Computed Tomography, Cardiac Scoring


Computed Tomography, Cardiac Scoring

Synonym/acronym: Computed axial tomography (CAT), computed transaxial tomography (CTT), heart vessel calcium CT, helical/spiral CT, cardiac plaque CT.

Common use

To visualize and assess coronary artery status related to plaque buildup, associated with coronary artery disease and heart failure. Used as an evaluation tool for surgical, radiation, and medical therapeutic interventions.

Area of application

Heart.

Contrast

None.

Description

Cardiac scoring computed tomography (CT) is a noninvasive procedure used to enhance certain anatomic views of the heart for quantifying coronary artery calcium content. Coronary artery disease (CAD) occurs when the arteries that carry blood and oxygen to the heart muscle become clogged or built up with plaque. Plaque buildup slows the flow of blood to the heart muscle, causing ischemia and increasing the risk of heart failure. During the procedure, the patient lies on a motorized table. The table is moved in and out of a circular opening in a doughnut-like device called a gantry, which houses the x-ray tube and associated electronics. A beam of x-rays irradiates the patient as the table moves in and out of the scanner in a series of phases. Multiple detectors rotate around the patient to produce cross-sectional views or slices. The slices can be viewed individually or as a three-dimensional image. Multislice or multidetector CT (MDCT) scanners continuously collect images in a helical or spiral fashion instead of a series of individual images as with standard scanners. Helical CT is capable of collecting many images over a short period of time (seconds), is very sensitive in identifying small abnormalities, and produces high-quality images. Cardiac scoring is a noninvasive test. Differences in plaque density are detected and recorded and are viewable as computerized digital images. The scanner takes an image of the beating heart while the patient holds his or her breath for approximately 20 sec. The procedure requires no contrast medium injections. These density measurements are sent to a computer that produces a digital analysis of the anatomy, enabling the health-care provider (HCP) to look at the quantified amount of calcium (cardiac plaque score) in the coronary arteries. The data can be recorded on photographic or x-ray film or stored in digital format as digitized computer data. The Agatson score is the most frequently used scale to quantitate the amount of calcium in atherosclerotic plaque. Higher scores, greater than 100, are associated with a higher risk of death from cardiac causes.

This procedure is contraindicated for

  • high alertPatients who are pregnant or suspected of being pregnant, unless the potential benefits of a procedure using radiation far outweigh the risk of radiation exposure to the fetus and mother.
  • high alertPatients who are claustrophobic.

Indications

  • Detect and quantify coronary artery calcium content
    • CAD is the leading cause of death in most industrialized nations.
    • Cardiac scoring is a more powerful predictor of CAD than cholesterol screening.
    • Of all myocardial infarctions (MIs), 45% occur in people younger than age 65.
    • Of women who have had MIs, 44% will die within 1 yr after the attack.
    • Women are more likely to die of heart disease than of breast cancer.
  • Family history of heart disease
  • Screening for coronary artery calcium in patients with:
    • Diabetes
    • High blood pressure
    • High cholesterol
    • High-stress lifestyle
    • Overweight by 20% or more
    • Personal history of smoking
    • Sedentary lifestyle
  • Screening for coronary artery plaque in patients with chest pain of unknown cause

Potential diagnosis

Normal findings

  • If the score is 100 or less, the probability of having significant CAD is minimal or is unlikely to be causing a narrowing at the time of the examination.

Abnormal findings related to

  • If the score is between 100 and 400, a significant amount of calcified plaque was found in the coronary arteries. There is an increased risk of a future MI, and a medical assessment of cardiac risk factors needs to be done. Additional testing may be needed.
  • If the score is greater than 400, the procedure has detected extensive calcified plaque in the coronary arteries, which may have caused a critical narrowing of the vessels. A full medical assessment is needed as soon as possible. Further testing may be needed, and treatment may be needed to reduce the risk of MI.

Critical findings

    N/A

Interfering factors

  • Factors that may impair clear imaging

    • Retained barium or radiological contrast from a previous radiological procedure.
    • Metallic objects (e.g., jewelry, body rings) within the examination field, which may inhibit organ visualization and cause unclear images.
    • Improper adjustment of the radiographic equipment to accommodate obese or thin patients, which can cause overexposure or underexposure and a poor-quality study.
    • Patients with extreme claustrophobia unless sedation is given before the study.
    • Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status.

  • Other considerations

    • The procedure may be terminated if chest pain or severe cardiac arrhythmias occur.
    • Consultation with the HCP should occur before the procedure for radiation safety concerns regarding younger patients or patients who are lactating. Pediatric & Geriatric Imaging Children and geriatric patients are at risk for receiving a higher radiation dose than necessary if settings are not adjusted for their small size. Pediatric Imaging Information on the Image Gently Campaign can be found at the Alliance for Radiation Safety in Pediatric Imaging (www.pedrad.org/associations/5364/ig/).
    • Risks associated with radiation overexposure can result from frequent x-ray procedures. Personnel in the room with the patient should wear a protective lead apron, stand behind a shield, or leave the area while the examination is being done. Personnel working in the examination area should wear badges to record their level of radiation exposure.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in assessing the coronary arteries for the presence of plaque.
  • Obtain a history of the patient’s complaints or clinical symptoms, including a list of known allergens, especially allergies or sensitivities to latex, anesthetics, or sedatives.
  • Obtain a history of patient’s cardiovascular system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results, including examinations using barium- or iodine-based contrast medium. Ensure that barium studies were performed more than 4 days before the CT scan.
  • Record the date of the last menstrual period and determine the possibility of pregnancy in perimenopausal women.
  • Obtain a list of the patient’s current medications, including anticoagulants, aspirin and other salicylates, herbs, nutritional supplements, and nutraceuticals (seeEffects of Natural Products on Laboratory Values online at DavisPlus). Note the last time and dose of medication taken.
  • Review the procedure with the patient. Address concerns about pain and explain that there may be moments of discomfort and some pain experienced during the test. Inform the patient the procedure is usually performed in a radiology suite by an HCP specializing in this procedure, with support staff, and takes approximately 30 to 60 min.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Explain that an IV line may be inserted to allow infusion of IV fluids (e.g., normal saline), anesthetics, or sedatives.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction. Protocols may vary among facilities.
  • Instruct the patient to remove all external metallic objects from the area to be examined.

Intratest

  • Potential complications:

  • Establishing an IV line is an invasive procedure. Complications are rare but do include risk for hematoma related to blood leakage into the tissue following insertion of the IV needle or infection that might occur if bacteria from the skin surface is introduced at the IV needle insertion site.

  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Ensure the patient has complied with pretesting preparations.
  • Ensure that the patient has removed all external metallic objects from the area to be examined.
  • Administer ordered prophylactic steroids or antihistamines before the procedure if the patient has a history of allergic reactions to any substance or drug.
  • Have emergency equipment readily available.
  • Instruct the patient to void prior to the procedure and to change into the gown, robe, and foot coverings provided.
  • Instruct the patient to cooperate fully and to follow directions. Instruct the patient to remain still throughout the procedure because movement produces unreliable results.
  • Record baseline vital signs, and continue to monitor throughout the procedure. Protocols may vary among facilities.
  • Establish an IV fluid line for the injection of emergency drugs and sedatives.
  • Administer an antianxiety agent, as ordered, if the patient has claustrophobia. Administer a sedative to a child or to an uncooperative adult, as ordered.
  • Place the patient in the supine position on an examination table. A rapid series of images is taken of the vessels to be examined.
  • Instruct the patient to inhale deeply and hold his or her breath while the x-ray images are taken, and then to exhale after the images are taken.
  • Instruct the patient to take slow, deep breaths if nausea occurs during the procedure.
  • The IV needle is removed, and a pressure dressing is applied over the puncture site.
  • Observe/assess the needle site for bleeding, inflammation, or hematoma formation.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Instruct the patient to resume usual diet, fluids, medications, and activity, as directed by the HCP.
  • Instruct the patient in the care and assessment of the IV site.
  • Instruct the patient to apply cold compresses to the insertion site as needed, to reduce discomfort or edema.
  • Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Nutritional Considerations: Abnormal findings may be associated with cardiovascular disease. Nutritional therapy is recommended for the patient identified to be at risk for developing CAD or for individuals who have specific risk factors and/or existing medical conditions (e.g., elevated LDL cholesterol levels, other lipid disorders, insulin-dependent diabetes, insulin resistance, or metabolic syndrome). Other changeable risk factors warranting patient education include strategies to encourage patients, especially those who are overweight and with high blood pressure, to safely decrease sodium intake, achieve a normal weight, ensure regular participation in moderate aerobic physical activity three to four times per week, eliminate tobacco use, and adhere to a heart-healthy diet. If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The 2013 Guideline on Lifestyle Management to Reduce Cardiovascular Risk published by the American College of Cardiology (ACC) and the American Heart Association (AHA) in conjunction with the National Heart, Lung, and Blood Institute (NHLBI) recommends a “Mediterranean”-style diet rather than a low-fat diet. The new guideline emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed) along with fish and lean poultry. A similar dietary pattern known as the Dietary Approach to Stop Hypertension (DASH) diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium.
  • Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population ages 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the child and caregiver regarding health risks and weight control education.
  • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Heart Association (www.americanheart.org) or the NHLBI (www.nhlbi.nih.gov).
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be needed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include antiarrhythmic drugs, apolipoprotein A and B, AST, atrial natriuretic peptide, BNP, BUN, calcium, chest x-ray, cholesterol (total, HDL, LDL), CRP, CBC, CBC hematocrit, CBC hemoglobin, coronary angiography, CT thorax, CK and isoenzymes, creatinine echocardiography, echocardiography transesophageal ECG, glucose, glycated hemoglobin, Holter monitor, homocysteine, ketones, LDH and isoenzymes, lipoprotein electrophoresis, lung scan, magnesium, MRI chest, MI scan, myocardial perfusion heart scan, myoglobin, PET heart, potassium, PT/INR, triglycerides, and troponin.
  • Refer to the Cardiovascular System table at the end of the book for related tests by body system.