Superior Vena Cava

INTRODUCTION:
  • The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. 
  • It is a large-diameter (24 mm), yet short, vein that receives venous return from the upper half of the body, above the diaphragm. (Venous return from the lower half, below the diaphragm, flows through the inferior vena cava.) 
  • The SVC is located in the anterior right superior mediastinum.
STRUCTURE & COURSE OF SUPERIOR VENA CAVA:
  • It is formed by the left and right brachiocephalic veins (also referred to as the innominate veins), which also receive blood from the upper limbs, eyes and neck, behind the lower border of the first right costal cartilage.
  • It passes vertically downwards behind first intercostal space and receives azygos vein behind sternal angle just before it pierces the fibrous pericardium opposite right second costal cartilage and its lower part is intrapericardial And then,it ends in the upper and posterior part of the sinus venarum (coronary sinus)of the right atrium at the level of 3rd costal, at the upper right front portion of the heart.
  • No valve divides the superior vena cava from the right atrium. As a result, the (right) atrial and (right) ventricular contractions are conducted up into the internal jugular vein and, through the sternocleidomastoid muscle, can be seen as the jugular venous pressure.
CLINICAL SIGNIFICANCE :
  • Superior vena cava obstruction refers to a partial or complete obstruction of the superior vena cava, typically in the context of cancer such as a cancer of the lung, metastatic cancer, or lymphoma. 
  • Obstruction can lead to enlarged veins in the head and neck, and may also cause breathlessness, cough, chest pain, and difficulty swallowing
  • Pemberton's sign may be positive. 
  • Tumours causing obstruction may be treated with chemotherapy and/or radiotherapy to reduce their effects, and corticosteroids may also be given.
  • In tricuspid valve regurgitation, these pulsations are very strong. 
Exam Question
  • Left sided superior vena cava drains into coronary sinus
  • Azygous vein drains into Superior vena Cavas 
  • Superior vena cava enters the heart at the level of 3rd costal cartilage
  • Pierces paricardium at 2nd costal cartilage
  • Superior vena cava receive azygous vein behind sternal angle

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