During open-heart surgery, the surgeon passes a finger and then a ligature tape behind the pulmonary trunk and ascending aorta, anterior to the superior vena cava and left atrium. Which pericardial space has been entered?
- A Oblique pericardial sinus
- B Transverse pericardial sinus ✓
- C Pericardial cavity proper between parietal and visceral layers
- D Costomediastinal recess
Correct answer: B. Transverse pericardial sinus
Explanation
The transverse sinus is the horizontal passage between the arterial mesocardium (aorta and pulmonary trunk) in front and the venous mesocardium (superior vena cava and atria) behind. It develops from degeneration of the dorsal mesocardium and allows placement of an aortic cross-clamp or ligature around the great arteries. The oblique sinus is a blind cul-de-sac behind the left atrium and cannot be traversed.
Reference: Gray's Anatomy for Students, 4th ed.
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Written and medically reviewed by the StethoPrep medical team.