What is This Crease/line Under my Left Breast From?

My best guess, based on your past surgical history of correction of bottoming out of the left breast implant, is that the extra “crease” below your left breast is some “redundant” skin that was previously stretched out by the bottomed out breast implant. In other words, the crease is simply skin that has not adhered back down after the capsulorraphy technique probably used for the correction of the bottoming out.

 I hope this helps.

Without seeing both breasts in a photo it is not possible to comment on symmetry. Even on the affected breast I am not clear what I am seeing. I do suspect that you are looking at the suture line from the bottoming out repair, but that really is just a guess--your surgeon should be able to tell you this based on an in person exam.

Thanks for your question, all the best. 

can occur at the ends of the transverse incisions due to redundant skin.  It is still hard to speculate without an exam.  Your surgeon should be able to help you better understand this and you should discuss this with him/her.  If redundant skin, a simple office revision can take care of it.