A Transcatheter Aortic Valve (Replacement/Implantation, or TAVR/TAVI) is a minimally invasive procedure to replace a diseased aortic valve, typically due to narrowing (aortic stenosis), without open-heart surgery, using a catheter inserted through blood vessels (like the groin) to guide a new, expandable valve into place, offering a faster recovery for patients too frail for traditional surgery, though it has unique risks like stroke.