Coronary stenosis after treatment. Angiogram of the left coronary artery in the heart of a 60-year-old patient after balloon catheterisation. The anterior interventricular branch (upper centre-right) 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 and inflated for a predetermined amount of time to stretch and enlarge the narrowed (stenosed) section of the artery, thus improving blood flow.