COMPARISON OF EXERCISE, DIPYRIDAMOLE, AND ADENOSINE BY USE OF TECHNETIUM 99M SESTAMIBI TOMOGRAPHIC IMAGING

Background. Pharmacologic stress has been shown in animal studies to i nduce high degrees of myocardial hyperemia. At these levels of myocard ial blood flow, the myocardial uptake of technetium 99m sestamibi may plateau and may affect the diagnostic accuracy, This study compared th e effects of myocardial hyperemia induced by exercise, dipyridamole, a nd adenosine on Tc-99m sestamibi tomographic imaging in normal subject s and patients with ischemic coronary artery disease. Methods and Resu lts. Twenty subjects (group I, 10 normal subjects; group II, 10 patien ts with known coronary artery disease) underwent Tc-99m sestamibi tomo graphic imaging after rest, exercise, dipyridamole infusion, and adeno sine infusions on separate occasions. Total and background-corrected m yocardial counts of the resulting images were calculated. Visual and c omputer-generated quantitative myocardial perfusion defect analysis wa s performed in subjects in group II. For subjects in both groups I and II, there were no significant differences in the background-corrected myocardial counts obtained with exercise, dipyridamole, and adenosine stress. There were no significant differences in the myocardial perfu sion defects obtained after the three different modes of stress, inclu ding percentage defect size, stress deficit percentage, percentage of ischemia, count deficit index, and defect nadir. Conclusions. The myoc ardial uptake of Tc-99m sestamibi in normal subjects and patients with coronary artery disease is comparable after exercise, dipyridamole, a nd adenosine stress. In addition, the defect sizes and intensities wit h Tc-99m sestamibi after all forms of stress were equivalent. Thus Tc- 99m sestamibi, in combination with either adenosine or dipyridamole in fusions, provides imaging data equivalent to those with exercise and m ay be considered an alternative in patients unable to undergo adequate exercise.