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.