Half-Dose Radiopharmaceutical in Wide Beam Reconstruction

Not Applicable

Terminated

Brief Summary: This study is recruiting patients already scheduled for a single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) test. SPECT-MPI is a nuclear imaging technique that uses a radioactive substance, or radiotracer, and special equipment to create three-dimensional (3D) images of the heart. Radiotracer is a radioactive dye that will make the structures of the heart visible and is routinely used to view blood flow in the heart, scan for damaged heart tissue, or assess heart function.

For a routine SPECT-MPI test, the radiotracer is given in one dose at the beginning of the test, followed by taking resting images of the heart. For this study, researchers would like to administer half of the radiotracer, obtain resting images, administer the remainder of the radiotracer and obtain a second set of resting images. Participants will receive the same amount of radioactive material that would normally be given for this test; however, it will be administered in two half-doses. Participation in this study will add about 30 minutes to the time it takes to complete the routine test. The investigators expect to enroll about 160 subjects in this study at Northwestern.

Detailed Description: Subjects in this study will proceed to the nuclear cardiology laboratory for their scheduled nuclear stress test. After informed consent is obtained, the study doctor or research staff member will ask detailed questions about the subject's current health, medications and medical history, and the subject's medical chart will be reviewed including results of any previous nuclear images.

For the test, a small catheter (tube) will be placed in a vein in the subject's arm to administer the radioactive imaging agent, Tc-99m sestamibi. Subjects will be given half (1/2) of the normal Tc-99m sestamibi dose and then the study staff will obtain resting images pictures of the heart. After this set of images, the subject will be given the remaining half of the radioactive imaging agent followed by a second set of images.

After this, the subject will then undergo the stress portion of the test in the usual manner as prescribed by the referring physician.

Recruitment & Eligibility

Inclusion Criteria

Patients over the age of 18 years
Undergoing nuclear stress testing
History of myocardial infarction, cardiomyopathy, heart failure or prior nuclear studies with resting perfusion defects

Exclusion Criteria

Unwilling or unable to undergo an additional resting SPECT acquisition
Clinical contraindications to nuclear stress testing including acute myocardial infarction
- For patients undergoing exercise treadmill stress testing:
Left bundle branch block or artificial ventricular pacemaker
- For patients undergoing regadenoson (Lexiscan) stress testing:
Moderate to severe chronic obstructive pulmonary disease or asthma, second- or third degree atrioventricular block or sinus node disease (unless patients have a functioning artificial pacemaker), known hypersensitivity to aminophylline or adenosine
Inability to give informed consent

Arm && Interventions

Group	Intervention	Description
Half-dose radiotracer administration	Half-dose of the Tc99-m sestamibi (Cardiolite)	For this study, researchers would like to administer half of the radiotracer, obtain resting images, administer the remainder of the radiotracer and obtain a second set of resting images. Subjects will be given the same amount of radioactive material that would normally be given for this test; however, it will be administered in two ½ doses.

Primary Outcome Measures

Name	Time	Method
Segments With Resting Perfusion Defect	Baseline	Left ventricular myocardium was divided into standardized 17-segments with 6 equiangular segments in the basal region, 6 equiangular segments in the mid region, 4 equiangular segments in the apical regions, and 1 region in the apex (Cerqueira MD, et al., J Nucl Cardiol 2002;9:240-5). Each segment was scored on a scale from 0 to 4 to indicate the severity of the perfusion defect (0=no perfusion defect; 1=mild perfusion defect; 2=moderate perfusion defect; 3=severe perfusion defect; and 4=absent perfusion). The number of segments with a score of 1 or greater were summed to obtain the number of segments with a resting perfusion defect.
Sum Rest Score	Baseline	Left ventricular myocardium was divided into standardized 17-segments with 6 equiangular segments in the basal region, 6 equiangular segments in the mid region, 4 equiangular segments in the apical regions, and 1 region in the apex (Cerqueira MD, et al., J Nucl Cardiol 2002;9:240-5). Each segment was scored on a scale from 0 to 4 to indicate the severity of the perfusion defect (0=no perfusion defect; 1=mild perfusion defect; 2=moderate perfusion defect; 3=severe perfusion defect; and 4=absent perfusion). The scores over 17 segments were summed to report the Sum Rest Score (SRS), ie. the greater the SRS, the larger the perfusion defect.

Secondary Outcome Measures

Name	Time	Method
Image Quality Score	Baseline	Each reconstructed image was subjectively scored by the expert readers to determine the overall image quality. The Image Quality Score of the reconstructed images were graded on a 4-point scale. (1=Poor; 2=Fair; 3=Good; and 4=Excellent).
Diagnostic Confidence Score	Baseline	Each reconstructed image was subjectively scored by the expert readers to determine the expert reader's diagnostic confidence in scoring and interpreting the perfusion scores. The Diagnostic Confidence Score of the reconstructed images were graded on a 4-point scale. (1=Poor; 2=Fair; 3=Good; and 4=Excellent).