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DESCRIPTIONContrast-enhanced computed tomography angiography (CTA) is a noninvasive imaging test that requires the use of intravenously administered contrast material and high-resolution, high-speed CT machinery to obtain detailed volumetric images of blood vessels. CTA can be applied to image blood vessels throughout the body; however, for the coronary arteries, several technical challenges must be overcome to obtain high-quality diagnostic images. First, very short image acquisition times are necessary to avoid blurring artifacts from the rapid motion of the beating heart. In some cases, premedication with beta-blocking agents is used to slow the heart rate below approximately 60–65 beats per minute to facilitate adequate scanning, and electrocardiographic triggering or gating (retrospective or prospective) is used to obtain images during diastole when motion is reduced. Second, rapid scanning is also helpful so that the volume of cardiac images can be obtained during breath-holding. Third, very thin sections (1 mm or less) are important to provide adequate spatial resolution and high-quality 3D reconstruction images.
Volumetric imaging permits multiplanar reconstruction of cross-sectional images to display the coronary arteries. Curved multiplanar reconstruction and thin-slab maximum intensity projections provide an overview of the coronary arteries, and volume-rendering techniques provide a 3D anatomical display of the exterior of the heart. Two different CT technologies can achieve high-speed CT imaging. Electron beam CT (EBCT, also known as ultrafast CT) uses an electron gun rather than a standard x-ray tube to generate x-rays, thus permitting very rapid scanning, on the order of 50–100 milliseconds per image. Helical CT scanning (also referred to as spiral CT scanning) also creates images at greater speed than conventional CT by continuously rotating a standard x-ray tube around the patient so that data are gathered in a continuous spiral or helix rather than as individual slices. Helical CT is able to achieve scan times of 500 milliseconds or less per image, and use of partial ring scanning or post-processing algorithms may reduce the effective scan time even further.
Multidetector row helical CT (MDCT) or multislice CT scanning is a technologic evolution of helical CT, which uses CT machines equipped with an array of multiple x-ray detectors that can simultaneously image multiple sections of the patient during a rapid volumetric image acquisition. MDCT machines currently in use have 64 or more detectors.
A variety of noninvasive tests are used in the diagnosis of coronary artery disease. They can be broadly classified as those that detect functional or hemodynamic consequences of obstruction and ischemia (exercise treadmill testing, myocardial perfusion imaging [MPI], stress echo with or without contrast), and others identifying the anatomic obstruction itself (cardiac CTA and coronary magnetic resonance imaging [MRI]). Functional testing involves inducing ischemia by exercise or pharmacologic stress and detecting its consequences. However, not all patients are candidates. For example, obesity or obstructive lung disease can make obtaining echocardiographic images of sufficient quality difficult. Conversely, the presence of coronary calcifications can impede detecting coronary anatomy with cardiac CTA. Accordingly, some tests will be unsuitable for particular patients.
Evaluation of obstructive coronary artery disease (CAD) involves quantifying arterial stenoses to determine whether significant narrowing is present. Lesions with greater than 50% to 70% diameter stenosis accompanied by symptoms are generally considered significant and often result in revascularization procedures. It has been suggested that cardiac CTA may be helpful to rule out the presence of CAD and to avoid invasive coronary angiography (ICA) in patients with a low clinical likelihood of significant CAD. Also of note is the interest in the potential important role of non-obstructive plaques (i.e., those associated with <50% stenosis) because their presence is associated with increased cardiac event rates. Cardiac CTA can also visualize the presence and composition of these plaques and quantify the plaque burden better than conventional angiography, which only visualizes the vascular lumen. Plaque presence has been shown to have prognostic importance.
The information sought from angiography after coronary artery bypass graft surgery may depend on the length of time since surgery. Bypass graft occlusion may occur during the early postoperative period; whereas, over the long term, recurrence of obstructive CAD may occur in the bypass graft, which requires a similar evaluation as CAD in native vessels.
Congenital coronary arterial anomalies (i.e., abnormal origination or course of a coronary artery) that lead to clinically significant problems are relatively rare. Symptomatic manifestations may include ischemia or syncope. Clinical presentation of anomalous coronary arteries is difficult to distinguish from other more common causes of cardiac disease; however, an anomalous coronary artery is an important diagnosis to exclude, particularly in young patients who present with unexplained symptoms (e.g., syncope). There is no specific clinical presentation to suggest a coronary artery anomaly.
Cardiac CTA has several important limitations. The presence of dense arterial calcification or an intracoronary stent can produce significant beam-hardening artifacts and may preclude a satisfactory study. The presence of an uncontrolled rapid heart rate or arrhythmia hinders the ability to obtain diagnostically satisfactory images. Evaluation of the distal coronary arteries is generally more difficult than visualization of the proximal and mid-segment coronary arteries due to greater cardiac motion and the smaller caliber of coronary vessels in distal locations.
Radiation delivered with current generation scanners utilizing reduction techniques (prospective gating and spiral acquisition) has declined substantially—typically to under 10 mSv. For example, an international registry developed to monitor cardiac CTA radiation recently reported a median 2.4 mSv (interquartile range, [IQR]: 1.3 to 5.5) exposure. In comparison, radiation exposure accompanying rest-stress perfusion imaging ranges varies according to isotope used—approximately 5 mSv for rubidium-82 (positron emission tomography, PET), 9 mSv for sestamibi (single-photon emission computed tomography, SPECT), 14 mSv for F-18 FDG (fludeoxyglucose) (PET), and 41 mSv for thallium; during diagnostic invasive coronary angiography, approximately 7 mSv will be delivered. EBCT using electrocardiogram (ECG) (EKG) triggering delivers the lowest dose (approximately 0.7 to 1.1 mSv with 3-mm sections). Any cancer risk due to radiation exposure from a single cardiac imaging test depends on age (higher with younger age at exposure) and gender (greater for women). Empirical data suggest that every 10 mSv of exposure is associated with a 3% increase in cancer incidence over 5 years.
The use of Computed Tomography to Detect Coronary Artery Calcification (Electron-beam CT) is addressed in a separate policy.
POLICYI. Provider Accreditation for CCTA – Network Providers
Effective 01/01/2013, all Network Providers billing the technical component of the CT must be accredited in Coronary CTA by the Intersocietal Accreditation Commission (IAC) or a Cardiac CT module by the American College of Radiology (ACR). The professional component of the CT will be reimbursed based upon the accreditation of the facility as the ACR and the IAC facility accreditations require that interpreting professional physicians also be accredited by the ACR or Society of Cardiovascular Computed Tomography, respectively.
II. Medically Necessary CCTA
A diagnosis of chest pain (acute or non-acute) is not in itself an eligible indication for performing CCTA. CCTA using a 64-slice or greater CT scanner is considered medically necessary for the following:
A. Detection of CAD in Symptomatic Patients
1. Evaluation of chest pain syndrome
2. Evaluation of intra-cardiac structures
3. Acute chest pain
4. Abnormal electrocardiogram (ECG) (EKG)
Table A. Pre-test Probability of CAD by Age, Gender and Symptoms
B. Detection of CAD with Prior Test Results
1. Evaluation of chest pain syndrome
C. Evaluation of Acute Chest Pain in the Emergency Room/Emergency Department
1. Evaluation of acute chest pain in the Emergency Room/Emergency Department for patients with intermediate pre-test probability of CAD (see Table A) that meet ALL of the following criteria:
D. Evaluation of Cardiac Structure and Function
2. Evaluation of intra- and extra-cardiac structures
3. Evaluation of aortic and pulmonary disease
III. Not Medical Necessary CCTA
The following are considered not medically necessary for CCTA:
IV. Relative Contraindications to CCTA
The following are relative contraindications to CCTA:
POLICY EXCEPTIONSState Health Plan (SHP) Members: The Provider Accreditation requirements do not apply to SHP members. However, the medical necessity criteria outlined in the Policy section must be met for SHP members.
Federal Employee Program (FEP) Members: The Provider Accreditation requirements do not apply to FEP members. For FEP members, contrast-enhanced computed tomographic angiography for evaluation of anomalous (native) coronary arteries in symptomatic patients may be considered medically necessary when conventional angiography is unsuccessful or equivocal and when the results will impact treatment. Also, contrast-enhanced computed tomographic angiography for the evaluation of patients without known coronary artery disease and acute chest pain in the emergency room/emergency department setting is considered medically necessary.
POLICY GUIDELINESOnly one professional component and one technical component will be allowed for the performance of CCTA.
Investigative service is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized by certifying boards and/or approving or licensing agencies or published peer review criteria as standard, effective medical practice for the treatment of the condition being treated and as such therefore is not considered medically necessary.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
POLICY HISTORY12/17/2012: New policy approved by Cardiology Physician Advisory Committee. Effective 01/01/2013.
SOURCE(S)Cardiology Physician Advisory Committee
Blue Cross Blue Shield Association Policy # 6.01.43
Cardiac Computed Tomography (CCT), Cardiac Computed Tomography Angiography (CCTA) medical policy, Blue Cross and Blue Shield of Alabama
Computed Tomography, Cardiac and Coronary Artery medical policy, Arkansas Blue Cross and Blue Shield
Framingham Heart Study Coronary Heart Disease Risk Factors: http://www.framinghamheartstudy.org/risk/coronary.html
Intersocietal Accreditation Commission (IAC) CT/ICACTL Standards and Guidelines for CT Accreditation, August 2012.
This may not be a comprehensive list of procedure codes applicable to this policy.
The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.