This is a treatment for patients with coronary artery disease (obstructed blood flow through the coronary arteries). The physician inserts a special catheter (thin, flexible tube) into the femoral artery. The catheter has a sharp blade located in its tip. X-ray is used to help the doctor thread the catheter up to the heart and into the coronary artery where the obstruction is located. Once the catheter is in place, the physician "cuts" or grinds the hard, fatty plaque away to open up the blood vessel and improve blood flow through the coronary artery.