The heart is a four-chambered organ located in the upper left chest cavity that pumps blood throughout the body to distribute oxygen and nutrients. Angina is chest pain or discomfort caused by reduced blood flow to the heart, usually due to coronary artery disease. It is treated with medications like nitroglycerin, beta blockers, and calcium channel blockers to reduce the heart's workload and oxygen needs. Myocardial infarction, also known as a heart attack, occurs when blood flow to the heart is blocked, damaging heart muscle. It causes chest pain or discomfort and is usually due to coronary artery disease.