Pag 4. Upper panels. Frontal views of the mediastinum of the chest  showing cardiac margins. Note in  the left panel de fibrous pericardium Inserting into the diaphragm and the right phrenic nerve close to the superior cava vein. In the right panel the fibrous pericardium has been removed and the serous pericardium and pericardial space are observed. Ao, aorta; LPN, left phrenic nerve; LV, left ventricle;  PA, pulmonary artery; RA, right atrium; RV, right ventricle

Pag 4. Lower panels. Sternocostal and diaphragmatic views showing  the  ventricular surfaces, margins and grooves of a cadaveric heart photographed in attitudinal positions to simulate the views as seen  in living condition.  Note the subepicardial location of the sinus nodeat the level of the right atrium. Ao, aorta; ICV, inferior cava vein; LIPV, left inferior pulmonary vein; PA, pulmonary artery; RAA, right atrial appendage; RIPV, right inferior  pulmonary vein; RSPV, right superior pulmonary vein; SCV, superior cava vein

Pag 5. Upper panels. Sternocostal view of a heart after removing the serous pericardium and subsequent dissection of the coronary vessels. Note the location of the interventricular anterior descendingartery (ADA) and the right coronary artery (RCA). In the upper right panel note the origin of the sinus node artery from the circumflex  artery and which then runs by the epicardial ridge below the left pulmonary veins (LPVs), towards Bachmann’s bundle and superior cava vein (SCV). In the lower right panel showing how after moving up the left atrial appendage (LAA) covers  the left circumflex artery (LCx).RAA, right atrial appendage

Pag 5. Lower panels. This image is a  NavX system which allows a geometric visualization of the left atrium and pulmonary veins in a correct  attitudinal  orientation. The left atrial appendage is anterior to the left superior pulmonary vein, and the right superior pulmonary vein is related to the right pulmonary artery that passes close to the roof of the left atrium. The thoracic aorta runs behind the left atrium.

Pag 6. Upper panels. Opened right atrium (RA) and left atrium (LA) in a human specimen. Note the TV displaced apically in relation to the mitral valve (MV) and the apposition between the inferior/medial RA and the posterior region of the LV (double white arrow in panel. The smooth circumferential area of atrial wall surrounding the orifice of the TV and MV is described as the vestibule. The trabeculated wall of the RA anterior to the terminal crest is the right atrial appendage and contains multiple pectinate muscles, which arise from the crest and extends all round the vestibule.CS, coronary sinus; ICV, inferior cava vein; LAA, left atrial appendage; LV, left ventricle;  OF, oval fossa; RV, right ventricle

Pag 6. Lower panels. Longitudinal cut through the 4 cardiac chambers shows the atrial septum in profile. The surface of the venous component of the left atrium, where the pulmonary veins end, is indistinguishable from the posterior wall. The walls of the left atrium are smooth, as is the atrial vestibule close to the mitral valve (MV) and circumflex artery (Cx artery). On the right side the terminal crest branching into small pectinate muscles at the isthmus between the inferior cava vein (IVC) and the tricuspid valve (TV). Note the mouth of the coronary sinus relative to the inferior paraseptal wall. LAA, left atrial appendage; RSPV and LSPV, right superior and left superior pulmonary veins; VS, ventricular septum

Pag 7. Upper panels. Opened right atrium (RA) and left atrium (LA) in a human specimen. Note the TV displaced apically in relation to the mitral valve (MV) and the apposition between the inferior/medial RA and the posterior region of the LV (double white arrow in panel. The smooth circumferential area of atrial wall surrounding the orifice of the TV and MV is described as the vestibule. The trabeculated wall of the RA anterior to the terminal crest is the right atrial appendage and contains multiple pectinate muscles, which arise from the crest and extends all round the vestibule.CS, coronary sinus; ICV, inferior cava vein; LAA, left atrial appendage; LV, left ventricle;  OF, oval fossa; RV, right ventricle

Pag 7. Lower panels. Longitudinal cut through the 4 cardiac chambers shows the atrial septum in profile. The surface of the venous component of the left atrium, where the pulmonary veins end, is indistinguishable from the posterior wall. The walls of the left atrium are smooth, as is the atrial vestibule close to the mitral valve (MV) and circumflex artery (Cx artery). On the right side the terminal crest branching into small pectinate muscles at the isthmus between the inferior cava vein (IVC) and the tricuspid valve (TV). Note the mouth of the coronary sinus relative to the inferior paraseptal wall. LAA, left atrial appendage; RSPV and LSPV, right superior and left superior pulmonary veins; VS, ventricular septum

Pag 8. Upper panels. Simulated (gross human specimens) and fluoroscopic right anterior oblique (RAO) projection showing electrode catheters placed at the right atrial appendage (RAA), bundle of His (His), right ventricular apex (RVA) and coronary sinus (CS). Simulated and fluoroscopic left anterior oblique (LAO) projection. The CS runs on the atrial side of the mitral annulus along the inferior wall of the left atrium towards the posterior border of the heart. Both RAO and LAO projections define what is anterior, posterior, superior and inferior. The LAO view serves to demonstrate in an attitudinal orientation the septal location permitting the differentiation between the right and left atrioventricular grooves. AO, aorta; CSo, coronary sinus ostium; ICV, inferior cava vein; LV, left ventricle; MCV; mid cardiac vein; P; pulmonary valve;  RVOT, right ventricular outflow tract; TV, tricuspid valve.

Pag 8. Lower panels. Fluoroscopic 45° right anterior oblique projections showing the angiographic display of both the mitral valve and tricuspid valve  during the injection of radiographic contrast into the right atrium and the left ventricle (LV).CS, coronary sinus; PA, pulmonary artery; RAA, right atrial appendage; RV, right ventricle; RVOT, right ventricular outflow tract; SVC, superior vena cava

Pag 9. Upper panels. Short-axis heart in simulated LAO projections showing the right and left atrioventricular groove. The convergence of the left and right atria forms the lateral side of the inferior pyramidal space; the superior vertex is the central fibrous body and the coronary sinus limits the base of this space (yellow circles). Note the AV nodal artery originates from the apex of the U-turn of the distal right coronary artery and penetrates into the base of the inferior paraseptal region (inferior pyramidal space) at the level of the crux of the heart. Fluoroscopic limits of the inferior pyramidal space (yellow circles)in left anterior oblique projection  showing the nodal artery (AVNa) towards the His bundle. Left atrial angiography throughout a transseptal puncture in the left anterior oblique projection (LAO). The LAO projection makes it possible to define the anatomic relation between the right and left paraseptal regions and the fluoroscopic limits of the inferior pyramidal space. Note the variable relation of the coronary sinus catheter and the atrial side of the mitral annulus. LAA, left atrial appendage. NCC, (non coronary  cup), PV, pulmonary valve; LCC, (left coronary cup); RCC, (right coronary cup)

Pag 9. Lower panel. Sagittal histological section with Masson trichrome at the level of the base of the inferior paraseptal region. Note the proximity of the AV nodal artery to the endocardium of the vestibule and the coronary sinus orifice. This section shows the variable content of myocardial and fibro-fatty tissues of the inferior pyramidal space

Pag 10. Macroscopic endocardial aspect of the lateral wall of the right atrium opened. The terminal crest, which is usually the thickest muscular trabecula of the right atrium, arches anterior to the orifice of the superior cava vein and extends toward the inferior cava vein. Note that the pectinate muscles originate from the terminal crest have a non-uniform arrangement with abundant interlacing  trabeculations between them, ending in evestibule of the right atrium, right atrial appendage (RAA), the cavo-tricuspid isthmus and coronary sinus.SLTV, septal leaflet tricuspid valve; PM, papillary muscle

Pag 11. Upper panel. Opened right atrium in simulated right anterior oblique projection showing the terminal crest that distally ramifies to form the pectinate muscles. The Eustachian valve separates the inferior cava vein (ICV) from the inferior right atrial isthmus (cavo-tricuspid) where the pouch or subeustachian recess is located. The Thebesian valve guards the entry into the coronary sinus and more superiorly is the apex of the triangle of Koch.SLTV, septal leaflet tricuspid valve; SVC, supraventricular crest

Pag 11. Lower panel. Transillumination of the right atrium and fibromuscular membrane of the oval fossa and membranous septum (apex triangle of Koch). Note the endocardial view of the posterior and paraseptal walls of the right atrium showing the landmarks of the triangle of Koch.CSO, coronary sinus orifice; SPM, RVOT, right ventricular outflow tract; septal papillary muscle; TV, tricuspid valve

Pag 12. Transillumination to show the arrangementof the terminal crest (TC) and origin of the pectinate muscles, as well as the extremely thin wall separating the trabeculations

Pag 13. Upper panels. The right atrium opened along the incisions marked by white dashed lines and the lateral wall deflected so as to display the crest (TC) on the endocardial surface separating the smooth walled venous component from the trabeculated appendage. Note the ramifications in the inferior isthmus and vestibule of the right atrium. Transillumination  of the right atrium opened shows  branching of the pectinate muscles from the terminal crest (TC) (white dashed lines) to the inferior isthmus. The endocardial surface of the lateral wall has a variable trabecular architecture within the tip of the appendage whereas in the remaining wall the pectinate muscles have a uniform parallel alignment almost without crossoversbetween them. CSo, coronary sinus orifice; ICV; inferior vena cava, OF, oval fossa; SVC, superior vena cava; TV, tricuspid valve.

Pag 13. Lower panels. Scanning electron micrograph of non-macerated specimen shows a non-uniform arrangement  from the terminal crest (TC) with abundant interlacing trabeculations between the pectinate muscles (PM). Scanning electron micrograph of non-macerated specimen confirmed the irregular alignment (arrows) of the muscular myocytes within the pectinate muscles

Pag 14. Upper panel. Lateral view of the right atrium (RA) showing the location of the sinus node (SN) (fusiform green colour). LIPV, left inferior pulmonary Vein; LSPV, left superior pulmonary vein; PT, pulmonary trunk; RAA, right atrial appendage;  RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein.

The right atrium is shown in right anterior oblique projection to show the horseshoe shaped terminal crest (TC). The crest arches anterior  to the orifice of the superior vena cava (SCV) and extends to the area of the anterior interatrial groove. Inferiorly, the crest turns in beneath the orifice of the inferior vena cava (ICV), breaking up into a series of trabeculations in the area of the atrial wall known as the inferior isthmus. Note near the vestibule of the atrium and below the eustachian valve an obvious subeustachian recess.CS, coronary sinus; OF, oval fossa; RAA, right atrial appendage; SVC, supraventricular crest

Pag 14. Lower panel. Histological sections of the sinus node body (black dotted line delineates the nodal boundaries) (Masson trichrome stain) showing the subepicardial  location within a dense matrix of connective tissue (green) and showing nodal extensions to superior caval vein (SCV), epicardium and terminal crest (TC).  Note in the histological sections that the nodal body shows a irregular contour contacting with the neighboring myocardium.End, endocardium; Epi, epicardium,

Pag 15. Upper panels. Longitudinal histological section of the sinus node body (Masson trichrome stain) within a dense matrix of connective tissue. Note a sleeve of myocardium (arrow) from sinus nodal region to superior caval vein.

Macroscopic lateral view of the right atrium and superior cava vein with transillumination to demonstrate a sleeve of myocardium  to superior caval vein (arrow). RAA, right atrial appendage

Pag 15. Lower panels. Cross histological section through the terminal crest (TC) at its origin of the crest from the superior rim of the oval fossa showing its relation to the musculature of Bachmann’s bundle . Note mainly in the enlarged image the change between the predominantly transverse muscle fibres of the terminal crest and the longitudinal fibres of Bachmann’s bundle.

Pag 16. Upper panels. Right atrial angiogram in the right anterior oblique projection that show a large and deep pouch recess, and in other occasions there may be a thicker Eustachian valve and ridge, anatomic obstacles that may complicate isthmus ablation.

The right inferior cavo-tricuspid isthmus is a quadrilateral area in the floor of the right atrium bounded by the inferior caval vein and the Eustachian valve posteriorly and by the septal attachment of the tricuspid valve (STV) anteriorly. Note the complex endocardial topography of the isthmus with thicker trabeculations from the terminal crest and a deep subeustachian recess (pouch)

Pag 16. Lower panels. Sagittal histological sections with van Gieson’s and Masson trichrome stains, respectively, at the level of the central isthmus. Note the  proximity of the minor coronary vein and the right coronary artery to the endocardium of the vestibule. The sections shows the variable content of myocardial and fibro-fatty tissues with a thicker anterior vestibular area, and different depth of subeustachian recess (pouch)

Pag 17. Upper panels Macroscopic normal and  transillumination  endocardial surfaces of the right atrial isthmus is displayed to show the three level: paraseptal, medial and inferolateral. Note the pouch at the level  between of paraseptal and medial isthmus and the distal branching of the terminal crest (TC) that feed into the inferolatral isthmus. The anterior sector corresponds to the vestibule leading to the tricuspid valve.The posterior sector is closest to the orifice of the inferior cava vein (ICV) and contains the Eustachian valve/ridge. CS orifice, coronary sinus orifice

Pag 17. Lower panel. Fluoroscopic 45° left anterior oblique (LAO) and right anterior oblique (RAO) projections, respectively, showing the angiographic display at the level of the cavotricuspid isthmus. Note  LAO the three isthmus areas: inferolateral, medial and paraseptal. In RAO the location the pouch and vestibule of the right atrium can be seen.

Pag 18. Upper panel. Gross dissection of the human atrioventricular conduction axis relative to the triangle of Koch, revealing the location of the compact AV node and penetrating bundle. The right bundle branch (RBB) can be seen on the right side of the interventricular septum. CSO , coronary sinus orifice; LBB: left bundle branch; OF, oval fossa; RVOT, right ventricular outflow tract; STV = septal tricuspid valve

Pag 18. Lower panels. Schematic drawing representing the arrangement of the Atrioventricular conduction axis at the level of the Koch triangle. The AV conduction axis is made up of the compact node, the penetrating AV bundle, the non-branching AV bundle, the branching AV bundle, and the right and left bundle branches. The triangle of Koch is delimited by the hinge line of the septal tricuspid leaflet, the tendon of Todaro and the mouth of thecoronary sinus forming its base. The fibrous membranous septum  forms the apex of the triangle. The hinge of the septal leaflet of the tricuspid valve provides the dividing line between the AV (yellow star) and interventricular (pink star) components of membranous septum.

Simulated (gross human specimens) and fluoroscopic right anterior oblique (RAO) projection showing electrode catheters placed at the right atrial appendage, bundle of His (His), right ventricular apex , coronary sinus (CS) and radiofrequency  (RF)catheter at the base of Koch’s triangle. HRA: high right atrium, RVA,  right ventricular apex;

Pag 19. Upper panel. Gross dissection from the right atrial cavity, showing the limits of the triangle of Koch (dashed blue lines and the white one at the base).The membranous septum forms the apex of the triangle of Koch. The hinge of the septal leaflet of the tricuspid valve (TV) provides the dividing line between the atrioventricular and interventricular components of the membranous septum.OF = oval fossa; RAA, right atrial appendage; RVA, right ventricular apex; TC, terminal crest; TK, triangle of Koch

Pag 19. Lower panel. Histological  sagittal sections perpendicular to the hinge of  the septal leaflet of the tricuspid valve and stained with Masson trichrome technique. The conduction tissue is outlined with a dashed black line. The first section shows the extensions from the atrioventricular node that occupy the inner layers of the tricuspid and mitral vestibules. The second section, taken at a superior level within the floor of the triangle of Koch, shows how the cardiomyocytes derived from the deeper left side of the atrial septum provide the greatest inferior input to the compact AV node. The third section shows that the compact node takes a sloping shape as it approaches the AV component of the membranous septum, and at this level, its major myocardial connections are with the central part of the atrial septum (the final last input ). The fourth section shows that the fibrous tissue surrounds the conduction axis, and  is usually known as the penetrating His bundle (interventricular components of the membranous septum).

Pag 20. Upper panel. Short axis in an human specimen through the interatrial septum. Note by transillumination the so-called left atrial ridge that is a fold in the left atrial wall between the left atrial appendage and the left pulmonary veins. OF, oval fossa; LAA, left atrial appendage; LIPV, left inferior pulmonaryvein; LSPV, left superior pulmonary vein; RAA, right atrial appendage

Pag 20. Lower panel. Dissections to show Bachmann’s bundle, crossing the anterior interatrial groove and branching toward the left atrial appendage,and the septopulmonary bundle, which arises from the interatrial groove underneath Bachmann’s bundle, fanning out to line the pulmonary veins and to pass longitudinally over the dome of the left atrium. Note how the transverse sinus of the pericardium separates the aorta from the anterior wall of the left atrium.LAA, left atrial appendage; RAA, right atrial appendage

Pag 21. Upper panels. Sagittal sections of two macroscopic hearts illustrating endings of the left pulmonary veins into the left atrium. In the left panel note an individualized ending of the left superior PV (LS) and the left inferior PV (LI) into the left atrium. In the right panel, the specimen showing a short vestibule or funnel-like common vein for both left PVs. The left PVs lie superior and posterior to the mouth of the left atrial appendage (LAA), both separated by a muscular fold so-called Left lateral ridge. The anterior wall behind the ascending aorta can become very thin at the area near the vestibule of the mitral valve. Two heart specimens sectioned tranversally (short axis ) with the roof of the left atrium removed and viewed from above to shows the Entrance of the pulmonary veins. Note that in left panel, the arrangement of four individualized ending of the PVs into the left atrium. In right panel, there are four PVs. However, the left PVs show a vestibule or funnel-like common vein before opening into the left atrium (white arrow). LAA, left atrial appendage; LI, left inferior pulmonary vein; LS, left superior pulmonary vein; MV, mitral valve; RI, right inferior pulmonary vein; RS, right superior pulmonary vein.

Pag 21. Lower panel. Three dimensional reconstruction of the left atrium and pulmonary veins using the NavX system from data obtained with a 120 slice multidetector CT scanner to show the four pulmonary veins and left atrial appendage, as well as the superior or roof and anterior walls of the left atrium. The right panel show conjoined ostia on the left side, a common variant seen in up to 25% of cases, and a separate right middle pulmonary vein (PV), which drains the middle lobe of the lung.LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein

Pag 22. Upper panel. Transverse section of an heart specimens with the roof of the left atrium removed and viewed from above to show the entrance of the four pulmonary veins. Note the Bachmann’s bundle or anterior interatrial bundle extending from the anterior part of the superior vena cava (SVC) to the anterior aspect of the left atrium.

RAA, right atrial appendage

Pag 22. Lower panel. Cross histological section stained with elastic van Gieson of the left atrium, pulmonary veins and the superior vena cava (SVC). Note the variable myocardial content of the walls of the left atrium and the subepicardial  location of autonomic nerves and ganglia. Endo, endocardium; Epi, epicardium; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein

Pag 23. Upper panels. Cross-histological sections of the left pulmonary veins stained with Masson trichrome technique. Note the interpulmonary myocardial connections (arrow) between the left superior and inferior veins. Also note a non-uniform in circumferential thickness of the myocardial sleeves in left pulmonary veins.

Pag 23. Lower panels. Longitudinal histological sections stained with Masson trichrome showing the thicker atrial wall becoming thinner at the entrance of the left inferior pulmonary vein to form the muscular sleeve, which tapers toward the lung. Note the presence of gaps of connective tissue bridges between the myocytes  and the subepicardial  location of autonomic nerves and ganglia.

Pag 24. Upper panel. Endocardial left lateral atrial wall in two macroscopic  heart specimens showing, in the left panel, a short vestibule or funnel-like common vein for both left pulmonary veins (LPVs), the left lateral ridge is not observed in this specimen. However, in the right panel, there is a prominent left lateral ridge, extending to the inferior margin of the left inferior pulmonary veins and entrance to the left atrial appendage. Note in this specimen extra-appendicular pectinate muscles extending inferiorly from the appendage and located

between the crest and the vestibule of the mitral valve, and note the thinnest muscular wall in between the muscular trabeculae. Cx, circumflex artery; MV, mitral valve; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein;

Pag 24. Lower panels. Longitudinal histological sections (Masson’s trichrome stain) through the left lateral wall to illustrate its anatomic relations with the coronary sinus or great cardiac vein  and circumflex artery. Note in the lower panel the space between the pectinate muscles where the left atrial wall becomes extremely thin. Note also in the upper panel a muscular continuity between the sleeve of the coronary sinus and myocardial vestibule of the left atrial wall

Pag 25. Upper panels. Endoluminal CT (left panel)  view of the lateral wall of the left atrium showing the ostial relationship of the left superior pulmonary vein (LSPV) and the left atrial appendage (LAA). In the most common variant, the LAA ostium is seen at the same level or anterosuperior to the LSPV ostium. The thickness of the ridge between the pulmonary vein and LAA ostia varies in different specimens. The upper right panel is a macroscopic postmortem  view of the lateral wall of the left atrium. The prominent ridge between the pulmonary vein and LAA orifice. Note the extra-appendicular pectinate muscles or ‘remnant’ (arrows), extending inferiorly from the orifice of the left atrial appendage (LAA) towards the vestibule of the mitral valve (MV) demonstrate the non-uniform myocardial thickness of the left lateral atrial wall to the vestibule of the MV. 

Pag 25. Lower panels. The lower right panel (transillumination) which is the same specimen, shows the thinnest muscular wall  between the muscular trabeculae of extra-appendicular pectinate muscles. Sagittal histological section (lower left panel) of the mitral isthmus stained with Masson trichrome to illustrate its anatomic relations with the great cardiac vein (GCV) and the left circumflex artery (LCx),and vein of Marshall on the epicardium of the crest. Note the pectinate muscles, where the left lateral atrial wall becomes thinner due to the existence of extra-appendicular muscles. LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; LV, left ventricle; MV, mitral valve.

Pag 26. Upper panels. The figures shown a dissections of two macroscopic hearts  to illustrate Bachmann’s bundle (dashed white lines), crossing the anterior interatrial groove and branching toward the left atrial appendage surrounding the entrance or mouth of the left atrial appendage, and the septopulmonary bundle (dashed red lines), which arises from the rim of the oval fossa underneath Bachmann’s bundle, fanning out to line the pulmonary veins and to pass longitudinally over the dome of the left atrium.

Pag 26. Lower panel. Note the roof and posterior wall of the left atrium with transillumination to demonstrate the thinner parts of the walls, and non-uniform thickness of the walls of the left atrium.The epicardium has been removed to show the arrangement of the myocardial strands of the septopulmonary bundle in the subepicardial parts of the walls.ICV, inferior cava vein; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein;  RAA, right atrial appendage;  RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein: SCV, superior cava vein

Pag 27. Macroscopic postmortem  view with transillumination of the lateral wall of the left atrium. The image show a deeper dissection showing the myoarchitecture in the subendocardium. The septoatrial bundle (dashed white lines), arises from the anterior septal raphe and rim of the oval fossa underneath Bachmann’s bundle and septopulmonary bundle and its myocytes run obliquely in three directions: across the dome of the left atrium, also pass leftward into the lateral wall, and others continue into the fine ridges lining the cavity of the left atrial appendage. LAA, left atrial appendage; LPV, left pulmonary veins

Pag 28. Upper panels. Opened right atrium in simulated right anterior oblique view (upper panel) to show different components of the atrium. The impression in this image is that the septal wall of the right atrium is much larger than it really is. A red circle shows the relationship of the right atrium to the ascending aorta. Note the oval fossa (OF)

and the terminal crest which is a thick  C-shaped muscular trabecula that distally ramifies to form  the pectinate muscles. The Eustachian valve separates the inferior cava vein (ICV) from the inferior right atrial isthmus. The Thebesian valve  guards the entry into the coronary sinus (CS).RAA, right atrial appendage, RVA, right ventricular apex; RVOT, right ventricular outflow tract; SCV, superior cava vein

Pag 28. Lower panels. Short axis section in an heart specimen across the atrial chambers at the level of the flap  valve (arrow) and muscular rim  (asterisks) of the oval fossa (OF). Note the atrioventricular valves, the vestibules and the different shape and size of the atrial appendages. Cross-histological section taken through the short axis of the heart shows the thin flap valve (arrow) and the muscular rim of the fossa.Note the uneven thickness of the left atrial wall, the relationship of the right atrium to the ascending aorta through the transverse sinus. Ao, aorta; MV, mitral valve; LI, LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein;   PV: pulmonary valve; PT: pulmonary

trunk; TV, tricuspid valve

Pag 29. Upper panels. The figure shows a four chamber section through the heart profiles showing the true interatrial septum (oval fossa); the remaining parts mark the superior and inferior infolding of the atrial wall. The superior rim of the fossa is the infolded wall between the superior vena cava (SVC ) and the right pulmonary veins is known as Interatrial posterior groove (Waterston’s or Sondergaard’s groove). Anteriorly and nferiorly, the rim and its continuation into the atrial vestibules overlie the inferior pyramidal space.

Pag 29. Lower panels. In the same specimen a catheter  is passed through the membranous oval fossa  and its end is placed into the right inferior pulmonary vein (RIPV). ICV, inferior cava vein; IVS, interventricular septum; LA, left atrium;  MV, mitral valve; RIPV,  right inferior pulmonary vein;

RSPV, right superior pulmonary vein; TV, tricuspid valve; TC, terminal crest

Pag 30. Upper panels. Postmortem specimens and morphological variants of the left atrial  appendage. Common variants of the gross morphology of the LAA are: windsock (with few lobes and little trabeculated endocardium, chicken wing, cactus, and cauliflower  (multilobed and with extensive trabeculations endocardium)

Pag 30. Lower panels. Morphological shape in postmortem specimens of the left atrial appendage  ostium and its variations. Four common variants of the ostium of the left atrial appendage, round, elliptic, water drop-like, and foot-like, respectively. MV, mitral valve

Pag 31. Upper panels. Left panel. Longitudinal histological section (Masson’s trichrome stain) through the left atrial appendage (LAA). Note above the neck of the LAA that the left phrenic nerve is adherent to the fibrous pericardium, and below the neck of the LAA is located the circumflex artery (CX). Upper right panel. Left lateral view of the heart shown the left phrenic nerve in its course  adherent of the fibrous  pericardium has a close anatomic relationship with the body of the left atrial appendage (LAA) and the lateral wall of the left  ventricle (LV) to penetrate into the left part of the diaphragm close to the apex of the ventricle. LSPV, left superior pulmonary vein; PT, pulmonary trunk

Pag 31. Lower panels. Left panel is a view of the roof and posterior wall of theleft atrium showing the spatial relationship of the coronary sinus and the oblique vein of Marshall. The coronary sinus runs along the epicardial portion of the vestibular component of the left atrium and begins at the junction of the vein of Marshall with the great cardiac vein. Lower right panel is a left lateral view of the heart shows the relationship the vein of Marshall is in direct contact with the epicardium of the ridge below the left pulmonary veins towards the coronary sinus.ICV, inferior cava vein; LAA, left atrial appendage; LSPV, left superior pulmonary vein;  LV, left  ventricle; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein: SCV, superior cava vein

Pag 32. Upper panels. Dissection (left  upper panel) of the diaphragmatic surface of  the ventricles shown in the was made by removing or ‘peeling’  the epicardial covering of the ventricular cone.  It shows the obvious “grain” produced by the aggregation of the cardiomyocytes into  chains. Note that the superficial cardiomyocytes are shared between the ventricles, with no traceable division. LV, left ventricle; RV, right ventricleHistological section image shown (right upper panel) shows how the individual cardiomyocytes are aggregated together by  component  of the fibrous matrix into units that are separated by clefts (extracelullar components) containing loose connective tissue. There is, however, no uniformity in the thickness of the aggregated units, which can be seen to be heterogeneous and interconnected branching entities.

Pag 32. Middle panels. Cross histological section stained with Masson trichrome through the left and the right ventricles. Note the anatomic relation of the right ventricular ourflow tract (RVOT) with the interventricular septum. Note the close proximity to the epicardial coronary vessel,  the left phrenic nerve adherent to the fibrous pericardium, relevant during the epicardial approach for arrhythmia ablation. Also notethe right ventricle is crescent-shaped in cross section. DA, descending anterior artery Short-axis view from atria side of a dissection heart, after removal of  the epicardium and coronary vessels, shows the relationship of the  aortic valve and the right (yellow asterisk) and left (blue asterisk) fibrous trigones. Pulmonary sinuses are named according to their relationship to the heart, including anterior (ALP), left  (LL), and  right (RL) pulmonary cups or leaflets. Behind and to the right of the pulmonic valve are the three cups of the aortic valve: left cup (LC),  the right cup (RC), and the posterior or non coronary cup (Non-C).  Behind and to the sides of the aortic valve are the atrioventricular  valves, mitral, and tricuspid with their leaflets. Tricuspid valve:  ASL, anterosuperior leaflet; IL, inferior leaflet; SL, septal leaflet. Mitral valve: AL, anterior o aortic leaflet ;ML, mural leaflet

Pag 32. Lower panels. This is a right lateral view of a  macroscopic specimen showing the three components of the right  ventricle (RV) (inlet or inflow, outlet and apical) and the characteristic muscle bundles as septomarginal trabeculation or septal band and supraventricular crest or ventriculo infundibular fold  (marked witha green dashed line). Ao, Aorta; RA, right atriumLongitudinal section of a specimen to show the  three components of the left ventricle (LV) (inlet or inflow, outlet and apical).  Note the leaflets of the aortic valve and the fibrous continuity between the aortic leaflet of the mitral valve and non-coronary of the aortic cup are shownwith a green dashed line. There is no muscular infundibulum in the left ventricle. Ao, Aorta; LA, left atrium

Pag 33. Upper panel. Window dissection of a heart prepared by removing the anterior superior wall of the right ventricle and right atrium. The three components of the right ventricle are revealed: inflow tract (tricuspid valve ), apical trabecular, and right ventricular outflow tract (RVOT) or infundibulum. Note the location of the supraventricular crest (green dashed line) and septomarginal trabeculation  or septal band (SMT). The body of the SMT continues on the one hand towards the infundibulum and on the other, the moderator band, to the anterior papillary muscle and the parietal wall of the right ventricle. CS, coronary sinus; ER, Eustachian ridge; OF, oval fossa; PT, pulmonary trunk; RAA, right atrial appendage; RCA, right coronary artery

Pag 33. Lower panel. The anterior wall of the right ventricle is opened to show the leaflets of the pulmonary trunk mainly supported by the right ventricular outflow  tract (RVOT) ; however, at the level of their commissures and intervalvular trigones (asterisks) the leaflets are attached to the pulmonary artery trunk. The SMT (septal band) for its upper part consists of a body and two limbs anterior and posterior. The anterior limb extends along the infundibulum and the posterior limb runs toward the tricuspid valve. The septo-parietal trabeculations take their origin from the anterior margin of the SMT and extend along the parietal ventricular wall of the infundibulum.

Pag 34. Upper panels.  Histological  sagittal sections of the pulmonary valve shown how the hinge of the valvar leaflet is attached to the ventricular myocardium well proximal to the anatomic ventriculoarterial junction. Note the sinotubular junction and the semilunar attachment of the pulmonary leaflet. No “annulus” is supporting the attachments of the leaflets. The subendocardial fibres in the infundibulum run longitudinally.

Pag 34. Lower panels. The anterior wall of the infundibulum  was opened to show the leaflets of the pulmonary valve  supported by the right ventricular outflow tract. Note the  Infundibular musculature Incorporated within the sinuses of the pulmonary trunk and form the ventriculoarterial junction

Pag 35. Upper panel. Macroscopic  heart in which  the right side is opened to show the hinge of the tricuspid valve and the location of the right papillary muscles, tendinous chords and leaflets of the tricuspid valve.

Pag 35. Lower panels. It is an increase of the previous image to show the papillary muscles: septal, anterior and inferior-postero of the right ventricle. Note the moderator band extending from septal wall to anterior papillary muscle. ICV, inferior cava vein; PT, pulmonaru trunk; RAA, right atrial appendage;  RVOT, right ventricular outflow tract; SMT, septomarginal trabeculation; SVC, supraventricular crest

Pag 36. Upper panel.  Upper panel, macroscopic sagittal section through the parietal wall of the left ventricle that shows the subaortic outflow tract and how  the papillary muscles of the mitral valve (supero-lateral and infero-posterior) closely face each other. 

Pag 36. Lower panel.  The anterior wall of the left ventricle is opened to show the papillary muscles,  tendinous chords and leaflets of the mitral valve. The  anterior (aortic) leaflet is shorter than the posterior (mural) leaflet of the mitral valve. The base or attachment of the papillary muscle  is to the ventricular myocardium wall. LAA, left atrial appendage;  LVOT, left ventricular outflow tract

Pag 37. The kidney-shaped vestibule of the mitral valve is shown from the atrial side. Note the left  (with star) and right  (blue star) fibrous trigones, and the commissure between the leaflets of the mitral valve and the fibrous continuity between the aortic leaflet of the mitral valve and left coronary and noncoronary of the aortic sinuses are shown.  Also note the coronary sinus next to the left atrioventricular groove surrounding the mitral valve from behind. This basal view shows  after removal the medial wall of the right atrium at the triangle of Koch to expose the atrioventricular nodal artery (AV nodal artery); PT, pulmonary trunk; LCA, left coronary artery; RCA, right coronary artery

Pag 38. Upper panel.  Longitudinal section of the right ventricle shows that a small portion of the supraventricular crest  or crista supraventricularis (posterior wall of the right ventricular outflow tract) extends beyond the limits of left ventricular outflow tract and separates the leaflets of the pulmonary valve from the left ventricle.

IVS, interventricular sptum; L, left aortic sinus; LA, left atrium; PV, pulmonary valve; R, right aortic sinus; RV, right ventricle;

Pag 38. Lower panel.  Cross histological section stained with Masson trichrome through the left and the right atria. Note the anatomic relation of the right ventricular outflow tract (RVOT) with the subaortic outflow.Also note the close proximity to the epicardial coronary vessel, the left phrenic nerve and the left atrial appendage, relevant during the epicardial approach for arrhythmia ablation.DA, descending artery; LCx, left circumflex artery; LVOT, left ventricular outflow tract

Pag 39. Upper panel.  Opened view of the ventriculo-aortic junction shows the outlet portion of the left ventricle and the typical semilunar attachments of the leaflets of the aortic valve. Note fine trabeculations in the apical component. The antero-lateral and postero-medial papillary muscles are shown. Each mitral leaflet receives chordae fromboth papillary muscles. The antero-lateral papillary muscle is attached to by chordae tendineae to the left half of the anterior and mural leaflets, whereas the postero-medial papillary muscle is attached to by chordae tendineae to the right half of the anterior and mural leaflets LA, left atrium

Pag 39. Lower panels. Commonly the papillary muscles of the left ventricle contains 2-3 major muscle groups. When multiple muscle groups are present, they may share a common origin or may have separate origins

Pag 40. Upper panel.  Opened view of the ventricle shows the membranous septum located inferior to the interleaflet triangle between the right and non-coronary sinus of the aortic valve. Note that we have highlighted in dark colour the limits of the endocardial position of the left bundle branch of His and its three fascicles.

Pag 40. Lower panels. The right panel is a histological section that shows the extension of the crest of the muscular septum relative to the hinge of the noncoronary leaflet of the aortic valve, which could be used as a potential indicator of the proximity of the left bundle branch to the basal ring.The left panel shows by transillumination the level of the crest of the muscular ventricular septum and membranous septum relative to the basal ring of the aortic root. RCA, right coronary artery

Pag 41. Upper panel.  Left lateral view of a heart specimen showing a dissection of the Left ventricular summit bounded by the e left anterior descending artery (LAD)and  left circumflex artery (CX artery) which is bisected by the great cardiac vein (colored in blue), which defines the lower part or base of the triangle of Brocq and Mouchet that is crossed by the diagonal artery and other minor left ventricular branches LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; PA, pulmonary artery;

Pag 41. Lower panels. Macroscopic and histological longitudinal sections through the left atrial appendage (LAA),  ascending aorta and base of the left ventricle. Note the close relationship of the myocardium of the left atrial appendage with the left aortic sinus and its artery,and at the level below of the  appendage with the left circumflex artery and base of the left ventricle. Left, left aortic sinus

Pag 42. Upper panel.  Anatomic relation of the esophagus with the posterior wall of the left atrium. Note in the middle panel the artery esophageal artery. Ao, aorta; ESO; esphagus, LIPV, left inferior pulmonary vein, RSPV, right superior pulmonary vein; RVOT, right ventricular outflow tract

Pag 42. Lower panel.  Sagittal histological section showing the fibrous pericardium between the posterior left atrial wall and the esophageal wall, and the fatty tissue plane containing lymph nodes and esophageal arteries immediately behind that (Masson’s trichrome stain).Transverse histological section (Masson’s trichrome stain) showing the proximity of the esophagus to the posterior wall of the left atrium , and the left inferior pulmonary vein (LIPV) .

Pag 43. Upper panel.  This dissection of a cadaver showing the course of the right phrenic nerve is closely related to the superior cavo-atrial junction and the orifice of the right superior pulmonary vein. Histological section through the right superior pulmonary vein (RS),  and veno-atrial Junction. The right phrenic nerve (RPN) is adherent to the fibrous pericardium. Note the close relationship to the myocardial sleeve on the outer side of the RS and the superior cava vein (SCV)Ao, aorta; RA, right atrium; RB, right bronchus; RPA, right pulmonary artery;  RSPV, right superior pulmonary vein

Pag 43. Lower panel.  Note the anatomic relations between the right superior pulmonary and right phrenic nerve. The vagus nerve in relation with the esophagus and posterior wall of the left atrium can be seen