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A Dive Into Atherosclerosis

By Anaya Garg

Highlights:

  • Atherosclerosis is the thickening or hardening of the arteries; It is caused by a buildup of plaque in the inner lining of an artery

  • This gradual plaque buildup hinders the diffusion of nutrients from the blood to the deeper tissues of the artery wall.

  • This decreases the strength of the arterial walls, and eventually, as their strength decreases and blood pressure increases, the arteries may burst.

Introduction: Description of the Disorder


Atherosclerosis is the thickening or hardening of the arteries. It is caused by a buildup of plaque in the inner lining of an artery. The plaque is made up of deposits of fatty substances, cholesterol, cellular waste products, calcium, and fibrin. As it builds up in the arteries, the artery walls become thickened and stiff. There is not a specific cause of Atherosclerosis. However, an unhealthy diet and high cholesterol levels can lead to a gradual build-up of plaque in the arteries that reduces blood flow and oxygen supply to the vital body organs and extremities. In this disease, multiple arteries in the body can be involved simultaneously. The plaque buildup usually starts at the origin of the main arteries that are involved and then disseminates throughout the arteries. The abdominal artery is the main part of the body that is generally affected by the plaque buildup first. After that, the coronary arteries are affected. Gradually, the plaque buildup will occur in a variety of small vessels throughout the body. The symptoms of Atherosclerosis vary by patient and typically develop gradually based on the affected artery. However, when a major artery is blocked, signs and symptoms may be severe, such as those occurring with heart attack, stroke, or blood clot. Therefore, to diagnose atherosclerosis, doctors do a complete medical history and a physical examination. This is a very common disease that is more prevalent in older people and/or in those with an unhealthy lifestyle. Over the age of 40, people in general good health have about a 50% chance of developing serious atherosclerosis, with this risk increasing with age. Most people over the age of 60 have some atherosclerosis, but often do not have noticeable symptoms.


The Cardiovascular System During Normal Operation


Our circulatory system is responsible for circulating blood throughout the body; it transports oxygen-rich blood to our different body structures and removes waste products from our blood, which is essentially carbon dioxide. This system consists of the heart, blood vessels, and blood. The blood vessels can be divided into two different categories: the arteries, and the veins. The arteries are responsible for carrying blood away from the heart. Conventionally, this means that the arteries transport oxygenated blood throughout the body. The only exception to this is the pulmonary artery that carries deoxygenated blood away from the heart, and to the lungs, where gas exchange occurs. On the other hand, the veins are responsible for carrying deoxygenated blood into the heart. The heart has a 4 chambered structure that allows it to carry out the function of moving blood. The right side of the heart works as the pulmonary circuit pump, where the deoxygenated blood is taken to the lungs for gas exchange to happen. The left side of the heart is part of the systemic circuit, where oxygenated blood is carried to the body tissues. This chiefly explains how the circulatory system works.


However, Atherosclerosis is a disorder of a blood vessel, and this structure will be explained in a greater depth. The Aorta is the only artery that is connected to the blood; as the Aorta leaves the heart, other arteries connect to it, which then carry the oxygenated blood to the different anatomic structures. These arteries are named after the locations they travel through the body. However, the main arteries are the subclavian artery, the carotid artery, the thoracic aorta, and the femoral arteries. The subclavian artery is responsible for transporting oxygenated blood to the upper limbs. The carotid is responsible for transporting blood to the most superior body structures, like the brain. The thoracic aorta brings the oxygen-rich blood down to the inferior regions of the body, and from there, the two femoral arteries bring it to our lower extremities. Before we talk about how this disorder affects the vessels, we will talk about their microscopic anatomy. Except for the microscopic capillaries, the walls of blood vessels have three layers, also called tunics: tunica intima, tunica media, and tunica externa. The tunica intima lines the most interior side of the blood vessels also called the lumen. It is a thin layer of squamous epithelial cells that fit closely together and form a slick surface that decreases friction as the blood flows through the vessel lumen. The tunica media is the bulky middle layer. It mostly consists of smooth muscles and elastic fiber. In addition to the elastic fibers, some of the larger arteries have sheets of elastic tissue that give them more structures. In this layer, the smooth muscle, which is controlled by the sympathetic nervous system, is responsible for changing the diameter of the vessels. As the vessels constrict or dilate, the blood pressure increases or decreases, respectively. Lastly, the tunica externa is the outermost vessel layer. It is largely composed of fibrous connective tissue, and it functions to support and protect the vessels.


Due to the function of arteries, they have much thicker walls; the tunica media layer of arteries is especially thicker than that of the other vessels. These vessels, which are closer to the pumping action of the heart, must be able to expand as blood is forced into them and then recoil passively as the blood flows off into circulation during diastole, which is when the heart muscle relaxes and allows the chambers to fill with blood. Veins, in contrast, are further away from the heart and the pressure in them tends to be low all the time, and thus they have thinner walls.


Symptoms of Atherosclerosis

  • If you have atherosclerosis in your heart arteries, you may have chest pain or pressure (angina).

  • If you have atherosclerosis in the arteries leading to your brain, you may have sudden numbness or weakness in your arms or legs, difficulty speaking or slurred speech, temporary loss of vision in one eye, or drooping muscles in your face. These signal a transient ischemic attack (TIA). Untreated, a TIA can lead to a stroke.

  • If you have atherosclerosis in the arteries in your arms and legs, you may have symptoms of peripheral artery disease, such as leg pain when walking (claudication) or decreased blood pressure in an affected limb.

  • If you have atherosclerosis in the arteries leading to your kidneys, you may develop high blood pressure or kidney failure.



How Atherosclerosis Disrupts the Normal Cardiovascular Operation


In atherosclerosis, the gradual plaque buildup hardens the artery walls. This plaque buildup can cause the arteries to narrow, blocking blood flow. The narrowed artery limits or blocks the flow of blood to the heart muscle, which means it might not get enough oxygen. In addition, the plaque buildup occurs from the inside out; the walls of the vessels thicken and then protrude into the vessel lumen, which damages the vessel walls. Once this happens, the arterial passage is further constricted and thus it doesn’t take much for the vessel to close completely, which can lead to a heart attack or stroke. Furthermore, the plaque can also burst, leading to a blood clot. This gradual plaque buildup hinders the diffusion of nutrients from the blood to the deeper tissues of the artery wall. As nutrient diffusion decreases, the smooth muscle cells in the tunica media die and the elastic fibers deteriorate, and are gradually replaced by non-elastic scar tissue. This decreases the strength of the arterial walls, and eventually, as their strength decreases and blood pressure increases, the arteries may burst. Overall, this disease undermines the function of the circulatory system since the vessels are now impaired, and can’t deliver oxygen and nutrients to the body tissues effectively.


Treatment Plan


Assuming the plaque buildup in the coronary and right femoral arteries is constricting less than 30% of the blood flow, the doctor will most likely recommend medication. There are two types of medications that will be recommended: statins and blood thinners. The statins will decrease the cholesterol and triglyceride levels of Officer Wilson. Either Atorvastatin will be prescribed or Rosuvastatin. Both of these medications reduce cholesterol levels in the body, and in addition to lifestyle changes, will effectively carry out their function. In addition, a combination of medications will be prescribed that will thin the blood and reduce the risk of heart attack/ stroke. These are antiplatelet drugs (p2y12 inhibitors like aspirin), Clopidogrel 75, Prasugrel, and Ticagrelor. By prescribing antiplatelet drugs, the risk of platelet clotting is avoided and the blood thinners will reduce the risk of possible strokes and heart attacks by blood clots in the blood. If the plaque buildup increases, and more than 30% of the artery is constricted, then surgery procedures like Angioplasty and stent replacement, are recommended, to help open the clogged/ blocked artery.


References

Arteriosclerosis / atherosclerosis. (2021, March 16). Retrieved from https://www.mayoclinic.org/diseases-conditions/arteriosclerosis-atherosclerosis/diagnosis-treatment/drc-20350575

Atherosclerosis. (n.d.). Retrieved from https://www.hopkinsmedicine.org/health/conditions-and-diseases/atherosclerosis#:~:text=Key points of atherosclerosis, activity, and eating saturated fats.

Atherosclerosis and Heart Disease • Heart Research Institute. (n.d.). Retrieved from https://www.hri.org.au/health/learn/cardiovascular-disease/atherosclerosis#:~:text=Atherosclerosis is very common., do not have noticeable symptoms.

Marieb, E. N. (2022). Essentials of human anatomy & physiology. Pearson Education Limited.



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