EARLY INJURY TO THE MEDIA AFTER SAPHENOUS-VEIN GRAFTING

Background. Injury to the smooth muscle cells of the media affects the remodeling process of vein grafts. The purpose of this study was to d etermine whether different techniques of surgical preparation influenc e the degree of medial smooth muscle injury. Methods. Carotid-saphenou s vein interposition grafting was performed in crossbred pigs (n = 32) , using distended (n = 16) or nondistended (n = 16) conduits. After 3 to 90 days, the media was evaluated for the presence of smooth muscle cells (desmin stains), myofibroblast formation (transient cu-SM actin expression), and apoptosis (TdT-mediated dUTP nick end-labeling [TUNEL ]). Results. Smooth muscle loss was uniformly severe; only 5% +/- 5% ( p < 0.01) and 14% +/- 9% (p < 0.01) of the medial area of distended an d nondistended veins were desmin positive in comparison with 80% +/- 9 % of controls. Apoptosis appeared to contribute to medial smooth muscl e loss (5.7% +/- 4.3% in vein grafts versus 0.0% +/- 0.0% of TUNEL-pos itive cells in controls; p = 0.05). There was a time dependent increas e in medial myofibroblast formation (p < 0.05). Conclusions. Severe me dial smooth muscle loss occurs in vein grafts, even when prepared with out distension. Apoptosis contributes to the early disappearance of sm ooth muscle cells. Adjunctive measures, in addition to ideal surgical techniques, should be developed to prevent medial muscle loss. (C) 199 8 by The Society of Thoracic Surgeons.