The two hypotheses about the causes of coronary artery disease
The research into coronary artery disease in the 19th century lead the scientists to propose two hypotheses about how the disease develops. The first hypothesis claimed that incrustation was the cause of the disease. Rokitansky and Duguid proposed that the disease occurs as a result of deposition of fibrin and fibroblasts onto which lipids are accumulated. The lipid hypothesis which was put forth by Virchow claimed that coronary artery disease was caused by transduction of lipids into the walls of the artery which then entered into complex formations with mucopolysaccharides, The prevalence of lipid deposition systems over lipid removal systems leads to the accumulation of lipids in the arterial walls.
Injury hypothesis
Modern researches have found evidence that the correct way to describe the development of coronary artery disease is the so-called response to injury hypothesis that was first proposed by Ross. This hypothesis, in a way, unifies both of the earlier ones and makes some new proposals. The main idea is that in order for coronary artery disease to occur some kind of vascular injury has to take place and thrombus has to be formed (Samady et al., 2011, p. 782).
Types of the injury
There are three types of vascular injury that can cause the disease. The first one is in the cases when morphologically unchanged endothelial cells alternate their function. The second type occurs when some of the endothelial cells wear off and intima is damaged but the internal lamina remains without damage. Finally, the third type of injury is related to both the damage to intima and media together with the erosion of endothelial cells (Samady et al., 2011, p. 783).
Causes of injuries
Those different types of injuries are caused in different ways. It is widely believed that minimal injuries of the first type are caused in the disturbances in the blood flow. Type two is initiated when the macrophages release toxins in which case platelets grow together. Sometimes this process can cause a capsule to be formed over a lipid lesion. This usually leads to the formation of fibrointimal lesions. Finally, the third type of injury is created when sensitive capsules are disturbed and the thrombus is formed. Small thrombi can easily fuse together and large thrombi can cause unstable angina, myocardial infraction and ischemic death (Samady et al., 2011, p. 783).
Factors in the diagnosis
The diagnosis of coronary artery disease is very complex and there are several factors that can help when establishing a diagnosis. Anginal chest pain can be a reliable signal that the artery is narrowed but it can also be present in rheumatic diseases and hyperthyroidism. Furthermore, the pain should be dull and constricting never sharp and it should radiate. In addition, electrocardiogram and coronary angiography are used in order to spot irregularities in the function and morphology of the coronary arteries. However, recent studies (Heidenreich, 2010, p.5-7) suggest that new technologies such as CT coronary angiography are more reliable in diagnosing coronary artery disease than traditional practices of stress-testing and ECG.
Forms of therapy
As far as treatment is concerned there are several methods which are most often employed. Medical treatment includes such medications as nitroglycerin, beta-blockers, cholesterol lowering medications, etc. Surgical procedures are coronary artery by-pass, angioplasty and coronary stent implantation. A recent study by Serruys (2009)and colleagues was conducted in order to establish which of the two most widely used surgical procedures, namely coronary artery by-pass and angioplasty, was more efficient when dealing with severe coronary artery disease. The study involved 1800 patients who all suffered from the disease of approximately the same severity were divided into two groups. One group underwent angioplasty and the other coronary artery by-pass surgery. The aim was to see which group would have more cardiac events. It was proven that the at the end of one year period, which is how long the experiment lasted, that the group which underwent angioplasty had 17.8 per cent cardiac events which is significantly larger percentage than that of the other group where only 12.4 per cent of the patients suffered from cardiac events. It was concluded that coronary artery by-pass should be the primary mode of treatment of severe coronary artery disease (Serruys, 2009, pp. 961-972).
References
Heidenreich, P. (2010). CT coronary angiography was more accurate than stress testing for diagnosing CAD, especially in patients at intermediate risk.. Annals of Internal Medicine, 153(8), 4-9.
Samady, H., Eshtehardi, P., & McDaniel, M. (2011). Coronary artery wall shear stress is associated with progression and transformation of atherosclerotic plaque and arterial remodeling in patients with coronary artery disease. Circulation, 124(7), 779-788.
Serruys, P., et al. (2009). Percutaneous Coronary Intervention versus Coronary-Artery Bypass Grafting for Severe Coronary Artery Disease. New England Journal of Medicine, 360, 961-972.