Pericardium

The pericardium is a conical, flask-like, fibroserous sac which contains the heart and the roots of the great vessels and defines the middle mediastinum. 

Gross anatomy

The pericardium is made of two sacs in one. The outer sac is the fibrous pericardium and the inner sac is the double-layered serous pericardium. Layers of serous pericardium are divided by the pericardial space, which only contains 15-50 mL of serous fluid. Each layer has quite different structure and functions:

• fibrous pericardium: tough connective tissue continuous with and bound to the central tendon of the diaphragm (pericardiophrenic ligament), the roots of the great vessels, the pretracheal layer of the deep cervical fascia and the sternum via the superior (to manubrium) and inferior sternopericardial ligaments (to xiphoid process)
• serous pericardium: composed of a single layer of flattened mesothelial cells forming a closed sac and forms two continuous layers:
  • visceral serous pericardium (or epicardium): covers heart and great vessels
  • parietal serous pericardium: lines the fibrous pericardium and is inseparable

The serous pericardium is invaginated by the heart and great vessels forming two sinuses:

• oblique pericardial sinus: formed by the superior and inferior vena cavae and the four pulmonary veins (blind-ending) and thus sits posterior to the left atrium
  • may be mistaken for oesophageal masses or bronchogenic cysts ³
• transverse pericardial sinus: lies between the aorta/pulmonary artery anteriorly and the atria posteriorly, surrounding the ascending aorta; there are several pericardial recesses that may be mistaken for dissection or lymphadenopathy ³

​AdjacentAdjacent to these sinuses, there may be one or several pericardial recesses:

• aortic recesses
  • ​superior aortic recess
  • inferior aortic recess
• pulmonic recesses
  • right pulmonic recess
  • left pulmonic recess
• postcaval recess
• pulmonary venous recesses
  • right pulmonary venous recess
  • left pulmonary venous recess

Relations

• anteriorly: body of the sternum, cartilages of left third-to-seventh ribs, pleura and lungs, and thymus (in children)
• posteriorly: oesophagus, descending thoracic aorta, pleura and lungs
• laterally: pleura and lungs, phrenic nerves
• inferiorly: blends with central tendon of diaphragm

Blood supply

• arterial supply
  • internal thoracic artery and its pericardiacophrenic and musculophrenic branches
  • branches from the descending thoracic aorta
• venous drainage: pericardiacophrenic veins

Innervation

• phrenic nerves: to fibrous and parietal serous layers
• vagus nerve
• sympathetic trunks: for pain, muscles and vessels of heart

Lymphatic drainage

• tracheobronchial nodes
• prepericardial nodes ⁹
  • Tracheobronchial nodes
  • Prepericardial nodes

  Variant anatomy

  • pericardial agenesis

  Radiographic appearance

  CT

  • pericardium appears as a thin high-density line between the lower-density mediastinal and epicardial fat
  • fibrous and serous pericardium cannot be delineated and the upper limits of normal for pericardial thickness is 2 mm ²
  • often not imaged over the left ventricle ³

  MRI

  • T1 and T2: appears as a low signal rim between the higher-signal mediastinal and epicardial fat ^2-3

  Related pathology

  • pericardial agenesis
  • pericardial effusion
    • fetal pericardial effusion
  • pericardial tamponade
  • pneumopericardium
  • pericarditis
  • pericardial cyst
  • pericardial calcification
  • pericardial tumours
    • pericardial teratoma
      • fetal pericardial teratoma