Atlas Contents
Morphology of the normal heart
Surfaces and grooves of the heart
The external morphology of the heart reflects the spatial arrangement of its chambers, great vessels, atrioventricular junctions, and coronary vasculature. Understanding these relationships is essential when interpreting fluoroscopic projections, cross-sectional imaging, electroanatomical maps, and intracardiac echocardiography. The descriptions below follow the sequence of the existing media in the atlas. Attitudinal terminology and its procedural implications are developed in Chapter 2.
The cardiac silhouette
The heart and the proximal segments of the great vessels occupy the middle mediastinum between the lungs. The heart is enclosed by the pericardial sac and is covered to a variable extent by epicardial adipose tissue, which is continuous with mediastinal fat around the roots of the great vessels. Superiorly, the cardiac mass is connected to the ascending aorta, pulmonary trunk, and superior caval vein. Inferiorly, the inferior caval vein enters the right atrium close to the diaphragmatic surface.
Figure 1. Anterior views of the thoracic cavity after removal of the anterior chest wall. In the left panel, the lungs occupy most of the visible thoracic cavity and largely obscure the cardiac silhouette. In the right panel, lateral displacement of the lungs exposes the mediastinal pleura and the fibrous pericardium, which rests inferiorly on the diaphragm.
The sternum and costal cartilages lie anterior to the heart. The right ventricle is the most anterior cardiac chamber and forms most of the surface immediately behind the sternum. Inferiorly, the heart rests on the diaphragm. Posteriorly, the left atrium is related to the oesophagus, while the pulmonary arteries and pulmonary veins are related to the main bronchi and other structures of the posterior mediastinum. When viewed from the front, most of the cardiac mass lies to the left of the midline, and the apex is usually projected in the region of the left fifth intercostal space near the midclavicular line.
Figure 2. Spatial relationships of the heart and great vessels within the thorax. The transverse section in the left panel shows the relationship of the pulmonary veins to the oesophagus, thoracic aorta, and pericardial space. The right panel shows a right-sided view of the heart, illustrating the relationships between the caval veins, right atrium, right ventricular inlet, pulmonary arteries, and great vessels.
Abbreviations: LIPV, left inferior pulmonary vein; LPA, left pulmonary artery; LSPV, left superior pulmonary vein; RAA, right atrial appendage; RIPV, right inferior pulmonary vein; RPA, right pulmonary artery; RSPV, right superior pulmonary vein; RV, right ventricle.
The frontal cardiac silhouette has a roughly trapezoidal outline. Its inferior and leftward component is produced mainly by the ventricular mass, whereas the atrial chambers and the roots of the great vessels contribute to its superior portion. The anatomical base of the heart is directed posteriorly and is formed predominantly by the left atrium. This use of the term base differs from the conventional isolated-heart or Valentine orientation and is considered further in Chapter 2.
Figure 3. Relations of the fibrous pericardium and pericardial cavity. The left panel shows the fibrous pericardium resting on the diaphragm between the lungs, with the right phrenic nerve descending along its lateral surface. The middle panel shows the internal aspect of the pericardial sac after removal of the heart and the openings related to the caval veins, pulmonary veins, aorta, and pulmonary trunk. The right panel shows the heart within the opened pericardial cavity and the courses of the right and left phrenic nerves.
Abbreviations: ADA, anterior descending artery; Ao, aorta; ICV, inferior caval vein; LIPV, left inferior pulmonary vein; LPN, left phrenic nerve; LSPV, left superior pulmonary vein; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RIPV, right inferior pulmonary vein; RPN, right phrenic nerve; RSPV, right superior pulmonary vein; RV, right ventricle; SCV, superior caval vein.
Surfaces of the heart
For descriptive purposes in this atlas, six external aspects are considered: anterior, right lateral, left lateral, inferior or diaphragmatic, posterior, and superior. These surfaces merge with one another rather than being separated by fixed anatomical boundaries. Their appearance also depends on whether the heart is examined in situ or removed from the thorax.
Anterior Surface
The anterior or sternocostal surface is related to the sternum and costal cartilages and is formed predominantly by the right ventricle. Superiorly, the observer encounters, from right to left, the junction of the superior caval vein with the right atrium, the right atrial appendage overlapping the ascending aorta, the pulmonary trunk, and the tip of the left atrial appendage. The right atrium lies anterior and inferior to the left atrium, while the right ventricle occupies the most anterior position among the cardiac chambers.
Right Lateral Surface
The right lateral or pulmonary surface is formed mainly by the right atrium and its venous component. The terminal groove extends externally from the superior caval vein toward the inferior caval vein and corresponds internally to the terminal crest. It marks the junction between the smooth-walled venous component and the trabeculated right atrial appendage. Posterior to the superior caval vein, the right pulmonary artery, right pulmonary veins, right main bronchus, and azygos vein contribute to the regional relationships. Outside the fibrous pericardium, the right phrenic nerve descends along this surface between the pericardium and mediastinal pleura.
Left Lateral Surface
The left lateral or pulmonary surface is formed predominantly by the left ventricle. Superiorly, the left atrial appendage projects from the left atrium, with the left superior and inferior pulmonary veins entering the atrium posteriorly. This surface is related superiorly to the pulmonary trunk and posteriorly to the left main bronchus, left vagus nerve, and descending thoracic aorta. The left phrenic nerve descends outside the fibrous pericardium in relation to the mediastinal pleura.
Inferior or Diaphragmatic Surface
The inferior surface rests on the central tendon of the diaphragm. It is formed mainly by the left ventricle, with a smaller contribution from the right ventricle. The inferior interventricular groove separates the ventricular components and contains the inferior interventricular artery and the middle cardiac vein. The arterial branch may arise from the right coronary artery or the circumflex artery according to coronary dominance.
Posterior Surface and Cardiac Base
The left atrium forms most of the posterior surface and receives the right and left pulmonary veins. The posterior wall of the right atrium, including the caval venous junctions, lies to its right and slightly anterior. The fibrous pericardium and oesophagus are immediately posterior to the left atrium. Superiorly, the pulmonary arteries and main bronchi cross behind the great arterial roots. These relationships are important during left atrial ablation because extracardiac structures can lie close to the atrial wall.
Superior Surface
The superior aspect is dominated by the roots of the great arteries and the superior caval vein. The ascending aorta occupies a central and posterior position relative to the pulmonary trunk. The pulmonary trunk arises anteriorly from the right ventricle and courses leftward before bifurcating. The spatial relationship between the arterial roots reflects cardiac looping and separation of the outflow tract during development.
Grooves and Borders of the heart
Atrioventricular Grooves
The right and left atrioventricular grooves mark the epicardial plane of the atrioventricular junctions. They are not arranged in a single plane. The right atrioventricular groove contains the right coronary artery along much of its course. The left atrioventricular groove contains the circumflex artery and, posteriorly, the coronary sinus or its continuation as the great cardiac vein. Adipose tissue within the grooves surrounds the coronary vessels and separates adjacent atrial and ventricular myocardium.
Figure 4. Sternocostal surface of the heart in an anatomical specimen and a colour-coded preparation. The right ventricle forms most of this surface, while the left ventricle contributes the leftward border and obtuse margin. The right and left atrioventricular grooves separate the atrial and ventricular components, and the anterior interventricular groove marks the plane between the ventricles.
Abbreviations: Ao, aorta; AV, atrioventricular; LAA, left atrial appendage; LSPV, left superior pulmonary vein; PA, pulmonary artery; RAA, right atrial appendage.
The tricuspid and mitral junctions have different spatial orientations. The tricuspid valve is displaced inferiorly toward the ventricular apex relative to the mitral valve. Consequently, the right and left atrioventricular grooves cannot be understood accurately from a single frontal view. Their attitudinal orientation and their appearance in right and left anterior oblique projections are described in Chapter 2.
Figure 5. Inferior and posterior aspects of the heart in an anatomical specimen and a colour-coded preparation. The inferior interventricular groove separates the ventricular components on the diaphragmatic surface. At the crux, it meets the right and left atrioventricular grooves. The posteriorly located left atrium receives the pulmonary veins, while the coronary sinus courses in the left atrioventricular groove.
Abbreviations: AV, atrioventricular; LA, left atrium; LIPV, left inferior pulmonary vein; RAA, right atrial appendage; RSPV, right superior pulmonary vein.
Interventricular Grooves and the Crux
The anterior interventricular groove marks the external plane between the right and left ventricles on the anterior surface. It contains the anterior interventricular artery and the great cardiac vein within epicardial adipose tissue. The groove approaches the apex but does not necessarily coincide with the internal limits of the muscular ventricular septum.
On the diaphragmatic surface, the inferior interventricular groove courses toward the crux of the heart. It contains the inferior interventricular artery and the middle cardiac vein. The crux is the external point at which the inferior interventricular groove meets the atrioventricular groove. The terms anterior and inferior are attitudinally appropriate; the traditional term posterior descending artery refers to the inferior interventricular artery.
Figure 6. External surfaces, grooves, and coronary vessels shown in three anatomical views. The left panel demonstrates the right lateral, left lateral, and diaphragmatic surfaces. The middle panel shows the ventricular outflow tracts and the anterior interventricular groove. The right panel shows the inferior interventricular groove, the crux, and the coronary sinus within the atrioventricular groove.
Abbreviations: AD, anterior descending; AV, atrioventricular; CS, coronary sinus; CX, circumflex; LA, left atrium; LAA, left atrial appendage; LV, left ventricle; MC, middle cardiac; PA, pulmonary artery; PD, posterior descending; RA, right atrium; RAA, right atrial appendage; RC, right coronary; RV, right ventricle; RVOT, right ventricular outflow tract; SCV, superior caval vein.
Cardiac Borders or Margins
The acute margin is formed at the junction between the anterior and diaphragmatic surfaces and corresponds mainly to the right ventricle. It may be accompanied by an acute marginal branch of the right coronary artery. The obtuse margin is the rounded junction between the left lateral and diaphragmatic surfaces and is formed by the left ventricle. One or more obtuse marginal branches of the circumflex artery may descend along this region.
Figure 7. Relationships of the valvar orifices and coronary arteries at the cardiac base. The left panel shows the central position of the aortic root between the mitral and tricuspid valves, together with the origins and proximal courses of the coronary arteries. The right panel shows the aortic root between the atrioventricular junctions and its relationship to the atrial appendages and coronary sinus.
Abbreviations: LAA, left atrial appendage; LCS, left coronary aortic sinus; NCS, non-coronary aortic sinus; PT, pulmonary trunk; RAA, right atrial appendage; RCS, right coronary aortic sinus.
Key Anatomical Messages
- The right ventricle is the most anterior cardiac chamber, whereas the left atrium forms most of the posterior cardiac base.
- The atrioventricular and interventricular grooves are external landmarks, but they do not reproduce all internal septal boundaries.
- The tricuspid and mitral junctions occupy different levels and orientations within the thorax.
- The inferior interventricular groove and the crux should be described according to their true inferior location.
- The relations of the atrial walls to the oesophagus, phrenic nerves, lungs, and mediastinal vessels have direct procedural relevance.
Media
