Sunday, 24 November 2013

Coronary heart disease - Causes and Risk Factors

Cardiovascular Disease
Cardiovascular disease is defined as medical conditions affecting the cardiovascular system, including heart, blood vessels(arteries and veins).
I. Coronary heart disease
Coronary heart disease is defined as a condition of narrowing coronary arteries that lead to blockage of the blood flow in the arteries as a result of hardening arterial wall, cholesterol building up in the arteries, chemicals, such as cadmium clog up arteries, etc. affecting the small blood vessels that supply blood and oxygen to the heart. Coronary heart disease (CHD) is the leading cause of death in the United States.
B. Causes and Risk Factors
B.1. Causes
Causes of Coronary heart disease is due to narrowing coronary arteries that lead to the blockage of the blood flow in the arteries as a result of hardening arterial wall, cholesterol and plague building up on the arterial wall, affecting the small blood vessels that supply blood and oxygen to the heart.
B.2. Risk Factors
1. Heredity
Coronary heart disease runs in the family. Dr. Swerdlow DI and the research team at the University College London indicated that Recent major advances in genomic science and technology have opened new avenues of investigation in the pathogenesis of CHD, some of which are leading to clinical translation. Sources of data, the published literature in CHD genetics has burgeoned in the last 5 years with the reporting of genome-wide association studies (GWASs) and many other findings.Areas of agreementIdentification of many genetic variants with small effects on CHD risk has been a common finding(7).
2. High level of cholesterol
People with levels of cholesterol in the blood are above healthy levels are at increased risk of coronary heart disease. In the study of  4444 patients with angina pectoris or previous myocardial infarction and serum cholesterol 5.5-8.0 mmol/L on a lipid-lowering diet were randomised to double-blind treatment with simvastatin or placebo. Over the 5.4 years median follow-up period, simvastatin produced mean changes in total cholesterol, low-density-lipoprotein cholesterol, and high-density-lipoprotein cholesterol of -25%, -35%, and +8%, respectively, with few adverse effects. 256 patients (12%) in the placebo group died, compared with 182 (8%) in the simvastatin group. The relative risk of death in the simvastatin group was 0.70 (95% CI 0.58-0.85, p = 0.0003). The 6-year probabilities of survival in the placebo and simvastatin groups were 87.6% and 91.3%, respectively(8). High density lipoprotein cholesterol (HDL-cholesterol) has emerged as a negative risk factor for coronary heart disease(9).
3. Obesity
Waist circumference (WC), is associated with increased coronary heart disease (CHD) risk regardless of the level of BMI. Men with normal BMI and obese WC tend to be associated with CHD risk than those with obese BMI and obese WC(10).
4. High blood pressure
In  the study to evaluate  the joint effects of managing low-density lipoprotein cholesterol (LDL-C) and systolic blood pressure (SBP) on cardiovascular outcomes showed that at 3 months’ follow-up, patients were stratified according to SBP (< 140 mm Hg vs > or = 140 mm Hg) and tertiles of LDL-C. At 4.9 years’ median follow-up, the rate of major cardiovascular events was reduced most in patients with lower LDL-C (P < .001) and in patients with SBP < 140 mm Hg (P = .014). A 42% relative risk reduction was observed for patients in the lowest LDL-C tertile with an SBP < 140 mm Hg(11).
5. Diabetes
People who have Diabetes are not only at increased risk of coronary heart disease, but also are dramatically increased risks of death from fatal CHD. Dr/ Hu FB, at Harvard School of Public Health indicate that among women, history of diabetes is associated with dramatically increased risks of death from all causes and fatal CHD. The combination of diabetes and prior CHD identifies particularly high-risk women(12).
6. Processed meats and high saturated and trans fat diet
Consumption of processed meats, but not red meats, is associated with higher incidence of CHD and diabetes mellitus. These results highlight the need for better understanding of potential mechanisms of effects and for particular focus on processed meats for dietary and policy recommendations(13). other researchers indicated that based on consistent evidence from human studies, replacing saturated fatty acids SFA with polyunsaturated fat modestly lowers coronary heart disease risk, with ~10% risk reduction for a 5% energy substitution; whereas replacing SFA with carbohydrate has no benefit and replacing SFA with monounsaturated fat has uncertain effects. Evidence for the effects of SFA consumption on vascular function, insulin resistance, diabetes, and stroke is mixed, with many studies showing no clear effects(14). Controlled trials and observational studies provide concordant evidence that consumption of TFA from partially hydrogenated oils adversely affects multiple cardiovascular risk factors and contributes significantly to increased risk of CHD events(15).

7. Personality

In the study of A total of 14,445 participants, aged 39-54 in 1993, completed the personality questionnaires composed of the Bortner Type-A scale, the Buss-Durkee Hostility Inventory (for total, neurotic and reactive hostility) and the Grossarth-Maticek-Eysenck Personality Stress Inventory that assesses six personality types [cancer-prone, coronary heart disease (CHD)-prone, ambivalent, healthy, rational, anti-social], showed that after mutually adjusting personality traits for each other, only high ‘neurotic hostility’ remained a robust predictor of excess mortality from all causes [RII = 2.62; 95% confidence interval (CI) = 1.68-4.09] and external causes (RII = 3.24; 95% CI = 1.03-10.18). ‘CHD-prone’ (RII = 2.23; 95% CI = 0.72-6.95) and ‘anti-social’ (RII = 2.13; 95% CI 0.61-6.58) personality types were associated with cardiovascular mortality and with mortality from external causes, respectively, but CIs were wider. Adjustment for potential behavioural mediators had only a modest effect on these associations(16).
8. Chronic kidney disease and Periodontal disease
More than half a million Americans die each year from coronary heart disease (CHD), 26 million suffer from chronic kidney disease (CKD), and a large proportion have periodontal disease, a chronic infection of the tissues surrounding teeth. Periodontal pathogens cause both local infection and bacteremia, eliciting local and systemic inflammatory responses. Periodontal disease is associated with the systemic inflammatory reactant C-reactive protein (CRP), a major risk factor for both CHD and CKD(17). 

9. Age
Higher than 80% of coronary heart disease-related mortality occurs in patients ≥65 years of age
10. Gender
Studies suggest that diabetes is a stronger coronary heart disease (CHD) risk factor for women than men but but men had more CHD deaths attributable to diabetes than women(18).
12. Race
Dr. Escobedo LG and scientists at the National Center for Chronic Disease Prevention and Health Promotion, in the study of Socioeconomic status, race, and death from coronary heart disease, showed that African Americans had about twice the risk for sudden, nonsudden, or other coronary death as did Caucasians. Adjusted risks for coronary death for Caucasians associated with modifiable risk factors (cigarette smoking, body weight, diabetes, and hypertension) either resembled or were slightly greater than those for African Americans. Half or more of all excess risks for African Americans in multivariate models could be explained by socioeconomic status. About 18% of excess sudden coronary death risk could be further explained by known modifiable coronary heart disease risk factors(19).
13. Substance abuse
Although there are some controversy regarding the effect of opium addiction on the coronary artery disease (CAD), researchers at the Kerman University of Medical Sciences in the study of the relationship of opium addiction with coronary artery disease, indicated that opium was an independent risk factor for CAD. Health managers and policy makers should try to aware general population and prepare many preventive programs against substance abuse(20).
14. Lack of regular exercise
Few older adults in the United States achieve the minimum recommended amount of physical activity. Lack of physical activity contributes to many chronic diseases that occur in older adults, including heart disease, stroke, diabetes mellitus, lung disease, Alzheimer disease, hypertension, and cancer. Lack of physical activity, combined with poor dietary habits, has also contributed to increased obesity in older persons(21).
15. Smoking 
Smokers with serum cholesterol and systolic BP levels in the highest quintiles had CHD death rates that were approximately 20 times greater than nonsmoking men with systolic BP and cholesterol levels in the lowest quintile(22).
16. Psychological stress and chronic anxious behavior
Psychological stress and chronic anxious behavior have a tremendous impact on our heart and biological rhythm of the body. Both are responsible for new development or promotion of coronary heart disease and may be associated with unpredictable adverse coronary events(23).
17.  Hyperuricemia (HUA)
HUA is a associated with diabetic micro- and macroangiopathies. HUA is a predictor of coronary heart disease and renal dysfunction in patients with type 2 diabetes mellitus. However, the influence of HUA is considered to be limited(24).
18. Other factors
Other researchers suggested that the relation between ankle-brachial index (ABI) and angiographic findings and major cardiovascular risk factors, the prevalence of ABI(+) among men and women was 25.9% and 7.5%, respectively (P=0.01). The prevalence of atherosclerotic risk factors was significantly higher in ABI(+) patients than in ABI(-) ones (P<0.05). ABI(+) patients had more significant stenosis than ABI(-) ones. The mean of occlusion was significantly higher in ABI(+) patients with left main artery (LMA), right coronary artery (RCA), left anterior descending artery (LAD), diagonal artery 1 (D1) and left circumflex artery (LCX) involvements (P<0.05)(25).

Finally, we would like to summarize the risks with a study of of Dr. Walden R and Dr. Tomlinson B. at the Biomolecular and Clinical Aspects. The underlying pathology is atheromatous vascular disease, resulting in coronary artery disease (CAD), cerebrovascular disease, and peripheral vascular disease, and the subsequent development of heart failure and cardiac arrhythmias. The major risk factors for these disorders were recognized over many years, and they include high levels of low-density lipoprotein (LDL) cholesterol, smoking, hypertension, diabetes, abdominal obesity, psychosocial factors, insufficient consumption of fruits and vegetables, excess consumption of alcohol, and lack of regular physical activity(25a).


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