Adenosine Stress Test

What is an adenosine stress test?

An adenosine stress test is a diagnostic test healthcare providers use to check the blood flow to your heart. The test can help determine if your heart is getting enough blood while you’re active compared to while you’re resting. An adenosine injection makes your heart’s arteries act like they do during exercise.

This test helps your provider determine if you have:

• Any permanent damage to your heart muscle.
• Enough blood — and oxygen — moving through your heart.
• Coronary artery disease (CAD), which makes it hard for blood to get to your heart muscle.

When is an adenosine stress test performed?

A healthcare provider may give you an adenosine stress test because you:

• Can’t do the exercise that a stress test requires, like walking on a treadmill.
• Can’t bring your heart rate up enough with exercise.
• Take certain medicines, like beta-blockers.
• Have a ventricular pacemaker.
• Have left bundle branch block.

How does an adenosine stress test work?

During an adenosine stress test, a provider will give you a small amount of adenosine medication to make your coronary arteries open (dilate) like they do when you exercise. This causes more blood to flow and simulates the effect of exercise for people who can’t exercise on a treadmill.

A provider will inject a small amount of contrast or radioactive marker, depending on the type of imaging scan, into your vein while you’re resting and again after you receive the adenosine medication. Using a special imaging scanner, a provider will take pictures of the contrast or marker as it passes from your blood vessels through your heart muscle.

Depending on the test requested, sometimes this scanner is a magnetic resonance imaging (MRI) scanner or a special type of computed tomography (CT) scanner. This creates computer images of your heart for your provider to review.

During the test, a provider will take images of:

• Your heart size and function.
• Blood flow through your heart when it’s at rest.
• Blood flow through your heart when it’s under stress.

How do I prepare for an adenosine stress test?

Be sure to tell your healthcare provider about all medical conditions you have and all medications you take. This includes those you buy without a prescription (including herbal supplements). You shouldn’t receive adenosine if you have certain conditions, like severe asthma or certain unmanaged abnormal heart rhythms.

Don’t take theophylline for asthma for two days before your test. Bring your asthma inhaler medication to your test appointment.

Avoid anything that contains caffeine for 24 hours before your test. This includes coffee, tea, soft drinks and chocolate. You should also avoid decaffeinated products, as they include trace amounts of caffeine. Don’t take any over-the-counter (OTC) medication that contains caffeine (like Excedrin®, Anacin®, diet pills or NoDoz®) for 24 hours before the test.

What should I do on the day of my test?

On the day of your test:

• Don’t eat or drink except for small sips of water to help you swallow your medications.
• Don’t smoke.
• Bring a list of all the medications you routinely take. The list should include all over-the-counter medications, vitamins and herbal supplements you take.
• Bring your diabetes medication with you so you can take it when the test is complete. Don’t skip a meal when you take your diabetes medication. Doing so can cause your blood sugar levels to drop too low.
• If you take insulin, take the amount your provider recommends for managing your blood sugar. They may tell you to take only half of your usual morning dose and to eat a light meal four hours before the test.
• If you take pills to regulate your blood sugar, don’t take your medication until after the test is complete.
• If you own a glucose monitor, bring it with you to check your blood sugar levels before and after your test. If you think your blood sugar is low, tell a provider immediately. Plan to eat and take your blood sugar medication after your test.
• Take only the heart medications your provider advises on the day of the test. If you have any questions about which medications are OK to take that day, ask your provider before the day of your test.

What should I expect during an adenosine stress test?

During an adenosine stress test, a provider will:

1. Place two IVs in your arm before starting the scan.
2. Place electrodes (small, sticky patches) on your chest to monitor your heart using an electrocardiogram (EKG).
3. Put a blood pressure cuff on your arm to monitor your blood pressure.
4. Monitor your heart rate, EKG and blood pressure throughout the test.
5. Ask you to lie very still inside the scanner. This can last for about 45 minutes.
6. Ask you to hold your breath for short periods of time while the scanner takes pictures of your heart.
7. Talk to you about the possible side effects of the medication before you receive it through the IV.

How long will the test last?

The scan can take about 45 minutes. You may spend up to two hours at your appointment.

What should I expect after?

After your adenosine stress test, healthcare providers will watch you for any side effects. You can go home after a few minutes if you feel well.

What are the side effects of an adenosine stress test?

Adenosine only goes into your body for about five minutes. Within 10 seconds, only half of the medicine is still in your system. This is why side effects go away seconds after your infusion ends (in most people).

About 80% of people have minor side effects from an adenosine stress test. The most common ones are:

• Flushing.
• Chest pain.
• Shortness of breath.

Sometimes, people can have side effects like:

• Heart block.
• Bronchospasm.

If you have side effects from your adenosine stress test, a provider may give you caffeine to treat them. Some people may need aminophylline.

What type of results do you get and what do the results mean?

The healthcare provider who reviews your test will put you into a low-risk, intermediate-risk or high-risk category. They’re looking at your risk of having a heart attack from a lack of oxygen or to see if symptoms you’re having could be due to poor blood flow to your heart.

A provider can tell you if some areas in your heart aren’t getting enough blood flow. This means they aren’t getting enough oxygen. They’ll want to investigate these areas further.

If your blood flow looks good and you’re low-risk, you may only need medication like beta-blockers or calcium channel blockers. Anticoagulants and statins can help with cardiovascular risks, too.

When should I know the results of an adenosine stress test?

It should only take a few days for a provider to review your test results. Your provider will have access to the results and will contact you to talk about them.

If the results are abnormal, what are the next steps?

Your provider may want to do more testing to look into the areas where blood isn’t getting through. Coronary angiography can help them see the source of the issue. If you have a blockage in your coronary artery, you may need a stent in your artery or a coronary artery bypass graft (CABG).

When should I call my provider?

Contact your provider if:

• You’re unsure about your next steps after an adenosine stress test.
• You haven’t heard anything about your test results in a week.

Why is adenosine used for stress tests?

Adenosine makes your coronary arteries open more, like they would if you were exercising. This sends more blood to your heart muscle. The medicine can increase blood flow to three to five times the amount of blood flow you have when you’re resting.

Is an adenosine stress test safe?

Yes, an adenosine stress test is generally safe. It has few side effects and they usually go away quickly. Researchers proved the safety of adenosine for a stress test by evaluating 15,000 people who received it.

What does adenosine do to your heart rate?

Adenosine can cause a decrease or increase in your heart rate. Your blood pressure may come down a little, as well.

What is the difference between Lexiscan® and adenosine stress test?

Both Lexiscan (regadenoson) and adenosine are medicines that open your blood vessels. Healthcare providers use regadenoson more than other medicines for stress tests. It only takes 10 seconds to inject a dose of regadenoson. Adenosine takes about five minutes.

Studies have shown that people tolerate regadenoson better than adenosine and have fewer side effects from it. People who receive regadenoson tend to have less flushing and chest pain, but are more likely to have a headache or seizure.

Talk with your provider about which medicine is best for you.