Frequently Asked Questions

Heart & Vascular Institute of Texas FAQ

What is a Holter Electrocardiogram?

Your doctor has ordered a Holter Electrocardiogram (ECG). You are probably curious to know exactly what a Holter ECG is, what the recorder is for and what you are expected to do during the test.

A Holter ECG is a relatively simple, and painless procedure. There is nothing to be afraid of or to worry about. Your doctor will arrange for a technician to connect you to a small lightweight portable recording unit that you will wear from 24 to 48 hours, depending on your doctor’s instructions. Monitoring electrodes will be put on your chest. These will pick up the signals from your heart and transfer them to the recorder, where a tape recording of the signals will be made. The recording will later be transformed into a report which your doctor will analyze.

The Holter ECG is basically a continuous electrocardiogram taken while you are performing your normal daily activities. This differs from a normal ECG in that a normal ECG records only a very small portion of your heart’s activity, less than of 1% of your daily heart beats. The normal ECG is also taken while you are at rest and, therefore, does not show how your heart will react to the stressful situations of normal daily life.

The reason for the Holter ECG is to provide your physician with a record of how your heart reacted to each stressful or unusual situation during the day as well as at rest situations.

You will be provided a diary to record the events that occur throughout the day. This diary will provide your doctor with a means of correlating the recording results with the various events that occurred during the day. He will look at the activities and symptoms you list and will see how your heart reacted during each of these events. It is extremely important that you record your daily activities and symptoms accurately.

What can I do while wearing the Holter?

The recorder you will be wearing should not interfere with your normal routine and there are only a few restrictions while you are wearing it. Obviously, you should not tamper with the recorder, electrodes or lead wires. You should not take a shower or bath or get the electrodes or recorder wet in any way. If you are wearing the recorder at night, you should not use an electric blanket, as it may interfere with the recording. If the electrodes do come loose, secure them with tape.

When the test is complete you will return to the doctors office who will remove the recorder and electrodes and take the diary from you. He will then process that day or the next the recording via a sophisticated, high speed computer resulting in a report highlighting various portions of the recording.

He will use this information along with your past medical history and results from other tests to make the most accurate diagnosis of your condition and provide the best medical care possible.

What do I need to know prior to my Exercise Treadmill Test?

The following are instructions for an Exercise Treadmill Test:

  • Medications
    Please take all medications as prescribed by your physician with exception of diabetic medications (insulin/pills) which need physician instructions.
  • Meals
    NO Caffeine (i.e. coffee, tea, cola), NO Alcohol, and NO Smoking (i.e. cigars, cigarettes, pipes, chewing tobacco) from Midnight until the time of the test.
  • Test Schedule
    If your exercise treadmill test is scheduled for the morning, DO NOT eat breakfast.


    If your exercise treadmill test is scheduled for the afternoon, DO NOT eat for at least four (4) hours before the test. Breakfast should be light (cereal, toast, juice). Lunch should also be light (fruit, salad, juice).

  • What to Wear
    Wear or bring appropriate clothing, rubber-soled running, flat or walking shoes are needed (no slippers, clogs or thongs). Pant legs should not be excessively long so as to get caught in the moving equipment.
  • Men – Should bring or wear gym shorts, Bermuda shorts or plain loose-fitting trousers, and shirts that button in the front.
  • Women – Should bring or wear short-sleeved, loose-fitting blouses that button in the front, and shorts or loose-fitting trousers. No one-piece undergarments or panty hose should be worn.
  • Post Test
    After your exercise treadmill test, do not plan to engage in vigorous activity. Delay hot showers for at least two hours, and eat a light meal afterwards.

What do I need to know about my Examination & Stress Test?

Your physician has scheduled a special examination of your heart. This test is performed after an intravenous catheter is placed. This is used for injection(s) of radioactive tracer that allows a scanner to take images of the heart. This procedure also includes a stress test either performed on a treadmill or if you are unable to walk, a medication will be used which will obtain similar results to that achieved by a treadmill stress. The radioactive tracers are not dyes containing Iodine, they are short-lived isotopes, which decay rapidly and also excrete from the body through the urine and feces.

Arrival Time: Please arrive 15 minutes prior to your appointment.

**Approximate time for test is 1-2 hours.**


Please follow these instructions carefully:

  • You may NOT have anything to eat or drink for at least four (4) hours before the exam. NO coffee, tea, soda, chocolate or any other foods or liquids containing caffeine should be consumed at least twenty-four (24) hours prior to the exam. NO ALCOHOL & SMOKING (i.e. cigars, cigarettes, pipes, chewing tobacco) FROM MIDNIGHT PREVIOUS DAY TO TIME OF THE TEST.
  • Wear comfortable clothing. These can be loose fitting garment, (T-shirts, Button down shirts, sweats, etc.) DO NOT WEAR ONE-PIECE GARMENTS, since you will be connected to an ECG during the stress part of the exam.
  • If you are walking on the treadmill, please wear comfortable shoes (rubber-soled running, flat, or walking shoes). DO NOT wear slippers, slides, clogs, or thongs.
  • Continue to take your medications as prescribes, unless otherwise ordered by your physician. Take your medications with a sip of water.
  • If you are diabetic, please bring a snack to eat after the exam and insulin should be regulated by physician order. DO NOT TAKE DIABETIC MEDICATIONS THE MORNING OF EXAM, PLEASE BRING MEDICATIONS WITH YOU.
  • Should you have to cancel your appointment, please notify the scheduling department at 210-804-6000. PLEASE GIVE AT LEAST 24 HR NOTICE AS A SPECIAL MEDICATION IS ORDERED AND CANNOT BE REUSED OR STORED.

What is a Nuclear Stress Test?

A nuclear stress test shows how well blood flows through your heart and arteries while you are resting and during physical exertion. In this test, a small amount of radioactive substance is injected into your body. This substance allows images of the heart to be recorded so that your doctor can see:

  • How well the heart is pumping blood
  • If a part of the heart has been damaged
  • If any of the arteries that feed the heart are blocked


What happens during the test?

Two sets of images will be taken, one while you are resting and one after you have exercised. This test is usually done in a special area called a lab. Images will be taken while you are resting:

You will be asked to lie down on an examining table. An IV will be placed into a vein in your arm or hand. A radioactive substance will then be injected through the IV. You will need to lie still with your arms above your head for a few minutes to allow the substance to circulate through your body.

You may be taken to another area of the lab where a special camera reads traces of the radioactive substance and sends images to a monitor. By looking at the monitor your doctor can see how blood flows through your heart and arteries.

Your exercise test

Before the exercise party of the test, small disks called electrodes will be placed on your chest. The electrodes are connected to an electrocardiogram machine. An electrocardiogram charts your heart’s electrical activity.

You will then walk on a treadmill or ride a stationary bike for a few minutes. Your rate of exercise will slowly increase.

You will be asked how you are feeling. Be sure to report any symptoms you may have, such as pain or discomfort in your chest, arm or jaw, shortness of breath or dizziness.

If you are unable to exercise, you will be given medications that cause the heart and blood vessels to react as they would during exercise. The medications may cause sensations such as tightness in the throat and chest along with a hot, flushed feeling. This is normal and will go away in 4-5 minutes.

Images will be taken after you have exercised:
After several minutes, you will be given another injection of the radioactive substance.

You will be asked again to lie down for another scan of your heart. Images taken at this time show how blood moves through the arteries to all areas of the heart during physical exertion. Your doctor will compare the images that were taken before and after exercise.

The test results will be discussed with you after your doctor has had a chance to review all of the information.

Your doctor’s recommendation

Feeling uncertain about your health can be stressful for you and your family. Because you have had this test, you know that any advice about treatment is based on facts discovered during your test. You may be advised to have more tests or you may need medication or a surgical or nonsurgical treatment. Whatever your doctor’s recommendation, you can rest assured that it is based on the best possible information.

  • Do not eat or drink anything for 4-6 hours before your test.
  • Do not eat or drink any caffeinated products (like cola, Mountain Dew, tea, coffee or chocolate) for 12 hours before the test.
  • Report all of the medications you take. Ask if you should stop taking any of your medications before the test. Some medications, such as blood pressure medication, nitroglycerin and beta blockers can interfere with the test.
  • Do not take over-the-counter medications that contain caffeine before your test. Some medications (diet, pills, Anacin, Excedrin, Vanquish) contain caffeine.
  • If are pregnant or nursing, tell the staff before your test.


For people with diabetes

If you take insulin, ask your doctor what amount you should take the day of your test. If you take diabetes pills, do not take your medication until after your test.

  • A nuclear stress test usually takes about 2 to 3 hours.
    • Ask your doctor when you can eat and drink.
    • Ask your doctor when you can take your medications.
    • Ask your doctor when you can return to your normal activities.

It is important to note that the radioactive substance used in this test is safe and will not harm your body. The substance will leave your body within a few hours.

Your test results

The heart normally pumps more blood during times of physical exertion. If the test shows that blood flow is normal while you are resting, but not normal while you are exercising, your heart may not be getting enough blood during physical exertion.

If blood flow is not normal during rest and exercise, this may mean that a section of the heart muscle has been permanently damaged or that one or more of the arteries that supply part of your heart with blood may be blocked.

Test results will be discussed with you after your doctor has had a chance to review all of the information.

What is a Cardiac Event Recorder?

Use of the Retrospective 30-day cardiac event recorder:

  • First and foremost…
    The recorder is designed to document symptoms and is not an intervention device. If you feel in peril, you should follow whatever emergency precautions given to you by your physician. Push the Symptom button first, then seek help.
  • When to wear the recorder…
    During daytime and sleeping hours, but not during bathing or showers. When bathing, the electrodes (only) may be left on. Water will not hurt them.
  • When to remove the recorder…
    Only during bathing. The purpose of the test is to capture unexpected cardiac arrhythmias that occur before the push of the button. If the recorder is not in place before the button is pushed, the data will be missed. Thus, it must be worn continuously to ensure its availability at the time of need.
  • When to push the button…
    Whenever you feel the symptom your doctor is trying to document. Obviously, unrelated symptoms are not useful, but anything you feel that may be heart related is a valid event. Push the button and call us.
  • How many times should I transmit?
    The typical patient will make 5-10 transmissions during the 30-day period, but there is no limit. On some, we’ll catch the event within the first few transmissions. Others will be caught later, maybe even on the 30th day.
  • When should I make the transmission?
    After every push of the button, as soon as you can reasonably get to a phone.
  • What are the hours that calls can be made?
    Receiving personnel are available 24 hours per day, 365 days per year. Even Sundays and holidays.
  • What number should I dial?
    800-327-7366. cec/CDC uses a double back-up telephone receiving system to minimize potential problems. Our primary receiver is in Milwaukee and our secondary center is in Cleveland. This provides us redundancy in the event of power or communication failures in a particular city. Our patient database is duplicated at both sites.
  • What if I receive no answer, or an answering machine?
    That should never happen, unless you’ve misdialed. Try calling again. You should reach a real, live person at one of the two centers. None of our patient lines are unattended or have an answering machine.
  • If you get the message
    We’re sorry, all circuits are busy. Please call again later.


    That means that the telephone company circuits are busy; not ours. Please wait a few minutes and try calling again. Your ECG data will remain in the recorder for hours or days (providing the battery is not removed), so it is not mandatory that it be transmitted immediately.

  • If you get our 24-hour back-up answering service
    That means that all of our receiving lines are busy, and your call was diverted to a message center. This should rarely occur, if ever at all. Please leave your name and phone number with the person answering the phone and the first available nurse will return your call. Stay off your phone so we can reach you (unless, of course, you are calling for emergency help).


    If you do not receive a call back within 15 minutes, please call again as we may be having trouble reaching you. Make sure you give the operator the phone number you are currently at, especially if not at home.

  • When should I return the recorder?
    At the end of the 30-day period, or when your doctor advises. Remember, like a library book, it is your responsibility to return the recorder or the monthly service charges will continue. Loss of the recorder is also the patient’s responsibility, so please do not let it out of your possession.