cardiac

Cardiac is simply the adjective for anything to do with the heart. Whenever you see it in a medical term, mentally translate it as heart: cardiac muscle means heart muscle, cardiac arrest means the heart has stopped, cardiac output means how much the heart pumps.

The word comes from the Greek kardia, heart, and it appears all over clinical language. Some common pairings: cardiac arrest (sudden loss of heart function), cardiac arrhythmia (an abnormal rhythm), cardiac catheterization (threading a tube into the heart's vessels), and cardiac enzymes or troponin (blood markers of heart-muscle injury).

Be careful not to confuse cardiac with cardiovascular. Cardiac refers to the heart specifically, while cardiovascular refers to the heart together with the blood vessels. Cardiac is also a different word from the unrelated cardia, the medical name for the upper opening of the stomach.