Pericardial Branches

The pericardial branches are small arteries that arise from the thoracic portion of the descending aorta. They supply the posterior surface of the fibrous pericardium - the tough connective tissue sac that encloses the heart. These arteries are part of a broader arterial network that ensures the pericardium receives adequate oxygenated blood along its entire surface.

Origin

Pericardial branches originate directly from the anterior or lateral surfaces of the descending thoracic aorta. They are multiple, small-caliber vessels and are often not individually named due to their variability and minor size.

• Location of origin: Posterior mediastinum, generally between the levels of T5 and T8

• Side of origin: Usually bilateral, but more frequent on the left due to the position of the aorta

Course

After arising from the thoracic aorta, the pericardial branches pass anteriorly through the posterior mediastinum to reach the posterior surface of the fibrous pericardium. Some vessels penetrate the fibrous pericardium to reach its deeper layers and may anastomose with other pericardial arteries on the anterior surface of the heart.

Distribution

These branches supply the:

• Posterior surface of the fibrous pericardium

• Adjacent connective tissue and fat

• Occasionally parts of the mediastinal pleura

Anastomoses

The pericardial branches of the thoracic aorta anastomose with other pericardial arteries from various sources:

• Pericardiacophrenic arteries: From the internal thoracic arteries, supply the anterior and lateral pericardium

• Musculophrenic arteries: From the internal thoracic arteries, contribute near the diaphragmatic surface

• Bronchial arteries: May contribute small branches to the pericardium

Venous Drainage

Venous return from the pericardium is via small pericardial veins that drain into:

• Azygos vein (on the right)

• Hemiazygos or accessory hemiazygos vein (on the left)

Topographic Relationships

• Anterior: Fibrous pericardium and heart

• Posterior: Descending thoracic aorta and vertebral bodies

• Inferior: Diaphragm

• Lateral: Mediastinal pleura and lungs

Histological Features

The pericardial branches are small-caliber arteries with typical arterial wall structure:

• Tunica intima: Thin endothelial lining with basal lamina

• Tunica media: Mostly smooth muscle with some elastic fibers

• Tunica adventitia: Connective tissue with sympathetic nerve fibers

Clinical Significance

• Pericarditis: While inflammation is typically not vascular in origin, increased perfusion from these arteries may contribute to symptoms in chronic cases

• Surgical relevance: These arteries are considered during thoracic aortic procedures and pericardial resections

Topographic Summary

• Number: Multiple small branches

• Origin: Descending thoracic aorta (T5–T8)

• Supply: Posterior fibrous pericardium

• Anastomoses: With pericardiacophrenic, musculophrenic, and bronchial arteries

• Drainage: Azygos and hemiazygos systems