BIOKINETICS OF TL-201 IN NORMAL SUBJECTS - COMPARISON BETWEEN ADENOSINE, DIPYRIDAMOLE, DOBUTAMINE AND EXERCISE

There are currently four common types of stress used with thallium-201 imaging in the diagnosis of coronary artery disease and risk assessme nt. The objective of this study was to examine the thallium biokinetic s during exercise, adenosine, dipyridamole and dobutamine stress testi ng in 15 healthy volunteers. Methods: Each subject underwent planar (2 01)TL imaging during maximal treadmill exercise testing, adenosine inf usion (140 mu g/kg/min for 6 min), dipyridamole infusion (142 mu g/kg/ min for 4 min) and dobutamine infusion (40 mu g/kg/min). Results: Abso lute myocardial thallium activity was greater after pharmacologic test ing than exercise, (p < 0.001 each). Thus, the activity was 505 counts /pixel with adenosine, 491 counts/pixel with dipyridamole, 517 counts/ pixel with dobutamine and 409 counts/pixel with exercise. The myocardi al thallium clearance was lower with pharmacologic testing than exerci se; 9.7%/hr with adenosine, 9.9%/hr with dipyridamole, 11.3%/hr with d obutamine and 13%/hr with exercise (p < 0.01 each). The thallium uptak e and clearance in the lung and liver were also greater with pharmacol ogic stress testing than exercise (p < 0.05). Conclusions: Thus, thall ium biokinetics are different during pharmacologic stress testing with adenosine, dipyridamole and dobutamine than during exercise. Diagnost ic criteria for quantitative analysis of myocardial perfusion imaging must therefore be specific for the type of stress used.