The oblique pericardial sinus is a blind pouch behind the heart. What structures form its boundaries, and what is its clinical significance?

• A Bounded by the reflections of pericardium around four pulmonary veins anteriorly and the left atrium posteriorly; cardiac surgery approach to left atrium ✓
• B Bounded by the four pulmonary veins and the inferior vena cava; surgeons use it to place tape around the aorta and pulmonary trunk
• C Between aorta and pulmonary trunk anteriorly and superior vena cava posteriorly; used for cardiopulmonary bypass
• D Bounded by the left phrenic nerve and left lung; important in pleuritis

Explanation

The oblique sinus is an inverted J-shaped reflection of serous pericardium formed by the four pulmonary veins (two on each side) and the inferior vena cava, with the left atrium lying anteriorly. It is a cul-de-sac that a finger can enter from below, lying behind the left atrium. In pericardial effusion, fluid accumulates here and may be approached surgically from below (posterior pericardiotomy). The transverse pericardial sinus — between the great arteries anteriorly (aorta and pulmonary trunk) and superior vena cava posteriorly — is used by surgeons to pass a clamp or tape around the aorta and pulmonary trunk during cardiac surgery.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.