Overview of Treadmill Stress Testing
A treadmill stress test, also called a cardiovascular stress test, measures how well your heart works during physical activity. This is done by monitoring your heart’s electrical activity with an electrocardiogram (ECG) and checking your blood pressure while you exercise on a treadmill or bicycle. For those who can’t do physical exercise, a drug can be used to stimulate your heart, mimicking the effects of exercise.
This test helps medical professionals understand how much physical activity a patient can handle. It can reveal indicate signs of heart diseases, such as coronary artery disease which clogs the heart’s blood vessels. It can also check the risks and how well you’re responding to treatments. Some studies show that cardiovascular fitness can lower the risk of irregular heart rhythms, especially for obese individuals.
Here’s a little background on how exercise affects your body: Exercise stimulates your body and makes changes in the blood vessels of your heart, known as coronary vessels, which deliver blood to your heart. When you exercise, these vessels open wider to let more blood through. This can happen due to changes in oxygen consumption, relaxation of the blood vessels due to increased pressure, and the body’s own mechanisms to control the effects of adrenaline.
During exercise, your heart requires more oxygen. The widening of blood vessels helps to deliver this increased demand, preventing heart muscle damage due to insufficient oxygen. Medical professionals can spot heart diseases through this process as the affected blood vessels don’t open wider as they should.
With increased activity, your body reacts by increasing heart rate and the amount of blood your heart pumps with every beat, known as stroke volume. Your breathing becomes faster and deeper, and your blood return to the heart increases because of constriction in certain blood vessels. The body’s response depends on how much muscle is used, how intense the exercise is, and your overall fitness level. As you exercise more, the blood flow to your muscles increases, and overall resistance in your blood vessels decreases. This makes your systolic blood pressure (the pressure in your blood vessels when your heart beats), mean arterial pressure (a measure of the average pressure in your arteries), and pulse pressure (the difference between your systolic and diastolic pressures) to rise. Your diastolic blood pressure (the pressure in the arteries when your heart rests between beats) may stay the same, slightly increase or slightly decrease.
The peak heart rate for your age plays a key role in measuring how much stress your heart is under during the test. Usually, the aim is to reach 85% of this rate which is calculated by subtracting your age from 220.
Why do People Need Treadmill Stress Testing
A treadmill stress test is used by doctors to diagnose and assess the severity of coronary artery disease (CAD), a condition that affects the blood vessels supplying the heart. This test is usually the first choice for patients who have a normal or almost normal resting ECG (or electrocardiogram, which is a test that checks the heart’s electrical activity) and who can perform adequate exercise.
The reasons you might need a treadmill stress test include:
- Experiencing symptoms that suggest lack of blood flow to the heart
- Having chest pain that isn’t due to acute coronary syndrome (ACS, a term for heart attacks and other serious heart conditions)
- Recently experienced ACS but no imaging of your heart’s blood vessels was done or the treatment didn’t fully restore blood flow
- Already been diagnosed with CAD but the symptoms are getting worse
- Undergone treatment for CAD through surgeries like coronary artery bypass grafting (CABG, where doctors create a new pathway around blocked heart arteries) or percutaneous coronary intervention (PCI, a non-surgical procedure that improves blood flow in your heart arteries) a while back
- Having valvular heart disease (problems with the heart valves) and doctors want to check how much you can exercise and if you need surgery
Certain heart rhythm disorders might need this test as well to see if the heart can increase its rate (beat faster) during stress or exercise. If you’ve been diagnosed with heart failure or cardiomyopathy (disease of the heart muscle), you may also need this test.
When a Person Should Avoid Treadmill Stress Testing
There can be reasons why certain people should not participate in treadmill stress testing, a test that monitors the heart rate while a person exercises on a treadmill. These can be split into two types: absolute and relative contraindications.
Absolute contraindications are situations where the testing should not be done:
– If someone had a severe heart attack within the last 2 to 3 days.
– If someone has unstable angina, a condition that causes chest pain, and it hasn’t been controlled with medication.
– If someone has heart rhythm problems that cause symptoms or affects their blood circulation.
– If someone has symptomatic severe aortic stenosis – a narrowing of the heart’s aortic valve that can cause symptoms like chest pain and breathing problems.
– If someone has heart failure symptoms that are not under control.
– If someone recently had a clot in their lungs, or if the tissue in their lungs died due to lack of blood.
– If someone has very high blood pressure in their lungs.
– Acute (meaning sudden or severe) inflammation of the heart muscle, outer lining of the heart, or within the heart.
– If someone has an acute aortic dissection, which is a serious condition where there’s a tear in the wall of the heart’s main artery.
Relative contraindications are situations where the test might be able to be done if the benefits outweigh the risks:
– Certain types of severe heart rhythm disorders.
– Very high blood pressure (over 200 for the top number or over 110 for the bottom number).
– If someone is so physically or mentally disabled or extremely overweight and cannot exercise.
– If someone has a narrowing of the main heart artery.
– Moderate heart valve narrowing or leakiness.
– Abnormal levels of electrolytes, minerals in the body that help the heart function normally.
– Abnormally fast or slow heart rhythms.
– If someone has hypertrophic cardiomyopathy, which is a heart muscle disease, or blockages in how blood leaves the heart.
– If someone’s mental or physical condition prevents them from being able to exercise adequately.
Preparing for Treadmill Stress Testing
Treadmill stress tests, a type of test used to assess heart health, are generally safe to undergo. There’s only a tiny risk of serious heart complications, such as a heart attack, abnormal heart rhythm, or even death, with roughly 1 in 10,000 patients experiencing these.
All professionals who are performing the treadmill stress test are well-prepared to recognize and handle any problems, if they do occur. Emergency resuscitation equipment and medications are always on hand. Moreover, before the test, it’s important for patients to understand what to expect during the procedure. Thus, doctors will explain the details to them and acquire their consent before proceeding.
How is Treadmill Stress Testing performed
A treadmill stress test is a medical test which takes place in a professional lab being supervised by a medically trained professional. In this test, you will have some stickers known as electrodes placed on your chest, which are connected to a machine called an ECG (Electrocardiogram). The ECG can capture and record the electrical activity in your heart. Before you start the test, the healthcare provider will note down your resting heart rate and blood pressure. They will also take an initial ECG reading while you’re in a resting state.
It’s important to take a good look at your ECG before any exercise begins because certain traces on the ECG can interfere with, or obscure, the test results, making it more difficult to interpret. Features on the ECG that could introduce complications include changes in special segments of the ECG, signs of an enlarged heart, certain heart rhythm problems, and unusual wave patterns, amongst others. If any of these irregularities do exist, the test may need to be adjusted to include some form of imaging. Normally, an ECG is taken both when you’re standing and lying down because your posture can affect the results. In general, a treadmill stress test is useful in ruling out the presence of coronary artery disease (CAD) more so than confirming it.
As long as there are no concerns with your initial ECG, you will be asked to walk on a treadmill and the intensity of exercise will gradually increase. All the while, your blood pressure and heart rate will be continuously monitored, and you’ll be closely watched for any symptoms such as chest pain, shortness of breath, dizziness, or extreme tiredness. The treadmill stress testing generally follows the “Bruce protocol”, a series of exercise stages each lasting 3 minutes. The goal is for you to exercise within 6 to 12 minutes of total duration.
All throughout the treadmill stress test, your doctor will collect data about your heart rate, blood pressure, and any changes in your ECG also at every stage. At any point, if there is a significant abnormality detected, the exercise test should promptly stop. Otherwise, mild symptoms such as a slight chest pain might not stop the test if the ECG is still normal and you’re still feeling okay overall.
The American College of Cardiology (ACC) and the American Heart Association (AHA) have set out clear guidelines on when the treadmill stress test should be stopped immediately. For instance, these include a significant drop in blood pressure, severe chest pain and dizziness, abnormal appearance like a bluish skin color (cyanosis), and complications with monitoring the ECG or abnormal heart rhythms. The presence of other features like chest pain and high blood pressure have more flexible criteria for ending the test.
After wrapping up the test, the healthcare provider will put together a detailed report outlining various aspects of the test including your initial ECG traces, heart rate, blood pressure, changes observed during the test, and reasons to stop the test, among other details. A successful test should show a steady increase in your heart rate and blood pressure in response to the exercises. Any abnormal patterns such as severe chest pain or significant changes in the ECG early in the exercise process, or those persisting long into the recovery period, can be warning signs of heart problems.
One useful tool used to assess the results of treadmill stress tests is the Duke treadmill score (DTS). This scoring system includes three details: the exercise duration, changes in the ECG, and presence of chest pain to determine if you’re at low, medium, or high risk of heart disease. The scores range from +15 to -25 where greater than or equal to 5 is considered low risk, while less than or equal to -11 is high risk. This scoring strategy helps predict the 5-year survival for people with suspected coronary artery disease. For example, those classified as low-risk have about 97% survival rate over 5 years, those in the medium risk category have about 90%, whilst high-risk category represents about a 65% 5-year-survival rate.
Possible Complications of Treadmill Stress Testing
A treadmill stress test is generally a safe procedure with few complications. However, there are few potential issues patients might face during or after the test:
- Low blood pressure, or Hypotension, might happen during or just after the exercise, which can make you feel dizzy. This typically resolves as soon as you stop exercising.
- Irregular heartbeats, or Arrhythmias, can occur during the test, but usually stop soon after the test ends.
- Though it’s exceedingly rare, the test might cause a heart attack, also known as a myocardial infarction.
Before the test, patients are advised not to eat, drink, or smoke for at least three hours. This is to make sure they can exercise to their full capacity during the test. It’s also advised to bring appropriate exercise clothes and shoes to the test. The healthcare provider should explain the pros and cons, and any possible complications of the test beforehand.
It’s important to disclose any medications before the test. Some drugs, such as beta-blockers, calcium-channel blockers, digoxin, and medications for irregular heartbeats can affect the maximum heart rate obtained during the test. Nitrates can also affect the test results. Before the test, it is crucial to provide a thorough medical history and go through a physical examination.
What Else Should I Know About Treadmill Stress Testing?
If a stress test comes back with abnormal results, it doesn’t necessarily mean that you have any blockages or disease in your heart’s arteries. The accuracy of the test and your individual risk factors play a big role in whether the test results are a true reflection of your heart’s condition. Guidelines from leading heart organizations propose that further testing, like heart imaging, could be useful in assessing your heart’s health if you have a medium or high risk of heart disease.
If the follow-up tests are also concerning, your doctors will discuss the best treatment plan for you. This could involve managing your condition with medicines, or it could mean a procedure to open up or bypass a blocked artery, known as ‘revascularization’. The decision to go ahead with revascularization, and what type of procedure is best, depends on things like the exact layout of your arteries, how well your heart is pumping blood, and whether you have any other health conditions, such as diabetes.
If your exercise stress test is reported to be positive or unclear, it’s key that you have a thorough conversation with your healthcare provider about what this means and what the next steps are.
