stress testing : what to expect

A stress test can be both a confusing and daunting experience to many patients, simply because they do not know what to expect. Let's first understand what a stress test is designed to test, and then explore the things patients should know.

In our offices, stress testing is performed in collaboration with the Memorial Hermann Sugar Land Hospital. This means, that our stress tests are performed by the hospitals' expert staff who have supervised and performed thousands upon thousands of stress tests. 

Your doctor might prescribe a stress test in a myriad of different forms. Briefly, all stress tests are designed to address two questions, and they are each addressed by separate components or parts, of the stress test. First, they ask what the functional capacity of the patient is. This is called the stress component. Second, they ask whether blood flow to the heart is compromised during peak exertion (perfusion component).  If blood flow to the heart is compromised during peak exertion, that would strongly suggest that there is a plumbing problem, and that one or more blood vessels supplying blood to the heart is narrowed or completely blocked. Usually when people have blockages or narrowing of blood vessels that supply blood to the heart, this is called coronary artery disease. So the purpose of the stress test (with both stress and perfusion components) is to get a reasonably good estimate of whether you may or may not coronary artery disease. 

STRESS COMPONENT

The stress component of the stress test evaluates your functional capacity. Functional capacity simply means how much vigorous physical activity your heart can tolerate. You might wonder why your doctor cannot simply ask you this question instead of testing you? The reason for a formalized test is so that cardiologists around the world can standardize your functional capacity. This enables us to predict exactly how someone of your age should perform if they are generally in good shape. Let's take an example. Through analyzing lots of data, cardiologists know that someone who is 50 years old should be able to achieve a peak heart rate of about 170 beats per minute (bpm). If you can roughly reach 85% of that, or 145 bpm, then your heart can be expected to sufficiently pump blood without functional limitation. This is what the first part of the stress test measures.

In a majority of cases, the stress component of your study will be done with the use of a treadmill.  This is called a exercise treadmill stress test.  In this study, you will run on a treadmill for as long as you can. This is very important so let me repeat it. You should go on the treadmill for as long as you can. Don't stop because you think the study is over. You need to go until you are completely fatigued, or until you have some symptom that prevents you from continuing.When you are on the treadmill, your heart rate, blood pressure, oxygen saturation, and your heart's electrical activity will be monitored in real time. This information is being fed into a computer that processes this information to see how your heart is behaving and adapting to the increasing workload. Every 3 minutes, the treadmill will get harder (the incline will get steeper and the belt will start moving faster). When you think you are going to need to stop because you are too tired, too short of breath, having chest pain, leg pain or feeling some other symptoms, let the staff know ahead of time so that they can stop the treadmill safely.

When the treadmill comes to a complete stop, you will continue to be monitored for about another 5-10 minutes in recovery to ensure that your heart can relax after strenuous activity.

In many cases, this ends the treadmill exercise stress test. 

how to prepare for your stress test

• Drink plenty of fluids the day before, and get a good night's rest. 
• Your dinner on the day before your stress test should be your last meal. Do not eat or drink anything after midnight. 
• If you have medications that you need to take at night, take them with your dinner. If you have morning medications, either postpone taking them until after the stress test or bring those medications with you.
• Avoid anything with Caffeine! - This means soda/carbonated beverages, coffee (including decaf), tea or chocolate.
• If you are scheduled to take a class of medications called beta blockers (this includes Metoprolol, Labetalol, Carvedilol, Bisoprolol and their trade names), please do not take the dose the evening before. If you are unsure, make sure you speak to your cardiologist or his office staff to verify. 
• Wear light clothing and good, comfortable, running shoes like sneakers.

What HAPPENS IF I FAIL THE STRESS TEST?

The short answer is, nothing happens. It is fairly common for some people to not be able to exercise enough to get their heart to work hard enough. When this happens,  it is impossible for us to accurately assess the patients' functional capacity.  If this happens to you, don't despair. By itself, it doesn't mean much. Many patients are unable to reach an adequate heart rate or unable to exercise sufficiently during their stress component. It could be even due to completely unrelated symptoms such as feeling light headed because of low blood sugar, pain in the leg, or arthritis or joint pain due to a hurt knee. Whatever the reason is, if you told by the stress lab staff that your failed the stress test, or could not get your heart rate high enough, it just means we will need to stress you using another strategy. Let's talk about how we do that.

The lEXISCAN or "CHEMICAL" stress test

When patients are unable to exercise adequately, we can stimulate their heart to behave as it would during exercise by giving you a medication called Regadenason, or commonly known by its tradename "Lexiscan". This chemical, when injected through your IV will cause your heart to behave as it would when it is exercising. It will force the heart to enlarge its blood vessels and allow more blood to flow through them, as would be the case if you were vigorously exercising. When you get the chemical stress test, for that reason, you will feel like you are exercising although you are simply resting on the exam table. You may feel fluttering in your chest, you may feel your breath quicken, and you may notice that you are getting flushed, or sweaty. This is all to be expected. Remember though, that the chemical stress test should be given very cautiously in patients who have had lung disease (asthma, COPD, bronchospasm) or a very slow heart rate. If you have had any of these conditions, make sure you notify the staff before the chemical stress test is started.

PERFUSION COMPONENT

commonly asked questions about stress testing:

1. how long does the whole procedure take?

The stress test itself is a short procedure. But there can be a lot of waiting time before and after. For example, if you get a treadmill stress test with perfusion, you will check in at the front desk at the hospital, wait for the staff to usher you into the stress lab area, and then have the rest imaging part done, then go on the treadmill for the stress component, and then have another series of stress images done. The whole procedure can therefore take in the order of 4-6 hours. We recommend that you take a half day off, at the very least.

2. Will I RECEIVE ANY SEDATION DURING THIS PROCEDURE?

The short answer is no. Stress testing requires no procedural sedation. 

3. CAN I DRIVE MYSELF BACK HOME OR DO I NEED A SOMEONE TO GIVE ME A RIDE?

You will not need a ride back home, if you can drive. The actual test itself does not impact your ability to drive after the fact. Of course, should you have some untoward reaction to the medication or require hospitalization then you will definitely need someone to drive you back, but this is not the norm for a vast majority of our patients.

4. HOW LONG DOES IT TAKE TO GET THE RESULTS?

Your cardiologist will generally call you on the same day, or rarely the next day, once the study is read. During that phone call we will discuss with you the options (what happens next) and when you will need to follow up with us.

5. when can i eat?

You can usually eat while you are finished with the stress component and waiting. Our stress lab staff knows exactly when the timing for this is, and it is best to ask them before you eat or drink anything. If you have a critical medication that you need to take, please discuss this with our staff. They can help figure out what the best course of action is.

6. WHAT HAPPENS IF I FAIL THE TREADMILL TEST?

As noted above, it's not a big deal. If you fail the treadmill test, we have options and can administer the chemical stress test instead, provided, that you were scheduled to originally have a stress test with perfusion. In the rare times when you were only scheduled for a treadmill stress test (without the perfusion study) and you fail the stress test, you may need to be rescheduled. This has nothing to do with you, and has everything to do with the complex intricacies of insurance pre-authorization. It's not the end of the world, and we can have you rescheduled quickly for the next appointment available. Our office staff will help with this process.

7. WHAT HAPPENS IF MY COPD/ASTHMA CAUSES ME TO HAVE A BAD REACTION DURING THE CHEMICAL STRESS TEST?

This is not a problem either, because luckily, we have excellent antidotes to the chemical we give you that can be given to quickly reverse its effects. In fact, reversing the effects of the chemical has no impact on the stress test itself and we can usually proceed to the perfusion component without a hiccup.

8. what happens next?

Usually, after the stress test is complete, you go home. Your cardiologist will then have an opportunity to examine the images captured from the SPECT camera and will call you with the results. Depending on what we find, you may be asked to come for a follow up appointment in the office, or maybe scheduled for a cardiac catheterization procedure to look at the arteries of your heart more directly.