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)](https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/019414Orig1s021lbl.pdf),
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

3\. Dobutamine is administered IV, starting at 0.5-1.0 mcg/kg/min and titrated
to reach the maximum heart rate for 2-5 minutes. The maximum dose is 40
mcg/kg/min. Atropine may be added in appropriate doses IV. Dobutamine is
contraindicated in patients with:

    * Idiopathic subaortic stenosis
    * AMI

**Physician Supervision Requirements**  
MPI and blood pool imaging require general supervision by a qualified
physician licensed to administer radioactive materials. Cardiology stress
procedures performed in conjunction with nuclear MPI studies are covered by
Medicare only when performed under the direct supervision of a qualified
physician, who provides:

    * Medical expertise required for performance of the test
    * Medical treatment for complications and side effects of the test
    * Medical services required as part of the test such as injections of medications
    * Medical expertise in the interpretation of the cardiovascular stress test component, some of which has to be provided during the test and before the patient is discharged from the testing suite