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Cardiac Imaging

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What is a CT coronary angiogram?

A new test is available to diagnose coronary artery disease. In the past, noninvasive functional tests of the heart were used, such as treadmill tests and nuclear studies, to indirectly assess if there were blockages in the coronary arteries. The only way to directly look at the coronary arteries was via a cardiac catheterization and coronary angiogram.

CT scans have been used to look at various anatomic regions, but have not been useful for the heart because the heart is continuously in motion. CT is very effective in looking at "static" areas, such as the brain, abdominal cavity, and extremities. Most early CT scanners take 1-8 pictures (slices) a minute, much slower than the rate of the heart. Just as taking a picture of a moving object with a camera results in a blurry picture, conventional CT scans of the heart are not helpful. A new generation of CT scanners which can take 64 pictures a minute is now available; with the use of a little medication to slow the heart rate to less than 64, CT images of the coronary arteries are now possible.

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How is CT coronary angiogram performed and what are the risks of the procedure?

This procedure use intravenous dye which contains iodine and CT scanning to image the coronary arteries. While the use of catheters is not necessary (thus the term "noninvasive" test applies to this procedure), there are still some risks involved. In people allergic to iodine, pretreatment with medications is necessary to prevent allergic reactions to the dye. In people with abnormal kidney function and/or diabetes, the dye may worsen kidney function. Finally, there is radiation exposure which is similar to, if not greater than, that received with a conventional coronary angiogram. Nonetheless, this is generally a very safe test for most people, but should only be undergone when ordered by a physician familiar with the patient and their underlying medical condition.

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Who should get a CT coronary angiogram?

While CT angiography should not be used as a "screening" test in the general population, it is a major new tool in the diagnosis of coronary artery disease. In patients at high risk for developing coronary disease (cigarette smokers, those with genetic risk, high cholesterol levels, hypertension, or diabetes), who have unclear results with treadmill or other testing, or who have symptoms suspicious of coronary disease, CT angiography is an excellent next step in the diagnosis. If the CT scan is normal or only mildly abnormal, it makes the likelihood of a severe blockage of the coronary arteries extraordinarily small. Conversely, if the CT scan is significantly abnormal, cardiac catheterization and angiography are then indicated, to see if angioplasty, stenting, or coronary bypass surgery may be indicated.

In people who have had bypass surgery, CT angiography is very effective at evaluating the patency of the bypass grafts. In people who have had coronary stents , it is sometimes difficult to image the inside of the stent to see if it is narrowed. Due to these complexities, while CT coronary angiography is an exciting new modality, it is imperative to discuss with your physician if this is the correct test for you. As more experience is obtained, the indications for the test will become even clearer.

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CT Cardiac Imaging includes:

  • Coronary CT angiography

    • Diagnosis of non-calcified plaques

    • Diagnosis and quantification of coronary artery stenoses

    • Follow up after surgical bypass procedures

    • Evaluation of myocardial perfusion, scarring and contractility

  • Coronary calcium scoring

 Preparation/instructions

    When you were referred by your physician for a radiological exam, you may have been told about certain instructions to be done prior to the exam, or when you were scheduling your appointment, the scheduler should have informed you about the preparations that should be done prior to your exam. If you did not or if you want a recheck, you can refer to the information listed below.

    Keep in mind that you may have been given some additional or different instructions, based on your own particular circumstances. If you have any questions, please call  our hotline 16171 or (202) 3336-3310 (Mohandeseen), (202) 2417 5556 (Heliopolis) or (202) 2528 4888 (Maadi) to speak with a radiologist or cardiologist if you have any questions. It is best to call between 10 a.m. and 10 p.m., Saturday through Thursday.

Instructions

   You should not eat or drink anything for six hours prior to your scheduled exam.

Your heart rate should not exceed 70 beats/min. It it does you will be asked to take a beta blocker drug to reduce it to the required rate 30 minutes prior to the examination.

    Check with your doctor to see if this pertains to your exam. If you are diabetic and take insulin, you must consult with your doctor to adjust your dose. You should not take insulin if you are fasting for this examination. When making an appointment for this test, tell the person scheduling the study that you are diabetic and request an appointment early in the day.

    Medications can be taken prior to your exam. Pills should be taken with only a small amount of water. Bring with you a list of medications you take.

    If you are allergic to any type of food, iodine or X-ray contrast material (dye) you should notify the responsible radiologist or technician.

    You will be asked by one of our doctors about some information regarding your medical history. This information helps to structure your exam.

    If you have any heart, asthma, kidney problems, sickle cell disease, or if you are or could possibly be pregnant, please let the technologist know before your exam.

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The procedure

    Children under the age of 18 years need to be accompanied by an adult (parent or guardian). We strongly advise that CT patients not bring children along without another responsible supervising adult. We cannot provide supervision for the children.

    The procedure can take between 10-45 minutes depending on the exact test performed.

    You must remove earrings, glasses, hearing aids and dentures prior to your exam.

    You will need to have an IV line so that IV contrast can be given just before imaging begins. The contrast may make you feel warm all through your body. Some patients experience a metallic taste during the injection. These sensations last until the injection is completed.

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After Care

    After the exam you can resume your normal activities. If you received IV contrast you may want to increase your normal fluid intake to help flush this material from your system. Unless your doctor objects you should increase your fluid intake over a 24 hour time period.

    Results of your exams will be discussed with you by your doctor.

Please call our hotline 16171 or (202) 3336-3310 (Mohandeseen), (202) 2417 5556 (Heliopolis) or (202) 2528 4888 (Maadi) to speak with a radiologist if you have any questions. It is best to call between 10 a.m. and 10 p.m., Saturday through Thursday.

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Last modified: 17-06-2009