Beta blockers are drugs that slow the heartbeat, lessen the force with which the heart muscle contracts and reduce blood vessel contraction in the heart, brain and throughout the body. This relieves stress on the heart. They may be used to treat abnormal heart rhythms and to prevent abnormally fast heart rates or irregular rhythms. Since they reduce the demand of the heart muscle for oxygen, they may be useful in treating angina, or chest pain, which occurs when the oxygen demand of the heart exceeds the supply. Beta blockers improve survival after a heart attack and also are used to treat high blood pressure and other heart conditions.