Coronary stenosis treatment. Coloured angiograms showing the left coronary artery in the heart of a 60-year-old patient before (top left), during (top right and bottom left) and after (bottom right) balloon catheterisation. The anterior interventricular branch of the left coronary artery was affected by severe stenosis (narrowing) that was the cause of a myocardial infarction (heart attack). The balloon catheter was inserted into the artery (top right) and inflated (bottom left) for a predetermined amount of time to stretch and enlarge the narrowed (stenosed) section of the artery, thus improving blood flow.