When the heart muscle isn't receiving a sufficient supply of well oxygenated blood, a person may experience chest pain, or angina pectoris (an-JIE-nuh pek-TORE-iss). Such a condition of inadequate blood supply is called ischemia (iss-KEE-mee-uh). There can be many reasons why the heart isn't receiving enough blood. Generally, ischemia is due to hardened or narrowed arteries, resulting from cholesterol deposit build up. These arteries may not be able to deliver blood to the heart muscle at the rate required for the work the heart is attempting to do. This condition can put a person at risk for heart attack. Although angina pectoris is most often noticed during sudden physical exertion, intense emotions or significant temperature fluctuations, a variation of the condition occurs during sleep or resting periods instead. This form of angina is caused by sudden spasms of the heart's main arteries, often due to extensive atherosclerosis (ath-er-o-skler-OH-sis), or hardening and narrowing of one or more of those arteries. It usually involves more painful attacks, sometimes continuing unprovoked, off and on, for several months. Treatment for these conditions depends greatly on the specific causes and may include something as simple as a diet and exercise change, or any of several cardiac (KAR-dee-ak) procedures designed to open and widen cardiac arteries. If you're concerned about the condition of your heart, or have further questions about angina, contact a healthcare provider.