Cardiology & Cardiovascular Surgery Resources Websites and Support Groups Adult Congenital Heart Association American Heart Association Mended Hearts Books Zip-Line is a charming book written for children that had open heart surgery and are left with a “zip-line” scar on their chest. This heart-warming rhyme book whimsically explains the answer to the question “How did that line get there?” Zip-Line helps children be comfortable with themselves, their scar, and the surgery they are too young to remember.