To better understand the effect of the internal thoracic artery on endothelial growth after open coronary endarterectomy, we designed an experimental test of the hypothesis that closing an endarterectomized artery by an arterial patch improves re-endothelialization. The two carotid arteries were endarterectomized in nine sheep and were randomly chosen for closure by native arterial femoral (ART) patch or polytetrafluoroethylene (PTFE) patch. Three animals were randomly chosen for sacrifice at 8, 15 and 21 days each. The endarterectomized segments were studied macroscopically and microscopically. The endarterectomized area covered with adhesive thrombus was more extensive in the PTFE than in the ART group (P=0.0117). In the ART group, the regenerated endothelium was normal and sprouted from the edges of both the endarterectomy and the arterial patch towards the central endarterectomized area. In the PTFE group, it sprouted from the edges of the endarterectomy and never reached the central endarterectomized area, where abnormal endothelium was observed. The endarterectomized area covered with normal endothelium was more extensive in the ART than in the PTFE group at 8 days, at 15 days, and 21 days (P<0.001). Arterial patch closure of open-endarterectomized artery improved regenerated endothelium quality.