LCD L33457: Cardiac Radionuclide Imaging

The 2 types of radionuclide studies commonly used for cardiac evaluation are myocardial perfusion imaging (MPI) and cardiac blood pool imaging (multiple gated acquisition scanning (MUGA), ventriculography). MPI is used primarily for the evaluation of coronary artery disease (CAD). Ventriculography is sometimes referred to as MUGA or cardiac blood pool imaging and is primarily used to evaluate valvular disease and cardiomyopathies. Either type of study may be obtained at rest or with stress. Stress may be provided by exercise or with pharmacologic agents.

MPI is a diagnostic procedure that evaluates blood flow to cardiac muscle using radionuclides. A gamma camera is used to record images in planar or tomographic (single photon emission computed tomography (SPECT)) projections. Use of dual radiopharmaceuticals permit concurrent studies at rest and after stress, which are then compared and interpreted by a nuclear physician. Since the radiopharmaceutical accumulates in the myocardium in relation to blood flow, ischemic and infarcted myocardium can be detected.

With the use of technetium based radiopharmaceuticals, the perfusion imaging may be linked to acquisition of “first pass” data to visualize blood flow through the right heart, lungs and left heart giving diagnostically useful information about cardiac chamber shunts, wall motion, cardiac output, ejection fraction (EF), left ventricular volume, shunt fraction and valvular regurgitation.

Positron emission tomography (PET) scans performed for the diagnosis and management of patients with known or suspected CAD, using the Food and Drug Administration (FDA) approved Rubidium 82 (Rb 82) , are covered when the following conditions are met:

• The PET scan (at rest or rest with stress) is performed in place of SPECT; or

• Is performed following an inconclusive SPECT (results that are equivocal, technically uninterpretable, or discordant with the patient’s other clinical data).

In such cases, the PET scan must have been determined to be medically necessary to guide further treatment of the patient.

When a PET scan is performed as an additional diagnostic test in the instance of an equivocal SPECT, the reason for performing the PET scan must be clearly documented in the patient’s record.

The following studies are considered investigational and will not be covered:

• Ambulatory radionuclide cardiac monitoring

• Monoclonal anti-myosin imaging

• Radionuclide imaging of thrombi

• Radionuclide imaging of cardiac adrenergic nerves

Myocardial Perfusion Imaging

Patients with a high pretest probability of disease are usually not candidates for this study unless determination of the size and reversibility of a defect are required for clinical decision making. Patients whose diagnosis is in question benefit most from this study. Patients with a low pretest probability of disease are usually not studied except when a prior exercise stress test by treadmill electrocardiogram (ECG) or echocardiogram (echo) is a presumed false positive. Stress MPI, preceded by satisfactory stress echo, is not medically necessary.

Indications for Myocardial Perfusion Imaging

1. Acute myocardial infarction (AMI) - MPI is not typically performed during the acute period of myocardial infarction (MI), if the diagnosis is established by other means. In selected patients, imaging is appropriate in the assessment of:

• Disease severity

• Risk assessment and/or prognosis

• Efficacy of acute reperfusion therapy

• Evidence of myocardial salvage

• Suspected infarction when the combination of history and other tests is not diagnostic

2. Unstable angina - MPI may be useful as an adjunct to other tests in the diagnosis or treatment of unstable angina only when the combination of history and other tests is not diagnostic. In selected patients, imaging is appropriate for:

• Identification of ischemia in the distribution of a known lesion or in remote areas

• Identification of the severity/extent of disease in patients with medically unstable angina or ongoing ischemia

• Measurement of left ventricular function (LVF)

3. Chronic ischemic heart disease - The use of MPI is well established in the diagnosis and management of CAD and is covered in these situations:

• Diagnosis of CAD, especially in patients with atypical chest pain

• Evaluation of abnormal or suspected false positive stress ECG

• Evaluation of other symptoms suspicious for the diagnosis of CAD such as syncope and ventricular arrhythmia

• Assessment of myocardial viability after revascularization or medical management

• Planning percutaneous transluminal coronary angioplasty (PTCA) to identify lesions causing ischemia, if unknown

• Evaluation of suspected or known CAD prior to high risk surgical procedure

• Identification of the presence, location, extent, and severity of myocardial ischemia

• Assessment of drug therapy

• Assessment of symptoms suggesting restenosis following PTCA

• Assessment of symptoms suggesting ischemia following coronary artery bypass graft (CABG)

• Follow up of symptomatic ischemic heart disease

4. Congenital heart disease (CHD) - Echo is the method of choice for evaluating patients with known or suspected CHD. Selected patients may benefit from MPI when assessing for:

• Diagnosis of anomalies of the coronary circulation

• Kawasaki’s disease

5. Post-transplant cardiac disease

• Assessment of coronary arteriopathy

• Evaluation for ventricular dysfunction with post-transplant rejection

Cardiac Blood Pool Imaging (MUGA, Ventriculography)

These services are allowed for the evaluation of ventricular size, wall motion, stroke volume, and EF when this information is medically necessary to direct further evaluation and management of the cardiac condition.

Indications for Cardiac Blood Pool Imaging (MUGA, Ventriculography)

1. Cardiomyopathy - Cardiac blood pool imaging (MUGA, ventriculography) is covered for:

• Diagnosis of hypertrophic cardiomyopathy and/or myocardial ischemia

• Differentiation of ischemic from non-ischemic cardiomyopathy

2. Post-transplant cardiac disease

• Assessment of coronary arteriopathy

• Evaluation for ventricular dysfunction with post-transplant rejection

3. Assessment of cardiac function for cardiotoxic chemotherapy

• A. One baseline study is considered medically necessary prior to the initiation of cardiotoxic chemotherapy when 1 of the following conditions is met:

1. No echo is planned or performed

2. Prior echo is uninterpretable due to poor visualization window

• B. Cardiac function monitoring during or at the completion of cardiotoxic chemotherapy. Cardiotoxic chemotherapy includes any of the following medications:

· 5-FU (5 fluorouracil)

· Adriamycin ® (doxorubicin)

· Avastin ® (bevacizumab)

· Cerubidine ® (daunorubicin)

· Clolar ® (clofarabine)

· Cytoxan ® (cyclophosphamide)

· Epirubicin (Pharmorubicin ® )

· Gleevec ® (imatinib)

· Herceptin ® (trastuzumab)

· Ifex ® (ifosfamide)

· Mutamycin ® (mitomycin)

· Nexavar ® (sorafenib)

· Novantrone ® (mitoxantrone)

· Sutent ® (sunitinib)

· Taxol ® (paclitaxel)

· Taxotere ® (docetaxel)

· Tykerb ® (lapatinib)

· Valstar ® (valrubicin)

· Xeloda ® (capecitabine)

· Zavedos ® (idarubicin)

Pharmacologic Stress Agents

For those patients who are unable to reach 75-100% of their age predicted maximum heart rate by physiologic exercise, vasodilation can be achieved with the use of either dipyridamole or adenosine. Use of pharmacologic agents in MPI is not a standard of care and is not medically necessary unless exercise is not possible. In some cases dobutamine may be used to effect stress through its inotropic effect.

1. Dipyridamole is typically administered intravenously (IV) at 0.57 mg/kg over a 4-minute period. The maximum dose should not exceed 60 mg. Since the dilation effect persists, after injection of the radiopharmaceutical, its effect is typically reversed with IV aminophylline, which must be available to reverse ischemia when it occurs. Dipyridamole is relatively contraindicated in patients with:

• Known bronchospastic lung disease (asthma)

• Systemic hypotension (systolic blood pressure (BP) below 100 mm Hg.)

• AMI less than 48 hours old

• Unstable angina

2. Adenosine is administered IV at 0.14 mg/kg/min over 6 minutes (0.84mg/kg). The vasodilation effect is short lived. Adenosine is contraindicated in patients with:

• Second or third degree atrioventricular (AV) block

• Sinus node disease, except for those with a functioning pacemaker

• Known or suspected bronchoconstrictive or bronchospastic lung disease

• Known hypersensitivity to adenosine

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