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Unstable Angina

Unstable Angina

Alternate Names

  • unstable angina pectoris
  • Coronary arteries

Definition

Angina is the term given to chest pain resulting from the lack of a sufficient oxygen supply to the heart muscle. It is caused by a significant blockage in one or more of the coronary arteries supplying the heart. If the pain occurs on exertion and goes away with rest, the condition is called stable angina.

What is going on in the body?

Atherosclerosis, or hardening of the arteries, is a condition in which fatty deposits, or plaque, form inside blood vessel walls. Atherosclerosis that involves the arteries supplying the heart is known as coronary artery disease. Plaque can block the flow of blood through the arteries. The tissues that normally receive blood from these arteries then begin to suffer damage from a lack of oxygen. When the heart does not have enough oxygen, it responds by causing the pain and discomfort known as angina.
Unstable angina occurs when the narrowing becomes so severe that not enough blood gets through to keep the heart functioning normally, even at rest. Sometimes the artery can become almost completely blocked. With unstable angina, the lack of oxygen to the heart almost kills the heart tissue.

Risks

What are the causes and risks of the condition?

The factors that increase the risk of unstable angina include:
  • cigarette smoking
  • high blood pressure
  • high levels of blood cholesterol, especially "bad" or "lethal" cholesterol (LDL)
  • low levels of "good" or "healthy" cholesterol (HDL)
  • male gender
  • increasing age
  • diabetes
  • lack of exercise
  • obesity
  • abdominal fat and abnormal waist circumference

Prevention

What can be done to prevent the condition?

A person may reduce the risk for developing unstable angina by:
  • following the healthcare provider's recommended treatment for stable angina
  • not smoking
  • controlling high blood pressure
  • controlling blood cholesterol
  • controlling diabetes
  • exercising regularly and losing weight if needed
  • eating a diet designed to minimize heart disease and lower cholesterol

Diagnosed

How is the condition diagnosed?

The diagnosis of unstable angina begins with a careful history of the person's symptoms and a physical examination. Unstable angina is usually diagnosed when:
  • a person with stable angina has a sudden increase in the number or severity of episodes of chest pain over the previous days or weeks
  • a person without angina develops increasing episodes of chest pain or chest pain at rest
  • a person, who may or may not have had angina in the past, develops prolonged chest pain but does not show evidence of a heart attack
The healthcare provider may order several diagnostic tests, including:
  • an electrocardiogram (ECG) which is a recording of the electrical activity of the heart. An ECG is usually normal when a person has no chest pain and often shows certain changes when pain develops.
  • a cardiac catheterization, which is an X-ray procedure that is used to look for narrowed coronary arteries. A contrast agent is injected so the doctor can watch blood flow through the heart and its arteries.
  • various blood tests

Long Term Effects

What are the long-term effects of the condition?

Unstable angina that is not controlled quickly can lead to a heart attack.

Other Risks

What are the risks to others?

Unstable angina is not contagious and poses no risks to others.

Treatments

What are the treatments for the condition?

A person who has unstable angina is usually hospitalized. This allows the healthcare provider to determine if the person is having a heart attack, which can cause the same symptoms as unstable angina. The provider will attempt to optimize the person's medication regimen.
The types of medications include the following:
  • nitroglycerin, to expand the small arteries and veins
  • beta-blockers, to reduce the work of the heart
  • blood thinners, to reduce the chance of clotting in the already narrowed arteries
  • platelet inhibitors (clopidogrel, IIb/IIIa inhibitors)
Sometimes the even the best combination of medications fails to control angina. In this case, percutaneous intervention or surgery may be used to restore blood flow to the affected areas of the heart. Common procedures include:

  • percutaneous transluminal coronary angioplasty, or PTCA. In this procedure, a tube containing a balloon is inserted into the blocked artery and inflated. This reopens the artery and allows blood to flow.
  • heart bypass surgery, also known as coronary artery bypass graft or CABG. In this procedure, veins taken from the legs or arteries taken from the chest or arm (radial artery) are used to bypass the narrowed or blocked portion of the arteries in the heart
  • a stent, or narrow tube, which is placed into the artery at the reopened area to keep it from narrowing again
  • atherectomy, a surgical procedure in which plaque that causes narrowing of a blood vessel is removed

Side Effects

What are the side effects of the treatments?

Beta-blockers can cause:
  • a slow heartbeat
  • low blood pressure
  • depression
  • erectile dysfunction
  • unpleasant dreams
Nitrates can cause headaches and low blood pressure. Aspirin and warfarin increase the risk of bleeding. Surgery can be complicated by infection, bleeding, or an allergic reaction to anesthetic.

After Treatment

What happens after treatment for the condition?

A person whose unstable angina has been relieved will be monitored in the hospital to be sure the treatment continues to work. If the person has had surgery, the healthcare provider will also check to be sure that the blood flow does not suddenly become blocked again. A cardiac rehabilitation program will be started and will continue after the person leaves the hospital.
A person with unstable angina should make every effort to reduce coronary risk factors. This may include the following: smoking cessation, control of other diseases such as diabetes and high blood pressure, and following a healthy diet to minimize heart disease. Medications may need to be adjusted to achieve the best response.

Monitor

How is the condition monitored?

A person who has been treated for unstable angina will periodically have an ECG done during exercise. This will show how the heart is working with the remaining blood supply. Cardiac catheterization may need to be repeated in the future, especially if chest discomfort returns. Any new or worsening symptoms should be reported to the healthcare provider.

Sources

Scientific American Medicine 2000 (updated monthly)

Medical Knowledge Self Assessment Program (MKSAP 11) 1998

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