Muscular Septum Research Articles

Swiss Cheese–Like Atrial Septal Defect

Atrial septal defects (ASDs), apart from the bicuspid aortic valve, are the most common congenital heart malformations, and it is not uncommon for them to go undiscovered until a patient reaches adulthood.1 An ostium secundum ASD is the most common septal defect, comprising 75% of all these defects.2 Elective closure should be considered in patients with signs of right heart dilatation and in those who have a presumed paradoxical event.3 In patients with an ostium secundum ASD, percutaneous closure–first reported in 19744—is now well established. Before a percutaneous closure attempt, the suitability of the defect for device implantation should be assessed with transesophageal echocardiography. Associated malformations (eg, partial anomalous pulmonary venous drainage) and the number, location(s), and the dimensions of the defect(s) should be known before the procedure. A defect in the atrial septum can exist when the flap valve derived from the septum primum does not overlap its rim (eg, because of atrial dilation) or because the flap …

Congenital Aneurysm of the Muscular Interventricular Septum

Congenital aneurysms of the muscular interventricular septum are rare. We report the diagnosis of such an aneurysm by fetal echocardiography at 19 weeks' gestation and the subsequent follow-up through early neonatal life, with the ultimate progression to a dilated cardiomyopathy requiring cardiac transplantation. This case highlights the early diagnosis of this rare finding and the unusual clinical course to include the confounding features of endocardial fibroelastosis, left ventricular noncompaction, and a lymphocytic infiltrate demonstrated on pathologic examination. Most infants with congenital septal aneurysms are asymptomatic, but this case demonstrates the need for careful serial assessment and clinical follow-up because of the unclear origin and natural history of this entity.

Creation of Ventricular Septal Defects on the Beating Heart in a New Pig Model

Background/Aims: So far, surgical and interventional therapies for muscular ventricular septal defects (mVSDs) beyond the moderator band have had their limitations. Thus, alternative therapeutic strategies should be developed. We present a new animal model for the evaluation of such strategies. Methods: In a pig model (n = 9), anterolateral thoracotomy was performed for exposure of the left ventricle. mVSDs were created under two- and three-dimensional echocardiography with a 7.5-mm sharp punch instrument, which was forwarded via a left ventricular puncture without extracorporeal circulation. Results: Creation of mVSDs was successful in all animals (n = 9) confirmed by echocardiography, hemodynamic measurements and autopsy. The defects were located in the midmuscular (n = 4), apical (n = 1), inlet (n = 2) and anterior part (n = 2) of the muscular septum. All animals were hemodynamically stable for further procedures. The diameter and shunt volume of the mVSDs were 4.8–7.3 mm (mean: 5.9 mm) and 12.9–41.3% (mean: 22.1%), respectively. Autopsy confirmed in all animals the creation of a substantial defect. Conclusion: The described new technique for creation of an mVSD on the beating heart in a pig model is suitable for the evaluation of new therapeutic strategies for mVSD closure.

Experience With Using a Safe Landmark the Fossa Ovalis in Transseptal Procedures

Background and Objectives: Pressure monitoring and injection of contrast media after piercing the fossa ovalis are used to avoid life-threatening complications during transseptal procedures. However, when performing those maneuvers, the information provided can only be obtained after having pierced structures that may not have been the intended target. When we injected the contrast media through a Brockenbrough needle before piercing the fossa, the dye that had collected under the membranous septum tented by the transseptal equipment (tenting) was observed on the left anterior oblique (LAO) projection and this indicated the fossa ovalis. This study was performed to evaluate the usefulness and safety of tenting in order to identify the membranous septum during transseptal procedures. Subjects and Methods: Contrast injections were performed on the fossa ovalis and the septal wall surrounding it during 64 transseptal procedures. The rates of dye staining and tenting in both the muscular and membranous septums were compared. Results: No areas of the muscular septum exhibited any tenting. Various rates of dye staining of those areas were observed. However, the membrane of the fossa exhibited tenting without dye staining in all 64 cases. The sensitivity of the tenting without dye staining to identify the Fossa was 98%, and the specificity was 100%. Conclusion: Tenting without dye staining could differentiate the membranous septum from the muscular one with high diagnostic accuracy. This method could be used as a safe landmark for the fossa ovalis before piercing it during transseptal procedures. (Korean Circ J 2008;38:544-550)

Familial muscular ventricular septal defects and aneurysms of the muscular interventricular septum

We describe 3 siblings with muscular ventricular septal defects, two requiring surgical closure. One of their offspring had a rare congenital aneurysm of the muscular ventricular septum, also requiring surgery. Another had a small muscular ventricular septal defect which closed spontaneously. Their father had echocardiographic evidence suggestive of a closed muscular defect. Paternal cousins have had ventricular septal defect, hypertrophic cardiomyopathy, and tetralogy of Fallot. There was no evidence of 22q11 deletion. Although ventricular septal defects are the most common congenital heart defect, such familial clustering is uncommon. The distribution of cases in this family suggests autosomal dominant inheritance. With echocardiography, and more precise diagnosis of defects which close, a larger genetic component may be revealed in other families.

AJR Teaching File: Infertility in a Young Woman

Radiologic Description An oblique axial T2-weighted MR image (Fig. 1) through the horizontal long axis of the uterus shows a muscular septum arising from the fundus and extending into the body region; the overlying junctional zone is continuous over the lateral walls of the uterus. The outer contour of the fundus is flattened, whereas a normal uterine fundus is convex on the outer aspect. The left ovary seen in this image is unremarkable. The right ovary, seen better on a different image (not shown), is also normal in appearance.

Interferon-γ Induces Chronic Active Myocarditis and Cardiomyopathy in Transgenic Mice

Chronic heart failure is associated with an activation of the immune system characterized among other factors by the cardiac synthesis and serum expression of proinflammatory cytokines. There is unequivocal clinical and experimental evidence that the cytokine tumor necrosis factor-alpha is involved in the development of chronic heart failure, but a putative cardiotoxic potential of the proinflammatory cytokine interferon (IFN)-gamma remains primarily unknown. To investigate this issue we analyzed the cardiac phenotype of SAP-IFN-gamma transgenic mice, which constitutively express IFN-gamma in their livers and hence exhibit high circulating serum levels of this cytokine. SAP-IFN-gamma mice spontaneously developed chronic active myocarditis, characterized by the infiltration of not only CD4(+) and CD8(+) T cells but also Mac2(+) (galectin 3(+)) macrophages and CD11c(+) dendritic cells, eventually culminating in cardiomyopathy. Echocardiographic analyses exhibited a left ventricular dilation and impaired systolic function induced by IFN-gamma overexpression. IFN-gamma-mediated cardiotoxicity was associated with high-level cardiac transcription of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-12 and the macrophage-attracting chemokines MCP1 and MIP1-alpha. Myotoxic IFN-gamma effects could not be detected in smooth or striated muscle tissue, suggesting cardiomyocellular specificity of the toxic IFN-gamma effect. The precise mechanism of IFN-gamma cardiotoxicity remains to be elucidated.

Deep recessus of the muscular interventricular septum documented with echocardiography and magnetic resonance imaging

We describe a case of a male patient in whom a routine transthoracic echocardiography reveals a deep recessus of the muscular interventricular septum, without evidence of left-to-right shunt. The helical myocardial band, a new concept of myocardial architecture, could help in the interpretation of the genesis of this anatomic finding.

Adult Congenital Heart Disease

It has variably been estimated that between 800 000 and 1 million patients with congenital heart disease are now adults and that by 2010 more patients older than 16 years will undergo surgery for congenital heart disease than those younger than 16 years.1 This review will focus on the clinical aspects of identifying and caring for the portion of the unique population that have right ventricular (RV) outflow tract lesions. The left ventricle (LV) and RV both have inlet, apical, and outlet portions, although they differ considerably.2 The inlet of the RV includes the tricuspid valve, and it is separated from the pulmonary valve (PV) by the crista supraventricularis. This structure results in the PV being raised upward. The apical portion of the RV has coarse trabeculations. As shown in Figure 1, the septum is home to a large septomarginal (septal) trabeculation that divides into the anterior and posterior limbs in the outflow tract. A series of septoparietal trabeculations arise along the free wall. The crista supraventricularis inserts between these limbs and is made up of 3 components: the muscular outlet septum, the ventriculoinfundibular fold, and the inner curvature of the RV.3 The small part that separates the RV and LV cavities is the outlet or conal septum. A loop including the septal trabeculation, the moderator band, septoparietal trabeculations, and the outlet septum can be conceptualized as circling the RV outflow tract. The PV is supported by the circular muscular infundibulum rising outside the RV proper. Abnormalities involving the RV outflow tract involve malpositioning of 1 or more of these structures. Figure 1. The anatomy of the RV outflow tract.2 There is a large septomarginal (septal) trabeculation that divides into 2 limbs. The anterior limb supports the leaflets of the PV, and the posterior limb …

The optimal procedure for the great arteries and left ventricular outflow tract obstruction. An anatomical study☆

To describe the optimal surgical strategy in heart specimens with transposition of the great arteries (TGA) and left ventricular outflow tract obstruction (LVOTO). Thirty-three specimens with LVOTO were selected: TGA with intact ventricular septum (TGA/IVS) (10), TGA/VSD (21), and Taussig-Bing (2). LVOTO in TGA/IVS consisted of combinations of bicuspid pulmonary valve (four), subpulmonary fibrous ridge (four), obstructive muscular conus (two) and bulging muscular septum (four). Arterial switch operation (ASO) with LVOTO resection/valvotomy was feasible in nine hearts. Obstructive anterior papillary muscle prohibited LVOTO relief in one specimen. In TGA/VSD and Taussig-Bing LVOTO consisted of combinations of bicuspid (nine) or unicommissural (one) pulmonary valve, fibrous ridge (three), obstructive muscular conus (five), malaligned outlet septum (six), accessory mitral valve tissue (two), straddling mitral valve (two) and anterior mitral valve rotation (four). VSDs were subpulmonary in 13 (9 perimembranous, 4 muscular), subaortic in 3 (2 perimembranous, 1 anterior muscular), doubly committed in 2, inlet in 3 (2 perimembranous, 1 muscular), non-committed and anterior in 1, and finally 1 VSD extended both into inlet and subpulmonary outlet septum. LVOTO resection and ASO with VSD closure was possible in 10. In six specimens, both a Rastelli and a Nikaidoh operation were feasible. For two hearts, a Nikaidoh procedure was the only option, while Rastelli was considered optimal in another specimen. Mitral valve anomalies prevented LVOTO relief in four, only permitting for Senning/VSD closure (one) or univentricular palliation (three). LVOTO resection and pulmonary valvotomy frequently permits an ASO. Inlet VSD, impossibility of VSD enlargement, straddling mitral valve, distant aorta and small right ventricle make the Nikaidoh procedure the best option. Mitral anomalies preventing LVOTO relief can make biventricular repair impossible.

'Cobra malformation' of an Amplatzer device during percutaneous closure of a ventricular septal defect

A 76-year-old man presented with successfully resuscitated cardiac arrest due to ventricular tachycardia. He was in florid pulmonary oedema, but maintaining a blood pressure and electrically stable. Past medical history included hypertension and a permanent pacemaker for syncope. Transthoracic echocardiography revealed a muscular ventricular septum rupture with gross left-to-right shunting (Panel A). Clinical progress was marked by refractory pulmonary oedema and recurrent gastrointestinal bleeding. Due to excessive surgical risk he underwent …

Double-outlet right ventricle with left malposition of the great arteries and total anomalous pulmonary venous connection

The patient was diagnosed with double-outlet right ventricle with left malposition of the great arteries, total anomalous pulmonary venous connection, and pulmonary stenosis at 2 months of age. Because the progression of pulmonary venous obstruction was suspected at 2 years of age, the patient was catheterized and underwent a definitive repair. The patient had a right aortic arch and left juxtaposition of the atrial appendages; the intraventricular anatomy exhibits malalignment between the conal septum and the muscular intraventricular septum, and the conal septum is well developed and dextroposed, resulting in pulmonary obstruction and multiple ventricular septal defects (VSDs). Because a supracardiac type (Darling's type Ib) of total anomalous pulmonary venous connection was also combined with such an anomaly, total correction consisted of an anastomosis of the left atrium and the common pulmonary vein, creation of an intraventricular tunnel, direct closures of muscular VSDs, pulmonary valvotomy, and infundibular resection. To our knowledge, this is the first description of the successful surgical correction of this type of anomaly in one stage.

Congenital Aneurysm of the Muscular Interventricular Septum in Association with Cardiac Arrhythmias and a Chromosomal Abnormality

We report a newborn with a congenital aneurysm of the muscular interventricular septum, a conduction system abnormality involving variable left and right bundle branch block, and an abnormality of the short arm of chromosome 20, This combination of anomalies has not been previously reported. To date, the infant has progressed well from a cardiac perspective but has poor muscle tone and developmental delay.

Magnetic Resonance Imaging of a Posttraumatic Myocardial Infarction and Ventricular Septal Defect With a Closure Device in Place

A 16-year-old boy sustained blunt trauma as a passenger in a high-speed motor vehicle accident 2 years earlier. Before the accident, he was healthy with no known cardiac disease or murmur. On admission after the accident, he was noted to have a loud IV/VI holosystolic murmur along the left sternal border. One month after admission, an echocardiogram revealed a 1.5-cm muscular ventricular septal defect with a left-to-right shunt, enlargement of the right atrium and ventricle, elevated pulmonary arterial pressure, and moderate tricuspid regurgitation (Figure 1 and Movie I). Figure 1. Delayed contrast enhancement in the short-axis plane demonstrates both sides of the …

Function of Intracoelomic Septa in Lung Ventilation of Amniotes: Lessons from Lizards

Aspiration breathing is the dominant mechanism of lung inflation among extant amniotes. However, aspiration has two fundamental problems associated with it: paradoxical visceral translation and partial lung collapse. These can constrain the inspiratory tidal volume, reduce the effective lung ventilation, and ultimately curtail the aerobic capacity of an animal. Separation of the pleural and peritoneal cavities by an intracoelomic septum can restrict the cranial shift of abdominal viscera and provide structural support to the caudal lung surface. A muscular septum, such as the diaphragm of mammals or the diaphragmaticus of crocodilians, can exert active control over visceral translation and the degree of lung inflation. To a lesser degree, a nonmuscular septum can also function as a passive barrier when stretched taut by rib rotation. Studies of the posthepatic septum in teiid lizards and the postpulmonary septum in varanid lizards underscore the importance of nonmuscular septa in aspiration. These septa provide plausible functional models that help us infer the evolution of mammalian and avian lung ventilatory systems, respectively.

The pathologic substrate of left ventricular outflow tract obstruction

Left ventricular outflow tract (LVOT) obstruction remains a major challenge in pediatric cardiology and surgery. One of the reasons being that the anatomy of the LVOT is complex, because of the participation of several components of different origin, such as the muscular outlet septum and the mitral valve apparatus. As a consequence, the pediatric cardiologist has to face the fact that imaging techniques may fail to demonstrate the subtle intricate anatomy of the LVOT, and the surgeon often will have to improvise once confronted with the anatomic details.

Two Distinct Pools of Mesenchyme Contribute to the Development of the Atrial Septum

Closure of the primary atrial foramen is achieved by fusion of the atrioventricular cushions with the mesenchymal cap on the leading edge of the muscular primary atrial septum. A fourth component involved is the vestibular spine, originally described by His in 1880 as an intra-cardiac continuation of the extra-cardiac mesenchyme of the dorsal mesocardium. The morphogenesis of this area is of great clinical interest, because of the high incidence of atrial and atrioventricular septal defects. Nonetheless, the origin of the participating components is largely unknown. Here we report that the primary atrial foramen is surrounded in its entirety by mesenchyme derived from endocardium. A second population of mesenchyme not derived from endocardium was observed at the caudal margin of the mesenchymal atrial cap, entirely embedded within the mesenchyme derived from endocardium and contiguous with the mesenchyme of the dorsal mesocardium. Our reconstructions show this second population does indeed take the form of a short spine, albeit that it is the right pulmonary ridge, rather than this spine, that protrudes into the atrial lumen. From the stance of morphological description, therefore, there is little thus far to substantiate the existence of an atrial spine.

Infective endocarditis with an aortic periannular abscess extending along the right coronary artery

A 50-year-old male underwent surgery for infective aortic valve endocarditis, which had been refractory to medical treatment. The valve was bicuspid, and involvement of the annular and subannular structures was recognized. A large suppurative discharge was obtained on incising this portion. Although there was no interventricular shunt, the abscess cavity was revealed to extend through the epicardial surface of the right atrioventricular groove. Following extensive debridement and irrigation, the defect was closed by an autologous pericardial patch. A 23 mm mechanical valve was implanted placing some of the stitches deep into the muscular interventricular septum. Infection was controlled by six-week administration of cefazolin sodium and gentamicin sulfate, and the patient survived.

VEGF Family Members Regulate Myocardial Tubulogenesis and Coronary Artery Formation in the Embryo

This study tested the hypothesis that coronary tubulogenesis and coronary artery formation require VEGF family members. Quail embryos were injected with soluble vascular endothelial growth factor (VEGF) receptors R1 (Flt-1), R2 (Flk-1), R3 (Flt-4), VEGF-Trap (a chimera of R1 and R2), or neutralizing antibodies to VEGF-A, VEGF-B, or fibroblast growth factor (FGF)-2. Our data document that tubulogenesis is temporally dependent on multiple VEGF family members, because the early stage of tubulogenesis was markedly inhibited by VEGF-Trap and to a lesser extent by soluble VEGFR-1. Some inhibition of tubulogenesis was documented when anti-FGF-2, but not anti-VEGF-A, antibodies were injected at embryonic day 6 (E6). Most importantly, we found that VEGF-Trap injected at either E6 or E7 prevented the formation of coronary arteries. Soluble VEGFR-1 and soluble VEGFR-2 modified the formation of coronary arteries, whereas soluble VEGFR-3 was without effect. Antibodies to VEGF-B, but not VEGF-A, had a strong inhibitory effect on coronary artery development. The absence of coronary artery stems, and thus a functional coronary circulation, in the embryos injected with VEGF-Trap caused an accumulation of erythrocytes in the subepicardium and muscular interventricular septum. Using retroviral cell tagging, we showed that some of the erythrocytes in blood islands and small vascular tubes were progeny of the proepicardium. Thus, another salient finding of this study is the first definitive documentation of proepicardially derived hemangioblasts, which can differentiate into erythrocytes.

Essential role of Hand2 in interventricular septum formation and trabeculation during cardiac development

Interventricular septum (IVS) formation is one of the key events in the development of a four-chambered heart. We previously showed that the basic helix–loop–helix transcription factor Hand1 plays an important role in the formation of the IVS. Here, we found that the other Hand gene, Hand2, regulated expansion, trabeculation, and IVS formation in the embryonic heart. In transgenic embryos expressing Hand2 in the whole ventricles, the boundary region between the left and right ventricles expanded outwards, resulting in complete absence of the IVS. Moreover, trabecular formation was observed even in a region where the IVS was expected to form. In some transgenic embryos with heterogeneous expression of the transgene, a muscular septum did not form in a region where Hand2 was expressed, but an incomplete septum was identifiable in a region where Hand2 was not expressed, suggesting that septum formation was strictly regulated by the expression domain of Hand2. Furthermore, expression of trabecular markers including ANF, BNP, and connexin40 was significantly up-regulated in the ventricles of Hand2 transgenic embryos as well as in H9c2 cells over-expressing Hand2. These results suggested that the absence of Hand2 expression in the interventricular boundary region inhibits expansion and trabeculation in this area, contributing to the proper formation of the IVS.