The aorta the main blood supplier to the body branches off into two main coronary blood vessels also called arteries. These coronary arteries branch off into smaller arteries, which supply oxygen-rich blood to the entire heart muscle. Extravascular compression shown to the right during systole markedly affects coronary flow; therefore, most of the coronary flow occurs during diastole. Because of extravascular compression, the endocardium is more susceptible to ischemia especially at lower perfusion pressures.
Furthermore, with tachycardia there is relatively less time available for coronary flow during diastole to occur — this is particularly significant in patients with coronary artery disease where coronary flow reserve maximal flow capacity is reduced. In the presence of coronary artery disease , coronary blood flow may be reduced. This will increase oxygen extraction from the coronary blood and decrease the venous oxygen content. This leads to tissue hypoxia and angina. If the lack of blood flow is due to a fixed stenotic lesion in the coronary artery because of atherosclerosis , blood flow can be improved within that vessel by 1 placing a stent within the vessel to expand the lumen, 2 using an intracoronary angioplasty balloon to stretch the vessel open, or 3 bypassing the diseased vessel with a vascular graft.
If the insufficient blood flow is caused by a blood clot thrombosis , a thrombolytic drug that dissolves clots may be administered. Anti-platelet drugs and aspirin are commonly used to prevent the reoccurrence of clots. If the reduced flow is due to coronary vasospasm , then coronary vasodilators can be given e. Together with the left anterior descending artery, the right coronary artery helps supply blood to the middle or septum of the heart.
Smaller branches of the coronary arteries include: obtuse marginal OM , septal perforator SP , and diagonals. Since coronary arteries deliver blood to the heart muscle, any coronary artery disorder or disease can have serious implications by reducing the flow of oxygen and nutrients to the heart muscle.
This can lead to a heart attack and possibly death. Atherosclerosis a buildup of plaque in the inner lining of an artery causing it to narrow or become blocked is the most common cause of heart disease. Health Home Conditions and Diseases. Figure 7. Drawing of the coronary arterial circulation in the human heart.
The normal human hears does not typically elicit collateralization; each area of myocardium is usually supplied by a single coronary artery. Coronary arteries are so vital to the function of heart; whenever disease states are associated with flow restriction through the coronary arteries, and subsequently the remainder of the coronary circulations capillaries and veins , the effects on cardiac performance are quite dramatic and often fatal. Coronary artery disease CAD is generally defined as the gradual narrowing of the lumen of the coronary arteries due to coronary atherosclerosis.
Atherosclerosis is a condition that involves thickening of the arterial walls from cholesterol and fat deposits that build up along the endoluminal surface of the arteries.
With severe disease, these plaques may become calcified and so large that they produce stenoses within the vessels, and thus permanently increase the vascular resistance which is normally low. When the walls of the coronary arteries thicken, the cross-sectional area of the arterial lumen decreases; resulting in higher resistance to blood flow through the coronary arteries. This steady decrease in cross-sectional area can eventually lead to complete blockage of the artery.
As a result, oxygen and nutrient supply to the myocardium drops below the demand of the myocardium. As the disease progresses, the myocardium downstream from the occluded artery becomes ischemic. Eventually, myocardial infarction or known as a MI may occur if the coronary artery disease is not detected and treated in a timely manner.
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