Think of the heart as muscular pump tasked with distributing blood throughout the body. The amount of blood the heart pumps out is not fixed, but increases and decreases to match to the body’s immediate needs. And like any other organ, the myocardium or heart muscle requires blood and the nutrients and oxygen dissolved in blood in order to function. With activity or during times of stress the heart beats much faster and more forcefully. As a result, the hearts requirements for blood increases correspondingly . Angina or angina pectoris refers to chest pain or discomfort resulting from an imbalance in the myocardium's need for blood, and the amount of blood it actually receives. This condition is also referred to as myocardial ischemia. In the majority of cases, angina is caused by narrowing or obstruction of the arteries supplying the myocardium, also called the coronary arteries.
Typically angina affects men over the age of 50 and women over the age of 60. The discomfort is described as an uncomfortable sense of pressure, fullness, squeezing, choking or pain in the middle of the chest. When describing their symptoms, a patient with angina may make a fist over his chest (the so called Levine's sign). The discomfort also may be felt in the neck, jaw, shoulder, back or arm. Anginal symptoms usually last for 2 to 5 minutes and are precipitated by physical exertion or emotional stress. In some patients, the amount of activity required to cause anginal symptoms may vary with the time of day, type of activity or temperature. Rest will relieve exceptional anginal symptoms within 5 minutes or less, especially with sublingual nitroglycerine use. Occasionally symptoms occur at night when the patient lies recumbent. 
Some individuals with angina do not experience chest pain or discomfort at all but instead experience upper abdominal discomfort, shortness of breath or arm or neck discomfort exclusively. This is also referred to as anginal equivalents. Others may suffer from ischemia but not experience any symptoms whatsoever. This phenomena is referred to as silent ischemia. 
Many types of chest discomfort aren't related to angina. A number of cardiac conditions can cause chest pain unrelated to angina. These include pericarditis (an inflammation to the lining surrounding the heart) and myocarditis (inflammation to the heart muscle). In addition noncardiac disorders can also present as chest discomfort or pain. Acid reflux (heartburn), esophageal spasm, asthma and lung infections or inflammation are examples of non-cardiac conditions that can cause chest discomfort.
Abraham Salacata, MD, FACC