Atherosclerosis, Coronary Artery Disease, And Medication And Surgical Interventions

Prevalence and Symptoms of Atherosclerosis and Coronary Artery Disease

Atherosclerosis is a worldwide prevalent disease affecting a major portion of the population leading to morbidity and even death (Schelbert 2010). Though the condition is prevalent amongst aged, a majority of the young proportion of the population is also affected by it. Affected patients need medical intervention in form of either surgery or therapy to lower LDL levels in bloodstream. The scope of this analysis includes clinical management procedure and search strategy that can critically help arrive at patient analysis.    

Atherosclerosis of coronary arteries is a disease of the artery by narrowing up of building up of plaque. Stone (2011) shows that the disease at the onset does not show any symptoms, when symptoms progresses in severity can lead to stroke, periphery artery disease, coronary artery disease or kidney diseases, even death sometimes (Stone 2011). It is characterised as change s brought in intima of arteries. Coronary artery disease
(CAD) with high risk factors affects a high proportion of the world population. CAD has several symptoms and risk factors as diabetes, high blood pressure, obesity, smoking, unhealthy diet, family history and so on (Hansson 2009). Plaque formed in the intima is composed mostly of fat, calcium, cholesterol and other substances. It can be diagnosed using exercise stress test, electrocardiogram and other suitable tests. Though there are various intervention methods available, prevention includes not smoking, eating healthy diet, exercising, maintain normal weight amongst others. Medication are available that are known to reduce cholesterol levels in blood stream as statins, blood pressure medications, medications that decreases clotting and so on. Coronary Artery Bypass Grafting is the most used intervention method for overcoming this diseases or avoiding possible future complications or reoccurrence of the same. This diseases initiates when a person is young and deteriorates as age progresses. It has been estimated that almost all people are affected by this disease once to some degress till the reach age of 65 years.     

In the cardiovascular system of the human body, coronary arteries includes the two main arteries as the right and left arteries. Coronary arteries is responsible for supplying blood to muscles of the heart. Similar to other tissues in the body, muscles in the heart also requires oxygen-rich blood for its functioning (Gould 2013). The arteries wrap around the outside walls of the heart with small branches going inside the heart muscles for transporting blood. These arteries initiates from the valsalva sinuses located above the aortic valve. The left coronary artery (LMCA) divides itself into left anterior descending artery (LAD) and circumflex artery. The left anterior descending artery branches off from left coronary artery supplies blood into left front portion of the heart. The circumflex artery branches from left coronary artery encircling muscles of the heart, it is responsible for supplying blood to outer and back side of the heart (Knight 2010). The right coronary artery (RCA) is responsible for supply of blood to right ventricle, SA (sinoatrial), right atrium and AV (atrioventricular) nodes. These nodes are responsible for regulating heart rhythm. As the right coronary artery divides itself into smaller branches with acute marginal artery and right posterior descending artery. The left anterior descending artery along with right coronary artery allows blood supply into the middle or septum part of the heart. The smaller branches of coronary arteries is constituted by obtuse marginal (OM), diagonals and septal perforator (SP). Several anastomoses present between the coronary arteries allows collateral blood supply at the time of myocardial ischemia (Ferrari 2013).

Risk Factors for Atherosclerosis and Coronary Artery Disease

Conductance Vessels is the circulation of coronary arteries into two compartments of epicardial vessels. They do not cause resistance blood flow. The small intramuscular vessels are often referred to as resistive vessels. Blood flow within coronary arteries is regulated by the blood pressure and from intramuscular vessel resistance. During systolic contraction stage of the heart cycle, blood inflow in coronary arteries on the epicardial layer nearly stops.  During the diastolic relaxed stage myocardium is perfused in the cycle (Jellinger 2012). Pressure in normal conditions in distal part of the coronary central aortic pressure and epicardial artery is equal. Heart’s function is to pump blood throughout the body at every time, this continuous function of heart helps meet high oxygen demand. The myocardium is responsible for maximum oxygen extraction compared to other body organs. Regulating myocardial blood flow is tight as it is essential in order for wall motion abnormalities be avoided (Voros 2011). Vasocontriction and vasodilation substances present in the inner lining of coronary arteries, referred to as endothelium allows blood delivery constantly to the myocardium by auto-regulation mechanism. Atherosclerosis arises from unhealthy endothelial cells getting inflamed. Hence it can be concluded atherosclerosis results from early manifestation in endothelial cell lining (Taylor 2013).       

Cholesterol in blood stream is carried by low-density lipoproteins (LDL) and lipoproteins and high density lipoproteins (HDL). In order for prevention of atherosclerosis, it becomes essential that healthy levels of all lipoproteins are maintained (Ishigaki 2008). Higher levels of LDL in the blood raises bad cholesterol leading to harming of the endothelium lining in coronary arteries. LDL upon entering into coronary walls injures coronary arteries between outer and inner layers, at locations of formation of primary atherosclerotic plaque. In case there is increase in levels of LDL blood pressure will rise causing tremendous damage to artery wall structure with proliferation of plaques taking place. Atherosclerosis condition attempts at coronary auto regulation mechanism impacted by narrowing of coronary arteries for the purpose of regulating blood flow into the myocardium (Johnsen 2008). It is undertaken by reducing resistance caused by distal perfusion beds by means of dilating distal arterioles for regulating blood flow in dilated vascular streams. This allows oxygenated blood flow in myocardium, which in case of critical atherosclerosis cannot be conducted. In severe cases oxygen supply is inhibited into myocardium which affects functioning of heart in a negative manner. There are other risk factors that affects seriousness of atherosclerosis that enhances oxidative stress factors as aging, coronary artery disease risk factors as smoking, genetically transmitted diseases, Type 2 diabetes and so on (Nishimura 2014).              

Prevention Methods for Atherosclerosis and Coronary Artery Disease

Patients with coronary artery diseases require medical therapy for prevention of diseases, progressing into recurrent cardiovascular events (Tweet 2012). Various classes of medication therapy is available towards prevention of the condition as antiplatelet, anti-hypertensive and lipid-lowering agents. Thromboembolic agents are able to effectively manage patients diagnosed with CAD (Summers 2010). At other instances surgical interventions as angioplasty or coronary artery bypass graft surgery (CABG) is suggested by doctors. Symptoms associated with CAD is chest pain or experiencing discomfort in the chest, indicating that the heart is not receiving sufficient oxygenated blood for its functioning in the systolic stage. Contradictions indicate that CAD might be prevalent without any symptoms when patient experiences co-morbidity. Appropriate treatment at the right time might be effective in reducing symptoms of CAD and enhancing heart functions (De Bruyne 2014).

CABG procedures have been known to experience better quality of life with enhanced heart functionality. In CABG procedure involving major intervention vessels is harvested by replacing artery from foot by replacing them in the heart. Transplanted vessels acts as new grafts allowing blood perfusion into the ischemic area of the myocardium, which might have previously been restricted. For success of CABG procedure conduit of high quality from the body of the patient must be selected. Vessel selected is generally left internal mammary artery (LIMA), long saphenous vein (LSV) and radial artery (RA) (Haddad 2008). LIMA being grafted into LAD provides longer term in CABG procedure. There is a debate circling regarding choice of RA or LSV in second choice graft for CABG that has greater effects on post-operative survival rates. The scope of this paper evaluates regarding the effectiveness of LSV over RA which needs be used as second choice for bypass grafts in CABG (McCord 2008). It is performed for the purpose of relieving angina that is maximum tolerated by anti-ischemic medication for preventing or relieving left ventricular dysfunction and reduce chances of mortality. The surgery is conducted by stopping the heart and using cardiopulmonary bypass. CABG has not been seen to prevent occurrence of myocardial infarction.  CABG can be conducted in beating heart by off-pump surgery, which minimizes side effects (Marcassa 2008). CABG is indicated to patients with 50 to 99 percent coronary arteries obstructions. Atherosclerosis is characterized by either formation of plaques or lost in elasticity, resulting in narrowing of artery. The 2004 ACC/AHA CABG guidelines provides it as a treatment for disease of left main coronary artery (LMCA), diffuse disease that is not treatable with PCI, disease of all three coronary arteries of LAD, LCX and RCA (Slaughter 2010). It is also used for treating patient with high risk with severe ventricular dysfunction or diabetes mellitus. CABG has various proven benefits compared to stent replacements.                     

Medications for Atherosclerosis and Coronary Artery Disease

An electronic database was provided by Cardiff University department of Cardio-Respiratory and Pathophysiology as provided in the table below. A comprehensive literature review using backward chain analysis was undertaken, where multiple articles in similar area was explored (Liu 2011). All database were regarding human subjects, where RA as a graft for CABG was used. In order to critically evaluate the issue six randomized control traits (RCTs) was elected.  

Table 1

Cardiac Artery Bypass Grafting (CABG) surgery is known to increase blood flow to the heart (Nabel 2012). It is undertaken in patients having severe coronary heart disease (CHD) as atherosclerosis. Functional and morphological variance between veins and arteries have tremendous implications on CABG survival rates. Debate in differences evaluating LSV and RA have been seen to have subjective differences. Studies have mostly not been able to quantify findings related to the same. All studies posts introduction of LSV have been focused on assessing and comparing in-vivo graft flow rates of LSV as against RA aorta-coronary grafts. Studies conducted by Chong, Collins, Webb, De Souza, Pepper, Hayward and Moat (2006) analysed 3-month post-operative nature along with in-vivo flow response related to LSV and RA grafts (Chong 2006). This study was focused on analysis of basal velocity but similar volumes that corresponded to higher levels in RA as compared to LSV grafts. RA grafts showed endothelium based vasodilatation. With growing interests in RA as coronary artery bypass graft a rise in replacing veins with arterial grafts has seen a rise. Observational series with longer-term patency results favor it as a successful conduit. This research was conducted using 52 males months after their surgery were analysed by use of Thrombolysis in Myocardial Infarction (TIMI) frame count. Target coronary artery and graft was measured using quantitative coronary angiography, then velocity and volume flow was computed. Moreover, analysis of 7-patients, who underwent in-vivo graft flow response by use of intravascular Doppler methods was used. The research design adopted facilitates reader’s usability to assessing final findings related to the study.      

Gaballah and Elnor (2013) studied LSV and RA graft procedure in CABG found highly successful outcomes posts surgery (Gaballah 2013). However, surgery with LSV in this study showed significant rise in morbidity. Though this study analyses risk factors associated with infections in coronary artery bypass grafting surgery but its findings have been significant for grafts to be used for CABG. LSV was shown to increase incidence of leg infection in patients ranging from moderate to high levels. The study made use of data collected from patients with coronary artery disease were admitted in Shebien El-Kom Teaching Hospital. Data from 100 patients had been collected and then risks of infection was analysed using ASEPSIS scoring methods. 10 risk factors was analysed from entire cohort of patients, who underwent bypass surgery at the same time period. The research procedure and findings were suitable to comprehend and understand relative to the topic. All factors were taken into consideration for analysis of risk factors and then multivariate analysis was conducted. Prevalence of risks of infection in patient using LSV procedures reflected that RA was a more suitable graft process in CABG. LSV was thus concluded to increase risk factors post-operative amongst patients.        

Surgical Interventions for Atherosclerosis and Coronary Artery Disease

Taggart (2013) analysed current state of coronary bypass surgery used amongst patients (Taggart 2013). This paper makes use of decade old evidences for usage of single graft for coronary artery bypass grafting procedures. All studies have been focussed on ways and methods by which clinical outcomes can be improved in bypass grafting procedures. It has been noted that patients across developed countries receive single arterial conduit even in case of multivessel coronary artery disease. Second internal mammary artery and radial artery graft usage has been analysed in findings of this study.  This study establishes that while comparing usage of LSV as against RA, there is a consistent supremacy patency of RA in long term. Loop along with his colleagues in their landmark study described usage of internal mammary artery (IMA) over saphenous vein graft (SVG) in CABG procedure. This process was shown to reduce mortality and myocardial infarct as it impacted reduced usage of angina and interventions. Other researchers who were promoting usage of IMA for CABG identified its clinical benefits in the Cleveland Clinic publications. Radial artery was first used by Carpentier and his colleagues in the year 1974 but was abandoned for its high rates of failures. RA having thin continuous intima of endothelium cells structurally predisposes occlusion, thrombosis and spasm. RA and SVG has reflected with superior outcomes. This paper reflects no functional difference between RA and LSV grafts in the first year duration. In longer period RA depicts stronger potency.  

Prim, Zhou, Hartstone-Rose, Uline, Shazly, Eberth (2016) analyses differential performance related to coronary artery grafts (Prim 2016). Authors of this articles assumes CABG to disrupt homeostatic state of transplanted vessel. This study established RA as being a superior method compared to LSV. The research design proposed by authors here are extremely expensive compared to other researches. Intervention procedure used in this research process was focussed on understanding the various techniques used in developed countries related to CABG procedures. Success of CABG with RA grafts is dependent on various procedures as a graft lasts typically for 8 to 15 years. CABG increase survival chances in patients who are at high risks. Age has been considered to a critical factor prognosis  as in older patients it is higher compared to younger patients. Older patients are expected to suffer more blockage of coronary arteries compared to younger patients. Grafts  have tendencies to become partially or completely occlude and diseases losing their patency. In case a graft months are performing the surgery has normal flow then it is considered to be highly effective in nature. Nature of graft used, size of coronary artery and skill of surgeon performing surgery are factors that affect graft patency. Arterial grafts as LITA and radial are considered to be more sensitive in rough handling compared to saphenous veins. It is more likely to go into spasm I n case not handled properly. Most successful patency rates are achieved with in-situ internal thoracic artery with its distal end being anastomosed with coronary artery. Radial grafts in this case is expected to have less patency. Complications can arise with CABG procedures as postperfusion syndrome. In this case a transient neurocognitive impairment with cardiopulmonary bypass takes place. Other complications include non-union of the stern um or internal   thoracic artery. Myocardial infarction, late graft stenosis, stroke, graft failure, hemothorax and so on. These complications can be reduced or removed by clinical examination of patient thoroughly prior to suggesting an intervention procedure. Clinical intervention suing CABG can have significant potential impacts on patients which has to be reduced using post-operative procedures.                

Clinical Management Procedure and Search Strategy

Conclusion

Critical analysis of various literatures provides that RA bypass grafts have better patency when compared to LSV graft procedures. RA is however not often used due to the several limitations that are involved with RCTs. Most studies conducted are using male participants; hence conclusion related to findings cannot be generalized. Healthcare practioner needs to evaluate patient basis CABG graft procedure for suggesting whether RA or LSV should be used.      

Reference Lists

De Bruyne, B., Fearon, W.F., Pijls, N.H., Barbato, E., Tonino, P., Piroth, Z., Jagic, N., Mobius-Winckler, S., Rioufol, G., Witt, N. and Kala, P., 2014. Fractional flow reserve–guided PCI for stable coronary artery disease. New England Journal of Medicine, 371(13), pp.1208-1217.

Chong, W.C., Collins, P., Webb, C.M., De Souza, A.C., Pepper, J.R., Hayward, C.S. and Moat, N.E., 2006. Comparison of flow characteristics and vascular reactivity of radial artery and long saphenous vein grafts [NCT00139399]. Journal of cardiothoracic surgery, 1(1), p.4.

Ferrari, R., Abergel, H., Ford, I., Fox, K.M., Greenlaw, N., Steg, P.G., Hu, D., Tendera, M. and Tardif, J.C., 2013. Gender-and age-related differences in clinical presentation and management of outpatients with stable coronary artery disease. International journal of cardiology, 167(6), pp.2938-2943.

Gaballah, K. and Elnor, M.A., 2013. Long saphenous vein harvesting site infection after coronary artery bypass grafting. Tanta Medical Journal, 41(4), p.306.

Gould, K.L., Johnson, N.P., Bateman, T.M., Beanlands, R.S., Bengel, F.M., Bober, R., Camici, P.G., Cerqueira, M.D., Chow, B.J., Di Carli, M.F. and Dorbala, S., 2013. Anatomic versus physiologic assessment of coronary artery disease: role of coronary flow reserve, fractional flow reserve, and positron emission tomography imaging in revascularization decision-making. Journal of the American College of Cardiology, 62(18), pp.1639-1653.

Haddad, F., Hunt, S.A., Rosenthal, D.N. and Murphy, D.J., 2008. Right ventricular function in cardiovascular disease, part I: anatomy, physiology, aging, and functional assessment of the right ventricle. Circulation, 117(11), pp.1436-1448.

Hansson, G.K., 2009. Atherosclerosis—an immune disease: the Anitschkov Lecture 2007. Atherosclerosis, 202(1), pp.2-10.  

Ishigaki, Y., Katagiri, H., Gao, J., Yamada, T., Imai, J., Uno, K., Hasegawa, Y., Kaneko, K., Ogihara, T., Ishihara, H. and Sato, Y., 2008. Impact of plasma oxidized low-density lipoprotein removal on atherosclerosis. Circulation, 118(1), pp.75-83.

Jellinger, P., Smith, D., Mehta, A., Ganda, O., Handelsman, Y., Rodbard, H., Shepherd, M. and Seibel, J., 2012. American Association of Clinical Endocrinologists’ guidelines for management of dyslipidemia and prevention of atherosclerosis. Endocrine practice, 18(Supplement 1), pp.1-78.

Johnsen, S.H. and Mathiesen, E.B., 2009. Carotid plaque compared with intima-media thickness as a predictor of coronary and cerebrovascular disease. Current cardiology reports, 11(1), pp.21-27.

Electronic Database for Literature Review

Knight, J., Olgac, U., Saur, S.C., Poulikakos, D., Marshall, W., Cattin, P.C., Alkadhi, H. and Kurtcuoglu, V., 2010. Choosing the optimal wall shear parameter for the prediction of plaque location—a patient-specific computational study in human right coronary arteries. Atherosclerosis, 211(2), pp.445-450.

Liu, L., Gardecki, J.A., Nadkarni, S.K., Toussaint, J.D., Yagi, Y., Bouma, B.E. and Tearney, G.J., 2011. Imaging the subcellular structure of human coronary atherosclerosis using micro–optical coherence tomography. Nature medicine, 17(8), p.1010.

Marcassa, C., Bax, J.J., Bengel, F., Hesse, B., Petersen, C.L., Reyes, E. and Underwood, R., 2008. Clinical value, cost-effectiveness, and safety of myocardial perfusion scintigraphy: a position statement. European heart journal, 29(4), pp.557-563.

McCord, J., Jneid, H., Hollander, J.E., de Lemos, J.A., Cercek, B., Hsue, P., Gibler, W.B., Ohman, E.M., Drew, B., Philippides, G. and Newby, L.K., 2008. Management of cocaine-associated chest pain and myocardial infarction: a scientific statement from the American Heart Association Acute Cardiac Care Committee of the Council on Clinical Cardiology. Circulation, 117(14), pp.1897-1907.

Nabel, E.G. and Braunwald, E., 2012. A tale of coronary artery disease and myocardial infarction. New England Journal of Medicine, 366(1), pp.54-63.

Nishimura, R.A., Otto, C.M., Bonow, R.O., Carabello, B.A., Erwin, J.P., Guyton, R.A., O’Gara, P.T., Ruiz, C.E., Skubas, N.J., Sorajja, P. and Sundt, T.M., 2014. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. The Journal of Thoracic and Cardiovascular Surgery, 148(1), pp.e1-e132.

Prim, D.A., Zhou, B., Hartstone-Rose, A., Uline, M.J., Shazly, T. and Eberth, J.F., 2016. A mechanical argument for the differential performance of coronary artery grafts. Journal of the mechanical behavior of biomedical materials, 54, pp.93-105.

Schelbert, H.R., 2010. Anatomy and physiology of coronary blood flow. Journal of nuclear cardiology, 17(4), pp.545-554.

Slaughter, M.S., Pagani, F.D., Rogers, J.G., Miller, L.W., Sun, B., Russell, S.D., Starling, R.C., Chen, L., Boyle, A.J., Chillcott, S. and Adamson, R.M., 2010. Clinical management of continuous-flow left ventricular assist devices in advanced heart failure. The Journal of Heart and Lung Transplantation, 29(4), pp.S1-S39.

Summers, K.M., Martin, K.E. and Watson, K., 2010. Impact and clinical management of depression in patients with coronary artery disease. Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy, 30(3), pp.304-322.

Stone, G.W., Maehara, A., Lansky, A.J., de Bruyne, B., Cristea, E., Mintz, G.S., Mehran, R., McPherson, J., Farhat, N., Marso, S.P. and Parise, H., 2011. A prospective natural-history study of coronary atherosclerosis. New England Journal of Medicine, 364(3), pp.226-235.

Taggart, D.P., 2013. Current status of arterial grafts for coronary artery bypass grafting. Annals of cardiothoracic surgery, 2(4), p.427.

Taylor, C.A., Fonte, T.A. and Min, J.K., 2013. Computational fluid dynamics applied to cardiac computed tomography for noninvasive quantification of fractional flow reserve: scientific basis. Journal of the American College of Cardiology, 61(22), pp.2233-2241.

Tweet, M.S., Hayes, S.N., Pitta, S.R., Simari, R.D., Lerman, A., Lennon, R.J., Gersh, B.J., Khambatta, S., Best, P.J., Rihal, C.S. and Gulati, R., 2012. Clinical features, management and prognosis of spontaneous coronary artery dissection. Circulation, pp.CIRCULATIONAHA-112.

Voros, S., Rinehart, S., Qian, Z., Joshi, P., Vazquez, G., Fischer, C., Belur, P., Hulten, E. and Villines, T.C., 2011. Coronary atherosclerosis imaging by coronary CT angiography: current status, correlation with intravascular interrogation and meta-analysis. JACC: Cardiovascular Imaging, 4(5), pp.537-548.

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