If there is a tiny defect anywhere in that suture line, there is going to be added stress at that point and it may start to tear. Once a tear has begun, it becomes a progressive weakness, like tearing a stamp along the perforation. So the tear may very well be progressive. It is one of the reasons I don't do this type of repair anymore. There is a higher incidence of leaflet dehiscence in the one patch repair than some other types of repair.
Dehiscence means the coming apart of the surgical incision or suture line.
It was Cornel's view that the leaflet tissue remaining on the mitral valve that had been sutured to the patch had come away from the suture line. It depends how much tissue you have to work with. This valve was behaving satisfactorily at the completion of the surgery, but I presume either the sutures pulled out or maybe became infected and pulled through, I don't know. But for whatever reason, the valve began to perform much worse in a relatively short period of time and just became progressively more so. De Nanassy disagreed that there was valve dehiscence, because, he said, there was no valve tissue to dehisce in the first place.