Myocardial Perfusion Imaging With
99m
Tc Tetrofosmin
Authors: Zaret Barry L. , Rigo Pierre , Wackers Frans J.T. , Hendel Robert C. , Braat Simon H. , Iskandrian Ami S. , Sridhara Bangalore S. , Jain Diwakar , Itti Roland , Serafini Aldo N. , Goris Michael L. , Lahiri Avijit 
Published: June 2012

Background
Our objective was to compare the sensitivity and specificity of tetrofosmin, a new
99m
Tc-labeled myocardial perfusion imaging agent for the detection of myocardial perfusion abnormalities, with those of
201
Tl and coronary angiography. Our hypothesis was that same-day stress/rest tetrofosmin imaging could provide data comparable to those of
201
Tl imaging. Myocardial perfusion imaging plays an important role for the evaluation of coronary artery disease. Newer
99m
Tc-labeled agents offer several advantages over
201
Tl, the conventional myocardial perfusion imaging agent. Tetrofosmin is a new
99m
Tc-labeled agent with promising results in preliminary studies.

Methods and Results
Two hundred fifty-two patients with suspected coronary artery disease were enrolled in 10 centers in the United States and Europe. All patients underwent exercise and rest myocardial perfusion imaging with
99m
Tc-tetrofosmin using two separate injections of the radiotracer 4 hours apart on the same day. Planar images were obtained in three standard views 15 to 60 minutes after radiotracer injection. Patients also underwent standard exercise and redistribution planar
201
Tl imaging within 2 weeks of tetrofosmin imaging. In addition, 58 healthy subjects with low likelihood of coronary artery disease underwent exercise and rest tetrofosmin imaging. Coronary angiograms were available in 181 patients with suspected coronary artery disease. All radionuclide images were processed in the central core laboratory and interpreted blindly by a panel of four experienced readers.
201
Tl images and tetrofosmin images were read separately. Discrepancies were resolved by consensus. The workload, peak heart rate, and double products were comparable during exercise for both imaging agents. Technically acceptable paired
201
Tl and tetrofosmin images were available in 224 of 252 patients. Tetrofosmin images were generally of good quality, with low extracardiac activity, and easy to interpret. Patients were categorized as showing normal, ischemia, infarction, or mixture with each imaging modality. Precise concordance for each of these categories was 59.4% (κ=0.44; 95% CI, 0.35 to 0.53). When patients were categorized as normal or abnormal, the concordance was 80.4% (κ=0.55; 95% CI, 0.43 to 0.67). When each of five anatomic territories (septal, anterior, inferior, lateral, and apical) was categorized as normal versus abnormal, the concordance varied from 81% to 90%. When similar comparison was made for the specific category of abnormality, the concordance was 64% to 84%. When coronary angiography was used as the criterion, the sensitivity and positive and negative predictive accuracy of tetrofosmin and
201
Tl were comparable. The normalcy rate of tetrofosmin images in the healthy subjects with low likelihood of coronary artery disease was 97%.

Conclusions
99m
Tc tetrofosmin is a new myocardial imaging agent with favorable imaging characteristics with results comparable to those of
201
Tl.