Complex sentence: It is most commonly equated with atherosclerotic coronary artery disease, but coronary disease can be due to other causes, such as coronary vasospasm, where the stenosis to be caused by spasm of the blood vessels of the heart it is then usually called Prinzmetal's angina.
Split into simpler sentences: It is most commonly equated with atherosclerotic coronary artery disease, but it can also have other causes. If it is caused by coronary vasospasm,, a spasm of the blood vessels of the heart, it is usually called Prinzmetal's angina.