• Cardiovascular Disease

    Atherosclerosis: At the ‘Heart’ of the Matter

    The main function of the cardiovascular system is the transportation of blood throughout the body. So it should come as no surprise that cardiovascular disease is often characterized by the obstruction of blood flow. Atherosclerosis, a build-up of deposits on the inside of arteries, is a primary cause of impeded blood flow, and thus lies at the heart of most types of cardiovascular disease.
    Blocked Coronary Artery
    Blocked Coronary Artery
    © 2011 Nucleus Medical Media, Inc.
    Atherosclerosis is a gradual disease process. Normal, healthy arteries start out smooth, like the inside of a garden hose. At some point, usually during early adulthood, fatty particles from the blood make their way into the intima, or inner layer of the artery, and begin to accumulate there forming fatty streaks. Injuries to the intima, from factors such as smoking, high blood pressure, or diabetes, make it more susceptible to invasion from fatty particles.
    As time goes on, fat from low-density lipoproteins (LDLs) continues to accumulate. The lipids react with oxygen (a process called oxidation ), and are devoured by smooth muscle cells of the artery, which then take on a characteristic foamy appearance. The foam cells attract platelets from the blood stream as well as calcium deposits and cell debris. The wall of the artery becomes inflamed as white blood cells try to heal the injured area. In the meantime, a fibrous cap forms over the fatty mixture creating a hardened lesion called an atherosclerotic plaque. As the plaque continues to grow, it narrows the affected artery impeding the flow of blood through it.
    Atherosclerosis
    Atherosclerosis
    © 2011 Nucleus Medical Media, Inc.
    At times, the fibrous caps covering atherosclerotic plaques may rupture. When this occurs, blood cells called platelets are exposed to the contents of the plaque. This causes them to aggregate and form a clot at the site of the rupture, a process called thrombosis. Sometime these clots can grow quite large, leading to the total obstruction of flow in the artery; or pieces of the clot, called emboli, can break off and travel downstream.
    Blood Clot Blocking Blood Flow
    Blood Clots
    © 2011 Nucleus Medical Media, Inc.
    Atherosclerosis can eventually lead to the following conditions:
    • Cerebrovascular Disease (Stroke) An ischemic stroke is when brain cells die because they are not getting enough oxygen via the bloodstream. Eighty percent of strokes are caused by blockage of an artery leading to the brain.
      Ischemic Stroke
      Stroke
      © 2011 Nucleus Medical Media, Inc.
    • Coronary Heart Disease
      • Angina —Narrowing of the coronary arteries, which carry blood to the heart muscle itself (the myocardium), may create a supply and demand problem for the heart. Myocardial ischemia results when demand for oxygen outstrips its supply, which often occurs at times of exertion. Most patients experience myocardial ischemia as chest pain, also known as angina.
        Angina: Most Common Areas of Pain
        Angina: Most Common Areas of Pain
        © 2011 Nucleus Medical Media, Inc.
      • Heart Attack (Myocardial Infarction) —Heart attack, a bit of a misnomer, refers to the death of heart cells due to a sustained lack of oxygen. Most heart attacks occur when a thrombus (large clot) forms in a coronary artery, cutting off completely the flow of blood to the heart. Complications include congestive heart failure and cardiac arrhythmias, which result from the abnormal conduction of electrical signals through heart tissue.
        Heart Attack
        Heart Attack
        © 2011 Nucleus Medical Media, Inc.
      • Congestive Heart Failure (CHF)—When the heart is incapable of pumping enough blood to meet the normal demands of the body, it is said to be failure. CHF is usually the result of a heart that has weakened over time, often because of long-standing coronary heart disease, high blood pressure or both. Other causes include myocardial infarction or abnormalities of the heart valves.
    • Peripheral Vascular Disease —Peripheral vascular disease refers to the atherosclerotic narrowing of arteries that carry blood to the legs. Patient with severe arterial narrowing often experience pain and fatigue in the affected extremity when they walk. A worrisome complication of PVD is an aneurysm or bulge in an artery due to its weakened wall. Aneurysms can occur anywhere, but when associated with atherosclerosis, they most commonly occur in the abdominal portion of the aorta.
    Other cardiovascular conditions unrelated to atherosclerosis include:
    • Congenital defects of the valves, chambers and great vessels
    • Some types of arrhythmias
    • Inflammation or infections of the valves or pericardial sac surrounding the heart
    • Cardiac tumors
    • Venous conditions such as varicose veins, thrombophlebitis, and deep venous thrombosis

    RESOURCES

    American Heart Association http://www.americanheart.org

    Texas Heart Institute Heart Information Center http://texasheart.org/HIC/his.cfm

    CANADIAN RESOURCES

    Health Canada http://www.hc-sc.gc.ca/index%5Fe.html

    Heart and Stroke Foundation http://ww2.heartandstroke.ca/

    References

    American Heart Association. Atherosclerosis. American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4440Accessed January 8, 2003

    Heart and Circulation. In: Fox SI, ed. Human Physiology . 4th ed. Dubuque, Iowa:Wm. C. Brown Publishers;1993:328-367.

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