Mechanisms of Occlusion
Most MIs are caused by a disruption in the vascular endothelium associated with an unstable atherosclerotic plaque that stimulates the formation of an intracoronary thrombus, which results in coronary artery blood flow occlusion. If such an occlusion persists long enough (20 to 40 min), irreversible myocardial cell damage and cell death will occur.5
The development of atherosclerotic plaque occurs over a period of years to decades. The initial vascular lesion leading to the development of atherosclerotic plaque is not known with certainty. The two primary characteristics of the clinically symptomatic atherosclerotic plaque are a fibromuscular cap and an underlying lipid-rich core. Plaque erosion may occur due to the actions of metalloproteases and the release of other collagenases and proteases in the plaque, which result in thinning of the overlying fibromuscular cap. The action of proteases, in addition to hemodynamic forces applied to the arterial segment, can lead to a disruption of the endothelium and fissuring or rupture of the fibromuscular cap. The degree of disruption of the overlying endothelium can range from minor erosion to extensive fissuring that results in an ulceration of the plaque. The loss of structural stability of a plaque often occurs at the juncture of the fibromuscular cap and the vessel wall—a site otherwise known as the plaque's "shoulder region." Any amount of disruption of the endothelial surface can cause the formation of thrombus via platelet-mediated activation of the coagulation cascade. If a thrombus is large enough to completely occlude coronary blood flow for a sufficient time period, MI can result.
Mechanisms of Myocardial Damage
The severity of an MI is dependent on three factors: the level of the occlusion in the coronary artery, the length of time of the occlusion, and the presence or absence of collateral circulation. Generally speaking, the more proximal the coronary occlusion, the more extensive is the amount of myocardium at risk of necrosis. The larger the MI, the greater is the chance of death due to a mechanical complication or pump failure. The longer the time period of vessel occlusion, the greater the chances of irreversible myocardial damage distal to the occlusion.
The death of myocardial cells first occurs in the area of myocardium that most distal to the arterial blood supply—that is, the endocardium. As the duration of the occlusion increases, the area of myocardial cell death enlarges, extending from the endocardium to the myocardium and ultimately to the epicardium. The area of myocardial cell death then spreads laterally to areas of watershed or collateral perfusion. Generally, after a 6- to 8-hour period of coronary occlusion, most of the distal myocardium has died. The extent of myocardial cell death defines the magnitude of the MI. If blood flow can be restored to at-risk myocardium, more heart muscle can be saved from irreversible damage or death.
You May Also Find These Documents Helpful
-
d. When the foam cells rupture and die, they spill their cholesterol debris within the plaque. Over time, the plaque begins to harden, and at this point it is prone to cracks or ulcerations, which leads to the formation of blood clots. It is these clots that can eventually become thromboses or emboli, leading to heart attacks or…
- 915 Words
- 4 Pages
Good Essays -
Myocardial infarction (heart attack) – death of myocardial tissue caused by the inefficient blood supply.…
- 595 Words
- 3 Pages
Good Essays -
Describe where atherosclerotic plaques form in the body and list the possible consequences of developing plaques in those areas.…
- 437 Words
- 2 Pages
Satisfactory Essays -
I declare that all material in this assessment is my own work except where there is a clear acknowledgement and reference to the work of others. I have read the University’s Academic and Scientific Misconduct Policy and understand its implications.* http://www.cdu.edu.au/governance/documents/3.3academicandscientificmisconduct.pdf…
- 841 Words
- 4 Pages
Satisfactory Essays -
2. Plaque can build up in the artery walls, which can cause the arteries to thicken and lose their elasticity.…
- 263 Words
- 2 Pages
Satisfactory Essays -
The aetiology of atherosclerosis is not fully understood, but there are certain factors that contribute to atherosclerosis plaque progression. These include genetic and acquired factors. The processes involved in atherosclerosis include coagulation, inflammation, lipid metabolism, intimal injury, and smooth muscle cell proliferation. Certain risk factors have also been identified to explain the development of atherosclerosis and these can be separated into two groups, genetics and environmental:…
- 1254 Words
- 6 Pages
Better Essays -
There are five types of ischaemic stroke (Smelzter et al 2008, p.2206). They include large artery thrombotic strokes occurring in the blood vessels of the brain; small artery thrombotic stroke penetrating one or more blood vessels; cardiogenic embolic strokes related to dysrhythmia; cryptogenic strokes of unknown cause and others related to illicit drug taking, migraine and cutting of carotid or vertebral arteries (Smeltzer et al 2008, p.2206). Atherosclerosis builds up fatty deposits in the coronary artery, causing them to narrow (Harris, Nacy & Vardaxis 2006, p.151) and is predominant cause of ischaemic stroke (Newby & Grubb 2005, p.38). Symptoms of ischaemic stroke may include confusion, headache, numbness on one side of the body, slurred speech and poor visibility (Smeltzer et al 2008, p.2207).…
- 2243 Words
- 9 Pages
Powerful Essays -
The carotid arteries are normally smooth and unobstructed on the inside, but as one ages, a sticky substance called plaque, “which is made out of cholesterol, calcium, and fibrous tissue” can build up in the walls of these arteries. The carotid arteries will then become stiff and narrow. The most common location of plaque buildup is the Carotid bifurcation. 3 [change slide] Carotid artery disease is a serious health problem and a major cause of strokes, which can lead to brain damage or even death. There are three ways in which carotid artery disease can increase the risk of a stroke. (1). Plaque deposits can grow larger and larger; severely narrowing the artery and reducing blood flow to the brain, where Plaque can eventually completely block the artery. (2). Plaque deposits can roughen and deform the artery wall, causing blood clots to form and blocking blood flow to the brain. (3). Plaque deposits can rupture and flow to the brain. This fragment may get stuck in one of the smaller arteries, creating a blockage that cuts off blood supply to that area of the brain causing a stroke 2 [change slide]…
- 1783 Words
- 8 Pages
Powerful Essays -
Blockage of your arteries can occur in your limbs and brain. Having this condition causes many risk factors. You have chances of having coronary diseases, heart attacks and chest pain. Chest pain is the most specific symptom that comes along with arteriosclerosis. Chest pain can turn into a fatal condition such as myocardial infarction, because the arteries become so clogged that the aorta works harder and longer which progresses and causes into myocardial infarction. A clinical syndrome caused by an underprovided coronary arterial blood supply to a area of myocardium is a Myocardial infraction. This results in cellular death and breakdown of cells. This syndrome usually arises from an imbalance in oxygen supply and demand. The prodominant cause of myocardial infarction is plaque rupture and blood clotting formations in the coronary vessel, this results in acute reduction of blood supply of a small portion of the heart. Blood platelets stick to tears in the plaque and form a blood clot that blocks blood from flowing to the heart . Approximately 90% of myocardial infarctions result from an acute thrombus that obstructs an atherosclerotic coronary artery. Without blood supply the living tissues in the heart muscle die. This is the leading cause of death in the U.S. There are complications such as myocardial ischemia or heart failure might develop for people with myocardial…
- 958 Words
- 4 Pages
Good Essays -
The Cardiopulmonary Department focuses on the diagnosis and treatment of heart and lung conditions.One example of a heart conditoin is a myocardial infarctions, more commonly known as heart attacks, are typically caused by a blood clot in the coronary artery which can restrict blood flow, this in turn can cause the heart’s pumping function to decrease ( Heart Attack. 2017). An example of a cardiovascular condition is a cerebrovascular accident (CVA), or a stroke, is caused by lack of bloodflow to the brain, often caused by a blood clot or a hemorrhaging. Another branch to this is atherosclerosis, a condition where there is plaque build up in the arteries. Atherosclerosis can cause a decrease in blood flow to the heart and other vital…
- 1459 Words
- 6 Pages
Good Essays -
CAD is thought to begin with damage or injury to the intimal layer of coronary artery, sometimes as early as childhood. The damage may be caused by various factors, including: smoking, hypertension, hypercholestromia, diabetes or insulin resistance, radiation therapy to the chest, as used for certain types of cancer, and sedentary lifestyle. Once the intimal layer of coronary artery is damaged, fatty deposits (plaques) made up of cholesterol and other cellular waste products tend to accumulate at the site of injury in a process called atherosclerosis. If the surface of these plaques breaks or ruptures, platelets will clump at the site to try to repair the artery. This clump can block the artery, leading to a heart attack. Recent research has…
- 409 Words
- 2 Pages
Good Essays -
The cardiac muscle of the heart wall depends on a constant flow of blood supply by the coronary arteries. Coronary arteries are blood vessels that arise from the base of the aorta and bring freshly oxygenated blood to the heart muscle. If this supply is restricted, then oxygen and nutrients can’t reach the muscles and the result could be a form of coronary artery disease (CAD). It can also be known as coronary heart diseases (CHD). This form of partial or complete block can be caused by fatty deposits, blood clots, or both. Overall, the extent of the symptoms of coronary artery disease depends on the location, severity, and how fast the disease will start from the limited blood supply.…
- 267 Words
- 2 Pages
Good Essays -
Atherosclerosis is a form of cardiovascular disease in which the inner layers of artery walls are made thick and irregular by plaque deposits; arteries become narrow and blood supply can be reduced. (pg. 409) Atherosclerosis is deposited by fatty substances (called plaques) in the walls of the arteries. (pg.249) The arteries become narrow due to a person having high blood pressure which makes the heart work harder which forces the blood through the arteries making it narrow and stiffen. They also become narrowed buy deposits of fat, cholesterol, and other substances. The lining arteries gets damaged by the endothelial cells (cells that line the arteries) becomes damaged. This is caused by smoking, high blood pressure, high insulin or glucose levels, and deposits of oxidized LDL particles. Next the body responds to these damages by causing information and changes in the artery lining that…
- 389 Words
- 2 Pages
Good Essays -
Coronary heart disease is most often caused by a condition called arteriosclerosis, which takes place when a fatty material along with a substance called plaque builds up along the walls of the coronary arteries causing them to become narrow and restrictive. As the coronary arteries grow rigid and narrow, the combination can restrict the blood flow to the heart causing it to stop or slow down resulting in chest pain, stable angina, shortness of breath, along with other symptoms, eventually resulting in a heart attack (Blank & Smithline, 2002). However, most individuals with coronary artery disease do not display symptoms of the disease for decades, even as it progresses. The first onsets of symptoms are often sudden resulting in myocardial infarctions, also known as heart attacks. (American Heart Association, 2011; DeVon, & Zerwic, 2003).…
- 3418 Words
- 14 Pages
Powerful Essays -
one of the coronary arteries supplying blood to heart is blocked,If attack is severe, victim may die. If…
- 1179 Words
- 5 Pages
Good Essays