Although there are many causes of chest pain, the two large groups of causes are cardiac-related problems and non-cardiac causes. Cardiac chest pain is caused by an imbalance between the blood supply to the heart and oxygen needs of the heart muscle. Cardiac chest pain is most commonly a result of atherosclerosis (leading to fixed narrowing of coronary arteries), but also can be caused by coronary spasms that narrow the arteries intermittently. Cardiac chest pain is also referred to as angina or angina pectoris. Non-cardiac chest pain has many causes, ranging from infections and muscle or bone problems to conditions such as lung tumors, lung collapse, chest trauma, upper abdominal pain, and gastric reflux. Although some of the non-cardiac causes of chest pain may require emergency care (for examples, lung collapse and severe chest trauma), most do not.