Atherosclerosis is characteristic inflammatory disease of the arteries. It is triggered by a process called atherogenesis in which there is an accumulation of low density lipoproteins causing the formation of plaque. The plaque thus formed gets accumulated in the arteries causing blockage in the blood flow. The most prominent arteries prone to these plaque accumulations are the elastic and muscular arteries.
Pathology of atherosclerosis
Atherosclerosis in the initial stages appears as a fatty streak and over time it develops into a more prominent condition causing hardening of the arteries. It results in the reduction of the arterial pathway of carotid, abdominal, cardiac and other arteries of the lower and upper extremities. The etiology associated with this condition is the deposition of cholesterol and lipids in the internal lumen of the artery. These depositions are focal in origin. The disruption caused in the endothelial lining because of cholesterol accumulation leads to the emergence of inflammatory disease and arterial injuries.
Atherosclerosis triggers many conditions such as atherosclerotic heart disease, peripheral vascular disorder, coronary artery disease, and carotid artery disease. In atherosclerotic condition, some diagnostic investigations may be non-specific to the patho-physiology associated with the disease. One such test is analysis of C reactive protein which is a non-specific marker of inflammatory disease. However, the fatty streaks and associated lesions caused are identified by the characteristic smooth muscles containing lipids in it.
A fibrous plaque is formed initiating the changes in the arterial wall. The cholesterol translocation in the arterial intima (inner region) is facilitated by the lipoproteins. The fibrous streak contains collagen which is grayish white or yellow in appearance resulting in the narrowing of the blood vessel. The emergence of a complicated lesion like this can induce the formation of ulcers leading to rupture and dissemination of the accumulated plaque to various regions. This leads to the occurrence of three types of strokes. The Thrombolytic stroke which is a result of a clot or thrombus formation, hemorrhagic stroke because of blood vessel damage and embolic stroke in which the clot does not pass through the narrow artery. This eventually results in the occurrence of ischemic stroke in which there is a lack of blood supply to the brain.
Factors associated with atherosclerosis
Hypercholesterolemia is one of the main causes as it causes the low density lipo-proteins to occupy the inner layer of the artery. Elevated homocysteine levels also play an important role in the occurrence of atherosclerosis. Homocyteine levels are generally high in patients who have a history of high red meat consumption rate. Increased homocysteine levels facilitate the hardening of the arterial wall causing atherosclerotic lesions. Increased angiotensin-II concentration is also an important factor in the initiation of atherosclerotic condition as it causes vasoconstriction and associated hypertension. Other factors include infections caused by Chlamydia and Herpes viruses.
In all these factors causing atherosclerosis, the nature of inflammatory response is associated with interactions related to the monocytes, endothelial cells and T cells. In most cases, plaques or associated clots occur in the region of branching, bifurcation or curvature of the arteries. This is because of the alternating blood flow path occurring in the respective region.
The risk factors associated with atherosclerosis are mainly because of lifestyle and preexisting medical conditions. Smoking, alcoholism, obesity and hereditary factors are the predominant reasons. Other factors include diabetes, hypertension and family history of which is associated with a specific altered gene.
Patients with atherosclerosis are advised to incorporate lifestyle changes with constant watch on their eating habits. Physicians and cardiologists recommend cardiovascular exercises on a regular basis apart from medication. Surgical interventions are required in case of increased coronary artery blockage and dispersed thrombus in the blood circulation.
The plaques formed in the arterial walls of one who suffers from atherosclerosis contain significant levels of cholesterol. The risk factor of Coronary Heart Disease (CHD) rises in direct proportion to the level of LDL - Low density Lipoprotein and comes down with an increase in the HDL cholesterol. The LDL is estimated by the following formula:
LDL Cholesterol = Total Cholesterol (mg/dL) - HDL Cholesterol (mg/dL) - (Triglycerides (mg/dL)/5)
Atherosclerotic Peripheral Vascular Disease occurs owing to Atherosclerosis in Aorta and Iliac Arteries which results in Claudication (pain on exertion) or in some cases lesions in the vessels of legs ( Occlusive Atherosclerotic Lesions). The severity of the symptom can vary from time to time and usually subsides after some rest. For men, bilateral common iliac disease can often start with Erectile Dysfunction (ED).
Homocysteine Blood Test
Homocysteine blood test measures the amount of amino acid homocysteine in the blood. High level of homocysteine is associated with low level of vitamin B6/ B12, and folate. This blood test helps us to identify the deficiency and get treated accordingly. The results of the blood test are generally ready within 24 to 72 hours. Homocysteine is measured in micromoles per liter of blood.
Homocysteine (HCY) is considered as the main biochemical marker of several primary and secondary disorders of methionine metabolism. Methionine is one of the essential Amino acids and sweeps the blood stream of heavy metals. It plays a major role in protecting the liver. Poor Methionine Metabolism can result in Homocysteinemia, Cystathionine Synthase (CS) deficiency (Homocystinuria) and Methylenetetrahydrofolate reductase (MTHFR) deficiency.
Homocysteine is a non protein amino acid that is produced by the body and is present in small levels in the blood. Amino acids are the building blocks of all proteins in the body. In our body, vitamins B6, B12 and folate convert homocysteine into other usable substances. A deficiency in these vitamins may cause an elevated level of homocysteine. Elevated levels in infants can prove fatal as the infant may be highly prone to develop heart or blood vessel diseases at an early age.
Reference Level of Homocysteine : Less than or equivalent to : 13 µmol/L (micromoles per liter)
Elevated levels of homocysteine could be due to genetic causes (a rare disorder called Homocystinuria that is caused by a dysfunctional enzyme that is essential for metabolism in the body) or due to other causes like atherosclerosis.
In addition to be the important marker for inherited disorders of methionine metabolism, the total homocysteine (HCY) level can accurately predict conditions such as cardiovascular disease (atherosclerosis, thromboembolism). Besides it can also indicate acquired folate or cobalamin deficiency - a contributing factor in the pathogenesis of neural tube defects.
Homocysteine is measured using a simple blood test. This blood test is done to identify
What causes high/low homocysteine value in blood ?
High values in blood may be caused by:
How is high level of homocysteine harmful ?
Higher levels of homocysteine can point to an underlying Cardiovascular disease or a Neuro vascular disease.
Elevated levels of homocysteine can:
Damage artery lining: Arteries tend to become damaged and begin to clog, thicken and become inflexible thus leading to atherosclerosis.
Create blood clots: Homocysteine can elevate the cholesterol levels thus clogging the arteries and thickening them thus leading to atherosclerosis. Blood clots form easily thus leading to heart attack.
Strokes: Elevated level of homocysteine can affect the arteries leading to and from the brain thereby causing a blood clot or a rupture in the blood vessel. This in turn can cut off/reduce the oxygen supply to the brain thereby starving the brain cells of nutrition and oxygen thus leading to a stroke.
Osteoporosis: Density of the bone mass reduces thus leading to fragile and weakened bones.
Cause infertility: Women with high level of homocysteine find it difficult to conceive and are at the risk of repeated miscarriages.
Cause dementia and Alzheimer's: Old age can contribute to high levels of homocysteine thus damaging the brain cells. Over time memory is lost thus killing more and more cells.
Homocysteine level in the blood can be lowered by:
Who should get this test done?
People who have a history of heart diseases and are at a high risk for heart disease should get their homocysteine level checked. People who are at risk for stroke also need to get this check done.
Dyslipidemia indicates the presence of increased cholesterol in the blood. In general the cholesterol in the body is categorized as good and bad forms, thus referring to its functionality. Good cholesterol also known as high density lipoproteins are required for the body to carry out regular metabolic activities. Estimation of triglyceride levels in the blood serves as a key factor in identifying the amount of disordered fats in the body or dyslipidemia. Dyslipidemia is one of the important causes for the onset of coronary artery disease.
Clinical evaluations of blood cholesterol levels
Clinical presentation of blood cholesterol levels aids estimation of the onset of conditions such as dyslipidemia which leads to cardio vascular disease. Blood cholesterol determination includes the estimation of high density lipoproteins, triglycerides and low density lipoproteins. Values in the case of dyslipidemia contain increased total cholesterol levels i.e. high LDL levels and decreased HDL levels. These levels are checked on fasting for at least 10 hours. Clinical interventions are recommended in the treatment of dyslipidemia to understand the possibility of cardio vascular disease in a patient and to differentiate the primary and secondary categories of this disease.
Diabetes and dyslipidemia
Type 2 diabetes is an underlying medical condition in which dyslipidemia is often noticed. It is measured by the lipid profile analysis. Insulin resistance is the predominant cause of low serum HDL. Insulin resistance promotes another condition called hypertriglyceridemia. This eventually leads to the increase of LDL or low density lipoproteins in the blood which can initiate the onset of atherosclerosis. Patients suffering diabetes with increased values of LDL and VLDL fall under the risk group for coronary artery disease. In addition to this, the metabolism of lipids is directly associated with the release of thyroid hormone. In patients with diabetes and hypothyroidism, the chance of cardiovascular disease is imminent.
Dyslipidemia can occur because of various factors. Most of them are induced by altered lifestyle patterns affecting the metabolism of a person. Obesity is the predominant cause of cardiovascular disease which is directly associated with the presence of dyslipidemia in the person. Symptoms associated are lethargy, gasping and difficulty in participating in any kind of physical activity. Alcohol consumption is also a major cause for the onset of dyslipidemia as it is related to the damage caused to the liver which produces major enzymes for lipid metabolism and fat emulsification processes. Other caused include Cushing's syndrome, Polycystic ovarian disease and liver cirrhosis.
Dyslipidemia is a condition which is treated with effective counseling about healthy lifestyle choices. Eating right and handling stressful factors can subsequently act on the regulation of metabolism. Patients are advised to exercise regularly to prevent the onset of atherosclerosis caused because of dyslipidemia.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 1, 2020