The cardiac structures most accessible to view are the superior vena cava, right atrium, right ventricle, main pulmonary artery, and aorta. Only a small portion of the anterior wall of the left ventricle is visible. Medial displacement of the right atrium exposes the left atrium and right pulmonary veins.

The right coronary artery is partly visible in the fat of the atrioventricular groove, with the ventricular branches and the acute marginal branch in full view. The posterior descending artery originates from the right coronary artery near the crux of the heart. The crux is defined as the cross point or junction of the atrioventricular septum and the atrioventricular groove. In its course in the atrioventricular groove, the right coronary artery is in close relation to the anterior portion of the annulus of the tricuspid valve. The distal portion of the right coronary artery supplies blood to the atrioventricular node and is in close proximity to the annulus of the mitral valve. The left coronary artery originates posteriorly from the aorta and, after a short distance, divides into the anterior descending and circumflex branches. The anterior descending coronary artery deviates from the atrioventricular groove onto the left ventricle, lateral to the pulmonary artery. Once it is on the anterior wall of the heart over the ventricular septum, the left anterior descending coronary artery becomes visible. The circumflex coronary artery lies in the atrioventricular groove posteriorly, in close relation to the annulus of the mitral valve. Marginal branches of the circumflex coronary artery supply the posterolateral surface of the left ventricle.

Visualization of the distal portion of the right coronary artery requires displacement of the acute margin of the heart to expose the diaphragmatic surface. The posterior descending coronary artery takes a course over the ventricular septum on the diaphragmatic surface of the heart. An exception to this anatomic configuration occurs when the posterior descending coronary artery originates from the left dominant coronary artery. The distal right coronary artery generally continues in the atrioventricular groove to supply one or more branches in the posterior wall of the left ventricle.

Exposure of the branches of the left coronary artery requires displacement of the heart superiorly and to the right. The circumflex branch of the left coronary artery is in the atrioventricular groove, giving off marginal branches to supply blood to the posterolateral surfaces of the left ventricle. The obtuse marginal branch is usually near the base of the left atrial appendage. The obtuse marginal branch may not be visible on the surface of the heart when it lies within the myocardium. In this situation it can usually be identified as a slightly yellowish discoloration of the otherwise red-brown myocardium. The anterior descending coronary artery takes a course along the ventricular septum anteriorly, providing one or more diagonal branches to supply blood to the anterolateral surfaces of the left ventricle. The size of the diagonal branches depends on the relative size of the circumflex marginal branches because the blood supply to the lateral wall of the ventricle is shared.

Coronary veins of the right ventricle drain directly to the right atrium or through thebesian veins to the right ventricle. Most of the venous return of the left ventricle is via the coronary sinus. Large cardiac veins located on the posterior surface of the heart collect through a common venous channel in the atrioventricular groove, which is anatomically related to the posterior portion of the annulus of the mitral valve. These veins drain into the right atrium at the coronary sinus. The orifice of the coronary sinus is located in close proximity to the septal portion of the annulus of the tricuspid valve. The sinoatrial node is located on the lateral surface of the right atrium at the junction with the superior vena cava at the origin of the crista terminalis. It occupies a considerable area, often greater than 1 cm in diameter, of the lateral wall of the right atrium.

Three interatrial conduction pathways are thought to arise from the sinoatrial node. The anterior and medial interatrial conduction pathways course anterior and posterior to the orifice of the superior vena cava and through the atrial septum, anterior to the foramen ovale. The posterior interatrial conduction pathway follows the crista terminalis and crosses the atrial septum caudal to the foramen ovale on the superior rim of the coronary sinus. The atrioventricular node is located in the floor of the right atrium at a point approximately one-third the distance along a line from the coronary sinus to the commissure of the anterior and septal leaflet of the tricuspid valve. The bundle of His generally follows this line to penetrate the annulus of the tricuspid valve and enter the ventricular septum just below the membranous portion. The triangle of Koch is bounded by the coronary sinus, the septal attachment of the tricuspid valve, and (laterally) a ridge of tissue referred to as the tendon of Todaro. The commissure of the septal and anterior leaflet of the tricuspid valve is usually well defined. The commissure of the septal and posterior leaflet of the tricuspid valve may be less obvious. This commissural cleft can generally be identified by the relationships of the chordae tendineae of the papillary muscle attached to the leaflets. The commissure of the anterior and posterior leaflets may also be poorly defined, but this is not of great anatomic importance because these leaflets function as a unit to approximate the septal leaflet.

A magnified view of the tricuspid valve shows the details of the septal leaflet, with the delicate chordae tendineae and papillary muscle attached. A portion of the posterior leaflet is seen, with the commissure between the posterior and septal leaflets. The coronary sinus is in the lower right corner of the image.

With the atrial septum removed, the anatomic relations of the right and left atrioventricular valves and the aortic valve are delineated at the fibrous body of the heart. Anatomically, the commissure of the septal and anterior leaflet of the tricuspid valve is closely related to the aortic annulus and the right atrium. Similarly, the noncoronary portions of the annulus of the aortic valve are closely related to the superior wall of the left atrium and the anterior leaflet and annulus of the mitral valve.

With the anterior wall of the right ventricle opened, the crista supraventricularis, with its septal and parietal bands, separates the tricuspid valve annulus from the annulus of the pulmonary valve. Space between the crista supraventricularis and the pulmonary annulus forms the infundibular chamber. The papillary muscle of the conus is attached to the ventricular septum caudal to the crista supraventricularis and marks the most distal portion of the bundle of His on the ventricular septum. The surface of the right ventricle is trabecular, making identification of small defects of the muscular portion of the ventricular septum extremely difficult.

Right ventricle, normal. The thin wall of the right ventricle is compared with the thick wall of the left ventricle (behind and to the left of the image). Trabeculations are coarse in the right ventricle. The tricuspid valve septal leaflet is barely visible, attached by chordae to the papillary muscle of the conus on the ventricular septum. The pulmonary valve is separated from the tricuspid valve by the infundibular (conus) portion of the right ventricle. The pulmonary valve is attached directly to the right ventricular outflow tract, with myocardium completely surrounding it.

Right ventricle, normal. This specimen shows the three segments of the right ventricle. The smooth wall of the right ventricle directly below the tricuspid valve is the inflow segment. This gives way almost immediately to the coarsely trabeculated body of the right ventricle, constituting most of the pumping chamber. The free wall portion is reflected to the left of the image, and the septal wall of the body of the right ventricle is on the right. The infundibular or conal segment of the right ventricle is smooth and is delineated by the ventricular-infundibular fold on the left and the trabecula septomarginalis on the right. These myocardial muscle bundles are minimally defined in the normal right ventricle but become prominent when the right ventricle is hypertrophied. These muscle bundles are also called the parietal and septal bands when they are sufficiently hypertrophied to obstruct the right ventricular outflow tract. In this state, a ridge forms on the infundibular septum, separating the body of the right ventricle from the conus portion, called the crista supraventricularis.