In surgical procedures, and specifically in cardiovascular operations, the polypropylene monofilament is a widely used suture material. We report an unexplained case of early rupture of a 4-0 polypropylene suture used for the distal anastomosis after replacement of the ascending aorta with a Dacron (Vaskutek, Sulzer Medica, Austin, TX) prosthesis. By trying to identify if intraoperative mechanical damage could have led to the rupture, we obtained impressive results of how different manipulations of suture material using surgical instruments can damage those delicate filaments. Pictures were obtained by light microscopy and electron microscopy.