Forming a proximal anastomosis on an aortic wall includes method and instrumentation and apparatus for forming an aortic puncture and inserting into the vessel through the puncture a fluid-impervious sealing element with a protruding retainer. An anastomosis of a graft vessel over the puncture is partially completed with the retainer of the sealing element protruding through the partial anastomosis. The retainer facilitates removal of the sealing element from the partial anastomosis prior to completion of the procedure.