Cardiac Stress Test

Introduction

Heart disease is difficult to diagnose when a patient is resting as the physical examination and ECG of the patient are often normal at rest. In these cases, cardiac abnormalities may become apparent only when the heart has to perform at increased workloads.

Preparation:

• Patient should not eat or drink anything except water for about four hours before the test.

• Food and drinks containing caffeine should be avoided for 12 hours before the test as it can interfere with the results of the test.

• Heart medications such as isosorbide dinitrate, isosorbide mononitrate and nitroglycerin should be continued on the day of the test unless the doctor tells otherwise. The doctor may also ask the patient to stop taking other heart drugs on the day of the test. Do not discontinue any drug without first informing the doctor.

• If an inhaler is needed for asthma, it should be brought to the test.

Procedure:

1. Electrodes for ECG are placed on the chest of the patient. These electrodes chart the heart’s electrical activity during the test.

2. Before starting the exercise, a resting ECG and blood pressure are recorded.

3. The exercise is started either in the form of walking on a treadmill or pedaling a stationary bicycle. The rate of exercise or degree of difficulty is gradually increased. Exercise is continued till full exhaustion.

4. It should be informed to the technician if there is any chest, arm, or jaw pain or discomfort, shortness of breath, dizziness, lightheadedness, or any other unusual symptom. The heart rate, blood pressure, breathing rate, and perspiration increases during the test normally. The lab personnel will watch for any symptoms or changes on the ECG monitor that suggest the test should be stopped.

5. After the test the walking or pedaling is slowed down gradually. The heart rate, blood pressure and ECG are monitored until the levels begin returning to normal.

Although the duration of test is about 60 minutes, but the actual exercise time is usually between 7 and 12 minutes.

Indications:

• The stress test is useful mainly in the diagnosis of coronary artery disease. If a partial blockage is present in the coronary artery, the blood supply to the heart muscle may still be adequate. But if the patient exercises, the blood supply from the partially blocked artery may not be sufficient for the high level of activity now needed. This state of inadequate blood supply to heart muscle is called as ischemia which can lead to chest discomfort (called as “angina”) and characteristic changes on the ECG. The stress test can bring out the abnormalities caused by partial blockages which may be unapparent at rest.

• As exercise raises adrenaline levels, stress tests can also be used to detect certain cardiac arrhythmias that tend to occur at adrenaline rush.

• Stress tests are also useful in measuring the functional capacity of patients with heart disease. If signs of ischemia occur at a low level of exercise, the blockages are considered as significant. But if ischemia does not occur or occurs only at very high levels of exercise, the blockages are possibly less significant.

• This test can also be useful for monitoring the progress of patients with congestive heart failure. If the peak level of attainable exercise is worsening over time, the underlying heart disease may be worsening.

Risks:

The stress test is remarkably safe. Very rarely, the ischemia provoked by stress test can lead to a heart attack or a serious heart rhythm disturbance. Even if these serious events occur, the medical personnel present at the test can deal with them immediately.

Types of Stress Tests:

There are many different types of stress tests, including:

• Treadmill stress test: in patients with normal ECG, this is the first stress test performed. Patient walks on a treadmill while being monitored for distance of walking and development of chest pain or any changes in the ECG that can suggest inadequacy of blood supply to the heart.

• Dobutamine or Adenosine Stress Test: This pharmacological stress test is used in people who are unable to exercise. A drug is given to make the heart respond as if the person were exercising.

• Stress echocardiogram: An echocardiogram is a graphic outline of the heart’s movement. A stress echo can accurately visualize the motion of walls of the heart and also it’s pumping action when the heart is under workload. This test may reveal a lack of blood flow which may not be apparent on other heart tests.

• Nuclear stress test: This test can help to determine which parts of the heart are functioning normally and which are not. A small amount of radioactive tracer is injected into the patient. Then the doctor uses a special camera to identify the radiations emitted from the substance within the body. This produces clear pictures of the heart tissue on a video monitor. These pictures are taken both at rest and after exercise.