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).