transected the right ventricle from a free wall to ventricular septum, resulting in division of the right ventricle into two chambers (left panels: A, transverse section; B, coronal section).

Tricuspid Valve Repair for Ebstein's Anomaly

E bstein's anomaly is a malformation of the tricuspid valve and right ventricle that is characterized by a spectrum of several features which include: 1) adherence of the tricuspid leaflets to the underlying myocardium (failure of delamination); 2) downward (apical) displacement of the functional annulus (septal > posterior > anterior); 3) dilation of the portion of the right ventricle with variable degrees of hypertrophy and thinning of the wall; 4) redundancy, fenestrations, and tethering of the anterior leaflet; and 5) dilation of the right atrioventricular junction (true tricuspid annulus). 1 With increasing degrees of anatomic severity of malformation, the fibrous transformation of leaflets from their muscular precursors remains incomplete, with the septal leaflet being the most severely involved and the anterior leaflet being the least severely involved. This results in a downward displacement of the hinge point of the posterior and septal leaflets in a spiral fashion below the true annulus. The tricuspid leaflets are usually bizarre and dysplastic, and are tethered by short chordae and papillary muscles or attached to the underlying myocardium directly by muscular bands. Chordae may be few to absent, and leaflet fenestrations are common. The spectrum of severity is variable, and no two hearts with the malformation are exactly alike. In the most severe cases, the septal leaflet is only a ridge of fibrous tissue that originates below the membranous septum and is directed toward the apex. There are varying degrees of delamination of all three leaflets. While the anterior leaflet is the most likely to have some degree of delamination, it may also be severely deformed so that the only mobile leaflet tissue is displaced into the right ventricular outflow tract. The malformed tricuspid valve is usually incompetent, but it may occasionally be stenotic or, rarely, imperforate. In less severe cases, the anterior leaflet may form a large sail-like intracavitary curtain; this structure forms the basis of tricuspid valve repairs. A littlementioned characteristic of the anterior leaflet that is critical to most tricuspid valve repairs is the presence of a free leading edge. The leading edge of the anterior leaflet can be free and mobile (no attachments to underlying endocardium), have hyphenated attachments (focal, segmental direct attachments to the underlying endocardium), or linear direct attachment (entire leading edge is attached to the endocardium). 2 In each case, there can be partial or complete delamination of the remaining portion of the leaflet. In the absence of a free leading edge, suboptimal repairs have been achieved. The atrialized ventricle is characteristically thinned and dilated, but careful observation shows that the entire wall of the right ventricle, both proximal and distal to the abnormal insertion of the tricuspid leaflets, including the infundibulum, is also dilated. Dilation of the right ventricular wall is associated not only with thinning of the wall, but also with an absolute decrease in the number of myocardial fibers. 3 The atrioventricular node is located at the apex of the triangle of Koch, and the conduction system is in its normal position. Atrial septal defect and other associated anomalies are common. A biventricular repair is usually possible. Adjunctive use of atrial fenestration or a bidirectional cavopulmomary shunt is controversial; neither is used routinely in our practice. We occasionally use bidirectional cavopulmonary shunt selectively when the right ventricle is severely dilated and functioning poorly. Since concomitant left ventricular dysfunction may be present when the right ventricle fails, it is important to document by direct pressure measurements that the pulmonary arterial and left atrial pressures are low; otherwise, the bidirectional cavopulmonary shunt will not be feasible. In some circumstances when significant left ventricular dysfunction has occurred, cardiac transplantation may be the best option.

Discrete subaortic stenosis: incidence, morphology and surgical impact of associated subaortic anomalies

Background The association between discrete subaortic stenosis and other subaortic anomalies is a well known but rarely reported occurrence. The aim of this study is to define the incidence, morphology, and surgical impact of associated anomalies of the left ventricular outflow tract in children operated on for discrete subaortic stenosis. Methods Between 1994 and 2000, 45 consecutive children were operated on for discrete subaortic stenosis. Patients were divided in two groups according to the obstructive lesion detected by echocardiography. Results A localized shelf was found as an isolated lesion in 31 patients (group A), whereas additional subaortic anomalies were found in 14 cases (31%) and were multiple in 5 cases (group B). The anomalies included anomalous septal insertion of mitral valve (7 cases); accessory mitral valve tissue (2 cases); anomalous papillary muscle (2 cases); anomalous muscular band (8 cases); and muscularization of the anterior mitral valve leaflet (1 case). Cardiopulmonary bypass and aortic cross-clamping times were significantly shorter in group A. There were no operative deaths nor major complications or deaths during follow-up. A gradient of 15 mm Hg or more was found at follow-up in 5 cases whereas aortic regurgitation was estimated to be not clinically significant in all but 1 patient. Six cases of recurrent subaortic stenosis were found in our series, 3 of them with other subaortic anomalies. Conclusions This study shows that discrete subaortic stenosis can often be associated with other subaortic abnormalities. Surgical treatment of these anomalies produces excellent early and mid-term relief of obstruction without any increase in mortality and morbidity.

The diaphragm: two physiological muscles in one.

To the respiratory physiologist or anatomist the diaphragm muscle is of course the prime mover of tidal air. However, gastrointestinal physiologists are becoming increasingly aware of the value of this muscle in helping to stop gastric contents from refluxing into the oesophagus. The diaphragm should be viewed as two distinct muscles, crural and costal, which act in synchrony throughout respiration. However, the activities of these two muscular regions can diverge during certain events such as swallowing and emesis. In addition, transient crural muscle relaxations herald the onset of spontaneous acid reflux episodes. Studying the motor control of this muscular barrier may help elucidate the mechanism of these episodes. In the rat, the phrenic nerve divides into three branches before entering the diaphragm, and it is possible to sample single neuronal activity from the crural and costal branches. This review will discuss our recent findings with regard to the type of motor axons running in the phrenic nerve of the rat. In addition, we will outline our ongoing search for homologous structures in basal vertebrate groups. In particular, the pipid frogs (e.g. the African clawed frog, Xenopus laevis) possess a muscular band around the oesophagus that appears to be homologous to the mammalian crural diaphragm. This structure does not appear to interact directly with the respiratory apparatus, and could suggest a role for this region of the diaphragm, which was not originally respiratory.

Tetralogy of Fallot: Total Correction

he events that give rise to the c1evelol)iiieiit of the T constellation of lesions that we refer to as tetralogj of Fallot are still micertain. Regardless of the true teleological cause, it is hel1)ful for the surgeon to approach this defect as resulting from anterocephalad deviation of the ventricular outlet septum. "monology with sequellae." The resulting malalignment ventricular septal defect (VSD), aortic override, ancl right ventricular outflow tract ol~struction are thus easily understood. The right ventricular hypertrophy can he appreciated as secondary to the VSD and right ventricular outflow tract ohstructioii. Right ventricular outflow obstruction is increased by hypertrophy of the anterior limb of the septal ]land, anomalous anterior muscular bands, and outlet septum as well as pulmonary valve and arterial anomalies (Fig I). Classically the VSD is circular, juxtaaortic, and nonrestrictive and results from the malalignment of the parietal extension of the infundibular and trabecular septae. As such, the defect lies between the infundibular septum and is cradled by the anterior and posterior limbs of the septal band (Fig 11).

Invited commentary

This article by Van Praagh and associates presents the pathological findings and clinical management of apical muscular ventricular septal defects. This is an uncommon problem seen in 0.5% of the 3,155 heart specimens in the Cardiac Registry of the Boston Children’s Hospital. This article gives a detailed pathologic description of the morphology of the apical ventricular septal defect, which will not only help clinicians with the closure of these defects, but equally importantly, will allow for a common definition as to what constitutes an apical ventricular septal defect. The distinction between the infundibular apical recess (where apical muscular ventricular septal defects occur) and the right ventricular sinus is an important one nicely depicted in Figures 1B and 2A. It will be interesting to see if the description of a muscular band separating the infundibular apical recess from the right ventricular sinus apex (newly termed the infundibulosinus partition) is a true structure that will be recognized by others and will be adopted into our lexicon of cardiac anatomy.