Calcium channel blockers (CCBs) are used to treat heart disease, angina (chest pain), heart arrhythmias, and cardiomyopathy. They also may be used to treat high blood pressure in individuals with angina and/or a high risk of stroke, and alongside other drugs to treat resistant high blood pressure. CCBs increase the supply of blood and oxygen to the heart by relaxing blood vessels. They achieve this effect by attaching to the surface membrane of the muscles in the arteries, slowing the rate at which calcium passes into the heart muscle and into the blood vessel walls, which, in turn, decreases the contraction of both. The effect is to slow the rate at which the heart beats, reducing its workload and treating any arrhythmia, and also to increase the diameter of the arteries so that blood pressure falls-this also relieves pressure on the heart, by making it easier to pump blood.