Have you ever been asked to do an Adenosine Stress Test? Let's talk about it simply.

It's normal to feel a little nervous and apprehensive when your doctor tells you that you need to have a heart test. When we hear the word "stress test," most of us think of a test that involves running on a treadmill. But not everyone can do that kind of exercise. In such a situation, a special test called an adenosine stress test is done to check how well your heart is getting blood. So, let's talk about it in simple terms, without any fear or doubt.

What exactly is this adenosine stress test?

Simply put, this is a test that checks how well your heart is working. When we exercise, run, or jump, our heart beats faster. This causes the heart muscles to need more blood. This test involves giving you a small amount of a drug called adenosine, which opens up the blood vessels in your heart as if you were exercising.

Imagine, this drug artificially creates a situation where you're running on a treadmill. Then, doctors can see if there's a difference between the way your heart pumps blood when you're at rest and the way it pumps blood under this kind of "stress."

There are several main things that this test looks for:

• Check to see if there is any permanent damage to your heart muscle.
• Make sure the heart is getting enough blood and oxygen .
• Coronary Artery Disease (CAD) , which is when the arteries that carry blood to the heart become narrowed or blocked.

When should this test be done?

This test is not for everyone. A doctor may recommend it for someone who has difficulty performing a regular stress test. Here are some examples:

• If you are unable to exercise on a treadmill, such as walking or running (for example, someone with joint problems or breathing difficulties).
• If you can't get your heart rate up to the desired level despite exercising.
• If you are taking certain medications, such as beta-blockers .
• If you have a pacemaker implanted in your heart.
• If you have a problem with the way electrical signals travel in the heart called left bundle branch block .

How does this test work?

Although this may seem a bit complicated, it is actually a very systematic process.

First, a small amount of radioactive material (radioactive marker) or a special liquid (contrast) is injected into a vein while you are at rest. Then, a special camera (scanner) takes pictures of your heart. This can show how blood flows through your heart during normal resting times.

Next, a drug called "Adenosine" is given into your vein for a few minutes. When this drug is injected into your body, the blood vessels in your heart (coronary arteries) dilate, as if you were exercising hard. This increases the speed at which blood flows to your heart.

At that time, the radioactive material is injected into the body again, and the scanner takes pictures of the heart. Now the doctors can compare the first pictures with these second pictures.

The scanner used to take these images can sometimes be an MRI (Magnetic Resonance Imaging) scanner, or a special CT (Computed Tomography) scanner.

How should I prepare before the test?

This is a very important part. You must follow these instructions exactly for the test results to be accurate.

What should I follow on the day of the test?

Your preparation is also very important on the day of the test.

What happens during a test? Should I be afraid?

There is no reason to be afraid. The medical staff will take good care of you. Here are some things that will happen:

• They'll put two IV lines in a vein in your arm. One to give you the medicine, and the other to give you the radioactive material.
• Electrodes , which are small stickers, are placed on your chest. These are used to continuously monitor your heart's activity using an EKG (Electrocardiogram) machine.
• A blood pressure cuff is placed on your arm and your blood pressure is continuously measured.
• You will be taken into the scanner and asked to lie still for about 45 minutes .
• They tell you to hold your breath for a few seconds while taking pictures.
• Before you are given adenosine, you will be informed about its possible side effects.

The entire process can take about two hours, but the scan itself takes about 45 minutes.

Are there any side effects to this?

The adenosine drug stays in the body for a very short time. So even if side effects occur, they usually go away within seconds after the drug is stopped. About 80% of people who take this test experience minor side effects.

Common side effects:

• Redness of the face, flushing
• Chest pain or tightness
• Shortness of breath

Rare side effects:

• Heart block
• Wheezing (Bronchospasm) - especially in asthmatics

What do the test results say?

The doctor, who analyzes the images from your test, will classify you into three categories based on your heart risk: low-risk, intermediate-risk, or high-risk .

The results mainly tell you how much risk you have of having a heart attack, and whether your current symptoms (such as chest pain) are caused by reduced blood flow to the heart.

• If the results are normal: This means that all parts of your heart are getting enough blood flow, both when you are at rest and under stress. Since you are in a low-risk group, you may be advised to use some medication (such as beta-blockers) and make some lifestyle changes.
• If the results are abnormal: This means that some parts of the heart are not getting enough blood, especially under stress. This means that blood vessels in that area may be blocked.

Results are usually available within a few days. Your doctor will call you to discuss the results and what to do next.

If the results are abnormal, what do you do next?

Don't worry. This test will help you pinpoint the problem and treat it. Your doctor may recommend something like this:

• Coronary angiography: This involves inserting a camera into the blood vessels of the heart to see exactly where the blockage is and how severe it is.
• Stent placement: Placing a small mesh-like device inside a blocked blood vessel to reopen it.
• Coronary Artery Bypass Graft (CABG): If the blockage is severe, a new blood vessel is implanted to bypass it.

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

Lexiscan® (regadenoson) is a drug that, like adenosine, also works by opening blood vessels. In fact, this drug is now the one most often used for this test. While adenosine takes about 5 minutes to inject, Lexiscan® can be administered in 10 seconds. Also, some studies have found that Lexiscan® has fewer side effects than adenosine. However, your doctor will decide which drug is best for you.