To Cross-clamp or Not to Cross-clamp
When David and colleagues retrospectively analyzed Type-A dissection surgical outcome, they noted worse results in the group with retrograde perfusion through a femoral artery and a cross-clamp applied to the ascending aorta during cooling 31. They believed this may be due to increased pressure in the false lumen occurring when the largest connection between the 2 lumens (the primary tear) is excluded by the application of the cross clamp, creating more distal re-entry points. A more recent report utilizing axillary artery cannulation has also recommended a no-clamp technique32. However safety in cross clamping the ascending aorta has been amply demonstrated as long as antegrade true lumen perfusion is achieved either through a direct aortic or axillary artery cannulation 33-35 36. Applying a cross clamp in the early cooling phase reduces the chances of myocardial ischemic injury that may arise from a flap obstructing the flow into either coronary artery, prevent left ventricular distension from severe aortic regurgitation that can overwhelm the LV vent, and finally allows an efficient use of the cooling period to work on the proximal aorta and root, saving precious bypass time. If the application of cross clamp leads to any pressure changes in the radial or femoral artery pressure lines 34, it may be a sign of malperfusion despite the best efforts in ensuring true lumen cannulation. The cross-clamp should then be removed to allow restoration of more normal flow patterns with reassessment of the etiology for the malperfusion.