The superior vena cava forms the upper third of the right cardiac border. The inferior vena cava forms an extremely short segment on the lower part of the right border. Both drain into the right atrium. The right atrium forms the lower two thirds of the right cardiac border. The tricuspid valve, which is situated behind the lower end of the sternum, connects it to the right ventricle. The right ventricle is pyramidal in shape. It is separated from the right cardiac border by the right atrium and from the left border by the left ventricle. Thus it does not appear on any of the cardiac borders in the PA view. It forms the anterior surface of the heart and is thus better delineated in the lateral view. The pulmonary artery segment forms a concavity on the left border of the heart at the medial end of the second left intercostal space. The left atrium is an oval chamber in the middle of the cardiac shadow. The left atrial appendage extends to the left and forms a part of the left cardiac border at the medial end of the third left intercostals space. The left ventricle is oblong in shape and forms the lower half of the left border of the heart. Its long axis is directed downwards and to the left. The aorta is subdivided into three parts: The ascending aorta extends upwards and to the right. It comes very close to the upper third of the right cardiac border. The aortic arch curves to the left and posteriorly and forms a prominence on the left cardiac border at the medial end of the first left intercostals space. The descending aorta runs medially and downwards and does not normally form any part of the cardiac borders.
The Lateral View: In the lateral view the right ventricle and the pulmonary artery are the most anterior structures. They are seen immediately under the sternum. The right ventricle comes in contact with the lower third of the sternum but is normally separated from its upper two thirds by the lung (the retrosternal space ). The left atrium and the left ventricle are situated posteriorly. The left atrium is the most posterior structure and lies directly in front of the esophagus, (Fig. 47) . The left ventricle is separated from the vertebral column by the retrocardiac space.
This causes displacement of the lower two thirds of the right cardiac border outwards, (Fig. 49) . It is usually associated with right ventricular enlargement but may rarely be isolated in cases of tricuspid stenosis
Course of persistent left SVC Draining into right atrium Starts at junction of left subclavian vein and left internal jugular Passes lateral to aortic arch Receives left superior intercostal vein Anterior to left hilum Joined by hemiazygous system Crosses posterior wall of left atrium Receives great cardiac vein to become coronary sinus (common)
MRI-signaal kan niet direct, maar na een tijdje (daarom echo).