This common procedure is performed in order to measure pressures inside the heart and take pictures of the coronary arteries – usually in order to look for blockages or atherosclerotic plaques that can cause chest pains and shortness of breath as well as a variety of other symptoms, and when severe can even cause a myocardial infarction (heart attack). Catheters are placed via a sheath (narrow tube) in the artery of the groin or arm, advanced into the heart, and pictures are taken with injectable contrast dye and X-ray.