Causes. The majority of angina cases are going to be due to coronary artery diseases involving the build up of plaque in the arteries. The plaque build up makes it harder for the heart to get a proper supply of oxygen from the blood because the narrowed arteries reduce the amount of blood flow in the coronary arteries that supply the heart. In cases of unstable angina, the cause usually has something to do with a blood clot or blood clots that entirely or partly obstruct an artery. These blood clots develop, break free, float around, dissolve, and then develop all over again, angina will frequently happen with each obstruction. Often times an artery will begin to have a spasm, or a sudden narrowing and tightening action that disturbs the hearts normal blood supply, and this will result in Variant angina. Variant angina can be provoked by smoking, stress, drug abuse, certain medications, and exposure to cold.
