Arteriosclerosis and atherosclerosis are two terms that sound so similar that they sometimes confuse even the new doctors. These two terms refer to conditions that are lightly related by the fact that both narrow the arteries. Age, smoking, obesity, family history are definite risk factors for both conditions and prevalence of both rise with the increasing age, pack years of smoking, BMI and presence of similar conditions in relatives. Understanding these conditions needs a bit of background knowledge on arterial anatomy. The innermost lining in contact with blood is called the endothelium. It is made up of tightly interlinked squamous cells. Outside the endothelium is a thin layer of loose connective tissue called the “tunica intima”. Outside the tunica intima is the muscular “tunica media”. Outside the tunica media, the outermost layer of the arterial wall is called the “tunica adventitia”.
What is Arteriosclerosis?
Arteriosclerosis is a condition where arterial wall thickens. Larger the arteries, more severe the arteriosclerosis tends to be. Arteriosclerosis tends to be more pronounced in medium to large caliber arteries. There are two major types of arteriosclerosis. First type is called “arteriosclerosis obliterance”. In this, the tunica intima fibroses and the tunica media harden due to deposition of calcium salts. Arteriosclerosis obliternace is quite commonly seen in arteries of lower extremities. There may be significant narrowing of the atrial lumen. The second type is called the “medial calcific sclerosis”. This type is commonly seen in elderly people. Leg arteries are affected more than upper limb arteries.
Medial calcific sclerosis differs from arteriosclerosis obliterance because there is no thickening of the tunica intima. The only pathological change is hardening of the tunica media due to deposition of calcium salts. There is no narrowing of the lumen in medial calcific sclerosis, unlike the first type. Cholesterol lowering drugs, blood pressure lowering drugs slow the development of arteriosclerosis. Angioplasty, bypass, and endarterectomy are available surgeries to clear up the blocked lumen.
What is Atherosclerosis?
Atherosclerosis is a complex process involving circulating cells as well as the endothelium. When serum cholesterol levels are high, cellular uptake also rises. Macrophages take cholesterol in and turn into foam cells. These foam cells enter the tunica intima. Inflammatory reaction triggered by these cells increases endothelial permeability and damages the cells. More foam cells get attracted by the chemotaxic agents released by inflammatory cells. The chemicals released from the inflammatory cells trigger smooth muscle cell, interstitial cell proliferation leading to thickening of the tunica intima and media. There is significant luminal narrowing accompanied with thrombus formation upon the damaged cap of the atherosclerotic plaque. These thrombi may break off and block arteries forward of the blocked one. This is the pathophysiology of stroke, heart attacks, and peripheral vascular disease.
What is the difference between Arteriosclerosis and Atherosclerosis?
• Arteriosclerosis involves intimal fibrosis while atherosclerosis does not.
• Arteriosclerosis involves tunica media thickening due to calcification while in atherosclerosis media thickens due to inflammatory mediators.
• Arteriosclerosis may or may not narrow the lumen while atherosclerosis always does.
• Arteriosclerosis is not worsened by thrombus formation while atherosclerosis may be.
• There is plaque rupture in atherosclerosis and not in arteriosclerosis.