3.8 Posterior Cardiac and Pericardial Relations

Posterior Cardiac and Pericardial Relations describe the anatomical structures that lie directly behind the heart and its surrounding pericardium within the thoracic cavity. These relations are critical for understanding spatial orientation, clinical procedures, and pathological processes involving the heart and adjacent mediastinal contents. The posterior aspect of the heart and pericardium is closely related to several vital structures including parts of the esophagus, descending thoracic aorta, vertebral column, thoracic duct, azygos vein system, pulmonary veins, and various mediastinal tissues.

Esophagus-Pericardium Relationship

The esophagus runs posterior to the pericardium, specifically behind the left atrium. This close proximity allows the esophagus to be palpated during certain cardiac procedures and can affect the heart if esophageal pathologies such as tumors or inflammation occur. The fibrous pericardium separates the heart from the esophagus, but this layer is thin and allows for some transmission of pressure or pathological processes.

The esophagus lies in the posterior mediastinum, descending adjacent to the vertebral bodies, and crosses behind the left atrium and pericardial sac. It is partially covered by pericardium, which forms the anterior boundary of the posterior mediastinum.

Descending Thoracic Aorta-Pericardium Relationship

The descending thoracic aorta is situated to the left and behind the pericardium. It descends along the vertebral column on the left side, posterior to the heart and pericardium. The pericardium in this region is in close contact with the aorta, separated by loose connective tissue and mediastinal fat.

The aorta’s position relative to the pericardium is significant because any enlargement or aneurysm of the descending aorta can impinge on the pericardium or heart structures, potentially affecting cardiac function.

Vertebral Column-Cardiac Relationship

Posterior to the heart and pericardium lies the vertebral column, specifically the lower thoracic vertebrae (T5–T8). The pericardium is separated from the vertebral bodies by the posterior mediastinal tissues, including the esophagus, thoracic duct, lymph nodes, and connective tissue.

The vertebral column provides a rigid posterior boundary for the heart and pericardium. The distance between the pericardium and vertebral column is variable and influenced by the presence of intervening structures such as the esophagus and aorta.

Posterior Mediastinal Tissue Relationship

The posterior mediastinum contains loose connective tissue, lymph nodes, nerves, and vessels that lie between the pericardium and vertebral column. It includes the thoracic duct, azygos vein system, and sympathetic trunks.

These tissues provide a cushioning and supportive environment for the heart and pericardium, while also serving as conduits for neurovascular structures. The posterior mediastinal fat and lymphatic tissue fill the spaces around the pericardium and contribute to the mobility and protection of the heart.

Left Atrium-Esophagus Relationship

The left atrium forms the anterior boundary to the esophagus in the posterior mediastinum. This close anatomical relationship is clinically relevant because enlargement of the left atrium, such as in mitral valve disease, can compress the esophagus, leading to dysphagia or other esophageal symptoms.

This relationship is also exploited in transesophageal echocardiography, where an ultrasound probe placed in the esophagus provides detailed images of the left atrium and other cardiac structures without interference from the lungs or ribs.

Pulmonary Vein-Posterior Pericardial Relationship

The pulmonary veins, particularly the left pulmonary veins, lie in close relation to the posterior pericardium as they enter the left atrium. These veins are ensheathed by pericardium and connective tissue, and their proximity to the posterior pericardial surface means that pericardial diseases can affect pulmonary venous return.

Additionally, the pulmonary veins are important landmarks for cardiac electrophysiology procedures, especially in the treatment of atrial fibrillation where ablation around pulmonary vein ostia is performed.

Inferior Vena Cava-Posterior Pericardial Relationship

The inferior vena cava (IVC) ascends through the diaphragm and enters the right atrium at the posterior inferior aspect of the heart. The pericardium surrounds the IVC as it passes into the pericardial cavity, forming the inferior portion of the posterior pericardial surface.

This relationship is essential in venous return dynamics and is relevant in procedures involving central venous access or in pathologies causing compression or obstruction of the IVC.

Thoracic Duct-Cardiac Spatial Relationship

The thoracic duct ascends in the posterior mediastinum posterior to the esophagus and to the right of the descending thoracic aorta before arching laterally to drain into the venous system near the junction of the left subclavian and internal jugular veins.

Its position posterior to the pericardium and heart makes it vulnerable during cardiac surgeries or mediastinal interventions. Injury to the thoracic duct can result in chylothorax due to lymphatic leakage.

Azygos System-Cardiac Spatial Relationship

The azygos vein system lies to the right of the vertebral bodies and posterior to the pericardium. The azygos vein arches over the right main bronchus and empties into the superior vena cava near its entry into the pericardium.

This relationship is important during thoracic surgery and imaging, as enlargement or thrombosis of the azygos system can affect the venous drainage and may simulate cardiac or mediastinal masses.

Posterior Cardiac Relation Map

The posterior surface of the heart is predominantly formed by the left atrium and partially by the right atrium and pulmonary veins. The pericardium covers this surface and separates the heart from the adjacent posterior mediastinal contents.

The spatial arrangement can be summarized as follows:

• Directly posterior: left atrium and pulmonary veins covered by pericardium
• Immediately posterior to pericardium: esophagus centrally, descending thoracic aorta to the left, azygos vein system to the right
• Posterior to these structures: thoracic duct, mediastinal lymph nodes, vertebral bodies