Balloon angioplasty. Artwork showing balloon angioplasty treatment for stenosis (narrowing) of a coronary artery. A balloon catheter (blue) is inserted into the affected artery and inflated to open the artery up and restore normal blood flow. The most common cause of stenosis is atheroma (yellow), fatty deposits that thicken the inner coat of arteries. This can cause a reduction in blood flow (ischaemia) to the surrounding tissue and lead to a myocardial infarction (heart attack).