Stress Echocardiogram - Uses, Preparation, Procedure, Interpretations, and Complications

Introduction:

A stress echocardiogram, also called stress echo or stress echocardiography, uses ultrasound imaging to detect how well your heart muscles are able to pump blood into your body.

How Will Stress Be Triggered During the Stress Echocardiogram?

1. Exercise Stress Cardiogram:

• Treadmill exercise cardiogram (exercising on a treadmill to detect the heart function).

• Upright bicycle exercise echocardiogram (exercising on an upright bicycle to detect the heart function).

• Supine bicycle exercise echocardiogram (exercising on a supine bicycle to detect the heart function).

2. Pharmacological Stress Echocardiogram:

• Dobutamine stress echocardiogram (injection of Dobutamine into the body to create the effects of exercise).

• Dipyridamole stress echocardiogram (injection of Dipyridamole into the body to create the effects of exercise).

What Are the Uses of Stress Echocardiograms?

• Used to diagnose coronary artery disease (narrowing or blockage of blood vessels supplying the heart), myocardial infarction (irreversible death of heart muscles due to the lack of oxygen supply)

• Used to detect the results of the treatments such as bypass grafting (a procedure to redirect blood around the blocked artery in your heart), angioplasty (procedure to widen narrowed or blocked blood vessels supplying the heart)

• Used to detect the effects of antianginal or antiarrhythmic drugs.

What Are the Factors Affecting the Result of Stress Echocardiogram?

1. False Positives:

• Over interpretation.

• Cardiomyopathy (a disease in which heart muscles lose their ability to pump effectively).

• Hypertensive responses to stress.

• Abnormal septal motion (left bundle branch block [LBBB], post- coronary artery bypass graft).

2. False Negatives:

• Inadequate stress.

• Poor image quality.

• Delayed images post-stress.

• Antianginal treatment (especially beta-blockers - drugs used to lower the stress on blood vessels).

How Do You Prepare for Your Stress Echocardiogram?

• You are asked not to eat or drink at least three hours before the test.

• You are asked to sign in a consent form that gives permission to do the test.

• Inform your doctor about your regular medicine. You should not stop taking them without your doctor’s advice. Sometimes, you may be asked by your doctor to skip some medications on the day of the test, such as beta-blockers and nitroglycerin.

• If you are under insulin to control your blood sugar level, you might be asked to take only half of your regular dose before the test and eat light food four hours before the test.

• Avoid tobacco products such as cigarettes before the test. Nicotine in tobacco products may affect the test results.

• Do not drink coffee or take medications containing caffeine for 24 hours before the test.

• Inform your doctor if you are pregnant.

• Wear a loose, comfortable dress during your test.

How Is the Stress Echocardiogram Taken?

1. Resting Echocardiogram: Before the stress echocardiogram, a resting cardiogram is taken in an echo lab. It is used to detect how well your heart works when you are at rest. During the test, your doctor may place ten small patches called electrodes on your chest, which are connected to an electrocardiogram (ECG). The ECG measures the electrical activity of your heart and monitors the regularity of heartbeats. Your blood pressure is recorded throughout the procedure.

2. Exercise Stress Echocardiogram: After your resting echocardiogram, you will be asked to walk slowly later to walk faster on a treadmill or pedal the exercise cycle. You need to walk for about 5 to 15 minutes, depending on your age and your fitness level. Your doctor tells you to stop the exercise when your heart rate has increased or when it reaches a peak. Exercise echocardiography is preferred over non-exercise echocardiography as it more closely reproduces our daily activities. After that, you will lie on your side for the resting echocardiogram of your heart. They will apply a special gel over your skin and place a device called a transducer.

3. Pharmacological Stress Echocardiogram: In 2007, the American society of echocardiography (ASE) recommended “Dobutamine” as the first-line agent for pharmacologic stress echocardiography. Dobutamine is a sympathomimetic drug that causes increased inotropic (changes the force of your heart contractions), chronotropic(changes the heart rate), and increased blood pressure. Dipyridamole maintains the blood flow and keeps the heart blood vessels open.

The Dobutamine stress echocardiogram (DSE) test is used for patients who are not able to exercise. Dobutamine has a similar effect to exercising on the heart. In the DSE test, Dobutamine is introduced into the vein as an intravenous line (IV) which makes the heart beat faster. It should not be given to people having unstable ventricular arrhythmias (abnormal heartbeats originate in the lower chambers of your heart).

4. Recommended Dose of Dobutamine: Start with 10 microgram/kg/min and then increase every three minutes to 20,30,40 microgram/kg/min. If 85 percent of age-predicted maximal heart rate (APMHR) is not achieved at 40 microgram/kg/min, then a 3 minute 50 microgram may be used. If Dobutamine alone is not effective, we may use an atropine injection (25 to 50mg) IV every minute starting at 40 microgram/kg/min. A maximum of 2 mg of Atropine can be used.

After that, the images of your heart working under stress will be recorded. For that, you will be asked to lie on your left side with your left arm out.The technician will apply a special gel and move the transducer over the chest, which produces soundwaves to form images of your heart and other internal structures. During this time, your heart rate, electrocardiogram (ECG), and blood pressure are also recorded.

Finally, the technician will wipe the gel and remove the electrodes placed over the chest and the IV line in a pharmacological stress echocardiogram. This test usually takes around one hour to complete. The test has to be performed within 90 seconds after your exercise; otherwise, the sensitivity of the test will be reduced.

What Is the Emergency Management for DSE?

If the patient is facing any side effects from Dobutamine, it may be reversed by:

• Injection of Esmolol (0.5 to 1 mg/kg body weight) over one minute.

• Injection of Metoprolol (2 to 5 mg/kg body weight) over two to five minutes.

What Are the Interpretations of Stress Echocardiograms?

1. Normal Results: When you are able to exercise as long as most people of your age and sex, your result is normal. During the test, you should not have abnormal symptoms and no changes in your blood pressure and ECG. Your heart should respond to increased stress. A normal result shows that your coronary artery blood flow is normal.

2. Abnormal Results: When you are not able to exercise as long as most people your age, you may have reduced blood flow to your heart due to coronary artery disease or from scarring of the heart muscles due to a past heart attack.

What Are the Treatment Options for an Abnormal Stress Echocardiogram?

You may be suggested any of the following treatments:

• Angioplasty (a procedure to open narrow blood vessels supplying the heart by placing a small metal mesh tube called a stent).

• Changes in your regular heart medicines.

• Coronary angiography (a procedure used to look at the blood vessels of the heart with the help of imaging techniques).

• Heart bypass surgery (a procedure that takes blood vessels from the healthy part of the body and connects it above the blocked blood vessels).

What Are the Complications of Stress Echocardiograms?

• Abnormal heartbeats.

• Dizziness (feeling faint or unsteady).

• Chest pain.

• Severe high blood pressure.

• Vomiting.

• Tiredness.

• Heart attack (rare).

Conclusion:

A stress echocardiogram or stress echo is an effective tool in the diagnosis of heart diseases. This test has an accuracy of 80 to 90 percent in the detection of coronary artery disease. The major advantage of this test is that it is safe, economically affordable, and lacks radiation exposure. It has better visualization and higher specificity when compared to nuclear stress testing.