3.9 Lateral Cardiac and Pericardial Relations

Lateral Cardiac and Pericardial Relations define the anatomical structures adjacent to the heart and pericardium on their right and left sides within the thoracic cavity. These relations are critical for understanding the spatial orientation of the heart relative to surrounding organs, pleura, nerves, vessels, and lung structures. They influence clinical approaches in cardiothoracic surgery, imaging, and pathological assessments.

Right Lateral Cardiac and Pericardial Relations

The right side of the heart and pericardium is closely related to several thoracic structures:

Right Mediastinal Pleura

The right mediastinal pleura forms the lateral boundary of the pericardium on the right side. It separates the pericardium from the right pleural cavity and right lung. The pleura closely invests the lateral surface of the pericardium, allowing for smooth gliding movements during cardiac and respiratory cycles.

Right Lung

The anterior margin of the right lung, particularly the anterior border of the middle lobe, is adjacent to the right side of the pericardium. The lung and pericardium are separated by the mediastinal pleura and connective tissue. The relationship is important during thoracic surgical approaches to avoid lung injury.

Right Phrenic Nerve

The right phrenic nerve descends on the lateral aspect of the right pericardium, lying anterior to the root of the right lung. It courses between the pericardium and mediastinal pleura and provides motor innervation to the diaphragm and sensory innervation to the pericardium, pleura, and diaphragmatic peritoneum.

Pericardiacophrenic Vessels (Right Side)

The right pericardiacophrenic artery and vein accompany the right phrenic nerve along the lateral pericardium. These vessels provide vascular supply to the pericardium and adjacent diaphragmatic structures. They are branches of the internal thoracic artery and vein.

Right Pulmonary Hilum and Cardiac Relations

The right pulmonary hilum lies posterior and lateral to the right atrium and superior vena cava. The cardiac impression on the right lung at the hilum reflects the close relationship between lung structures and right cardiac chambers. The ascending aorta lies anterosuperiorly to the right pulmonary hilum.

Left Lateral Cardiac and Pericardial Relations

The left side of the heart and pericardium has distinct anatomical relations involving the lung, pleura, nerves, and vessels:

Left Mediastinal Pleura

The left mediastinal pleura forms the lateral boundary of the pericardium on the left side. It separates the pericardium from the left pleural cavity and lung. This pleura is closely applied to the pericardium, permitting smooth cardiac movement against the lung.

Left Lung

The anterior border and medial surface of the left lung, particularly the lingula and upper lobe, closely overlie the left pericardium. The lung and pericardium are separated by the mediastinal pleura and connective tissue sheath. The cardiac impression on the left lung corresponds to the left ventricle and left atrium.

Left Phrenic Nerve

The left phrenic nerve descends along the lateral aspect of the left pericardium, anterior to the root of the left lung. It travels between the pericardium and the mediastinal pleura, providing motor and sensory innervation similar to the right phrenic nerve.

Pericardiacophrenic Vessels (Left Side)

The left pericardiacophrenic artery and vein accompany the left phrenic nerve along the lateral pericardium. These vessels supply the pericardium and diaphragm, branching from the internal thoracic vessels.

Left Pulmonary Hilum and Cardiac Relations

The left pulmonary hilum lies lateral and slightly posterior to the left atrium and left ventricle. The cardiac impression on the left lung corresponds to these chambers. The descending thoracic aorta lies posteriorly and medial to the left hilum.

Integrated Anatomical Overview

The lateral surfaces of the heart and pericardium are enveloped in fibrous pericardium, which is in turn covered by mediastinal pleura on either side. The phrenic nerves and pericardiacophrenic vessels run in close proximity to the fibrous pericardium between it and the pleura, making them vulnerable during pericardial or thoracic interventions.

The right lateral surface is predominantly related to the right atrium and superior vena cava, while the left lateral surface corresponds mainly to the left ventricle and left atrium. Both sides have intimate relationships with their respective lungs and pleura, which facilitates efficient cardiopulmonary function but also requires careful consideration during surgical approaches.

Summary

The lateral cardiac and pericardial relations incorporate the right and left mediastinal pleura, lungs, phrenic nerves, and pericardiacophrenic vessels. The right side primarily relates to the right atrium and superior vena cava, whereas the left side corresponds mainly to the left atrium and ventricle. Understanding these relationships is essential for surgical navigation, avoiding nerve injury, and comprehending the functional anatomy of cardiopulmonary interactions.