The presence of advanced plaques of types IV and Va allows clinical symptoms to develop. Atherosclerosis is a biphasic disease; in the first stage, advanced plaques are generated but the patient is asymptomatic; in the second stage, symptoms develop. In all geographic populations, the mean number of coronary plaques present in a large number of autopsied patients who die from all caused predicts the incidence of ischaemic heart disease in that population. Smokers will, on average, have more plaques than nonsmokers. Similar data exist for hyperlipidemia, hypertension, and diabetes. Thus risk factors operate in part by increasing the number of plaques that can potentially progress to cause symptoms. Common to all type Va plaques is the presence of a fibromuscular cap.The cap may be relatively thick and uniform, or it may vary in thickness with interspersed thin areas.