(Also called Exercise Thallium, Stress Thallium, Cardiac Nuclear Imaging, Adenosine Thallium Scan, Cardiolyte Scan; type depends on the exact type of stress and drugs used)
Overview
Coronary Artery Disease
Coronary artery disease (CAD) is the narrowing of the coronary arteries (the blood vessels that supply oxygen and nutrients to the heart muscle), caused by a buildup of fatty material within the walls of the arteries. This buildup causes the inside of the arteries to become rough and narrowed, limiting the supply of oxygen-rich blood to the heart muscle.
To better understand how coronary artery disease affects the heart, a review of basic heart anatomy and function follows.
The heart is basically a pump. The heart is made up of specialized muscle tissue, called the myocardium. The heart's primary function is to pump blood throughout the body, so that the body's tissues can receive oxygen and nutrients and have waste substances taken away.
Like any pump, the heart requires fuel in order to work. The myocardium requires oxygen and nutrients, just like any other tissue in the body. However, the blood that passes through the heart's chambers is only passing through on its trip through the body - this blood does not give oxygen and nutrients to the myocardium. The myocardium receives its oxygen and nutrients from the coronary arteries. The coronary arteries lie on the outside of the heart and supply oxygenated blood to the heart tissue.
When the heart tissue does not receive an adequate blood supply, it cannot function as well as it should. If the myocardium's blood supply is decreased for a length of time, a condition called ischemia may develop. Ischemia can decrease the heart's pumping ability, because the heart muscle is weakened due to a lack of food and oxygen. Think about how you may feel when you go too long without eating - you may become tired and feel weak. The heart muscle reacts in a similar way when its blood flow (food) is decreased.
Unfortunately, you may not have any symptoms of beginning coronary artery disease, yet the disease will continue to progress until sufficient artery blockage exists to cause symptoms and problems. Some symptoms of coronary artery disease include chest pain, jaw pain, arm pain, fatigue, palpitations, and shortness of breath. If the blood supply to the heart muscle continues to decrease as a result of increasing obstruction of a coronary artery, a myocardial infarction, or heart attack, may occur. If the blood flow cannot be restored to the particular area of the heart muscle affected, the tissue will actually die.
Fortunately, the technology is available to restore blood flow to heart tissue when coronary artery blockages are diagnosed. One of several diagnostic procedures used to diagnose and evaluate coronary artery disease is the myocardial perfusion scan.
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