Atherosclerosis in relation to heart diseasesIntroduction The leading cause of death in the world in the United States and several other developing nations has been cardiovascular diseases. More than 38 % of all deaths are from some form of cardiovascular disorder, and more than 70 million people in the US are affected with some form of the disease (Toth, 2007). Atherosclerosis is a process by which the walls of the artery become thickened leading to narrowing of the lumen of the artery.
This is due to the build up of fats and cholesterol in the arterial wall causing narrowing down of the lumen and a blockage in the blood flow (Warkentin, 2008). The process of atherosclerosis tends to affect several arteries in the body including those that supply the muscles of the heart (coronary arteries), brain (cerebral arteries), kidney, neck (carotid arteries). In the US, a majority of the people are affected with atherosclerosis responsible for causing cardiovascular disease and death. Atherosclerosis is responsible for various cardiac and systemic events including angina, ischemia, obesity, stroke, renal stenosis, peripheral vascular disease, hypercholesterolemia, hypertension, unstable angina, cerebrovascular events, arrhythmia, heart failure, etc (Toth, 2007). Aetiology and Pathophysiology Several risk factors may increase the chances of developing atherosclerosis including high cholesterol levels (of LDL over 100 mg per dl of blood), smoking, exposure to tobacco smoke, hypertension, obesity, diabetes mellitus, sedentary lifestyle, systemic inflammatory disorder, a family history of the disorder, etc (AHA, 2009). The process of atherosclerosis is a dynamic and ongoing.
Lipids tend to get deposited in the inner wall of the arterial wall. The process actually begins following inflammation of the vessel wall. The inner lining of the vessel known as endothelium becomes stressed out. In such a circumstance, the blood vessel dilates and would attract platelets at the site of injury. The inflammation may be caused by poor glycaemia control, hypertension, allergic reactions, use of nicotine, viral infections, etc. To contain the inflammation, white blood cells (namely monocytes and T-lymphocytes) would move in. These white blood cells consume cholesterol and would burst resulting in release of cholesterol.
The monocytes often get converted into macrophages which ultimately get converted into foam cells. The foam cells unite to form huge streaks of fat within the vessel wall. The foam cells tend to age and also provoke an inflammatory response (Libby, 2007). Platelets soon begin to migrate to the vessel wall and would adhere and aggregate at the injury site. Scar tissue is later formed which results in the formation of a plaque. These plaques begin to grow very slowly in the wall of the artery, penetrating into the lumen and resulting in blockage of the blood flow. In certain cases, the blood flow is blocked by formation of clots at the plaque sites resulting in development of a heart attack or a cerebrovascular stroke (Toth, 2007 & Warkentin, 2008).Drug treatment for atherosclerosis Currently several groups of drugs are utilised to treat atherosclerosis including statins, fibrates, niacin, omega-3-fatty acids, bile acid binding agents and fibrates.
Usually a combination of drugs is given to treat dyslipidemia and hypercholesterolemia. This improves the effectiveness of the drugs and helps reduce the side-effects (Toth, 2007). Statins work by enzymes (namely HMG-COA) reductase inhibitors that work by limiting the production of cholesterol in the liver and its subsequent deposition in the vessels and the tissues. They help to eliminate several lipoproteins including VLDL, LDL and VLDL-remnants. They eliminate athrogenic apolipoprotein B-100 along with the lipoproteins, and also encourage HDL secretion and apolipoprotein A-1 release. Statins significantly help to reduce myocardial infarctions, coronary symptoms, strokes, stable and unstable angina, etc.
To certain extent, statins even help to reabsorb the plaques. There are six statins that are available currently, and the extent to which LDL and non-HDL cholesterol needs to be reduced determines which agent has to be utilised. Rosuvastatin would reduce LDL by 45 to 53% for 5 to 40 mg per day, whereas pravastatin would reduce it by 22 to 34 % for 10 to 80 mg per day.
Statins also help to reduce the serum triglyceride levels and raise the serum HDL levels. Lovastatin and fluvastatin have a very short half-life ranging from 1 o 4 hours and hence should be taken after the night meal to block the enzyme activity that occurs during sleep. Rosuvastatin and atorvastatin have a half life of 19 to 24 hours and can be taken at any time during the day.
Statins can cause problems when administered with several food substances and can also result in liver toxicity. Usually, a different statin is administered if liver problem develops with one (Toth, 2007). Bile acid binding agents combine with bile acids in the intestines and do not allow them to be reabsorbed into the enterobilary system. They increase the breakdown of cholesterol by 7-alpha-hydroxylase (which converts it into bile acids). There is also greater consumption of cholesterol by the liver resulting in a drop of LDL by about 15 to 30 % with a rise in HDL. Frequently, bile acid binding agents are utilised with statins.
They are given in doses ranging from 4 to 30 mg, two to three times daily. They would bind with several non specific negatively charged molecules and hence have the potential of reacting with several drugs and substances in the body (Toth, 2007). Niacin helps to raise the level of HDL and reduces the level of LDL by reducing the lipase activity and prevents formation of triglycerides within the liver. The drug when given as 3 gms per day doses, significantly helps to reduce heart attacks and cerebrovascular strokes. When niacin is usually administered, it is given in lower dosages, which are slowly increased over a period of time (Toth, 2007).Traditional Chinese medicine Traditional Chinese medicine has been utilised in China since a long time in the management of heart diseases and hypercholesterolemia. The Chinese usually utilise three modalities for managing atherosclerosis including acupuncture, Chinese medicines and massage therapy.
The Chinese medicine Qingzhi has been used since ancient times to lower lipid levels in the blood and prevent fatty degeneration of the liver. The study was performed on hyperlipidemic rats which were divided into 4 groups and being administered low-dose Qingzhi, high dose Qingzhi, XuezhiKang and distilled water. After a period of 3 weeks, the rats were killed and the total cholesterol level, the triglyceride level, the HDL levels, LDL levels were measured, and the liver was subjected to biopsy. The total cholesterol level and the triglyceride levels were lower in the Qingzhi groups. However, there were no significant differences between HDL and LDL levels in these groups (Tong, 2008). Acupuncture and moxibustion also seem to be very effective for atherosclerosis.
In a study conducted by Wang et al (2005), 60 patients took part in the trial, out of which 30 were administered acupuncture-moxibustion and 30 were given a drug. These patients had carotid plaques in their necks and were at the risk of developing cerebrovascular disorders. The size and quality of the plaque were measured using carotid ultrasonography. In the acupuncture-moxi group, the plaque reduced in size by about 53.9 %, whereas in the drug group it reduced by 10 %.
This suggests that acupuncture-moxibustion is more effective to treat atherosclerosis compared to convention western drugs (Wang, 2005). In patients suffering from hyperlipidaemia, several Chinese exercises and manipulation therapies such as Tai Chi Chuan seem to be effective in preventing coronary heart diseases. 53 participants with hyperlipidemia were divided into two groups, 28 were given a one year Tai Chi course and 25 were allowed to lead a sedentary lifestyle.
Several indicators such as blood pressure, cholesterol levels, triglyceride levels, body fat, LDL levels, HDL levels, insulin levels, etc were checked and monitored before and after the 12 month period. The case group showed an improvement in the blood pressure, cholesterol level, triglyceride level, LDL and the body fat levels. The control group did not show any positive outcome.
This goes on to show that Chinese manipulation techniques can reduce the risk of atherosclerosis and in this way prevent the development of coronary cardiac disorders (Lan, 2008).ReferencesAmerican Heart Association 2008. Atherosclerosis, AHA, viewed 25 January 2009.
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