coronary atherosclerosis

冠状動脈硬化症

WordNet

1. (botany) the trumpet-shaped or cup-shaped outgrowth of the corolla of a daffodil or narcissus flower
2. one or more circles of light seen around a luminous object
3. a long cigar with blunt ends
4. (anatomy) any structure that resembles a crown in shape
5. surrounding like a crown (especially of the blood vessels surrounding the heart); "coronary arteries"
6. a stage of arteriosclerosis involving fatty deposits (atheromas) inside the arterial walls, thus narrowing the arteries (同)coronary_artery_disease

PrepTutorEJDIC

1. コロナ(皆既日食のときに見える光冠) / (太陽・月などの)かさ
2. 冠状動脈の / 心臓の / 冠状動脈血栓(けっせん)症(coronary thrombosis)
3. 動脈硬化症

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/02 21:25:17」(JST)

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For the journal, see Atherosclerosis (journal).

Atherosclerosis
Classification and external resources
The progression of atherosclerosis (size exaggerated; see text)
ICD-10	I70
ICD-9	440, 414.0
DiseasesDB	1039
MedlinePlus	000171
eMedicine	med/182
MeSH	D050197

Atherosclerosis (also known as arteriosclerotic vascular disease or ASVD) is a specific form of arteriosclerosis in which an artery wall thickens as a result of the accumulation of calcium and fatty materials such as cholesterol and triglyceride. It is a syndrome affecting arterial blood vessels, a chronic inflammatory response in the walls of arteries, caused largely by the accumulation of macrophages and white blood cells and promoted by low-density lipoproteins (LDL, plasma proteins that carry cholesterol and triglycerides) without adequate removal of fats and cholesterol from the macrophages by functional high-density lipoproteins (HDL) (see apoA-1 Milano). It is commonly referred to as a hardening or furring of the arteries. It is caused by the formation of multiple plaques within the arteries.

The atheromatous plaque is divided into three distinct components:

1. The atheroma ("lump of gruel", from Greek ἀθήρα (athera), meaning "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
2. Underlying areas of cholesterol crystals
3. Calcification at the outer base of older/more advanced lesions.

The following terms are similar, yet distinct, in both spelling and meaning, and can be easily confused: arteriosclerosis, arteriolosclerosis, and atherosclerosis. Arteriosclerosis is a general term describing any hardening (and loss of elasticity) of medium or large arteries (from Greek ἀρτηρία (artēria), meaning "artery", and σκλήρωσις (sklerosis), meaning "hardening"); arteriolosclerosis is any hardening (and loss of elasticity) of arterioles (small arteries); atherosclerosis is a hardening of an artery specifically due to an atheromatous plaque. The term atherogenic is used for substances or processes that cause atherosclerosis.^{[citation needed]}

Atherosclerosis is a chronic disease that remains asymptomatic for decades. Atherosclerotic lesions, or atherosclerotic plaques are separated into two broad categories: Stable and unstable (also called vulnerable). The pathobiology of atherosclerotic lesions is very complicated but generally, stable atherosclerotic plaques, which tend to be asymptomatic, are rich in extracellular matrix and smooth muscle cells, while, unstable plaques are rich in macrophages and foam cells and the extracellular matrix separating the lesion from the arterial lumen (also known as the fibrous cap) is usually weak and prone to rupture. Ruptures of the fibrous cap expose thrombogenic material, such as collagen to the circulation and eventually induce thrombus formation in the lumen. Upon formation, intraluminal thrombi can occlude arteries outright (e.g. coronary occlusion), but more often they detach, move into the circulation and eventually occluding smaller downstream branches causing thromboembolism. Apart from thromboembolism, chronically expanding atherosclerotic lesions can cause complete closure of the lumen. Interestingly, chronically expanding lesions are often asymptomatic until lumen stenosis is so severe (usually over 80%) that blood supply to downstream tissue(s) is insufficient, resulting in ischemia.

These complications of advanced atherosclerosis are chronic, slowly progressive and cumulative. Most commonly, soft plaque suddenly ruptures (see vulnerable plaque), causing the formation of a thrombus that will rapidly slow or stop blood flow, leading to death of the tissues fed by the 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 coronary artery, causing myocardial infarction (a heart attack). The same process in an artery to the brain is commonly called stroke. Another common scenario in very advanced disease is claudication from insufficient blood supply to the legs, typically caused by a combination of both stenosis and aneurysmal segments narrowed with clots.

Atherosclerosis affects the entire artery tree, but mostly larger, high-pressure vessels such as the coronary, renal, femoral, cerebral, and carotid arteries. These are termed "clinically silent" because the person having the infarction does not notice the problem and does not seek medical help, or when they do, physicians do not recognize what has happened.

Signs and symptoms

Clinically, atherosclerosis is typically associated with men over the age of 45. Sub-clinically, the disease begins to appear at early childhood, and perhaps even at birth. Noticeable signs can begin developing at puberty. Though symptoms are rarely exhibited in children, early screening of children for cardiovascular diseases could be beneficial to both the child and his/her relatives. Atheroma in arm, or more often in leg arteries, which produces decreased blood flow is called peripheral artery occlusive disease (PAOD). Typically, atherosclerosis begins as a thin layer of white streaks on the artery wall (usually due to white blood cells) and progresses from there. While coronary artery disease is more prevalent in men than women, atherosclerosis of the cerebral arteries and strokes equally affect both sexes.

According to United States data for the year 2004, for about 66% of men and 47% of women, the first symptom of atherosclerotic cardiovascular disease is a heart attack or sudden cardiac death (death within one hour of onset of the symptom).^{[citation needed]}

Most artery flow disrupting events occur at locations with less than 50% lumen narrowing (~20% stenosis is average). The illustration above, like most illustrations of arterial disease, overemphasizes lumen narrowing, as opposed to compensatory external diameter enlargement (at least within smaller arteries, e.g., heart arteries) typical of the atherosclerosis process as it progresses (see Glagov or the ASTEROID trial). The relative geometry error within the illustration is common to many older illustrations, an error slowly being more commonly recognized within the last decade.

Cardiac stress testing, traditionally the most commonly performed non-invasive testing method for blood flow limitations, in general, detects only lumen narrowing of ~75% or greater, although some physicians claim that nuclear stress methods can detect as little as 50%.

A famous case study involved autopsies of American soldiers killed in World War II and the Korean War. Although these were mostly young, healthy men in their 20s, many already had evidence of developing atherosclerosis.^{[citation needed]} Other studies done on soldiers in the Second Indochina War showed similar results, although often worse than the ones from the earlier wars.^{[citation needed]} Theories include high rates of tobacco use and (in the case of the Vietnam soldiers) the advent of processed foods after WWII.

Causes

Atherosclerosis and lipoproteins

See also: Lipoprotein

The atherosclerotic process is not fully understood. Atherosclerosis is initiated by inflammatory processes in the endothelial cells of the vessel wall in response to retained low-density lipoprotein (LDL) molecules.

Lipoproteins in the blood vary in size. Some data suggests that only small dense LDL (sdLDL) particles are able to get behind the cellular monolayer of endothelium. LDL particles and their content are susceptible to oxidation by free radicals, and the risk may be higher while in the bloodstream. However, LDL particles have a half-life of only a couple of days, and their content (LDL particles carry cholesterol, cholesteryl esters, and tryglycerides from the liver to the tissues of the body) changes with time.

Once inside the vessel wall, LDL particles get stuck and their content becomes more prone to oxidation. The damage caused by the oxidized LDL molecules triggers a cascade of immune responses which over time can produce an atheroma. First the immune system sends specialized white blood cells (macrophages and T-lymphocytes) to absorb the oxidized LDL, forming specialized foam cells. These white blood cells are not able to process the oxidized LDL. They grow and then rupture, depositing a greater amount of oxidized cholesterol into the artery wall. This triggers more white blood cells, continuing the cycle. Eventually, the artery becomes inflamed. The cholesterol plaque causes the muscle cells to enlarge and form a hard cover over the affected area. This hard cover is what causes a narrowing of the artery, reducing blood flow and increasing blood pressure.

Some researchers believe that atherosclerosis may be caused by an infection of the vascular smooth muscle cells. Chickens, for example, develop atherosclerosis when infected with the Marek's disease herpesvirus. Herpesvirus infection of arterial smooth muscle cells has been shown to cause cholesteryl ester (CE) accumulation, which is associated with atherosclerosis. Cytomegalovirus (CMV) infection is also associated with cardiovascular diseases.

Risk factors

Various anatomic and physiological risk factors for atherosclerosis are known. These can be divided into various categories: congenital vs acquired, modifiable or not, classical or non-classical. The points labelled '+' in the following list form the core components of metabolic syndrome.

Risks multiply, with two factors increasing the risk of atherosclerosis fourfold. Hyperlipidemia, hypertension and cigarette smoking together increases the risk seven times.

Modifiable

• Diabetes or Impaired glucose tolerance (IGT) +
• Dyslipoproteinemia (unhealthy patterns of serum proteins carrying fats & cholesterol): +
  • High serum concentration of low-density lipoprotein (LDL, "bad if elevated concentrations and small"), and / or very low density lipoprotein (VLDL) particles, i.e., "lipoprotein subclass analysis"
  • Low serum concentration of functioning high density lipoprotein (HDL "protective if large and high enough" particles), i.e., "lipoprotein subclass analysis"
  • An LDL:HDL ratio greater than 3:1
• Tobacco smoking, increases risk by 200% after several pack years
• Elevated serum C-reactive protein concentrations
• Vitamin B₆ deficiency
• Dietary iodine deficiency and hypothyroidism, which cause elevated serum cholesterol and of lipid peroxidation

Nonmodifiable

• Advanced age
• Male sex
• Having close relatives who have had some complication of atherosclerosis (e.g. coronary heart disease or stroke)
• Genetic abnormalities, e.g. familial hypercholesterolemia

Lesser or uncertain

The following factors are of relatively lesser importance, are uncertain or unquantified:

• Obesity (in particular central obesity, also referred to as abdominal or male-type obesity) +
• Hypercoagulability
• Postmenopausal estrogen deficiency
• High intake of saturated fat (may raise total and LDL cholesterol)
• Intake of trans fat (may raise total and LDL cholesterol while lowering HDL cholesterol)
• High carbohydrate intake
• Elevated serum levels of triglycerides +
• Elevated serum levels of homocysteine
• Elevated serum levels of uric acid (also responsible for gout)
• Elevated serum fibrinogen concentrations
• Elevated serum lipoprotein(a) concentrations
• Chronic systemic inflammation as reflected by upper normal WBC concentrations, elevated hs-CRP and many other blood chemistry markers, most only research level at present, not clinically done.
• Hyperthyroidism (an over-active thyroid)
• Elevated serum insulin levels +
• Short sleep duration
• Chlamydia pneumoniae infection
• PM_2.5 air pollution, fine particulates less than 2.5 µm in diameter, have been associated with thickening of the carotid artery.

Dietary

The relation between dietary fat and atherosclerosis is a contentious field. The USDA, in its food pyramid, promotes a low-fat diet, based largely on its view that fat in the diet is atherogenic. The American Heart Association, the American Diabetes Association and the National Cholesterol Education Program make similar recommendations. In contrast, Prof Walter Willett (Harvard School of Public Health, PI of the second Nurses' Health Study) recommends much higher levels, especially of monounsaturated and polyunsaturated fat. Writing in Science, Gary Taubes detailed that political considerations played into the recommendations of government bodies. These differing views reach a consensus, though, against consumption of trans fats.

The role of dietary oxidized fats/lipid peroxidation (rancid fats) in humans is not clear. Laboratory animals fed rancid fats develop atherosclerosis. Rats fed DHA-containing oils experienced marked disruptions to their antioxidant systems, and accumulated significant amounts of phospholipid hydroperoxide in their blood, livers and kidneys. In another study, rabbits fed atherogenic diets containing various oils were found to undergo the greatest amount of oxidative susceptibility of LDL via polyunsaturated oils. In a study involving rabbits fed heated soybean oil, "grossly induced atherosclerosis and marked liver damage were histologically and clinically demonstrated." However, Kummerow, a prominent researcher, claims that it is not dietary cholesterol, but oxysterols, or oxidized cholesterols, from fried foods and smoking, that are the culprit.

Rancid fats and oils taste very bad even in small amounts, so people avoid eating them. It is very difficult to measure or estimate the actual human consumption of these substances.

Highly unsaturated omega-3 rich oils such as fish oil are being sold in pill form so that the taste of oxidized or rancid fat is not apparent. The health food industry's dietary supplements are self regulated by the manufacture and outside of FDA regulations. To properly protect unsaturated fats from oxidation, it is best to keep them cool and in oxygen free environments. Long term exposure to inorganic arsenic can cause atherosclerosis.

Pathophysiology

Atherogenesis is the developmental process of atheromatous plaques. It is characterized by a remodeling of arteries leading to subendothelial accumulation of fatty substances called plaques. The build up of an atheromatous plaque is a slow process, developed over a period of several years through a complex series of cellular events occurring within the arterial wall, and in response to a variety of local vascular circulating factors. One recent hypothesis suggests that, for unknown reasons, leukocytes, such as monocytes or basophils, begin to attack the endothelium of the artery lumen in cardiac muscle. The ensuing inflammation leads to formation of atheromatous plaques in the arterial tunica intima, a region of the vessel wall located between the endothelium and the tunica media. The bulk of these lesions is made of excess fat, collagen, and elastin. At first, as the plaques grow, only wall thickening occurs without any narrowing. Stenosis is a late event, which may never occur and is often the result of repeated plaque rupture and healing responses, not just the atherosclerotic process by itself.

Cellular

Micrograph of an artery that supplies the heart with significant atherosclerosis and marked luminal narrowing. Tissue has been stained using Masson's trichrome.

Early atherogenesis is characterized by the adherence of blood circulating monocytes (a type of white blood cell) to the vascular bed lining, the endothelium, followed by their migration to the sub-endothelial space, and further activation into monocyte-derived macrophages. The primary documented driver of this process is oxidized lipoprotein particles within the wall, beneath the endothelial cells, though upper normal or elevated concentrations of blood glucose also plays a major role and not all factors are fully understood. Fatty streaks may appear and disappear.

Low-density lipoprotein (LDL) particles in blood plasma invade the endothelium and become oxidized, creating risk of cardiovascular disease. A complex set of biochemical reactions regulates the oxidation of LDL, involving enzymes (such as Lp-LpA2) and free radicals in the endothelium.

Initial damage to the endothelium results in an inflammatory response. Monocytes enter the artery wall from the bloodstream, with platelets adhering to the area of insult. This may be promoted by redox signaling induction of factors such as VCAM-1, which recruit circulating monocytes, and M-CSF, which is selectively required for the differentiation of monocytes to macrophages. The monocytes differentiate into macrophages, which ingest oxidized LDL, slowly turning into large "foam cells" – so-called because of their changed appearance resulting from the numerous internal cytoplasmic vesicles and resulting high lipid content. Under the microscope, the lesion now appears as a fatty streak. Foam cells eventually die, and further propagate the inflammatory process. There is also smooth muscle proliferation and migration from the tunica media into the intima responding to cytokines secreted by damaged endothelial cells. This causes the formation of a fibrous capsule covering the fatty streak. Intact endothelium could prevent the proliferation by releasing nitric oxide.

Calcification and lipids

Calcification forms among vascular smooth muscle cells of the surrounding muscular layer, specifically in the muscle cells adjacent to atheromas and on the surface of atheroma plaques and tissue. In time, as cells die, this leads to extracellular calcium deposits between the muscular wall and outer portion of the atheromatous plaques. A similar form of an intramural calcification, presenting the picture of an early phase of arteriosclerosis, appears to be induced by a number of drugs that have an antiproliferative mechanism of action (Rainer Liedtke 2008).

Cholesterol is delivered into the vessel wall by cholesterol-containing low-density lipoprotein (LDL) particles. To attract and stimulate macrophages, the cholesterol must be released from the LDL particles and oxidized, a key step in the ongoing inflammatory process. The process is worsened if there is insufficient high-density lipoprotein (HDL), the lipoprotein particle that removes cholesterol from tissues and carries it back to the liver.

The foam cells and platelets encourage the migration and proliferation of smooth muscle cells, which in turn ingest lipids, become replaced by collagen and transform into foam cells themselves. A protective fibrous cap normally forms between the fatty deposits and the artery lining (the intima).

These capped fatty deposits (now called 'atheromas') produce enzymes that cause the artery to enlarge over time. As long as the artery enlarges sufficiently to compensate for the extra thickness of the atheroma, then no narrowing ("stenosis") of the opening ("lumen") occurs. The artery becomes expanded with an egg-shaped cross-section, still with a circular opening. If the enlargement is beyond proportion to the atheroma thickness, then an aneurysm is created.

Visible features

Severe atherosclerosis of the aorta. Autopsy specimen.

Although arteries are not typically studied microscopically, two plaque types can be distinguished:

1. The fibro-lipid (fibro-fatty) plaque is characterized by an accumulation of lipid-laden cells underneath the intima of the arteries, typically without narrowing the lumen due to compensatory expansion of the bounding muscular layer of the artery wall. Beneath the endothelium there is a "fibrous cap" covering the atheromatous "core" of the plaque. The core consists of lipid-laden cells (macrophages and smooth muscle cells) with elevated tissue cholesterol and cholesterol ester content, fibrin, proteoglycans, collagen, elastin, and cellular debris. In advanced plaques, the central core of the plaque usually contains extracellular cholesterol deposits (released from dead cells), which form areas of cholesterol crystals with empty, needle-like clefts. At the periphery of the plaque are younger "foamy" cells and capillaries. These plaques usually produce the most damage to the individual when they rupture.
2. The fibrous plaque is also localized under the intima, within the wall of the artery resulting in thickening and expansion of the wall and, sometimes, spotty localized narrowing of the lumen with some atrophy of the muscular layer. The fibrous plaque contains collagen fibers (eosinophilic), precipitates of calcium (hematoxylinophilic) and, rarely, lipid-laden cells.

In effect, the muscular portion of the artery wall forms small aneurysms just large enough to hold the atheroma that are present. The muscular portion of artery walls usually remain strong, even after they have remodeled to compensate for the atheromatous plaques.

However, atheromas within the vessel wall are soft and fragile with little elasticity. Arteries constantly expand and contract with each heartbeat, i.e., the pulse. In addition, the calcification deposits between the outer portion of the atheroma and the muscular wall, as they progress, lead to a loss of elasticity and stiffening of the artery as a whole.

The calcification deposits, after they have become sufficiently advanced, are partially visible on coronary artery computed tomography or electron beam tomography (EBT) as rings of increased radiographic density, forming halos around the outer edges of the atheromatous plaques, within the artery wall. On CT, >130 units on the Hounsfield scale (some argue for 90 units) has been the radiographic density usually accepted as clearly representing tissue calcification within arteries. These deposits demonstrate unequivocal evidence of the disease, relatively advanced, even though the lumen of the artery is often still normal by angiographic or intravascular ultrasound.

Rupture and stenosis

Although the disease process tends to be slowly progressive over decades, it usually remains asymptomatic until an atheroma ulcerates, which leads to immediate blood clotting at the site of atheroma ulcer. This triggers a cascade of events that leads to clot enlargement, which may quickly obstruct the flow of blood. A complete blockage leads to ischemia of the myocardial (heart) muscle and damage. This process is the myocardial infarction or "heart attack".

If the heart attack is not fatal, fibrous organization of the clot within the lumen ensues, covering the rupture but also producing stenosis or closure of the lumen, or over time and after repeated ruptures, resulting in a persistent, usually localized stenosis or blockage of the artery lumen. Stenoses can be slowly progressive, whereas plaque ulceration is a sudden event that occurs specifically in atheromas with thinner/weaker fibrous caps that have become "unstable".

Repeated plaque ruptures, ones not resulting in total lumen closure, combined with the clot patch over the rupture and healing response to stabilize the clot, is the process that produces most stenoses over time. The stenotic areas tend to become more stable, despite increased flow velocities at these narrowings. Most major blood-flow-stopping events occur at large plaques, which, prior to their rupture, produced very little if any stenosis.

From clinical trials, 20% is the average stenosis at plaques that subsequently rupture with resulting complete artery closure. Most severe clinical events do not occur at plaques that produce high-grade stenosis. From clinical trials, only 14% of heart attacks occur from artery closure at plaques producing a 75% or greater stenosis prior to the vessel closing.^{[citation needed]}

If the fibrous cap separating a soft atheroma from the bloodstream within the artery ruptures, tissue fragments are exposed and released. These tissue fragments are very clot-promoting, containing collagen and tissue factor; they activate platelets and activate the system of coagulation. The result is the formation of a thrombus (blood clot) overlying the atheroma, which obstructs blood flow acutely. With the obstruction of blood flow, downstream tissues are starved of oxygen and nutrients. If this is the myocardium (heart muscle), angina (cardiac chest pain) or myocardial infarction (heart attack) develops.

Diagnosis

Microphotography of arterial wall with calcified (violet colour) atherosclerotic plaque (haematoxillin & eosin stain)

Areas of severe narrowing, stenosis, detectable by angiography, and to a lesser extent "stress testing" have long been the focus of human diagnostic techniques for cardiovascular disease, in general. However, these methods focus on detecting only severe narrowing, not the underlying atherosclerosis disease. As demonstrated by human clinical studies, most severe events occur in locations with heavy plaque, yet little or no lumen narrowing present before debilitating events suddenly occur. Plaque rupture can lead to artery lumen occlusion within seconds to minutes, and potential permanent debility and sometimes sudden death.

Plaques that have ruptured are called complicated plaques. The extracellular matrix of the lesion breaks, usually at the shoulder of the fibrous cap that separates the lesion from the arterial lumen, where the exposed thrombogenic components of the plaque, mainly collagen will trigger thrombus formation. The thrombus then travel downstream to other blood vessels, where the blood clot may partially or completely block blood flow. If the blood flow is completely blocked, cell deaths occur due to the lack of oxygen supply to nearby cells, resulting in necrosis. The narrowing or obstruction of blood flow can occur in any artery within the body. Obstruction of arteries supplying the heart muscle result in a heart attack, while the obstruction of arteries supplying the brain result in a stroke.

Doppler ultrasound of right internal Carotid artery with calcified and non-calcified plaques showing less than 70% stenosis

Lumen stenosis that is greater than 75% were considered as the hallmark of clinically significant disease in the past because recurring episodes of angina and abnormalities in stress test are only detectable at that particular severity of stenosis. However, clinical trials have shown that only about 14% of clinically debilitating events occur at sites with >75% stenosis. Majority of cardiovascular events that involve sudden rupture of the atheroma plaque do not display any evident narrowing of the lumen. Thus, greater attention has been focused on "vulnerable plaque" from the late 1990s onwards.

Besides the traditional diagnostic methods such as angiography and stress-testing, other detection techniques have been developed in the past decades for earlier detection of atherosclerotic disease. Some of the detection approaches include anatomical detection and physiologic measurement.

Examples of anatomical detection methods include (1) coronary calcium scoring by CT, (2) carotid IMT (intimal media thickness) measurement by ultrasound, and (3) intravascular ultrasound (IVUS). Examples of physiologic measurement methods include (1) lipoprotein subclass analysis, (2) HbA1c, (3) hs-CRP, and (4) homocysteine. Both anatomic and physiologic methods allow early detection before symptoms show up, disease staging and tracking of disease progression. Anatomic methods are more expensive and some of them are invasive in nature, such as IVUS. On the other hand, physiologic methods are often less expensive and safer. But they do not quantify the current state of the disease or directly track progression. In the recent years, ways of estimating the severity of atherosclerotic plaques is also made possible with the developments in nuclear imaging techniques such as PET and SPECT.

Prevention

Combinations of statins, niacin, intestinal cholesterol absorption-inhibiting supplements (ezetimibe and others, and to a much lesser extent fibrates) have been the most successful in changing common but sub-optimal lipoprotein patterns and group outcomes. In the many secondary prevention and several primary prevention trials, several classes of lipoprotein-expression-altering (less correctly termed "cholesterol-lowering") agents have consistently reduced not only heart attack, stroke and hospitalization but also all-cause mortality rates. The first of the large secondary prevention comparative statin/placebo treatment trials was the Scandinavian Simvastatin Survival Study (4S) with over fifteen more studies extending through to the more recent ASTEROID trial published in 2006. The first primary prevention comparative treatment trial was AFCAPS/TexCAPS with multiple later comparative statin/placebo treatment trials including EXCEL, ASCOT and SPARCL. While the statin trials have all been clearly favorable for improved human outcomes, only ASTEROID and SATURN showed evidence of atherosclerotic regression (slight). Both human and animal trials that showed evidence of disease regression used more aggressive combination agent treatment strategies, which nearly always included niacin.

Treatment

If atherosclerosis leads to symptoms, some symptoms such as angina pectoris can be treated. Non-pharmaceutical means are usually the first method of treatment, such as cessation of smoking and practicing regular exercise. If these methods do not work, medicines are usually the next step in treating cardiovascular diseases, and, with improvements, have increasingly become the most effective method over the long term.

Statins

In general, the group of medications referred to as statins has been the most popular and are widely prescribed for treating atherosclerosis. They have relatively few short-term or longer-term undesirable side-effects, and several clinical trials comparing statin treatment with placebo have fairly consistently shown strong effects in reducing atherosclerotic disease 'events' and generally ~25% comparative mortality reduction, although one study design, ALLHAT, was less strongly favorable.

The newest statin, rosuvastatin, was the first to demonstrate regression of atherosclerotic plaque within the coronary arteries by IVUS (intravascular ultrasound evaluation). The study was set up to demonstrate effect primarily on atherosclerosis volume within a 2 year time-frame in people with active/symptomatic disease (angina frequency also declined markedly) but not global clinical outcomes, which was expected to require longer trial time periods; these longer trials remain in progress. In the 2011 SATURN study, atorvastatin was also shown to effect regression of atherosclerotic plaque to a degree roughly equivalent to the regression brought about by rosuvastatin. However, for most people, changing their physiologic behaviors, from the usual high risk to greatly reduced risk, requires a combination of several compounds, taken on a daily basis and indefinitely. More and more human treatment trials have been done and are ongoing that demonstrate improved outcome for those people using more-complex and effective treatment regimens that change physiologic behaviour patterns to more closely resemble those that humans exhibit in childhood at a time before fatty streaks begin forming.

The success of statin drugs in clinical trials is based on some reductions in mortality rates, however by trial design biased toward men and middle-age, the data is, as yet, less strongly clear for women and people over the age of 70. For example, in the Scandinavian Simvastatin Survival Study (4S), the first large placebo-controlled, randomized clinical trial of a statin in people with advanced disease who had already suffered a heart attack, the overall mortality rate reduction for those taking the statin, vs. placebo, was 30%. For the subgroup of people in the trial who had Diabetes Mellitus, the mortality rate reduction between statin and placebo was 54%. 4S was a 5.4-year trial that started in 1989 and was published in 1995 after completion. There were three more dead women at trial's end on statin than in the group on placebo; whether this was due to chance or some relation to the statin remains unclear. The ASTEROID trial has been the first to show actual disease volume regression (see page 8 of the paper, which shows cross-sectional areas of the total heart artery wall at start and 2 years of rosuvastatin 40 mg/day treatment); however, its design was not able to "prove" the mortality reduction issue since it did not include a placebo group: the individuals offered treatment within the trial had advanced disease, and treatment with placebo was judged to be unethical.

Studies in mice show that statin promotes the emigration of monocytes out of atherosclerotic plaques to regional and systemic lymph nodes, resulting in the regression of plaques. The C-C chemokine receptor type 7 (CCR7) on the surface of monocytes is crucial for the migration of monocytes. Statin increases the activation of SRE binding protein 2 (SREBP-2), which promotes the transcription of CCR7 gene.

Diet

Changes in diet may help prevent the development of atherosclerosis. Researchers at the Agricultural Research Service have found that avenanthramides, which are chemical compounds found in oats, may help reduce the inflammation of the arterial wall, this contributes to the development of atherosclerosis. Avenanthramides have anti-inflammatory properties that are linked to activating proinflammatory cytokines. Cytokines are proteins that are released by the cell to protect and repair tissues. Researchers have found compounds in oats have the ability to reduce inflammation and help prevent atherosclerosis.

Surgical intervention

Other physical treatments, helpful in the short term, include minimally invasive angioplasty procedures that may include stents to physically expand narrowed arteries and major invasive surgery, such as bypass surgery, to create additional blood supply connections that go around the more severely narrowed areas.

Prophylaxis

Patients at risk for atherosclerosis-related diseases are increasingly being treated prophylactically with low-dose aspirin and a statin. The high incidence of cardiovascular disease led Wald and Law to propose a Polypill, a once-daily pill containing these two types of drugs in addition to an ACE inhibitor, diuretic, beta blocker, and folic acid. They maintain that high uptake by the general population by such a Polypill would reduce cardiovascular mortality by 80%. It must be emphasized however that this is purely theoretical, as the Polypill has never been tested in a clinical trial.

Medical treatments often focus predominantly on the symptoms. However, over time, clinical trials have shown treatments that focus on decreasing the underlying atherosclerosis processes—as opposed to simply treating symptoms—more effective.

In summary, the key to the more effective approaches has been better understanding of the widespread and insidious nature of the disease and to combine multiple different treatment strategies, not rely on just one or a few approaches. In addition, for those approaches, such as lipoprotein transport behaviors, which have been shown to produce the most success, adopting more aggressive combination treatment strategies has generally produced better results, both before and especially after people are symptomatic.

Because many blood thinners, particularly warfarin and salicylates such as aspirin, thin the blood by interfering with Vitamin K, there is recent evidence that blood thinners that work by this mechanism can actually worsen arterial calcification in the long term even though they thin the blood in the short term.

Prognosis

Lipoprotein imbalances, upper normal and especially elevated blood sugar, i.e., diabetes and high blood pressure are risk factors for atherosclerosis; homocysteine, stopping smoking, taking anticoagulants (anti-clotting agents), which target clotting factors, taking omega-3 oils from fatty fish or plant oils such as flax or canola oils, exercising and losing weight are the usual focus of treatments that have proven to be helpful in clinical trials. The target serum cholesterol level should ideally not exceed 4 mmol/L (160 mg/dL), and triglycerides should not exceed 2 mmol/L (180 mg/dL).

Evidence has increased that diabetics, despite not having clinically detectable atherosclerotic disease, have more severe debility from atherosclerotic events over time than even non-diabetics who have already suffered atherosclerotic events. Thus diabetes has been upgraded to be viewed as an advanced atherosclerotic disease equivalent.

Research

An indication of the role of HDL on atherosclerosis has been with the rare Apo-A1 Milano human genetic variant of this HDL protein. A small short-term trial using bacterial synthetized human Apo-A1 Milano HDL in people with unstable angina produced fairly dramatic reduction in measured coronary plaque volume in only 6 weeks vs. the usual increase in plaque volume in those randomized to placebo. The trial was published in JAMA in early 2006. Ongoing work starting in the 1990s may lead to human clinical trials—probably by about 2008. These may use synthesized Apo-A1 Milano HDL directly. Or they may use gene-transfer methods to pass the ability to synthesize the Apo-A1 Milano HDLipoprotein.

Methods to increase high-density lipoprotein (HDL) particle concentrations, which in some animal studies largely reverses and remove atheromas, are being developed and researched.

Niacin has HDL raising effects (by 10–30%) and showed clinical trial benefit in the Coronary Drug Project and is commonly used in combination with other lipoprotein agents to improve efficacy of changing lipoprotein for the better. However most individuals have nuisance symptoms with short term flushing reactions, especially initially, and so working with a physician with a history of successful experience with niacin implementation, careful selection of brand, dosing strategy, etc. are usually critical to success.

However, increasing HDL by any means is not necessarily helpful. For example, the drug torcetrapib is the most effective agent currently known for raising HDL (by up to 60%). However, in clinical trials it also raised deaths by 60%. All studies regarding this drug were halted in December 2006. See CETP inhibitor for similar approaches.

The ERASE trial is a newer trial of an HDL booster, which has shown promise.

The ASTEROID trial utilizing a high-dose of rosuvastatin in the aggressive lowering of LDL-C was found to cause a reduction in plaque formation. Another approach used in lowering LDL-c ( the amount of cholesterol found in low-density lipids) can be seen through reducing the production of its pre-cursor, VLDL (Very Low-density Lipoproteins) . Microsomal -triglyceride transfer protein (MTP) is required for the proper formation of the VLDL precursor. Recent studies have shown that that the conditional inactivation of the MTP protein, in turn leads to the regression of atherosclerosis.

The actions of macrophages drive atherosclerotic plaque progression. Immunomodulation of atherosclerosis is the term for techniques that modulate immune system function to suppress this macrophage action. Immunomodulation has been pursued with considerable success in both mice and rabbits since about 2002. Immunotherapy is now regarded as a possible means of treatment of atherosclerosis, and attempts to suppress the pro-atherogenic auto-immune response has been seen as a potential avenue of research, which may aid in its treatment. Recent follow-up studies in 2011 showed that the manipulation of the tolerogenic property of dendritic cells, by means of immuno-modulatory mediators (such as cytokines), led to a significant 70% reduction of atherosclerotic lesions.

Research on genetic expression and control mechanisms is progressing. Topics include

• PPAR, known to be important in blood sugar and variants of lipoprotein production and function;
• The multiple variants of the proteins that form the lipoprotein transport particles.

Some controversial research has suggested a link between atherosclerosis and the presence of several different nanobacteria in the arteries, e.g., Chlamydophila pneumoniae, though trials of current antibiotic treatments known to be usually effective in suppressing growth or killing these bacteria have not been successful in improving outcomes.

The immunomodulation approaches mentioned above, because they deal with innate responses of the host to promote atherosclerosis, have far greater prospects for success.

See also

• Angiogram
• Arterial stiffness
• Arteriosclerosis
• Atheroma
• Chelation therapy
• Coronary catheterization
• Coronary circulation
• Fatty streaks
• Intravascular ultrasound
• Monckeberg's arteriosclerosis

Footnotes

• Rajavashisth TB, Andalibi AK Territo MC, Berliner JA, Navab M, Fogelman AM, Lusis AJ. Induction of endothelial cell expression of granulocyte and macrophage colony-stimulating factors by modified low-density lipoproteins. Nature. 1990;344:254-257

External links

• Atherosclerosis at the Open Directory Project
• An open access review entitled Hypertension and the Pathogenesis of Atherosclerosis on Pharma Mirror Magazine.
• A four-minute animation of the atherosclerosis process, entitled "Pathogenesis of Acute MI," commissioned by Paul M. Ridker, MD, MPH, FACC, FAHA, at the Harvard Medical School, can be viewed at pri-med.com.

UpToDate Contents

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• 1. 安定した虚血性心疾患：ケアの概要stable ischemic heart disease overview of care [show details]
  … diagnosis of coronary atherosclerosis, it is not a reliable indicator of the functional significance of any single coronary stenosis . However, the extent and severity of coronary heart disease identified …
• 2. 冠動脈疾患の疫学epidemiology of coronary heart disease [show details]
  …artery disease are discussed elsewhere. The terms incidence, prevalence, coronary heart disease, coronary artery disease, and cardiovascular disease, as used in this topic, are defined as follows: Prevalence …
• 3. 冠動脈疾患および脳卒中の一次予防の概要overview of primary prevention of coronary heart disease and stroke [show details]
  …United States and most developed countries, cardiovascular disease (CVD), which includes coronary heart disease (CHD), stroke, and peripheral artery disease, is and will remain the leading cause of death …
• 4. 安定冠動脈疾患患者ににおける血行再建術：冠動脈バイパス移植術と経皮的冠動脈形成術の比較revascularization in patients with stable coronary artery disease coronary artery bypass graft surgery versus percutaneous coronary intervention [show details]
  …left anterior descending (LAD) coronary artery is greater than that for the right or circumflex coronary artery. Our approach to patients with LAD coronary artery disease is discussed separately. In general …
• 5. 安定した虚血性心疾患：血行再建術の適応stable ischemic heart disease indications for revascularization [show details]
  …with stable ischemic heart disease are discussed separately. We recommend coronary artery bypass graft surgery (CABG), as opposed to medical therapy, for patients with ischemic heart disease in whom a …

English Journal

• Antioxidant Activity of Heracleum persicum Fruit Extract: Evidence from a Randomized Controlled Trial.

• Panahi Y1, Dadjou Y2, Pishgoo B2, Akbari A2, Sahebkar A3,4.
• Journal of dietary supplements.J Diet Suppl.2016 Sep 2;13(5):530-7. doi: 10.3109/19390211.2015.1120842. Epub 2016 Jan 28.
• Oxidative stress is a unifying feature of several cardiometabolic risk factors, and has been suggested to be implicated in atherogenesis. This study aimed to investigate the efficacy of supplementation with Heracleum persicum fruit-a common dietary spice-in modulating systemic biomarkers of oxidativ
• PMID 26820395

• Evaluation of the Usability of Selected Questionnaires Assessing Physical Activity in the Prophylaxis of Cardiovascular Diseases.

• Czeczelewska E1, Czeczelewski J2, Wasiluk A3, Saczuk J3.
• Advances in clinical and experimental medicine : official organ Wroclaw Medical University.Adv Clin Exp Med.2016 Jul-Aug;25(1):59-67. doi: 10.17219/acem/39157.
• BACKGROUND: The main health problem of the Polish population is posed by cardiovascular diseases (CDVD), coronary artery disease (CAD) in particular. Respectively higher physical activity linked with energy expenditure of at least 1000 kcal/week may significantly reduce the risk of CAD development.
• PMID 26935499

• Impacts of common variants in ALDH2 on coronary artery disease patients.

• Zhao J1, You L2, Wang DW3, Cui W4.
• Gene.Gene.2016 Jul 1;585(1):104-9. doi: 10.1016/j.gene.2016.03.022. Epub 2016 Mar 16.
• Genome-wide association studies (GWAS) have identified Aldehyde dehydrogenase 2 (ALDH2) as a susceptibility locus for coronary artery disease (CAD) previously. However, the impacts of common variants in this gene on CAD and its outcomes have not been extensively studied. This study explored the asso
• PMID 26995653

Japanese Journal

• 腸管免疫,腸内細菌と冠動脈硬化 (第1土曜特集 虚血性心疾患UPDATE) -- (冠動脈疾患基礎研究の進歩)

• 医学のあゆみ 259(6), 597-603, 2016-11-05
• NAID 40020978842

• 冠動脈硬化の新しい分子機序 : 炎症・免疫からみた最新の知見 (第1土曜特集 虚血性心疾患UPDATE) -- (冠動脈疾患基礎研究の進歩)

• 医学のあゆみ 259(6), 590-596, 2016-11-05
• NAID 40020978832

• 冠動脈硬化症とステント留置血管の病理組織像 (第1土曜特集 虚血性心疾患UPDATE) -- (冠動脈疾患基礎研究の進歩)

• 医学のあゆみ 259(6), 579-589, 2016-11-05
• NAID 40020978823

Related Links

• What Is Coronary Atherosclerosis? (with pictures)

Coronary atherosclerosis is a condition in which a person's arteries become clogged and hardened. This puts the person at high... ... An individual with coronary atherosclerosis might not notice symptoms until a dangerous amount of ...

• Atherosclerosis and Coronary Artery Disease

Atherosclerosis can create life-threatening blockages in the arteries of your heart, without you ever feeling a thing. Learn more about coronary artery disease. ... Atherosclerosis can create life-threatening blockages ...

Related Pictures

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★リンクテーブル★

リンク元	「冠状動脈硬化症」「冠動脈硬化」「冠動脈硬化症」「冠状動脈硬化」「冠動脈粥状硬化症」
関連記事	「coronary」「atherosclerosis」「corona」

「冠状動脈硬化症」

　　[★]

英

coronary atherosclerosis、coronary arteriosclerosis

関

冠動脈疾患、冠動脈硬化、冠状動脈硬化、冠状動脈アテローム性硬化症、冠動脈硬化症、冠動脈粥状硬化症

ICD-10

I.251

冠状動脈アテローム性硬化症、冠状動脈狭窄症、冠状動脈硬化症、冠動脈硬化性心疾患、冠動脈疾患、冠動脈石灰化、動脈硬化性冠不全

[show details]

冠状動脈アテローム性硬化症 : 14 件
冠状動脈狭窄症 : 約 56 件
冠状動脈硬化症 : 約 595,000 件
冠動脈硬化性心疾患 : 76 件
冠動脈疾患 : 約 214,000 件
冠動脈石灰化 : 約 11,100 件
動脈硬化性冠不全 : 23 件

「冠動脈硬化」

　　[★]

英

coronary atherosclerosis、coronary arteriosclerosis

関

冠状動脈硬化症、冠状動脈硬化、冠状動脈アテローム性硬化症、冠動脈硬化症、冠動脈粥状硬化症

「冠動脈硬化症」

　　[★]

英

coronary atherosclerosis、coronary arteriosclerosis

関

冠動脈硬化、冠状動脈硬化症、冠状動脈硬化、冠状動脈アテローム性硬化症、冠動脈粥状硬化症

「冠状動脈硬化」

　　[★]

英

coronary atherosclerosis、coronary arteriosclerosis

関

冠動脈硬化、冠状動脈硬化症、冠状動脈アテローム性硬化症、冠動脈硬化症、冠動脈粥状硬化症

「冠動脈粥状硬化症」

　　[★]

英

coronary atherosclerosis

関

冠動脈硬化、冠状動脈硬化症、冠状動脈硬化、冠状動脈アテローム性硬化症、冠動脈硬化症

「coronary」

　　[★]

• adj.

• 冠血管の、冠状動脈の

関

coronary artery、coronary vessel

　 　

「atherosclerosis」

　　[★] アテローム性動脈硬化、粥状硬化症 　 　

「corona」

　　[★] コロナ帯