Risk Factors for Atherosclerosis − Rakyat Biologi

Any factor associated with a doubling in the incidence of ischemic heart disease has been defined as a “risk factor". A major advance in the clinical assessment and treatment of atherosclerosis is a through screening for risk factors, followed by aggressive treatment to eliminate the risk factor. Risk factors can be categorized as genetic and environmental.

Hypertension: An increase in blood pressure is consistently associated with an increased risk of myocardial infarction. Although the incidence of complications of hypertension was previously attributed to the diastolic component, there is increasing evidence that the systolic pressure is equally important. In fact, men with systolic blood pressures over 160 mm Hg have almost three times the incidence of myocardial infarction as those with blood pressures under 120 mm Hg. Treatment of hypertension, which is usually clinically silent, especially in the early stages of hypertension, has resulted in a significant reduction in the incidence of myocardial infarction and stroke.

Serum cholesterol level: Numerous epidemiology and clinical studies have show that the levels of serum cholesterol have been directly correlated with the incidence of ischemic heart disease. Indeed, of all the known risk factors, serum cholesterol seems to be the most important determinant of the geographical differences in the incidence of atherosclerotic coronary artery disease. In the absence of genetic disorders of lipid metabolism such as familial hypercholesterolemia, the amount of cholesterol in the blood is related to the dietary intake of saturated fat. A number of studies have demonstrated a reduction in the incidence of myocardial infarction following treatment with cholesterol-lowering drugs.

Cigarette smoking: Atherosclerosis of the coronary arteries and the aorta is more severe and extensive among cigarette smokers than among nonsmokers, and the effect is dose-related. Second hand smoke is a risk factor. As a result, the incidence of myocardial infarction, ischemic stroke, and abdominal aortic aneurysms is markedly increased among smokers. Smoking is an environmental risk factor that is best addressed by eliminating smoking in preteens and teens and eliminating environments with second hand smoke.

Diabetes Mellitus: Diabetics have a substantially greater risk of occlusive atherosclerotic vascular disease in many organs, but the relative contributions of carbohydrate intolerance itself, advanced glycation end-products, and secondary changes in blood lipids are not well defined. The metabolic syndrome consisting of hypertension, glucose intolerance, truncal obesity and dyslipidemias has become an important target for early diagnosis and treatment.

Increasing age and male gender: These factors are strong determinants of the risk for myocardial infarction.

Physical inactivity and stressful life patterns: Both of these factors have been correlated with an increased risk of ischemic heart disease, although their precise relationship to the evolution of atherosclerosis is not established.

Homocysteine: Homocystinuria is a rare autosomal recessive disease caused by mutations in the gene encoding cystathionine synthase. The disorder results in premature and severe atherosclerosis. Mild elevations of plasma homocysteine are common and represent an independent risk factor for atherosclerosis of the coronary arteries and other large vessels. Homocysteine is toxic to endothelial cells and inhibits several anticoagulant mechanisms in endothelial cells. It inhibits thrombomodulin on the endothelial cell surface, the antithrombin III binding activity of heparan sulfate proteoglycan, the binding of tissue plasminogen activator, and the ecto-ADPase activity on the endothelial cell surface, which promotes the aggregation of platelets. In addition, oxidative interactions between homocysteine, lipoproteins, and cholesterol have been shown. A low dietary intake of folic acid may aggravate an underlying genetic predisposition to hyperhomocysteinemia, but it has not been established that treatment with folic acid actually protects against atherosclerotic vascular disease.

C-Reactive Protein and Inflammation Biomarkers: Elevated concentrations of C-reactive protein (CRP), an acute phase reactant produced mainly by hepatocytes, is a marker for systemic inflammation, and has been linked to an increased risk of myocardial infarction and ischemic stroke. This finding and the presence of CRP in atherosclerotic plaque tissue suggests that systemic inflammation may indeed contribute to atherogenesis. Studies are ongoing to test the hypothesis that CRP is a causative factor in atherogenesis and to show the usefulness of CRP testing in guiding therapeutic interventions in atherosclerosis. Quality control of clinical biochemistry measurement of CRP must be rigorously applied. High sensitivity (HS) CRP is currently the measurement of choice. Another inflammatory protein under study is serum amyloid A (SAA). Other proteins associated with inflammation, such as leukocyte adhesion molecules, and fibrinogen are considered to be biomarkers of disease.