Atherosclerosis
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Commonality is common |
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Efficacy of Alternative and Other Treatments According to GRADE* Ranking:
Green Tea [1, 2, 3, 4, 5, 6]:
Please note, this management does NOT treat the condition itself. It may mildly help with some of the symptoms, and even then has insufficient evidence to back up this claim at present.
Recommendation: Weakly in favor (There is insufficient evidence to support claims that Green Tea helps to treat atherosclerosis in any way. Although reports are positive, more studies are needed.)
Grade of Evidence: low quality of evidence
* www.gradeworkinggroup.org
Atherosclerosis
Atherosclerosis is a disease affecting arterial blood vessels. It is a chronic inflammatory response in the walls of arteries, in large part due to the accumulation of macrophage white blood cells and promoted by low density (especially small particle) lipoproteins (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 [[atheroma|atheromatous plaque]]' is divided into three distinct components: # The atheroma ("lump of porridge", from Athera, [[porridge]] in Greek,), 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 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 the Greek Arterio, meaning artery, and sclerosis, 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. Therefore, atherosclerosis is a form of arteriosclerosis. Atherosclerosis causes two main problems. First, the atheromatous plaques, though long compensated for by artery enlargement (see IMT), eventually lead to plaque ruptures and [[stenosis]] (narrowing) of the artery and, therefore, an insufficient blood supply to the organ it feeds. If the compensating artery enlargement process is excessive, then a net [[aneurysm]] results. These complications are chronic, slowly progressing 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). Another common scenario in very advanced disease is [[claudication]] from insufficient blood supply to the legs, typically due to a combination of both stenosis and aneurysmal segments narrowed with [[thrombus|clots]]. Since atherosclerosis is a body-wide process, similar events occur also in the arteries to the brain, intestines, kidneys, legs, etc.
Causes
Atherosclerosis develops from low-density lipoprotein cholesterol (LDL), colloquially called "bad cholesterol". Many believe that, when this lipoprotein gets through the wall of an artery, oxygen free radicals react with it to form oxidized-LDL. The body's immune system responds by sending specialised white blood cells (macrophages and T-lymphocytes) to absorb the oxidised-LDL. Unfortunately, these white blood cells are not able to process the oxidised-LDL, and ultimately grow then rupture, depositing a greater amount of oxidised 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, reduces the blood flow and increases 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. Cholesteryl ester accumulation is associated with atherosclerosis.
Symptoms
Atherosclerosis typically begins in early adolescence, and is usually found in most major arteries, yet is asymptomatic and not detected by most diagnostic methods during life. The stage immediately prior to actual atherosclerosis is known as subclinical atherosclerosis. The majority of the process leading to subclinical atherosclerosis can happen without our knowing it, especially given the large variety of risk factors. Summary of [http://www.itamar-medical.com/Product.asp?pid=3983&ppid=3005 subclinical atherosclerosis] at Itamar Medical. Autopsies of healthy young men that died during the Korean and Vietnam Wars showed evidence of the disease. It most commonly becomes seriously symptomatic when interfering with the coronary circulation supplying the heart or cerebral circulation supplying the brain, and is considered the most important underlying cause of strokes, heart attacks, various heart diseases including congestive heart failure, and most cardiovascular diseases, in general. Atheroma in arm, or more often in leg arteries, which produces decreased blood flow is called Peripheral artery occlusive disease (PAOD). According to United States data for the year 2004, for about 65% of men and 47% of women, the first symptom of atherosclerotic cardiovascular disease is heart attack or sudden cardiac death (death within one hour of onset of the symptom). Most artery flow disrupting events occur at locations with less than 50% lumen narrowing (~20% stenosis is average). [The reader might reflect that 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 and the ASTEROID trial, the IVUS photographs on page 8, as examples for a more accurate understanding. 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%.
Atherogenesis
Atherogenesis is the developmental process of atheromatous plaques. It is characterized by a remodeling of arteries involving the concomitant accumulation of fatty substances called plaques. One recent theory 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 of the artery opening, called the lumen; stenosis is a late event, which may never occur and is often the result of repeated plaque rupture and healing responses, not just the atherosclerosis process by itself.
=Cellular =
The first step of atherogenesis is the development of fatty streaks, which are small subendothelial deposits of oxidized cholesterol and monocyte-derived macrophages. The exact cause for this process is unknown, and fatty streaks may appear and disappear. LDL in blood plasma poses a risk for cardiovascular disease when it invades the endothelium and becomes oxidized. A complex set of biochemical reactions regulates the oxidation of LDL, chiefly stimulated by presence of free radicals in the endothelium or blood vessel lining. The initial damage to the blood vessel wall results in a "call for help," an inflammatory response. Monocytes (a type of white blood cell) 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. The monocytes differentiate macrophages, which ingest oxidized 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 tunica media to intima responding to cytokines secreted by damaged endothelial cells. This would cause the formation of a fibrous capsule covering the fatty streak.
=Calcification and lipids =
Intracellular microcalcifications form within vascular smooth muscle cells of the surrounding muscular layer, specifically in the muscle cells adjacent to the atheromas. 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.Glagov S, Weisenberg E, Zarins CK, Stankunavicius R, Kolettis GJ. Compensatory enlargement of human atherosclerotic coronary arteries
=Rupture and stenosis =
Although the disease process tends to be slowly progressive over decades, it usually remains asymptomatic until an atheroma obstructs the bloodstream in the artery. This is typically by rupture of an atheroma, clotting and fibrous organization of the clot within the lumen, covering the rupture but also producing stenosis, or over time and after repeated ruptures, resulting in a persistent, usually localized stenosis. Stenoses can be slowly progressive, whereas plaque rupture 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. If the fibrous cap separating a soft atheroma from the bloodstream within the artery ruptures, tissue fragments are exposed and released, and blood enters the atheroma within the wall and sometimes results in a sudden expansion of the atheroma size. 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
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 is ideally equal or less than 4mmol/L (160 mg/dL), and triglycerides equal or less than 2mmol/L (180 mg/dL). Evidence has increased that people with diabetes, despite their not having clinically-detectable atherosclotic disease, have more severe debility from atherosclerotic events over time than even non-diabetics that have already suffered atherosclerotic events. Thus diabetes has been upgraded to be viewed as an advanced atherosclerotic disease equivalent.
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. However, medicines are criticized for their expense, patented control and occasional undesired effects.
=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 multiple comparative treatment/placebo trials have fairly consistently shown strong effects in reducing atherosclerotic disease 'events' and generally ~25% comparative mortality reduction in clinical trials, although one study design, ALLHAT. was less strongly favorable. The newest statin, rosuvastatin, has been 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. 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 statins, and some other medications, have been shown to have antioxidant effects, possibly part of their basis for some of their therapeutic success in reducing cardiac 'events'. 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, as yet, less strongly clear for women and people over the age of 70 [http://www.cmaj.ca/cgi/content/full/173/10/1207-a CMAJ]. 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 that 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 3 more dead women at trial's end on statin than in the group on placebo drug whether 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 promoting a comparison placebo arm was judged to be unethical.
==Primary and Secondary Prevention
=Diet and dietary supplements =
Vitamin B3, AKA niacin, in pharmacologic doses, (generally 1,000 to 3,000 mg/day), sold in many OTC and prescription formulations, tends to improve (a) HDL levels, size and function, (b) shift LDL particle distribution to larger particle size and (c) lower lipoprotein(a), an atheroslerosis promoting genetic variant of LDL. Additionally, individual responses to daily niacin, while mostly evident after a month at effective doses, tends to continue to slowly improve further over time. (However, careful patient understanding of how to achieve this without nuisance symptoms is needed, though not often achieved.) Research work on increasing HDL particle concentration and function, beyond the usual niacin effect/response, even more important, is slowly advancing. Dietary changes to achieve benefit have been more controversial, generally far less effective and less widely adhered to with success. One key reason for this is that most cholesterol, typically 80-90%, within the body is created and controlled by internal production by all cells in the body (true of all animals), with typically slightly greater relative production by hepatic/liver cells. (Cell structure relies on fat membranes to separate and organize intracellular water, proteins and nucleic acids and cholesterol is one of the components of all animal cell membranes.) Caldwell B Esselstyn Jr. MD has had an article published in Preventive Cardiology 2001;4: 171-177 in which he has published angiograms showing regression of atherosclerosis brought about by a very low fat vegan diet in some cases with cholesterol lowering medications.http://www.heartattackproof.com/resolving_cade.htm Resolving the Coronary Artery Disease Epidemic through Plant-Based Nutrition Caldwell B. Esselstyn, Jr., MD While the absolute production quantities vary with the individual, group averages for total human body content of cholesterol within the U.S. population commonly run about ~35,000 mg (assuming lean build; varies with body weight and build) and ~1,000 mg/day ongoing production. Dietary intake plays a smaller role, 200-300 mg/day being common values; for pure vegetarians, essentially 0 mg/day, but this typically does not change the situation very much because internal production increases to largely compensate for the reduced intake. For many, especially those with greater than optimal body mass and increased glucose levels, reducing carbohydrate (especially simple forms) intake, not fats or cholesterol, is often more effective for improving lipoprotein expression patterns, weight and blood glucose values. For this reason, medical authorities much less frequently promote the low dietary fat concepts than was commonly the case prior to about year 2005. However, evidence has increased that processed, particularly industrial non-enzymatic hydrogenation produced trans fats, as opposed to the natural cis]]-configured fats, which living cells primarily produce, is a significant health hazard. Dietary supplements of Omega-3 oils, especially those from the muscle of some deep salt water living fish species, also have clinical evidence of significant protective effects as confirmed by 6 [[double blind placebo controlled human clinical trials. There is also a variety of evidence, though less robust, that homocysteine and uric acid levels, including within the normal range promote atherosclerosis and that lowering these levels is helpful, up to a point. In animals Vitamin C deficiency has been confirmed as an important role in development of hypercholesterolemia and atherosclerosis, but due to ethical reasons placebo-controlled human studies are impossible to do. Vitamin C acts as an antioxidant in vessels. Trials on Vitamin E have been done, but they have failed to find a beneficial effect, for various reasons, but for some patients at high risk for atherosclerosis there may be some benefits. Menaquinone (Vitamin K2), but not phylloquinone (Vitamin K1), intake is associated with reduced risk of CHD mortality, all-cause mortality and severe aortic calcification. It has been suggested that excess iron may be involved in development of atherosclerosis, but one study found reducing body iron stores in patients with symptomatic peripheral artery disease through phlebotomy did not significantly decrease all-cause mortality or death plus nonfatal myocardial infarction and stroke. Further studies may be warranted.
=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 LawWald NJ, Law MR. A strategy to reduce cardiovascular disease by more than 80%. [[British Medical Journal|BMJ]] 2003;326:1419. PMID. 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, the treatments which focus on decreasing the underlying atherosclerosis processes, as opposed to simply treating the symptoms resulting from the atherosclerosis, have been shown by clinical trials to be 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. However, treating asymptomatic people remains controversial in the medical community.
Recent 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 necessary 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. The ERASE trial is a newer trial of an HDL booster which has shown promise. The ASTEROID trial used a high-dose of rosuvastatin—the statin with typically the most potent dose/response correlation track record (both for LDLipoproteins and HDLip
Summary References
Treatments:
1. Ades T, Alteri R, Gansler T, Yeargin P, "Complete Guide to Complimentary & Alternative Cancer Therapies", American Cancer Society, Atlanta USA, 2009
2. http://www.cancer.org/Treatment/TreatmentsandSideEffects/ComplementaryandAlternativeMedicine/HerbsVitaminsandMinerals/green-tea
3. http://www.ncbi.nlm.nih.gov/pubmed/16968850
4. http://www.denverpost.com/nationworld/ci_4326770
5. http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-green_tea.html
6. http://nccam.nih.gov/health/greentea/index.htm
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