Atherosclerosis (also known as ArterioscleroticVascular Disease or ASVD)is the condition in which an artery wall thickens as the result of a build-upof fatty materials such as cholesterol. It is a syndromeaffecting arterialbloodvessels, a chronic inflammatory response in the walls of arteries, in largepart due to the accumulation of macrophage whiteblood cells and promoted by Low-density lipoproteins (plasma proteinsthat carry cholesterol and triglycerides)without adequate removal of fats and cholesterol from the macrophages byfunctional high density lipoproteins (HDL). It iscommonly referred to as a hardening or furring of the arteries. It is caused bythe formation of multiple plaques within the arteries.
The atheromatousplaque is divided into three distinct components:
- The atheroma ("lump of gruel"), which is the nodular accumulation of a soft, flaky, yellowish material at the center of large plaques, composed of macrophages nearest the lumen of the artery
- Underlying areas of cholesterol crystals
- Calcification at the outer base of older/more advanced lesions.
The following terms are similar, yet distinct, in both spelling andmeaning, and can be easily confused: arteriosclerosis,arteriolosclerosis, and atherosclerosis. Arteriosclerosis is a generalterm describing any hardening (and loss of elasticity) of medium or largearteries; arteriolosclerosis is any hardening (and loss of elasticity)of arterioles(small arteries); atherosclerosis is a hardening of an arteryspecifically due to an atheromatous plaque. The term atherogenic is usedfor substances or processes that cause atherosclerosis.
Atherosclerosis, though typically asymptomatic for decades, eventuallyproduces two main problems: First,the atheromatousplaques, though long compensated for by artery enlargement, eventually leadto plaque ruptures and clots inside the artery lumenover the ruptures. The clots heal and usually shrink but leave behind stenosis(narrowing) of the artery (both locally and in smaller downstream branches), orworse, complete closure, and, therefore, an insufficient blood supply to thetissues and organ it feeds. Second,if the compensating artery enlargement process is excessive, then a net aneurysmresults.
These complications of advanced atherosclerosis are chronic, slowlyprogressive and cumulative. Most commonly, soft plaque suddenly ruptures (see vulnerableplaque), causing the formation of a thrombus thatwill rapidly slow or stop blood flow, leading to death of the tissues fed bythe artery in approximately 5 minutes. This catastrophic event is called an infarction.One of the most common recognized scenarios is called coronary thrombosis of a coronaryartery, causing myocardial infarction (a heart attack). Evenworse is the same process in an artery to the brain, commonly called stroke. Anothercommon scenario in very advanced disease is claudicationfrom insufficient blood supply to the legs, typically due to a combination ofboth stenosis and aneurysmal segments narrowed with clots. Sinceatherosclerosis is a body-wide process, similar events occur also in thearteries to the brain, intestines, kidneys, legs, etc.
Yet, many infarctions involve only very small amounts of tissue and aretermed clinically silent, because the person having theinfarction does not notice the problem, does not seek medical help or when theydo, physicians do not recognize what has happened.
Atherosclerosis typically begins in early adolescence, and is usually foundin most major arteries,yet is asymptomatic and not detected by most diagnostic methods during life. Atheroma inarm, or more often in leg arteries, which produces decreased blood flow iscalled peripheral artery occlusive disease(PAOD).
For about 65% of men and 47% of women, the first symptom ofatherosclerotic cardiovascular disease is heart attack or sudden cardiac death (death within one hour ofonset of the symptom).
Most artery flow disrupting events occur at locations with less than 50% lumennarrowing (~20% stenosisis average).
Cardiac stress testing, traditionally the mostcommonly performed non-invasive testing method for blood flow limitations, ingeneral, detects only lumen narrowing of ~75% or greater, although somephysicians claim that nuclear stress methods can detect as little as 50%.