What does "cardiac" mean?

From Latin, cardiacus, the term cardiac means anything pertaining to the heart. This word is typically used as a noun, as in cardiac arrest -- heart arrest -- or an adjective, as in the term cardiac patient, or heart patient. The lower portion of the esophagus has a musculature known as the cardiac sphincter -- aptly named in its proximity to the heart, although it has nothing to do with the heart muscle.