MYOCARDIAL PERFUSION IMAGING WITH TC-99M TETROFOSMIN - COMPARISON TO (TL)-T-201 IMAGING AND CORONARY ANGIOGRAPHY IN A PHASE-III MULTICENTER

Background Our objective was to compare the sensitivity and specificit y of tetrofosmin, a new Tc-99m-labeled myocardial perfusion imaging ag ent for the detection of myocardial perfusion abnormalities, with thos e of Tl-201 and coronary angiography. Our hypothesis was that same-day stress/rest tetrofosmin imaging could provide data comparable to thos e of Tl-201 imaging. Myocardial perfusion imaging plays an important r ole for the evaluation of coronary artery disease. Newer Tc-99m-labele d agents offer several advantages over Tl-201, the conventional myocar dial perfusion imaging agent. Tetrofosmin is a new Tc-99m-labeled agen t with promising results in preliminary studies. Methods and Results T wo hundred fifty-two patients with suspected coronary artery disease w ere enrolled in 10 centers in the United States and Europe. All patien ts underwent exercise and rest myocardial perfusion imaging with Tc-99 m-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 unde rwent standard exercise and redistribution planar Tl-201 imaging withi n 2 weeks of tetrofosmin imaging. In addition, 58 healthy subjects wit h low likelihood of coronary artery disease underwent exercise and res t tetrofosmin imaging. Coronary angiograms were available in 181 patie nts with suspected coronary artery disease. All radionuclide images we re processed in the central core laboratory and interpreted blindly by a panel of four experienced readers. Tl-201 images and tetrofosmin im ages were read separately. Discrepancies were resolved by consensus. T he workload, peak heart rate, and double products were comparable duri ng exercise for both imaging agents. Technically acceptable paired Tl- 201 and tetrofosmin images were available in 224 of 252 patients. Tetr ofosmin images were generally of good quality, with low extracardiac a ctivity, and easy to interpret. Patients were categorized as showing n ormal, ischemia, infarction, or mixture with each imaging modality. Pr ecise concordance for each of these categories was 59.4% (kappa=0.44; 95% CI, 0.35 to 0.53). When patients were categorized as normal or abn ormal, the concordance was 80.4% (kappa=0.55; 95% CI, 0.43 to 0.67). W hen each of five anatomic territories (septal, anterior, inferior, lat eral, and apical) was categorized as normal versus abnormal, the conco rdance Varied from 81% to 90%. When similar comparison was made for th e specific category of abnormality, the concordance was 64% to 84%. Wh en coronary angiography was used as the criterion, the sensitivity and positive and negative predictive accuracy of tetrofosmin and Tl-201 w ere comparable. The normalcy rate of tetrofosmin images in the healthy subjects with low likelihood of coronary artery disease was 97%. Conc lusions Tc-99m tetrofosmin is a new myocardial imaging agent with favo rable imaging characteristics with results comparable to those of Tl-2 01.