More detailed description about atherosclerotic coronary artery disease

Atherosclerotic coronary artery disease is the leading cause of death in the developed world. The research shows that, on average, 30% of the people succumb to this disease. Due to their greater exposure to the risk factors, men in their 5th and 6th decade of life are more likely to be affected by this disease than the women at the same age. At older ages, however, the incidence of this disease is the same in both sexes. The difference is observed among different nations and geographical areas; the incidence is the lowest in certain coastal countries such as Greece or Japan and highest in the North, for instance, in Finland. There are also some racial differences with the black race being twice as commonly affected as the white race.

An atheromatous plaque forms due to the accumulation of white blood cells, macrophages, lipids (cholesterol and fatty acids), calcium and connective tissue. The pathogenesis of atherosclerosis has not been completely elucidated. In essence, it is a chronic inflammatory process in the arterial walls with the low-density lipoprotein (LDL) cholesterol, also termed the "bad cholesterol", playing an important role. LDL is a protein that transports cholesterol and triglycerides and crosses the arterial wall primarily at sites of arterial bifurcations and at sites of high blood turbulence. Upon entering the arterial wall it undergoes oxidation; in its oxidized state the LDL then triggers an immune response. Macrophages appear and engulf the oxidized LDL but cannot metabolize it. Thus, it keeps accumulating in macrophages until they burst and release the accumulated material which further attracts additional macrophages, fuelling a vicious cycle. Due to the accumulation of fats and inflammatory cell debris, the atheromatous plaque grows and increasingly blocks the vessel with time.

The end result of such an atheromatous plaque growth is narrowing of the lumen of the arterial vessels that nourish the heart, thereby effectively reducing the volume of blood reaching the heart. When the vessel lumen is narrowed to more than 75%, the typical symptoms of disease appear. Consequently, there is lack of oxygen and nutrients that are required for normal heart function. Atherosclerotic changes in the vessels occur due to various factors such as cigarette smoking, increased blood cholesterol level, hypertension, increased blood sugar (i.e. diabetes), blood clotting disorders, stressful lifestyle and genetic factors affecting the structure of the vessel walls.

Happening in atherosclerotic coronary artery disease

Coronary artery disease can be divided into several stages. When the plaque occludes more than 75% of the vessel lumen, symptoms of angina pectoris develop. It is characterized by appearing predominantly when the patient is physically active (climbing the stairs, running, etc.) rather than when performing everyday chores that are physically less demanding. The typical symptoms are a squeezing substernal chest pain which may radiate to the neck, arms and the lower jaw. It characteristically lasts only a relatively short time with the symptoms disappearing when the patient takes nitroglycerin and ceases to be physically active.

When more than 90% of the vessel lumen becomes occluded, myocardial infarction (heart attack) develops. Due to the critical vessel occlusion, the perfusion is severely reduced. The symptoms of a heart attack are similar to those of angina pectoris; however, the pain typically does not disappear upon administration of nitroglycerin. Pathological changes accompanying myocardial infarction may lead to arrhythmias (irregular heart rhythm), shock and thromboembolism (i.e. the formation of blood clots at the site of infarction that can break off, travel and block a different segment of the blood vessel or even another organ). The most severe consequence of myocardial infarction is a dangerous arrhythmia called ventricular fibrillation that can be fatal in a few minutes if not treated adequately and on time.

Diagnosis

The disease is usually discovered on the basis of a physical exam. In addition, there are numerous diagnostic modalities available such as the electrocardiography (EKG), echocardiography (ultrasound) and computer tomography (CT). Lately, coronary angiography has gained recognition—a contrast material is injected into the coronary arteries and possible stenoses of the coronary arteries are visualized under x-ray.

Prevention

Prevention is directed at slowing down the appearance of atherosclerotic plaques that appear as a result of the accumulation of fat, inflammatory cells and calcium in the vessel walls. This accumulation may lead to vessel narrowing. The risk factors that cannot be modified include sex, age and genetic factors.

Nevertheless, one can do much good for one's health; essential measures are smoking cessation, maintenance of a normal body weight, regular physical activity, a low-fat healthy diet, stress reduction, as well as regulation of hypertension, diabetes mellitus and blood cholesterol (initially with a diet, and, if unsuccessful, with medications).

Therapy

Therapy of coronary disease involves a lifestyle change. In the presence of a low-grade narrowing of the coronary artery, the lack of oxygen in the heart and the associated chest pain occur only in times of great physical stress on the body, and the following medications are used:

• Nitroglycerin - helps relieve pain by dilating coronary arteries and allowing adequate blood flow. It is available in the form of patches, sublingual tablets and sublingual sprays.
• Anti-hypertensives – include beta blockers which, in addition to lowering the blood pressure, lower the heart rate and thereby reduce its oxygen requirements. To that effect, ACE inhibitors as well as calcium channel blockers are beneficial as well. They relax the muscles in the vessel walls and dilate the vessels.
• Aspirin – Low doses taken daily prevent blood clotting and reduce the risk of vessel blockage.
• Drugs to lower the blood cholesterol level, especially the LDL or the "bad" cholesterol. In this way, the amount of substances that accumulate in the vessel walls is reduced. Increasing the HDL level (i.e. the "good" cholesterol) that removes fat from the vessel walls is also beneficial.

However, when the coronary arteries are narrowed to the extent that pain is experienced already during periods of low physical stress and the patient's life is seriously endangered, a more aggressive therapy must be instituted. The following are the options:

• Angioplasty – a procedure whereby a balloon catheter is inserted through the narrowed part of the vessel and inflated, thereby dilating the vessel lumen. In order to achieve long-lasting results, it is often necessary to place a stent at the site of the narrowing. This kind of treatment is possible when the narrowing occurs in one or two coronary arteries. Patients with stents need to take anti-thrombotic prophylaxis in the first year after undergoing the procedure.
• In the case of a three-vessel-disease, a bypass from the aorta to the part of the coronary artery distal to the narrowing needs to be performed surgically. In this way, blood bypasses the narrowed or blocked part; a vein harvested from the lower extremity is used for this purpose.

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