Coronary artery supply blood and oxygen to the heart. This blockage can disturb the blood supply supply to heart. There are 2 main coronary arteries like left and right. Left coronary artery supply blood to left side of the heart while right coronary artery to right side of the heart. Blockage of the any main or branch of the coronary artery can cut down the oxygen supply to that part of the heart to which affected coronary artery supply blood. This condition can lead to heart attack.