Angioplasty. Coloured angiogram taken during a percutaneous transluminal coronary angioplasty (PTCA) to the right coronary artery. It is done to treat a severe stenosis (narrowing, upper centre left) caused by plaques of atheroma lining the inside of the artery; the blood flow is also impaired by a clot seen in the same area just below the stenosis. A special double lumen catheter (top centre inside the artery) is used with a cylindrical-shaped balloon surrounding a portion of it. The inflation of the balloon with a pressure up to 620,000 Pascal dilates the narrowed vessel. The large dark area at top centre is one of the heart's major blood vessels.