During cardiopulmonary bypass, the surgeon passes a finger through a pericardial sinus located behind the aorta and pulmonary trunk and in front of the superior vena cava and left atrium. This allows placement of an arterial cross-clamp across both great arteries simultaneously. Which sinus is this?

• A Oblique pericardial sinus
• B Costomediastinal recess
• C Pericardiacophrenic recess
• D Transverse pericardial sinus ✓

Explanation

The transverse sinus lies between the arterial mesocardium (aorta and pulmonary trunk) anteriorly and the venous mesocardium (superior vena cava and left atrium) posteriorly. Passing a finger or clamp through it permits isolation of the arterial outflow for cross-clamping. The oblique sinus is a blind cul-de-sac behind the left atrium bounded by the pulmonary veins and cannot be traversed.

Reference: Gray's Anatomy for Students, 4th ed.

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