HUMAN MAMMARY ARTERY ENDOTHELIAL SPARING WITH FIBROUS JAW CLAMPING

Background. Temporary clamping of the internal mammary artery pedicle is required for visualization during coronary artery bypass grafting. A nylon fibril jaw surface has been developed for these clamps that ex erts pressure only at discrete sites on the pedicle surface. The effec t of this new jaw surface on endothelial cell function and integrity a fter compression is investigated in this study. Methods. Internal mamm ary artery specimens from 10 patients each were divided into three sep arate rings, and two of these rings were clamped for 30 minutes with e ither a smooth or fibrous jaw clamp. Isometric tensions were measured in organ chambers after contraction by relaxing the rings with the end othelium-dependent agent acetylcholine followed by the endothelium-ind ependent agent sodium nitroprusside. The intimal surfaces of similar r ings were silver stained to assess the percentage of intact endotheliu m. Results. Endothelium-dependent relaxation was spared after fibrous jaw clamping (75% versus 89%) but significantly impaired after smooth jaw clamping (25% versus 89%; p < 0.001). Endothelium-independent rela xation was unaffected by either intervention. The percentage of remain ing intact endothelium upon silver staining was significantly less aft er smooth than after fibrous jaw clamping (24% versus 48%; p < 0.01). Conclusions. Foam silicone with nylon fibrils on the jaw surface of in ternal mammary artery clamps preserves endothelial cell function and i ntegrity. The remaining undamaged cells also may facilitate the subseq uent regeneration of a confluent endothelial cell layer.