标题: Exams and Tests [打印本页] 作者: 12ab45cd 时间: 2008-8-5 08:51 标题: Exams and Tests
Your first symptom of coronary heart disease may be a heart attack or sudden cardiac arrest. This is why medical professionals use screening tests to detect the presence and severity of coronary disease before it causes problems or sends you to an emergency department with severe symptoms. The symptoms of coronary heart disease are what medical professionals call nonspecific.
This means the symptoms could be caused by many different conditions, some not related to the heart at all.
Upon hearing your symptoms, your health care provider (whether your primary care provider or a new provider in the emergency department) will begin a process of gathering information.
The purpose of this is to rule out conditions and pinpoint the correct diagnosis.
It includes asking questions about your symptoms, your medical and surgical history, your general health and specific medical problems, and the medications you take.
It will also include a physical examination, an electrocardiogram (ECG), and probably lab tests and imaging tests such as x-ray or CT scan.
Physical exam may reveal evidence of weakened or irritable heart muscle, including sounds called gallops or murmurs. There may be evidence of congestion in the lungs.
The first step will be to rule out a heart attack or other life-threatening condition. The usual tests include blood tests, ECG, and, possibly, chest x-ray.
Blood tests might check your blood cells, the chemical makeup of your blood, and enzymes leaking out of damaged heart muscle, that suggest that you are having a heart attack. Other tests might be ordered depending on the circumstances.
ECG is a painless test that measures the electrical activity of the heart. It can reveal several different heart problems, including ischemia, heart attacks, rhythm disorders, long-standing strain on the heart from high blood pressure, and certain valve problems. It gives clues as to the underlying cause of cardiac symptoms. The test takes just a few minutes. You lie on a table with electrodes fastened to the skin of your chest, arms, and legs.
Chest x-ray can show abnormalities in the size or shape of the heart and can show whether any fluid is building up in the lungs.
If you are having angina symptoms or your health care provider suspects that you have coronary heart disease, you may have an exercise (treadmill) stress test.
This test involves measuring ECG tracings before, during, and after stressing the heart by exercise.
You will walk on a treadmill while connected to an ECG machine.
This test is 60-70% accurate in showing blockages in blood flow in 1 or more of the 3 coronary arteries.
Sometimes its readings may be falsely abnormal for people taking certain medications or who have certain medical problems not directly related to coronary heart disease.
If other tests suggest blockage of the coronary arteries, you may undergo a nuclear (radionuclide) stress test.
After a tiny dose of a radioactive tracer is injected into a vein, a special camera can identify the quantity of blood flow that reaches different parts of the heart muscle.
The substance most often used is thallium, so this is often called a thallium stress test.
You will have 2 tests, one with stress, or exercise (on a treadmill), and the other at rest.
If you cannot exercise, you will be given a drug to temporarily stress your heart. The drugs used for this are adenosine (Adenocard), dipyridamole (Persantine), or dobutamine (Dobutrex).
This test is expensive, but it is noninvasive, and its accuracy is quite good.
Stress echocardiography is an alternative to the nuclear stress test. Many people prefer this test because it does not use a radioactive agent.
Echocardiography is a type of sonar that uses sound waves to bounce off walls and valves, creating an image of the heart as it beats.
The movements of the ventricular walls are compared during stress and at rest. Wall motion drops during stress if the coronary artery supplying that part of the heart has significant obstruction.
Like the other stress tests, the heart is stressed either by exercise on a treadmill or by administration of a drug.
Electron beam (ultrafast) CT scan (EBCT) is a new and noninvasive but somewhat controversial test. By measuring the amount of calcium deposited in the plaques of coronary arteries, it can detect blockages of only 10-20% of an artery, which may not show up in other tests.
Generally, such minor blockages are treated medically; lifestyle changes and risk factor modifications are recommended to prevent worsening of the blockage.
Because elderly people frequently have calcium in their coronary arteries without significant narrowing, EBCT is of limited value in this age group.
The advantage of EBCT comes in screening young people with one or more heart disease risk factors.
Coronary angiography by cardiac catheterization is the best way to evaluate coronary heart disease.
You will go to a hospital or an outpatient catheterization lab (for same-day surgery).
Under guidance of an x-ray camera, a long, thin plastic tube (catheter) is threaded into the opening of your coronary arteries from a blood vessel in either your groin (femoral artery) or your arm (brachial artery).
Once the catheter reaches the coronary artery opening, it injects a small amount of iodine dye, which makes the coronary arteries visible on the x-ray screen.
Pictures of the coronary arteries are then recorded in a computer for later review. The images show the diameter of the coronary arteries and any blockages narrowing them.
Coronary angiography is an invasive test. In experienced hands, the risk of complications is less than 1%.
It is the only test that helps a cardiologist to determine precisely whether to treat you with bypass surgery, a less-invasive technique such as angioplasty or stent placement, or just medications.
