Coronary Heart Disease - Lab Report Example

Introduction: Coronary Heart Disease (CHD) results from the thickening of the walls of the coronary arteries leading to reduced blood supplyto the heart muscles. Coronary Heart Disease (CHD): Deposits of plaque on the inner walls of the coronary arteries cause reduction in blood flow through them and thus depriving the heart muscles of much needed oxygen. This leads to the heart muscles facing oxygen deprivation stress. Incidence: Incidence of CHD is high all over the world including the United Kingdom and CHD is the single leading cause of premature death. Risk Factors: There are several risk factors for CHD and are divided into modifiable and un-modifiable. Many of the modifiable risk factors result from poor life styles and unhealthy eating habits. Prevention: Prevention of CHD targets the modifiable risk factors and attempts to reduce or negate the impact of these risk factors. Treatment: Treatment of involves the use of different types of drugs singly or in combination. As the disease progresses invasive intervention strategies may become necessary. Conclusion: CHD has severe consequences and it is necessary that poor life styles and unhealthy eating habits be avoided to reduce the impact of CHD. Table of Contents 1. Introduction 3 2. Coronary Heart Disease (CHD) 3 3. Incidence of CHD 4 4. Prevention of CHD 7 5. Risk Factors 7 6. Smoking 9 7. High Blood Pressure 10 8. Lipids and Lipoproteins 10 9. Diabetes Mellitus 15 10. Obesity 16 11. Treatment of CHD 16 12. Conclusion 17 13. Literary References 18 Coronary Heart Disease Introduction: The Report of the British Nutrition Foundation Task Force, 2005, defines coronary heart disease (CHD), as “a condition in which the walls of the arteries supplying blood to the heart muscle (coronary arteries) become thickened”. (p.1). Such thickening of the arteries results from the development of lesions on the walls of the arteries. Atherosclerosis is the name given to this condition of thickened arterial walls. The lesions responsible for the thickening of the arterial walls are termed as plaques. The result of the thickening of coronary arteries is restricted blood supply to the heart. This reduced availability of oxygen to the heart muscles causes silent heart attacks, acute pain in the chest on exertion called angina pectoris, or breathlessness on exertion. As the condition progresses there is the likelihood of the cap over the plaque rupturing’ leading to a blood clot, which could block the coronary artery and cause total obstruction to the flow of blood in the artery. This total block of blood flow in the coronary artery causes lack of availability of oxygen to the heart muscles leading to myocardial infarction or heart attack with the likelihood of death. (The Aetiology and Epidemiology of CardiovascularDisease, 2005). Coronary Heart Disease (CHD): Narrowing and hardening of the arteries that supply blood to the muscles of the heart muscle is called CHD. This narrowing and hardening is the result of the development of lesions on the inner walls of these arteries in the form of plaque. The progression in the narrowing of the artery occurs as the plaque increases in size. The blood supply to the hear muscles thus reduces. Blood carries the essential oxygen for the heart muscles and choking off the blood supply results in stress to the heart muscles. The stress experienced by the heart muscles is reflected in breathlessness experienced during exertion, which progressively leads to acute sub-sternal pain called angina pectoris. Rupture of the plaque could result in the clotting of blood and the result in a total block in the blood supply to the coronary arteries. The total block of the blood supply to the coronary arteries results in the acute stage of coronary heart disease termed myocardial infarction or heart attack, which could lead to death. (The Aetiology and Epidemiology of Cardiovascular Disease, 2005). Incidence of CHD: The severity of the concern for CHD arises from its prevalence and the possible morbidity and mortality or death that could result. CHD is a component of cardiovascular diseases (CVD) and according to the World Health Organization in 2001 CVD was the foremost cause of death around the world. It accounted for eighteen million deaths out of fifty five million deaths that occurred around the world, thus constituting thirty three percent of worldwide mortality. Of these deaths due to CVD, CHD was responsible for fifty percent of them. In the United Kingdom the scenario is hardly different. According to the British Heart Foundation in 2001 CVD was responsible for thirty six percent of the premature deaths in men and twenty seven percent of the premature deaths in women. Table -1 Deaths by Cause in Men in the United Kingdom 2001 Sl. No. Cause Percentage 01 Respiratory Disease 08 02 Lung Cancer 09 03 Colorectal Cancer 04 04 Other Cancers 20 05 Coronary Heart Disease 22 06 Other Cardiovascular Disease 07 07 Stroke 06 08 Injuries & Poisoning 08 09 All Other Causes 16 (The Aetiology and Epidemiology of CardiovascularDisease, 2005). Table -2 Deaths by Cause in Women in the United Kingdom 2001 Sl. No. Cause Percentage 01 Respiratory Disease 09 02 Lung Cancer 08 03 Colorectal Cancer 03 04 Breast Cancer 08 05 Other Cancers 23 06 Coronary Heart Disease 14 07 Other Cardiovascular Disease 07 08 Stroke 06 09 Injuries & Poisoning 08 10 All Other Causes 16 (The Aetiology and Epidemiology of CardiovascularDisease, 2005). CHD on its own is the leading cause of death in the United Kingdom, accounting for almost one out of every four deaths in men and one out of every six deaths in women, as can be seen from Table -1 and Table -2. A striking feature here is that men seem to be more prone to CHD, which shows in the marked elevated percentage of premature deaths in men, when compared to women (The Aetiology and Epidemiology of CardiovascularDisease, 2005). The silver lining in these statistics that inspire fear is that from 1970 onwards a decline has been witnessed in the death rates caused by CHD. This is highlighted by the drop in premature deaths due CHD in the period 1987 to 1992 for those under the age of sixty-five years by twenty-four percent. The sad part however is that those surviving bear a greater burden of cardiovascular morbidity (Gaw and Shepherd, 1999). Ethnicity is an important factor in the consideration of any disease and in the case of the United Kingdom this is even more significant with its diverse society. Blacks and minority ethnic groups make up almost eight percent of the population. Asians and black ethnic groups constitute the largest minority ethnic groups in the United Kingdom. In the black minority groups of Caribbean and West African the incidence of CHD is not frequent. This is not the case with East Africans and Asians. South Asians demonstrate a fifty percent higher rate of premature death in comparison to the general population. This can be seen in Figure -1. Such ethnic variances for higher incidence of CHD are important in the targeting of prevention of strategies (Lip, Barnett, Bradbury, Cappuccio, Gill, Hughes, Imray, Jolly and Patel, 2007). Figure -1 Sensitivity and specificity of thresholds for 10-year risk of CHD to identify 10-year risk of CVD 20% in different ethnic groups after exclusion of people with diabetes, target organ damage and CV complications. (Lip, Barnett, Bradbury, Cappuccio, Gill, Hughes, Imray, Jolly and Patel, 2007). Prevention of CHD: The primary means to reducing the incidence of CHD in any population is to identify the risk factors associated with CHD and target those risk factors that can be reduced or eliminated. The reduction of or elimination of such risk factors will contribute to the reduction of the prevalence of CHD. Thus an understanding of the risk factors and the manner in which these risk factors affect the incidence CHD is important (Pearson, 2007). An understanding of the risk factors also allows for screening of populations and early diagnosis of CHD. The benefits of early diagnosis of CHD are several. It allows for better compliance of corrective measures of life styles and medication and thereby the outcomes. This leads to lesser requirement of hospitalization and the economic benefits that accrue from it. In addition it prevents the progress of the disease to the acute stage of myocardial infarction and reduces premature death (Rutter and Nesto, 2007). Risk Factors: Risk factors as considered here are those characteristics that are found to cause a predisposition to the occurrence of CHD and include change of life styles, biological and physiological features and unchangeable personal characteristics like sex and family history of CHD. Thus there are two kinds of risk factors modifiable and non-modifiable. By modifiable it is meant that the risk factors are changeable by addressing them. By non-modifiable it is meant that these risk factors are unchangeable personal characteristics. Table-3 lists the modifiable and non-modifiable risk factors. (Gaw and Sheperd, 1999). The presence of a combination of these risk factors in an individual only increases the risk of CHD for that individual. For instance a male, with a family history of CHD, who smokes and leads a sedentary lifestyle, has a higher risk for CHD than a woman without a family history of CHD, who does not smoke and leads an active life. The benefit of understanding the risk factors associated with CHD is that it enables identifying individuals with a risk for CHD and taking steps to prevent the onset of CHD. Table -3 Risk factors for CHD Modifiable Non-modifiable Smoking Advance in Age Raised Blood Pressure Male Sex Raised Low-density Lipoprotein(LDL) Cholesterol Family History of CHD Low High-density Lipoprotein (HDL) Cholesterol Personal History of CHD Raised triglyceride Diabetes Mellitus Obesity Diet Thrombogenic Factors Lack of Exercise Poverty (Gaw and Shepherd, 1999). A recent study by Thomas Wang et al 2006 has added ten common contemporary biomarkers to the traditional risk factors to enhance the prediction of CHD and death due to CHD in individuals. The authors themselves comment that the additional biomarkers by themselves do not add to the prediction of future cardiovascular events, but in combination with the traditional risk factors provide a moderate means towards enhanced prediction. Table 4 list these biomarkers. (Wang, et al. 2006) Table – 4 Biomarkers That Predict Risk for Death* Biomarker Adjusted Hazard Ratio Per 1 SD in the Log Value BNP 1.40 CRP 1.39 Urinary Albumin-to-Creatinine Ratio 1.22 Homocysteine 1.20 Renin 1.17 *BNP indicates B-type natriuretic peptide; and CRP, C-reactive protein. (Wang, et al. 2006) Smoking: Smoking by far is the single largest contributor to elevated death rates of different causes around the world and is particularly significant in the case of CHD. These effects of smoking are preventable by change in behaviour. The exact mode of action of smoking in enhancing risk of CHD is still not very clear, but it is clear that smoking increases the development of atherosclerosis and blood clots. (Gaw & Shepherd, 1999). The development of atherosclerosis is believed to be due to the cigarette smoking influencing cytokines and causing a reduction in adiponectin levels, thereby causing dysfunction in the endothelial cells of the coronary arteries. This dysfunction aids in plaque build up on the inner walls of the coronary arteries. However it is not clear if these effects are caused directly by nicotine, carbon monoxide or the other components of cigarette smoke (Van Gaal, Mertens and De Block, 2006). The extent of risk due to smoking is dependant on the amount of tobacco smoked daily and the period since the onset of smoking. The more the quantum of smoking and the longer the duration since the onset of smoking results in higher risk for CHD. Smoking in women causes them to loose their reduced risk for CHD. (Gaw & Shepherd, 1999). However recent studies indicate that in heavy smokers, a reduction of smoking up to fifty percent has no effect on the risk of CHD and premature death. The only manner in which the risk factor of smoking can be eliminated is by total cessation of smoking. Therefore for reduced incidence of CHD and premature death due to CHD it is essential that change in behaviour by cessation of smoking is significant component. (Tverdal, & Bjartveit, 2006). High Blood Pressure: High blood Pressure or hypertension is considered as a risk factor for CHD. The exact mechanism by which high blood pressure becomes a risk factor is still uncertain, though a number hypothesises exist. Earlier guidelines for normal blood pressure were elevated with age to 140/90. In recent times the norms for normal blood pressure even with advanced age is has been reduced to 120/80. Poor diet and life style are contributory factors for high blood pressure. Thos makes it possible to address high blood pressure even without drugs, by changing food habits and life style. Thus reduced common salt intake, weight loss, reduced alcohol consumption combined with an exercise regime can bring about a reduction in high blood pressure (Wong, Thakral, Franklin, L’Italien, Jacobs, Whyte and Lapuerta, 2003). Lipids and Lipoproteins: Lipids and lipoproteins are an important risk factor for CHD. Plasma consists of two major lipids called cholesterol and triglyceride and performs essential functions for the body. Cholesterol is an essential component of cell membranes acting as a barrier between the body of the cell and the environment. Triglycerides are major storehouse of the energy of the body with particular emphasis on the adipose tissues. Esterified forms of both cholesterol and triglycerides are found in plasma, but are insoluble in the aqueous environment. Incorporations into lipoproteins make them soluble. The lipoproteins are classified on the basis of their separation ultracentrifuge, which is dependant on the hydrated density of the lipoprotein. On this basis plasma lipoproteins are classified into Chylomicrons, very low density lipoproteins (VLDL), intermediate density lipoproteins, low density lipoproteins(LDL) and high density lipoproteins(HDL) shown in Table-5, giving diameter of particle size. VLDL, LDL and HDL make up the lipoproteins of particular significance to CHD (Betteridge and Morrell, 1998). Since lipids, lipoproteins and triglycerides have essential functions in the human body, there is a requirement for their presence in plasma. However the excess presence of most of these raises the risk factor for CHD. There are desirable measures for the presence of lipids, lipoproteins and triglycerides, which are given in Table – 6 (Betteridge and Morrell, 1998). Table – 5 Plasma Lipoproteins Lipoprotein Class Diameter Of Particle Size (A0) Chylomicrons 800-5000 VLDL 300-800 IDL 250-350 LDL 216 HDL 75-100 (Betteridge and Morrell, 1998). Table – 6 Significant Lipoproteins and Triglycerides Desirable Measurement Values Factor Desirable Measurement values Total Cholesterol Less than 200 mg/dl LDL Less than 130 mg/dl HDL More than or equal to 60 mg/dl Triglycerides Less than 150mg/dl (Betteridge and Morrell, 1998). The significance of VLDL for CHD lies in its requirement for the formation of the small yet dense LDL. Genetic traits are a factor in the formation of LDL, though the genes responsible are yet to be identified. The diet of the individual is another significant factor in the amount of LDL formed. The plasma concentration of triglycerides is a major influence in the formation of LDL and this concentration is dependant on dietary factors. In vitro based studies have demonstrated that triglycerides mediate the VLDL to LDL. Thus the concentration of the most atherogenic lipoprotein in the form of LDL is linked to the plasma concentration of triglycerides (Lipid-Related Factors). Table – 7 Typical plasma concentration and approximate residence time on plasma of atherogenic lipoproteins Lipoprotein Particle Typical Concentration ApoB mg/l Typical Concentration Cholesterol mmol/l Diameter (nm) Residence Time in Hours LDL 50-250 0.2-1.0 20-24 48-240 IDL & VLDL 20-100 0.05-0.5 30-75 2-8 Chylomicron Small 2.0-10 0.01-0.1 30-75 2-8 Chylomicron Large 0.2-1.0 0.01-0.1 75-500 Read More