Frequently Asked Questions: Cardiac Imaging
Learn more about what to expect during a cardiac MRI, echocardiogram and stress tests.
Cardiac Magnetic Resonance Imaging (MRI)
MRI (magnetic resonance imaging) uses radio waves and a strong magnetic field (and no x-rays) to provide remarkably clear and detailed pictures of internal organs and tissues. The procedure is valuable in diagnosing a broad range of conditions in all parts of the body, including heart and vascular disease. Cardiovascular MRI (CMR) is specialized MRI of the heart and vascular system. It requires specialized equipment and expertise.
Because the strong magnetic field used for CMR will pull on any iron-containing object in the body, CMR staff will ask whether you have a heart pacemaker or implanted defibrillator, implanted port (often referred to by brand names such as Port-o-cath, Infusaport or Lifeport), intrauterine device (IUD), TENS (transcutaneous electrical nerve stimulator), or any metal plates, pins, screws or surgical staples in your body. In most cases, surgical staples, plates, pins and screws pose no risk during a CMR examination. Red dyes used in tattoos and permanent eyeliner may contain metallic iron oxide and could heat up during CMR examination, but this is rare. You will be asked if you have ever had a bullet or shrapnel in your body, or ever worked in a metal or machine shop. If there is any question of metal fragments, you may be asked to have an x-ray that will detect any metal objects.
CMR provides abundant soft tissue contrast and, in many cases, allows additional and more precise differences to be recognized than is possible with cardiac ultrasound (echocardiography), standard X-ray examinations, computer tomography (CT) scans, or radionuclide imaging.
In many instances, a CMR contrast agent is injected into a vein to further improve the image quality contrast, and thus allow better differentiation of tissues. The most commonly used CMR contrast agents are a class of chemical compounds containing gadolinium as the substance which is decisive for improving contrast. Gadolinium is eliminated via the kidney and is very well tolerated. CMR contrast media can be used safely when allergy or kidney problems have resulted from the use of the x-ray or CT scan contrast media.
CMR poses no known risk to most patients if appropriate safety guidelines are followed. A CMR examination involves the use of a very strong magnet. For a very few patients CMR may be inadvisable due to metal or other implants in the body, so we require you to complete our safety checklist before beginning your exam. This assures that the study will be safe for you. You should tell us if you have or believe that you might have any of the following:
- Brain aneurysm clips
- Cardiac pacemaker or defibrillator
- Are or may be pregnant
- Implanted medication pumps
- Implanted nerve stimulating devices (TENS)
- Intrauterine device (IUD)
- Any other surgically implanted or other metallic object in your body, such as shrapnel metal or a bullet
Many implants used today are safe to go into the CMR magnet, but we will determine that for each individual patient. For the safety of staff and patients, the CMR environment needs to remain free of metal objects. We will ask that you remove all jewelry (except wedding rings), including watches, hair clips and pins, hearing aids, wallets and credit cards. You will have a locker for to keep your belongings safe while you are in the scanner.
People who are claustrophobic may find that a mild sedative helps them get through the exam. If you feel you need some sedation for the CMR study, then you should contact your physician and he or she will order it. Typically you should take the sedative one hour prior to your appointment time. You will also need to arrange for someone to drive you to and from your appointment. You should not plan to do any work or activity that requires you to be alert for the duration of that day. You will be discharged home with your escort.
Most CMR examinations require no preparation. We will however, ask that you avoid caffeinated beverages for several hours before your exam. You should take any medication you would normally take as directed by your doctor. Please let your technologist know if you have taken medications to relax you. If so, you must have someone with you to drive you to and from your appointment.
You will check in at the cardiology non-invasive testing waiting area, room ES405 at Beth Israel Deaconess Medical Center’s east campus. Tell the receptionist you are here for a CMR. She will alert us that you are here and we will come to meet you.
After the technologist reviews the CMR exam with you and answers any questions that you might have, you will be taken to a locker room where you will change into appropriate clothing and be able to secure your belongings in a personal locker. You will then be escorted into the scan room. In the scan room, you will be positioned on a special table and an IV (intravenous) catheter may be placed in your arm. You will have pillows under your knees and blankets to keep you warm. Electrocardiogram (ECG) leads and a special piece of equipment called a surface coil (which is like a radio antenna) will be placed over your chest. You will get hearing protection (earplugs) and a headset, which will lessen the volume of the buzzing and chirping sounds, allow you to listen to music, and communicate with the technologist during the exam. You will also be given an emergency call button in the very unlikely case of an emergency.
The noises you will hear are the sounds of the magnet working to generate images. The table will move you into the scanner so that your heart is in the center for the magnet. The technologist will leave the room and go to a booth immediately outside of the scan room. He or she can see and hear you at all times. The exam consists of a number of different scans that vary in length and the type of sounds that they make. The technologist will tell you how long each scan will be and will remind you to lie as still as possible. Some CMR exams have a few short scans during which you will be asked to hold your breath. These “breath holds” last from 10 to 20 seconds. Patients should expect to be in the scanner between 40 minutes and 90 minutes.
At the end of the exam, the technologist will remove the IV, help you off the table and escort you back to the locker area, where you can change back into your clothes. Unless you have taken a sedative before the exam, there will be no restrictions on your activities after you finish the CMR study.
A transthoracic echocardiogram is a medical test that produces detailed images of your beating heart. Using ultrasound technology, a transthoracic echocardiogram allows healthcare providers to see the walls, chambers and valves within your heart, as well as blood flow within your heart. The test is not invasive and does not use any radiation or require any sedation. You should take all of your usual medications prior to the test, and you can resume your usual activities after it is completed.
A transthoracic echocardiogram is a very accurate and useful tool in diagnosing, managing and treating heart problems. It can:
- Help assess your risk for heart disease
- Help in assessing symptoms such as shortness of breath, palpitations or chest pain
- Identify areas where arteries are blocked or narrowed
- Assess your heart valves to determine if they are functioning properly
- Identify heart walls that are not beating in a synchronized way
- Help your doctor monitor the progression of existing heart disease and your response to treatment
- Assess the heart’s activity and tissue damage following a heart attack or a diagnosis of heart failure
- Accurately locate tumors and blood clots within the heart
Having a transthoracic echocardiogram does not pose any health risks to you. It is the most common non-invasive cardiac test performed. More than 20 million studies are conducted in this country each year, and more than 12,000 transthoracic echocardiograms are performed at Beth Israel Deaconess Medical Center annually.
You do not need to make any special preparations before the test. You may eat, drink and take your medications as you normally do.
The Outpatient Echocardiography Laboratory is located on the seventh floor of the Carl J. Shapiro Clinical Center.
You should plan to be in the Echocardiography Laboratory for about one hour.
When you arrive, you will meet the sonographer who will perform the test. He or she will verify your name and birth date, explain the test, answer any questions you may have, and give you a gown to change into. After you privately remove your clothes from the waist up and change into the gown, the sonographer will place electrodes on the skin of your chest. Electrodes are round sticky patches that are attached to an electrocardiogram (EKG) machine, which monitors your heart rate for the duration of the test.
While you are lying on your left side, the sonographer will use a wand called a sound-wave transducer to capture ultrasound pictures of various areas of your heart. Gel on the end of the wand helps to produce clearer pictures; it may feel cool, but will not harm your skin. The sonographer will place the wand on several areas of your chest, and may ask you to change positions or to hold your breath for short periods of time during the test. You may hear some noise coming from the ultrasound machine if the sonographer is also gathering information about blood flow in your heart.
The lights in the room are dim so the sonographer can see the images on the monitor more clearly. When the test is complete, the sonographer will help wipe off any remaining gel. You will then change onto your own clothes, and you can resume your usual activities right away.
Your test results will be reviewed by a cardiologist, who will write a detailed report and send it to the doctor who referred you for the test. Your doctor will have the results within three business days of the test.
There are three different types of echocardiograms:
- Transthoracic echocardiogram (as described; also called TTE)
- Transesophageal echocardiogram (also called TEE)
- Stress echocardiogram
Exercise Stress Test
An exercise stress test is a medical test that helps your doctor to determine how well your heart functions during physical activity, specifically whether it is getting enough blood and oxygen when it is working hard.
An exercise stress test is usually conducted for one of these reasons:
- You have concerning symptoms and/or cardiac risk factors that indicate the potential for narrowed or blocked arteries to the heart (coronary artery disease) or an irregular heartbeat (arrhythmia).
- You have already been diagnosed with coronary artery disease, arrhythmia or another heart condition and your doctor is checking on the effectiveness of treatment and how the heart tolerates activity.
- You are recovering from a heart attack, heart surgery or angioplasty (a procedure to widen narrowed arteries) and a progress check is needed to check the heart’s function.
Complications during an exercise stress test are very rare. In the unlikely event of an emergency, our staff is exceptionally trained and our lab is fully equipped to provide any necessary interventions. Possible complications during an exercise stress test are:
- Falling getting on or off the exercise equipment
- Low blood pressure
- An abnormal heart rhythm
- A heart attack
- Death (extremely rare)
Many people do not need to make special preparations before having an exercise stress test. Just wear comfortable workout clothing and rubber-soled footwear. If you use an inhaler, bring it with you and let the doctor performing the test know that you use it.
You doctor will tell you if additional preparations are needed. For example:
- You may be asked to avoid eating, drinking and smoking for a period of time before the test.
- You may be asked to avoid caffeine, certain foods and certain over-the counter medications.
- You may be asked to adjust or discontinue certain medications before the test.
The Clinical Physiology Stress Testing Laboratory has multiple locations at Beth Israel Deaconess Medical Center. If you are scheduled to have a stress test, you will be given directions in your confirmation letter.
You should plan to be in the Clinical Physiology Stress Testing Laboratory for one to three hours, depending on the type of test you are having, but patients are usually on the treadmill for less than 15 minutes.
You will be joined in the Clinical Stress Testing Laboratory by a laboratory technologist and a clinical physiologist who are fully certified in cardiopulmonary resuscitation and advanced cardiac life support (ACLS). If you are also having an exercise echocardiogram, the echocardiography technologist will be there, too. If you are having a nuclear stress test, the nuclear medicine technologist will be present. A physician and an emergency response team are always available for immediate consultation.
Before the Test
First, you will meet the people who will be with you during the test. They will ask you some questions about your health history, smoking or smoking history, medications, symptoms you are experiencing, your weight, your age and your usual activity level. They will also explain the test and ask you to sign a consent form. Then, the technologist will place electrodes on the skin of your chest, arms and legs. Electrodes are sticky round patches that are attached to an electrocardiogram (EKG) machine, which measures and monitors your heart rate and heart rhythm throughout the test. The team will continuously monitor your blood pressure and EKG during the test, recording and documenting information that is needed by your physician. If you are having an echocardiogram, the echocardiography technician will perform that test before you start to exercise and immediately after you stop exercising. If you are having a nuclear stress test, the nuclear medicine technologist will provide appropriate care before, during and after your exercise.
During the Test
Exercise on the treadmill will begin, starting slowly and gradually increasing in intensity. While you are on the treadmill, your EKG will be monitored continuously and your blood pressure will be taken at regular intervals. The staff will also ask how you are feeling throughout the test. Be sure to speak up if you feel short of breath, dizzy, in pain, overheated or any other discomfort. To get the most accurate results, the goal is to get you to perform as much physical activity as you can, based on your age, weight, and health and activity history. This usually requires being on the treadmill from between seven and 12 minutes. However, if there is any clinical concern, your test will be stopped immediately. If you choose not to continue, we will stop the test at your request. Otherwise, we will continue until you are physically tired and cannot continue. You will probably begin to feel out of breath as the intensity of the exercise increases. Exactly when the test ends depends on your individual response. Every person is different, and your safety is our number one concern. The test will be stopped at the appropriate time to minimize any risks to you. The team will help you get off the treadmill and help you lie down. If you are having an echocardiogram, it will be performed immediately after you get off the treadmill. Your heart rate and blood pressure will be monitored until they return to baseline levels.
After the Test
The physician who ordered the test will give you the results, and the report will be available on PatientSite once it is finalized. Reports are generally available on PatientSite within 48 hours. If there is a serious concern, we will contact your physician with the results immediately.
If you are not able walk on the treadmill because of your health or mobility issues, the stress test can be performed using medications to evaluate your heart. Talk to your doctor about which variation of the test is best for you.
Radionuclide Stress Test
A radionuclide stress test, also call radionuclide myocardial perfusion scan, is a test that helps your doctor to determine if you have coronary artery disease (narrowing in the arteries that supply your heart with blood). If the heart muscle doesn’t get enough oxygen, you may have chest pain or angina. Because angina typically occurs while you are exercising, we often do this test with you walking/running on a treadmill. During this test, a radioactive material is used to take pictures of your heart. The substance is injected into your blood through an intravenous (IV) catheter and travels to the heart muscle. We then take pictures of your heart, which will help your doctor decide if you have coronary artery disease.
Do not smoke for two hours before this test. Do not eat or drink anything except water for two hours before this test. Do not eat or drink anything containing caffeine for at least 12 hours before your test, including cocoa and chocolate.
Over-the-counter medicines you should avoid taking:
Prescribed medications to avoid:
- Cafegot (all forms)
- Darvon Compound
- Synalog DC
- Wigraine (all forms)
You may be asked to decrease or stop certain medicines for this test. Follow your doctor’s instructions regarding medication. Do not stop your medication unless your doctor tells you to. You should start all your medicines again after the test is over. Please bring a complete listing of all your medicines with you. If you are a diabetic and take insulin or another diabetes medication, please check with your doctor for advice regarding doses before and after this test. Please bring your insulin or oral diabetes medicine to the hospital so you can take the dose recommended by your doctor.
Please wear comfortable clothes that break at the waist (a shirt or blouse) and flat, comfortable walking shoes or sneakers. Sneakers are strongly recommended. Electrodes will be placed on your chest so that your heart rhythm can be monitored during exercise. Women must remove their bras for the procedure. If you wear an unusually large or small size of clothing, please bring your own T-shirt and pants. You will be working hard during this test. Comfortable clothing will make things easier for you.
There are three parts to the test: Taking pictures, exercising, and taking more pictures.
For the first part of the test, we will put an intravenous (IV) line in your arm. This will feel like a pin prick like when you have blood drawn. The radioactive material is then injected through the IV. You will not feel anything from this injection. We will wait 30-45 minutes while the radioactive material circulates in your body. Then, while you are lying down, we will take pictures of your heart with a special camera for about 30 minutes.
For the second part of the test, you will exercise by walking on a treadmill. Every three minutes, the treadmill goes faster and the elevation is increased. Most people are on the treadmill for 7 to 10 minutes. Your heart will be monitored with an electrocardiogram (ECG), and we will take your blood pressure many times during this part of the test. A radioactive material will be injected into the IV about one minute before you stop exercising. You will not feel anything when the radioactive material is injected. We will again wait a short time while the radioactive material circulates in your bloodstream.
The third part of the test is taking more pictures. You will lie down as before and the camera will take pictures for about 30 minutes.
The test, including the imaging and exercise, takes a total of three to four hours. The vast majority of time is spent imaging. The total radiation exposure from this test is about 13 mSv.
All the pictures that result from the radionuclide exam are catalogued and stored as digital images. These are then displayed on specialized, high-resolution video monitors and interpreted by the nuclear medicine physician. The results of the radionuclide test results are generally available to your doctor within 24 business hours of your test. Your doctor will assess the test results along with your other tests, and then will explain the meaning of these results to you.