Uptake of seven myocardial tracers during increased myocardial blood flow by dobutamine infusion

RATIONALE AND OBJECTIVES. Direct comparison of myocardial perfusion tracers has been made difficult by variability in experimental models, and by a virtual absence of data comparing tracer uptake to myocardial blood flow under conditions of increased myocardial oxygen consumption, similar to what occurs with dynamic exercise. METHODS. Tracer uptake versus myocardial blood how was evaluated for thallium-201 (Tl-201) and six technetium-99m (Tc-99m) myocardial imaging agents in 24 open-chest canines with an occluded left-anterior descending coronary artery during dobutamine infusion, Data were fitted to the exponential model y = ax(1 - exp[-PSc/x]), where y is the tissue tracer/g normalized to normal (activity at 1 mL/minute/g) and x is the blood flow measured by the radioactive microsphere method. RESULTS. With dobutamine, myocardial tracer uptake was linear across a wide range of ischemic and hyperemic hows for each tracer. Based on the permeability surface area product, Tl-201 and Tc-99m Q3 provided the best tracer estimate of myocardial blood flow (5.30 +/- 0.86 mL/minute/g, r = 0.91; 5.46 +/- 0.58 mL/minute/g, r = 0.94, respectively). Correlation coefficient (r) values for other tracers studied were Tc-99m Q4 (r = 0.93), Tc-99m Q12 (r 0.93), Tc-99m sestamibi (r = 0.90), Tc-99m tetrofosmin (r = 0.96), and Tc-99m-N-Noet (r = 0.82). CONCLUSIONS. Of the Tc-99m tracers examined under conditions of dobutamine-altered myocardial contractility, the myocardial uptake properties of Tc-99m Q3 were most similar to those of Tl-201.