Atheroma plaque. Coloured doppler ultrasound scan of blood flow through a stricture in the left inner carotid artery. The blood flow is greatest when red and slowest when green. This stricture is due to atheroma, a fatty plaque deposit caused by atherosclerosis, on the inner wall of the artery. This disease is usually caused by excess cholesterol in the diet, although smoking and inactivity are also risk factors. The plaques of atheroma narrow the arteries, raising blood pressure. This places more strain on the heart, and can lead to heart disease. It also increases the chances of a thrombus (abnormal clot) forming, which can also lead to a heart attack or stroke.