Clinical Evaluation of 99mTc Tetrofosmin in the Detection of Ischaemic Heart Disease.

99mTc tetrofosmin is a new ethylene, diphosphine ligand with unique properties, developed for myocardial perfusion imaging. The aim of this study was to define the imaging characteristics which would allow proper structuring of imaging protocols based on the physical attributes. Furthermore, this study evaluates the diagnostic role of 99mTc tetrofosmin in the detection of ischaemic heart disease. The study was performed in three stages in a sequential manner. In the first stage, 23 patients with known ischaemic heart disease were studied to evaluate the safety, kinetics and the imaging protocol of 99mTc tetrofosmin. 99mTc and tetrofosmin labelling was carried out rapidly and at room temperature from a kit. 99mTc tetrofosmin was found to be safe in man with rapid myocardial uptake and good retention. There was rapid clearance from the background structures such as lung, blood and liver, allowing early diagnostic imaging (even 5 minutes post injection). There was no evidence of redistribution on serial imaging allowing imaging as late as 4 hours post injection. The one day protocol was as good as a two day protocol for the detection of reversible ischaemia. In the second stage, a further 50 patients with suspected and 10 persons with low probability of ischaemic heart disease were studied using 201T1 and 99mTc tetrofosmin imaging. 99mTc tetrofosmin images were of superior quality than 201T1. There was high concordance between 201T1 and 99mTc tetrofosmin images for the overall (90%) and regional (>82%) diagnosis of perfusion defects. The sensitivity for the detection of coronary artery disease (>50% luminal narrowing) was 82%, 85% and 91% using 201T1 planar and SPECT 99mTc tetrofosmin, respectively, with a normalcy rate of 100% for 99mTc tetrofosmin imaging. In the third stage, 30 patients with known or suspected ischaemic heart disease underwent dobutamine stress 99mTc tetrofosmin imaging and a separate day rest study. Excellent quality SPECT images were obtained using 99mTc tetrofosmin. The sensitivity for the detection of coronary artery disease was 96%. In conclusion, tetrofosmin is available in kit formulation and preparation of 99mTc tetrofosmin does not require boiling. Early imaging is possible and 99mTc tetrofosmin does not redistribute. One day protocol may suffice and diagnostic ability is comparable to 201T1 imaging. In this study a high overall sensitivity for the detection of coronary artery disease was shown by 99mTc tetrofosmin imaging