The membranous septum revisited: A glimpse of our anatomical past.

The so-called membranous septum is the fibrous component of the septal structures within the heart. It is relatively subtle in its appearance, but of considerable significance to the understanding of cardiac function and cardiac disease, both congenital and acquired. Surprisingly, its existence was seemingly unknown until the early decades of the 19th century. At this time, those writing in the English language described it as the "undefended space," recognizing its importance in the setting of its aneurysmal dilation, and as the site of septal defects. By the initial decade of the 20th century, it had come to be recognized as the landmark to the site of atrioventricular bundle. Over the first decade of the 21st century, its clinical significance has been emphasized in the context of transcutaneous replacement of the aortic valve. In this review, we describe our own recent investigations of this fibrous part of the septal structures. At the same time, we provide a glimpse of our anatomic past, explaining how its initial description relied on the observations of young physicians taking their first steps in the investigation of cardiac anatomy.

The artery of Mouchet: blood supply of the septomarginal trabecula in 50 human hearts.

The septomarginal trabecula is a muscular structure which transmits the right branch of the atrioventricular bundle. It is usually supplied by a branch from the second anterior septal artery. Anastomoses between the right and left coronary arteries may happen on the septomarginal trabecula. They are of great significance in order to prevent ischemia during a myocardial infarction. Surgeries such as Konno's and Ross' procedures implies in knowledge of these vessels anatomy. The coronary arteries of 50 human hearts were injected with latex and subsequentely dissected with the purpose of identifying the arterial branch that supplied the septomarginal trabecula. The trabecular branch arose from the second anterior septal artery in 38% of cases, and the branch arose from the first anterior septal artery in 26%. One of the hearts had its septomarginal trabecula supplied by the conus arteriosus arteryliterature. Anastomoses between the right and left coronary arteries were found inside the septomarginal trabecula. The right branch of the atrioventricular bundle is subject to a great number of clinical conditions and is often manipulated during surgery, thus, the study of the septal branches of the coronary arteries and the trabecular branch is essential.

The artery of Mouchet: blood supply of the septomarginal trabecula in 50 human hearts

SUMMARY The septomarginal trabecula is a muscular structure which transmits the right branch of the atrioventricular bundle. It is usually supplied by a branch from the second anterior septal artery. Anastomoses between the right and left coronary arteries may happen on the septomarginal trabecula. They are of great significance in order to prevent ischemia during a myocardial infarction. Surgeries such as Konno's and Ross' procedures implies in knowledge of these vessels anatomy. The coronary arteries of 50 human hearts were injected with latex and subsequentely dissected with the purpose of identifying the arterial branch that supplied the septomarginal trabecula. The trabecular branch arose from the second anterior septal artery in 38% of cases, and the branch arose from the first anterior septal artery in 26%. One of the hearts had its septomarginal trabecula supplied by the conus arteriosus arteryliterature. Anastomoses between the right and left coronary arteries were found inside the septomarginal trabecula. The right branch of the atrioventricular bundle is subject to a great number of clinical conditions and is often manipulated during surgery, thus, the study of the septal branches of the coronary arteries and the trabecular branch is essential.

RESUMO A trabécula septomarginal é uma estrutura muscular que transmite o ramo direito do feixe atrioventricular. É usualmente suprida por um ramo da segunda artéria septal anterior. Anastomoses entre as artérias coronárias direita e esquerda podem ocorrer na trabécula. São de grande significância especialmente na prevenção de isquemia durante um infarto do miocárdio. Procedimentos cirúrgicos como o de Konno's e Ross implicam conhecimento anatômico desses vasos. As artérias coronárias de 50 corações humanos foram injetadas com látex e dissecadas com o propósito de identificar o ramo arterial que supria a trabécula septomarginal. Em somente 38% dos casos o ramo foi proveniente da segunda artéria septal anterior, enquanto que em 26% dos casos a artéria se originou da primeira septal anterior. Um dos corações teve a trabécula septomarginal suprida por um ramo originário da artéria do cone arterioso. Além disso, foram encontradas anastomoses entre as artérias coronárias no interior da trabécula septomarginal. Em suma, o ramo direito do feixe atrioventricular está sujeito a inúmeras condições clínicas e é alvo de manuseio em cirurgias, logo, o estudo dos ramos septais das artérias coronárias, em especial o ramo trabecular é essencial.

Morfología ecocardiográfica de la atresia pulmonar con septum interventricular intacto, estudio de dos decenios / Echocardiographic morphology of the pulmonary atresia with intact ventricular septum. A 20-year study

Introducción: la atresia pulmonar con septum interventricular intacto es una malformación cardiovascular que representa el 1 por ciento de las cardiopatías congénitas observadas en vida extrauterina, y, dados sus resultados desfavorables, constituye un verdadero reto para la medicina contemporánea. Objetivo: la investigación condujo a la aplicación de pautas clasificatorias, a la caracterización del tracto de salida atrésico, al estudio morfológico ventricular derecho, a la valoración del anillo tricuspídeo y a la determinación de la presencia de anomalías en la circulación coronaria. Métodos: se estudiaron 43 pacientes con diagnóstico confirmado de la entidad remitidos al Cardiocentro Pediátrico William Soler entre enero de 1992 y noviembre de 2011. Se practicó a cada caso el examen ecocardiográfico bidimensional y doppler con codificación en colores. Resultados y conclusiones: se corroboró el predominio de la variante morfológica valvular de la entidad y la existencia de niveles moderados o severos de hipoplasia ventricular derecha en asociación con capacitancia volumétrica limitada de dicha cámara, con hipodesarrollo valvular tricuspídeo y con presencia de circulación coronaria anómala sinusoides dependiente. El foramen oval permeable constituyó el defecto septal interatrial más vinculado a la enfermedad, y se evidenciaron diversas anomalías estructurales del aparato tricuspídeo en conjunción o no con el hipodesarrollo anular imperante(AU)

Introduction: pulmonary atresia with intact ventricular system is a cardiovascular malformation accounting for 1 per cent of congenital cardiopathies seen in the extrauterine life; due to its unfavorable outcomes, this disease is a true challenge for the contemporary medicine. Objectives: the research study comprised the application of the classification guidelines, the characterization of the atresia outlet track, the morphological study of the right ventricle, the assessment of the tricuspid ring and the detection of anomalies in the coronary circulation. Methods: forty three patients diagnosed with this disease and referred to William Soler pediatric cardiocenter from January 1992 to November 2011 were studied. Each case was performed bidimensional echocardiography and color-coding Doppler. Results and conclusions: the study confirmed the predominance of the valvular morphological variant of the disease and the presence of moderate and severe levels of right ventricular hypoplexia associated with limited volumetric capacitance of this chamber, with tricuspid valvular hypodevelopment and with anomalous sinusoids-dependent coronary circulation. The permeable oral foramen was the interatrial septal defect that was most associated to this disease and several structural anomalies of the tricuspid system was evidenced in conjunction or not with the prevailing annular hypodevelopment(AU)

Morphological classification of the septomarginal trabecula in humans.

Although the septomarginal trabecula is a well-known anatomical structure, there continue to be different ways of studying it. In this study, we dissected the muscle bundles that form it, and this has enabled us to present a new classification based on the origin, path, and termination of these bundles. This study was conducted on 99 hearts removed from the cadavers of adult humans aged 18 to 82 years, of which 72 were male and 27 were female. The septomarginal trabecula presents two components in its composition: one septal and the other septal- papillary, i.e. extending from the septum to the anterior papillary muscle. The septal component may be visible macroscopically, forming a fleshy third-order column, or may only be visible by means of dissection. The septal-papillary component is always visible and is a fleshy column of either second-order or third- -order type. Another parameter takes into consideration the papillary-parietal connection, i.e. the junction of the septomarginal trabecula with the anterior papillary muscle, which may be single or present ramifications to the anterior wall and/or apex. Taking these criteria as references, we have classified the septomarginal trabecula into eight types.

Características morfológicas y biométricas del músculo papilar septal en corazones de individuos chilenos / Morphological and biometric characteristics of septal papillary muscle in hearts of chilean individuals

Se realizó un estudio descriptivo de las características anatómicas y biométricas del músculo papilar septal en 30 corazones de individuos adultos chilenos, en edades comprendidas entre 18 y 84 años de edad, de ambos sexos, sin aparente patología cardíaca, pertenecientes a la Unidad de Anatomía Humana Normal del Departamento de Ciencias Básicas de la Universidad de La Frontera. Los resultados mostraron que el músculo papilar septal, se presenta en un 83,3 por ciento de los corazones del estudio. De éstos, el 44,0 por ciento presenta un solo músculo, el 28 por ciento presenta dos músculos y el 28 por ciento tres músculos papilares septales. De los músculos papilares septales encontrados, el 71,1 por ciento correspondió a la forma cono libre, el 24,4 por ciento a la forma cono pegado y el 4,5 por ciento a la forma puente. En cuanto a la longitud de forma cono pegado y cono libre, el rango que se encuentra en mayor porcentaje está entre 4,0 mm ­ 5,99 mm; con un 45,5 por ciento y 42,4 por ciento, respectivamente. Este estudio nos demuestra la importancia de incorporar al músculo papilar septal a la nomenclatura anatómica internacional.

A descriptive research study was carried out on the anatomical and biometric characteristics of the septal papillary muscle in 30 hearts of adult Chilean subjects, between 18 and 84 years of age of both sexes and without apparent cardiac pathology, from the Normal Human Anatomy Unit, Basic Sciences Department of the Universidad de La Frontera. Results show that the septal papillary muscle was present in 83.3 percent of the hearts in the study. Of these 44.0 percent show one muscle only, 28 percent show two muscles and 28 percent show three septal papillary muscles. In the septal papillary muscles found, 71.1 percent are free cone-shaped, 24.4 percent were attached cone-shaped, and 4.5 percent were bridge-shaped. Regarding the length of attached cone and free cone shaped, the highest percentage range was between 4.0 mm and 5.99 mm, with 45.5 percent and 42.4 percent respectively. The present study shows the importance of integrating the septal papillary muscle to the International Anatomical Nomenclature.

Anatomy of the septomarginal trabecula in Landrace pig hearts.

The limitations on the availability of organs for transplantation have aroused interest in research on xenotransplantation of whole organs or certain parts of them. Thus, studies that confirm or reject similarities between the organs of different animals have started to have important clinical applications. In the present study, we investigated the septomarginal trabecula in 34 hearts from Landrace pigs with the aim of observing their similarities with the septomarginal trabecula in humans. In pigs, the muscle bundle of the septomarginal trabecula and the right branch of the stimulating complex are dissociated. The right branch is a narrow bridge that, after going out from the upper part of the interventricular septum, is attached to the upper part of the anterior papillary muscle. On the other hand, the muscle bundle of the septomarginal trabecula is generally a resistant crest that goes from the lower part of the septum to the lower part of the anterior papillary muscle. The septomarginal trabecula presents marked anatomical differences between humans and pigs.

El laboratorio quirúrgico y la enseñanza de la cirugía: el modelo quirúrgico

Se presenta la experiencia, realizada en la Unidad de Investigación Quirúrgica de la Escuela de Medicina Vargas, Facultad de Medicina, Universidad Central de Venezuela, durante casi dos décadas, reseñando brevemente los ensayos de investigación en cirugía realizados tanto en Caracas como en Maracaibo. El trabajo intenta demostrar la importancia que tiene el laboratorio quirúrgico para estimular la creatividad de los jóvenes aprendices de cirujanos, así como para desarrollar sus destrezas manuales y una mejor comprensión de las diversas técnicas quirúrgicas que deben aplicarse. El puente tendido entre la sala de hospitalización y el laboratorio permite llevar a éste los problemas de los pacientes y buscar soluciones nuevas que podrían o no usarse para mejorar el arsenal terapéutico del cual dispone el cirujano. También destaca la importancia en la creación de un equipo de trabajo unido, para el mejor logro de esta labor. Algo muy importante de esta tarea es la creación del modelo quirúrgico que imite en el animal, la patología observada en el hombre y de esta forma ensayar nuevas medidas terapéuticas para solucionar dichas enfermedades. En el trabajo se presentan algunos de los modelos quirúrgicos que se realizaron en razón de la mayor patología detectada en las salas de hospitalización

The work developed in almost two decades at Unidad de Investigation Quirurgica at Escuela de Medicina Vargas, Facultad de Medicina-Universidad Central de Venezuela is presented. With brief comments regarding surgical research proyects that were carried on at Caracas as well as Maracaibo. This work is done with the purpose to demostrate the importante that the surgical research laboratory in stimulating creativity in young surgical fellows, as well as helping to developed surgical skills and a better comprehension of each of the different surgical techniques that might be used. This work at the surgical laboratory also allow to take issues observed at the clinical wards with patients into experimental animals in order to search and or develop new or different surgical approach for the surgeon to use. Also establishes the importance of working as surgical team to facilitate a better outcome. Another goal accomplised was to create surgical models that would simulate the pathologic findings observed in the patients to allow for the development of new therapeutics options to bring solutions to the patients. This work presents several surgical models that were developed and used based on the most frequent disease observed at the surgical wards

Prevalência do forame oval patente em pacientes jovens com acidente vascular cerebral isquêmico atendidos em hospitais de reabilitação / Prevalence of patent foramen ovale in young patients with stroke admitted to rehabilitation hospitals

Estima-se que 40 por cento dos acidentes vasculares cerebrais isquêmicos (AVC) sejam classificados como criptogênicos. Essa cifra costuma ser maior nos pacientes jovens. A embolia paradoxal, cujo forame oval patente (FOP) é o principal exemplo, pode ser responsável por uma parcela desses casos. Entre janeiro de 2004 e novembro de 2004, 168 pacientes com diagnóstico de AVCI, entre 15 e 45 anos de idade, admitidos em unidades da Rede Sarah de hospitais foram admitidos, além da avaliação de rotina, a pesquisa de FOP com ecodopplercardiograma transesofágico e/ou Doppler transcraniano, ambos associados ao teste de bolhas.Usando a combinação dos dois métodos a prevalência da FOP em toda a amostra foi de 28 por cento (IC95 por cento 21,3-35,4).Nos pacientes com AVCI criptogênico essa prevalência sobe para 40 por cento e no grupo com etiologia definida foi de apenas 15 por cento, configurando uma razão de chances de 3,7 (IC 95 por cento 1,8-7,9). Esses resultados apontam para a necessidade de se considerar a possibilidade de embolia paradoxal na etiologia do AVCI criptogênico em pacientes jovens.

Anatomical study of the anterior interventricular septal branches and their relationship with the blood supply of the septomarginal trabecula

The aim of this study was to examine the morphological features of the anterior interventricular septal branches that supply blood to the septomarginal trabecula and to correlate the anatomical observations with the angiographic characteristics analyzed by hemodynamic procedures. Forty human hearts were dissected after injecting colored latex into the left coronary artery. The vascularization of the septomarginal trabecula was always derived from the anterior interventricular artery, via the first, second and third anterior interventricular septal branches in 21 hearts (52.5%), 17 hearts (42.5%) and two hearts (5%), respectively, and the distances from the left coronary artery ostium ranged from 22 to 51 mm. The external diameter of these vessels at their origin varied from 1.0 to 2.35 mm and the vessels were analyzed based on specific requirements for surgical and hemodynamic methods of myocardial revascularization. Myocardial bridges were located over or before the origin of the vessels studied.

Behavior of septum primum mobility in third-trimester fetuses with myocardial hypertrophy.

OBJECTIVES: The mobility of the septum primum (SP) in the fetus is a diastolic phenomenon and could be related to left atrial pressure. We studied the linear displacement of the SP in the left atrium in fetuses of diabetic mothers (FDM) with and without septal hypertrophy (SH) and in normal fetuses of normoglycemic mothers. In this study we set out to test the hypothesis that the linear displacement of the SP flap valve is less marked in fetuses with SH than in those without SH. METHODS: The ratio between the linear displacement of the flap valve and the left atrial diameter (excursion index (EI)) was compared in ten FDM with SH, eight FDM with normal septal thickness and eight normal fetuses of non-diabetic mothers. Atrioventricular flow velocities were also compared in the three groups. RESULTS: Comparison of the three groups showed that in FDM with SH, the mean EI was 0.36 +/- 0.09, in FDM without SH it was 0.51 +/- 0.09 (P = 0.001) and in the control fetuses it was 0.49 +/- 0.12 (P = 0.03). There was a significant negative correlation between septal thickness and EI in FDM with SH. There was no correlation between septal thickness and atrioventricular flow velocities. CONCLUSION: Mobility of the SP in FDM with SH is reduced and there is an inverse correlation between the linear displacement of the SP and septal thickness. These findings may be related to changes in left ventricular diastolic function secondary to myocardial hypertrophy.

An experimental contribution to the concept of "jumping wave" phenomenon in the interventricular septum.

OBJECTIVE: The purpose of this study was to evaluate the existence of a histologically bipartite interventricular septum and the electrical independence of both septal masses, as well as to understand the changes of septal activation fronts in the presence of bundle branch blocks. METHODOLOGY: We examined the histological characteristics of both septal masses in 12 canine hearts. Furthermore, in another 11 anesthetized dog hearts, we analyzed morphological and chronological data of intraseptal records with normal activation and in the presence of proximal blocks. RESULTS: A histological discontinuity between the two septal masses in canine hearts seems to exist. Analysis of intraseptal and intracavitary electrical records confirmed slow transmission of the activation fronts from one septal mass to the other when proximal blocks were present. Morphological and chronological changes of the intracavitary complexes agree with the "jumping wave" phenomenon theory. CONCLUSIONS: These results support the validity of this approach to the activation of both septal masses and explain the chronological and morphological changes of the intracavitary records in the presence of ventricular blocks. In addition, this approach is a useful tool to detect the possible coexistence of dead septal tissue.

An experimental contribution to the concept of "Jumping wave" phenomenon in the interventricular septum / Contribución experimental al concepto de "salto de onda" en el tabique interventricular

Objective: The purpose of this study was to evaluate the existence of a histologically bipartite interventricular septum and the electrical independence of both septal masses, as well as to understand the changes of septal activation fronts in the presence of bundle branch blocks. Methodology: We examined the histological characteristics of both septal masses in 12 canine hearts. Furthermore, in another 11 anesthetized dog hearts, we analyzed morphological and chronological data of intraseptal records with normal activation and in the presence of proximal blocks. Results: A histological discontinuity between the two septal masses in canine hearts seems to exist. Analysis of intraseptal and intracavitary electrical records confirmed slow transmission of the activation fronts from one septal mass to the other when proximal blocks were present. Morphological and chronological changes of the intracavitary complexes agree with the "jumping wave" phenomenon theory. Conclusions: These results support the validity of this approach to the activation of both septal masses and explain the chronological and morphological changes of the intracavitary records in the presence of ventricular blocks. In addition, this approach is a useful tool to detect the possible coexistence of dead septal tissue.

Objetivo: El propósito de nuestro estudio es aportar datos objetivos a la teoría de la bipartición histológica del tabique interventricular y de la independencia eléctrica de las dos masas septales, así como a la de los cambios de los frentes de la activación septal en los bloqueos de rama. Método: Hemos examinado las características histológicas de ambas masas septales en corazones caninos y humanos. Además, hemos analizado los datos morfológicos y cronológicos de los registros intraseptales con activación normal y en presencia de bloqueos tronculares de diferentes grados en 11 perros anestesiados. Resultados: Hallamos datos objetivos a favor de una discontinuidad entre las dos masas septales tanto en el corazón canino como en el humano. El análisis de los registros eléctricos intraventriculares ha confirmado la transmisión lenta de los frentes de activación de una a otra masa septal, en presencia de bloqueos tronculares. Los cambios morfológicos y cronológicos de los complejos QRS intraventriculares concuerdan con la teoría del fenómeno de "salto de onda". Conclusiones: Nuestros resultados apoyan la validez del punto de vista de la independencia funcional de ambas masas septales y permiten explicar los cambios morfológicos de los registros intraventriculares, en presencia de bloqueo de rama. Este enfoque es también de gran ayuda para detectar la posible coexistencia de miocardio septal inactivable.

[Is the concept of "jumping wave" still valid?]. / Es aún válido el concepto de "salto de onda"?

UNLABELLED: The concept of the "jumping wave" phenomenon, i.e. of the slow and difficult passage of activation fronts from one septal mass to the other through an "intraseptal barrier", is derived from experimental studies of the Mexican School of Electrovectorcardiography. OBJECTIVE: To confirm the existence of histologically bipartite interventricular septum and of the electric independence of both septal masses. METHODOLOGY: We examined the histological characteristics of both septal masses in rat, canine, and human hearts. We also analyzed the morphological and chronological data of intracavitary records in the presence of different degree proximal blocks, comparing these findings with those obtained when peripheral blocks existed. RESULTS: We found a medial, longitudinal band between the two septal masses in animal as well as in human hearts. The analysis of intracavitary electric records confirmed a slow and difficult transmission of the activation fronts from one septal mass to the other, in the presence of proximal blocks and ventricular arrhythmias. Morphological and chronological changes of intraventricular complexes could not be explained if the septal activation process were of syncytial type. CONCLUSIONS: Results of this study firmly support the validity of our approach to the septal activation process in the presence of ventricular conduction disorders and arrhythmias. This approach helps to detect the possible coexistence of dead septal tissue.

The membranous part of the human interventricular cardiac septum.

The arrangement of collagen and elastic fibers of the membranous part of the interventricular septum (PMS) was studied in hearts from adult humans. Connective bundles formed a network of fairly independent tendons arranged in two layers. The tendinous bundles consisted essentially of type I collagen fibers while type III fibers were visible as a thin network with transversely and longitudinally oriented meshes around the muscle bundles. Cranial and caudal to the PMS were narrow and irregular bands of collagen fibers that apparently represented zones of low resistance to the high blood pressures acting from the left to the right heart chambers. The predominance of fiber bundles arranged in an approximately transverse direction with regard to the arterial cone axis suggests a resistance to enlargement resulting from high aortic blood pressure. Elastic fibers were observed in the transitional zone between the cardiac muscle and the PMS. They were continuous with elaunin fibers and these with oxytalan fibers closely intermingled with the narrow network of type I collagen fibers of the PMS. The successive transformation of elastic fibers, which were very numerous in the muscle-tendon transition, into elaunin and these into oxytalan fibers toward the central portions of the PMS suggests a functional sequence characterized by a high elasticity and consequent mobility of the transition region itself and by a progressive increase of resistance in this portion.

Estudo morfométrico da fossa ovalis em coraçäo humano de adultos / Morphometric study of the fossa ovalis in the adult human heart

O septo interatrial apresenta uma característica anatômica importante, que é a presença de um vestígio embrionário denominado fossa oval, que pode ser permeável em aproximadamente um terço dos casos, sendo mais frequente na mulher que no homem. Os indivíduos que apresentam este defeito, sao assintomáticos no começo da vida, embora um número importante deles depois dos 40 anos, desenvolvem hipertensao arterial pulmonar, fibrilaçao atrial, comunicaçoes bidirecionais e insuficiência cardíaca. Foram estudados 50 coraçoes, adultos chilenos, com idades entre 18-76 anos, de ambos os sexos e sem patologia aparente, obtidos no Serviço de Anatomia Patológica, Medicina Legal e Unidade de Anatomia Normal da Universidad de la Frontera, Temuco, Chile. O septo dea forma oval em 56 por cento, triangular em 26 por cento e circular em 18 por cento dos casos. A área das fossas foi, em média, de 193mm2. A profundidade das fossas foi, em média, de 4,3 mm. A permeabilidade estava presente em 34 por cento dos casos. A posiçao mais freqüente correspondeu ao terço médio em 58 por cento dos casos.

[Embryologic and anatomic considerations on normal and pathologic heart separation. II. Atrioventricular and interventricular septum]. / Consideraciones embriológicas y anatómicas sobre la septación cardiaca normal y patológica. II. Septum atrioventricular e interventricular.

The atrioventricular septum is defined and its anatomical features are described. This consists of two regions, a muscular and a membranous region. Isolated atrioventricular types of defect are described. The normal and the pathological embryogenesis of the atrioventricular septum are discussed. A definition of the interventricular septum is given and its anatomical features are described. This septum is divided into two regions, a membranous and muscular region. The muscular region is divided into three regions: inflow region or inlet, trabeculated region and outflow region or outlet. Interventricular defects are classified according to the septal regions in which they are located. The anatomical features which characterize each type of interventricular septal defect are established. A brief comment on the normal and pathological morphogenesis of the interventricular septum is made.

Consideraciones embriológicas y anatómicas sobre la septación cardiaca normal y patológica: II. Septum atrioventricular e interventricular / Embriologycal and anatomycal conciderations on normal and pathological cardiac septation. II atrioventricular and interventricular septa (AU)

Se define el septum atrioventricular y sus características anatomicas. Este septum se divide en dos regiones: muscular y membranosa. Se describen los tipos de comunciación atrioventricular aisladas. Se discute la embriogénesis normal y patológica del septum atrioventricular. Se define el septum interventricular y se describen sus características anatómicas. Este septum se divide en dos regiones: fibrosa y muscular. La muscular se divide en tres regiones: porción de la cámara de salida o infundibular (outlet). Las comunicaciones inteventriculares se clasifican de acuerdo con las regiones septales en que están ubicadas. Se establecen las características anatómicas de identidad de cada una de ellas. Se hace un breve comentario sobre la morfogénesis normal y patológica del septum interventricular. Septum atrioventricular; septum interventricular