Heart CT scan

Answer 1

Definition

A computed tomography (CT) scan of the heart is an imaging method that uses x-rays to create detailed pictures of the heart and its blood vessels.

Alternative Names

CAT scan - heart; Computed axial tomography scan - heart; Computed tomography scan - heart; Calcium scoring; Multi-detector CT scan - heart; Electron beam computed tomography - heart

How the test is performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. You will lie on your back with your head and feet outside the scanner on either end.

Small electrodes will be placed on your chest and connected to an electrocardiograph (ECG) machine, which records your heart's electrical activity. You may be given medicine to slow your heart rate.

Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam in one continuous motion.)

Small detectors inside the scanner measure the amount of x-rays that make it through the heart. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of organs can be created by stacking the individual slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

The entire scan should only take about 10 minutes.

How to prepare for the test

Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast can highlight the heart, which creates a clearer image.

Contrast can be given through a vein (IV) in your hand or forearm. Some people have Allergies to IV contrast and may need to take medications before their test in order to safely receive this substance.

If contrast is used, you may also be asked not to eat or drink anything for 4 - 6 hours before the test.

If you weigh more than 300 pounds, have your doctor contact the scanner operator before the exam. CT scanners have a weight limit. Too much weight can cause damage to the scanner's working parts.

Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.

How the test will feel

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the test is performed

CT rapidly creates detailed pictures of the heart and its arteries. The test may be used to:

• Assess your risk for Heart disease by looking for the buildup of calcium plaque on the walls of the arteries that supply blood to the heart (coronary arteries)
• Find congenital heart disease
• Identify a blockage of the arteries that supply the heart
• Look for tumors of the heart

Based on the amount of plaque in the arteries, the health care provider will calculate your cardiac calcium score.

Normal Values

Results are considered normal if the heart and arteries being examined are normal in appearance.

If the calcium score is very low, you are unlikely to have coronary artery disease.

What abnormal results mean

Abnormal results may be due to:

• Aneurysm
• Congenital heart disease
• Coronary artery disease
• Narrowing of an artery (coronary artery stenosis)
• Tumors of the heart

What the risks are

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do create low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have heart disease.

The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting, sneezing, itching, or hives may occur. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

If you absolutely must be given such contrast, your doctor may choose to treat you with antihistamines (such as Benadryl) or steroids before the test.

The kidneys help filter the iodine out of the body. Therefore, those with kidney disease or Diabetes should receive plenty of fluids after the test, and be closely monitored for kidney problems. If you have diabetes or are on kidney dialysis, talk to your health care provider before the test about your risks.

Before receving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

References

Achenbach S, Daniel WG. Computed tomography of the heart. In: Libby P, Bonow RO, Mann DL, Zipes DP. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 18.

Huntzinger A. AHA guidelines on cardiac CT for assessing coronary artery disease. Am Fam Physician. 2008;77.

Answer 2

Definition

A computed tomography (CT) scan of the heart is an imaging method that uses x-rays to create detailed pictures of the heart and its blood vessels.

• This test is called a coronary calcum scan when it is done to see if you have a buildup of calcium in your arteries.
• It is called CT angiography if it is done to look at the arteries that bring blood to your heart.

Alternative Names

CAT scan - heart; Computed axial tomography scan - heart; Computed tomography scan - heart; Calcium scoring; Multi-detector CT scan - heart; Electron beam computed tomography - heart; Agaston score; Coronary calcium scan

How the test is performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. You will lie on your back with your head and feet outside the scanner on either end.

Small patches, called electrodes are put on your chest and connected to a machine that records your heart's electrical activity. You may be given medicine to slow your heart rate.

Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam without stopping.)

A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the heart can be created by stacking the slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

The entire scan should only take about 10 minutes.

How to prepare for the test

Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays.

• Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.
• Let your doctor know if you have ever had a reaction to contrast. You may need to take medications before the test in order to safely receive this substance.
• Before receiving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

If you weigh more than 300 pounds, find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the test will feel

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the test is performed

CT rapidly creates detailed pictures of the heart and its arteries. The test may diagnose or detect:

• Plaque build-up in the coronary arteries to determine your risk for heart disease
• Congenital heart disease (heart problems that are present at birth)
• Problems with the heart valves
• Blockage of the arteries that supply the heart
• Tumors of the heart

Normal Values

Results are considered normal if the heart and arteries being examined are normal in appearance.

Your doctor can use the results of this test to determine your "calcium score." The score is based on the amount of calcium found in the arteries of your heart.

The test is normal (negative) if your calcium score is 0.This means the chance of having a heart attack over the next 2 to 5 years is very low. If the calcium score is very low, you are unlikely to have coronary artery disease.

What abnormal results mean

Abnormal results may be due to:

• Aneurysm
• Congenital heart disease
• Coronary artery disease
• Heart valvue problems
• Inflammation of the covering around the heart (pericarditis)
• Narrowing of one or more coronary arteries (coronary artery stenosis)
• Tumors of the heart or surrounding areas

Your doctor may also give you a "calcium score" after this test. If your calcium score is high, it means you have calcium buildup in the walls of your coronary arteries. This is a sign of atherosclerosis, or hardening of the arteries. The higher your score, the more severe this condition may be. Talk to your doctor about the results of your heart CT scan and calcium score.

What the risks are

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Some people have allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

• The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting,sneezing, itching,or hives may occur.
• If you absolutely must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

References

Achenbach S, Daniel WG. Computed tomography of the heart. In: Libby P, Bonow RO, Mann DL, Zipes DP. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 18.

Taylor AJ, Cerqueira M, Hodgson JM, et al. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography: A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. Circulation. 2010 Nov 23;122(21):e525-55.

Reviewed By

Review Date: 03/06/2011

David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.; Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington.