Overview of Stress Echocardiography
Stress echocardiography is a test that combines an ultrasound of your heart (two-dimensional echocardiography) with some type of stress. This could be physical exercise, medication that mimics exercise, or less often, electrical pulses to increase the heart rate (atrial pacing).
This test is used to see how your heart handles stress. Sometimes, if a blood vessel that supplies the heart (coronary artery) is narrowed or blocked, areas of the heart don’t work as well when you’re exercising or under stress. These changes can show up on the echocardiography images as areas of heart muscle not moving as well as they should.
Stress echocardiography is an important tool in helping doctors understand if you have a heart condition like ischemic heart disease, which is when the heart muscle doesn’t get enough blood. It’s also used in evaluating other heart issues including heart failure, valve problems, nonischemic cardiomyopathy (a weakened heart muscle not due to blood flow issues), pulmonary hypertension (high blood pressure in the lungs), and congenital heart disease (heart problems present at birth).
Anatomy and Physiology of Stress Echocardiography
Anatomy often includes the study of different ways the walls of the heart can move abnormally. It’s also important to know which parts of the heart are supplied by different blood vessels. This information is collected from six different views or angles. These include the long and short side views, and views from the top part of the heart with four and two chambers respectively. To score these views, a system is used where a score from 1 to 4 is given based on how the wall of the heart moves, whether it moves normally, slightly abnormally, not at all, or in an unusual direction. This process uses a model with 17 sections for identifying abnormal heart wall movements.
Specific views help doctors to see different parts of the heart. These include:
Long side view (Parasternal long axis – PLAX): This view generally includes a part called the anteroseptal, which is supplied by a blood vessel known as left anterior descent artery, and a part called inferolateral, which is supplied by either right coronary artery or left circumflex artery.
Top view with four chambers (Apical four chambers – A4C): This view includes the apex of the heart and other parts supplied by major arteries- left anterior descending artery, right coronary artery and left circumflex artery.
Top view with two chambers (Apical two chambers – A2C): This view includes the inferior and anterior parts of the heart, which are supplied by right coronary artery and left anterior descending artery.
Short side view (Parasternal short-axis – SAX): This view includes the mid regions of the heart, specifically mid anteroseptal, mid anterior, mid inferoseptal, mid anterolateral, mid inferolateral and mid inferior. These regions are supplied by the major blood vessels of the heart- left anterior descending artery, right coronary artery, and left circumflex artery.
Why do People Need Stress Echocardiography
Stress echocardiography is a test done to look at how the heart works during physical stress. It might be done by having you exercise, or by giving you medicines that make your heart beat faster and harder.
This test helps doctors diagnose different heart conditions such as:
- Coronary artery disease – this is when the blood vessels that supply blood to your heart get narrow or blocked.
- Seeing how the heart is doing after a procedure to restore normal blood flow is done.
- Helping to determine risk levels for people already diagnosed with heart disease.
- Finding out where heart lack of blood supply is a problem.
- Checking the heart’s health before a surgery.
- Understanding if heart disease is the cause for difficulty in breathing especially when doing physical activities.
- Checking the heart valves to see if they are working properly.
- Left bundle branch block – this is when electrical signals can’t move properly through the heart.
By doing the stress echocardiography, your doctor can get a better picture of your heart health and determine the best treatment for your condition.
When a Person Should Avoid Stress Echocardiography
There are some situations where doing a stress test for your heart, whether it’s exercise-based or using drugs to simulate exercise, might not be safe:
Absolute cases (meaning a test absolutely should not be done) include:
* A heart attack experienced within the last 48 hours
* New inflammation around the heart
* A serious heart problem called aortic stenosis where the heart valve doesn’t open fully, causing symptoms
* Heart rhythm problems (uncontrolled arrhythmias) causing symptoms or instability
* A tear in the largest blood vessel in the body (aortic dissection)
* High-risk chest pain typically occurring at rest or with minimal exertion (unstable angina)
* Unstable or worsening heart failure where the heart can’t pump enough blood (left ventricle ejection fraction or LVEF less than 35%)
* A blood clot in the lung (acute pulmonary embolism or infarction)
Relative cases (meaning a test might be unsafe and should be done carefully) include:
* Narrowing of the main artery supplying blood to the heart (left main coronary artery stenosis)
* Block in electrical communication within the heart (atrioventricular or AV block)
* Extremely high blood pressure (greater than 180/100mm Hg)
* Abnormal levels of body salts (electrolyte abnormalities)
* Mental or physical disability
* Very fast or very slow heart rhythm (tachycardia or bradyarrhythmia)
* Moderate problems with heart valves (stenotic valvular heart disease)
In addition, certain heart-stress drugs like dipyridamole or adenosine and dobutamine, should not be used if a person has a type of heart condition that interferes with electrical signals (severe AV block without a pacemaker), active wheezing or asthma, a particular heart rhythm condition without a pacemaker (sick sinus syndrome), very low blood pressure (less than 90 mmHg), or unusually rapid heart rhythms like atrial fibrillation.
Equipment used for Stress Echocardiography
Stress echocardiography, a test used to analyze your heart health, involves a set of equipment like:
- Ultrasound machine: This device helps in producing images of your heart using sound waves.
- Probes of 3.5 MHz and 5 MHz: These are special equipment that go with the ultrasound to help generate the image of your heart.
- Image system: It captures and stores the images produced by the ultrasound.
- Blood pressure cuff and stethoscope: These are used to monitor your blood pressure and listen to your heartbeats during the test.
- Echo beds, workstations, and a comfortable chair for the person conducting the test.
- Contrast machine and contrast materials: These help in making the heart’s structures clearer in the images.
- Emergency equipment, including a portable defibrillator for heart emergencies, an oxygen mask, a bag-valve-mask for artificial breathing, intubation (tube inserting) equipment, emergency medical carts, suction machine, and other tools like syringes, needles, and tubing for injecting medicine.
The equipment facilitates several types of imaging to evaluate potential heart issues caused by lack of blood supply. Depending on the patient, contrast agents may be used to provide a clearer image of the heart if two or more sections of heart lining aren’t seen well on the initial images.
How is Stress Echocardiography performed
Tissue harmonic imaging is a method used in stress echocardiography, which is a test to see how well your heart and blood vessels are working. This technique improves the quality of the images taken by reducing unwanted noise and providing clearer, sharper images. It’s especially helpful in seeing greater depths into the body and improving the signals from the heart muscle (myocardium). It increases the overall accuracy of the test as it helps to define the inner layers of the heart (endocardium) more distinctly.
Using a substance referred to as contrast agents while performing harmonic imaging boosts the accuracy of the procedure even more. This allows the doctor to study a larger number of potential abnormalities in the movement of the wall segments of your heart.
The methods of testing stress on the heart can vary:
Exercise stress testing is done with those who are able to perform physical activity. Either a treadmill or a bicycle can be used for this. The ability to withstand exercise is evaluated, and images of the heart are taken at rest and immediately after finishing the exercise. Any changes in the heart’s movements are studied.
Pharmacologic stress testing is done in patients who cannot perform physical exercise. Medications are used instead to make the heart work harder and mimic the effects of exercise.
Dobutamine echocardiography uses a drug called dobutamine to make your heart beat faster and harder. The doctor monitors your heart’s response to the drug. If your heart isn’t reacting as expected, another medication called Atropine might be used to increase sensitivity, especially in patients taking beta-blockers or those with a single-vessel disease.
Vasodilator stress testing uses drugs called adenosine and dipyridamole in stress echocardiography. These medications widen, or dilate, your blood vessels, which increases blood flow to your heart. They help doctors to see how your heart would respond to stress. Sometimes, atropine is used alongside these medications to increase sensitivity.
If you have a permanent pacemaker, pacing stress testing can be used. Your heart rate can be increased by adjusting the pacemaker, which can be useful if you’re unable to perform physical exercise. The heart’s response is monitored at rest and at various heart rates.
After the test, doctors compare the images of your heart at rest and under stress. They look for any signs that the heart’s size, shape, and function have changed, which could indicate a problem. For instance, a dilated LV cavity with changes in the shape and reduced wall thickening after exercising might be a sign of multiple vessel diseases (diseases that affect more than one blood vessel).
The ability of different stress tests in identifying coronary artery disease (the narrowing of the arteries supplying blood and oxygen to your heart) may vary depending on the extent of narrowing. However, the accuracy of these tests tend to vary according to the pretest likelihood of the disease within the tested patient.
Possible Complications of Stress Echocardiography
A dobutamine stress echocardiogram is a type of heart test. However, it can lead to some heart-related side effects. These can include chest pain (also known as angina), low blood pressure (hypotension), and heart rhythm problems (cardiac arrhythmias). About 3% of people might experience an irregular heartbeat, either a fast and chaotic rhythm in the upper parts of the heart (atrial fibrillation) or short episodes of an abnormal rapid heartbeat (nonsustained ventricular arrhythmias). It’s also rare but possible for the dobutamine to cause blockages in the lower left part of the heart. About 10% of patients might have extra heartbeats (premature atrial or ventricular contractions).
A vasodilator stress echocardiogram can also cause major reactions. These can include a heart attack (myocardial infarction), a rare condition causing a sudden stop in heart function (asystole), and a rapid and regular heart rate that begins in the lower chambers of the heart (ventricular tachycardia). Low blood pressure and a slower-than-normal heart rate (bradycardia) might happen too. If these occur, a drug called aminophylline can be used for treatment.
A pacing stress echocardiogram, might sometimes result in a specific type of heart block called Wenckebach’s second-degree heart block. This means that some signals from the upper part of the heart are not reaching the lower parts. If this happens, a medication called atropine may be given to the patient to help resolve the problem.
What Else Should I Know About Stress Echocardiography?
Stress echocardiography (also known as a stress echo or heart stress test) has advantages when it comes to correctly identifying heart diseases, compared to a standard exercise electrocardiography, which is another kind of heart test. When measured against nuclear perfusion imaging studies (tests that show blood flow to your heart), stress echocardiography has a similar level of accuracy. It might not catch all cases (moderate sensitivity), but it excels at confirming when a disease is present (higher specificity).
Both dipyridamole and dobutamine, two drugs often used during these tests, are typically well tolerated and can be used safely. Whether one or the other is used depends on the individual patient’s health situation and the doctor’s preference.
It’s important to know that heart disease medication, especially beta-blocking agents (drugs that slow the heart rate), can affect the accuracy of these tests. That’s why it may be recommended to pause this medication during the time of the test. This way, you avoid a situation where the test might show you don’t have a disease (a false-negative result) when you actually do.
