Describe the Stages of Atherosclerosis ?
The process of atherosclerosis which gives rise to CAD marches in stages. The earliest recognizable pathologic lesions are the fatty streaks, small yellvwish focal lesions, which make their appearance in the aorta and big vessels even before three years of age, The fatty streaks are composed of intracellular collection of lipid materials with elastin and other fibre protein in the intima and inner media of blood vessels. These linear streaks increase in number, size and distribution during the second decade and become evident in coronary arteries. Gradually in the third decade, the fatty streaks progress to fibrous plaques - a firm raised white lesion containing increased amounts of lipids, collagen and fibrous tissue. As the fibrous plaque grows in bulk with more and more fatty substances, cel1ul:u infiltrates and connective tissue proliferation, it bulges into the lumen of the artery in the for111 of 'atheroma'. There are varying amounts of lipid in the core and a fibrous cap covers the inner core. This happens around the fourth decade in life. Subsequently there may be plaque fissure, rupture, haemorrhage, clot formation - the 'complicated' atheroma giving rise to acute coronary syndrome, heart attacks etc. The rate by which the lesion progresses through different stages varies in different ethnic group and individuals depending on various risk factors. New fatty streales continue to form throughout adult life and atheloselerotic lesions in different stages of development may be present in the same individual. The plaques ]nay be 'stable' or 'unstable' depending on the amount of lipid core and the thickness and hardness of the cap covering the plaque. While the stable plaques are responsibility for time ischaenlia and anginal symptoms, ~t is the soft unstable plaques which usually ruptures and initiates clotting process resulting in unstable angina, acute coronary syndromes and myocardial infarction. Atherosclerosis is not confined to the coronary arteries only; almost all medium sized arteries including arteries to the brains and limbs may be involved.