Miriam Margolyes has revealed she now has a “cow’s heart” after undergoing an operation to fix a worrying health problem. The 82 year old Harry Potter actress told how she'd had a transcatheter aortic valve replacement (TAVR) - a procedure that avoids the need for open heart surgery.The operation meant that her aortic valve was replaced by that of a cow. Miriam, who is known for playing Professor Sprout in the Harry Potter franchise, as well as for her chaotic appearances on This Morning, discussed the procedure on the Table Manners podcast with Jessie and Lennie Ware.