Ground beef heart might sound a little less appetizing than ground beef—but it might also be what you're actually eating, reports Consumerist. A 1981 policy under the Department of Agriculture's Food Safety and Inspection Service (page 24 here) decrees that meat from a cow's heart, tongue, and organs is "not acceptable" in chopped beef, ground beef, or hamburger," in part because consumers wouldn't expect to find it there. In a July 2016 post on its website, however, the FSIS says "cardiac muscle trimmed from the ventricular wall of a beef heart … can be used in unlimited quantities and declared as 'beef' on the label."
Other parts of the heart, like the aorta and atria, aren't allowed in ground beef or hamburger, the post states. A rep for Marina Meats tells CBS San Francisco that buyers likely wouldn't notice if their ground beef contained heart meat—high in iron and B-12—though beef with more than 10% heart meat has "a little more iron flavor." He does say heart meat should be mentioned on labels, though. Under another Department of Agriculture policy, ground beef containing beef cheek must carry a special label, but only if cheek makes up 25% of the product. (Your ground beef likely has fecal contamination, too.)