Comparison of sestamibi, tetrofosmin, and Q12 retention in porcine myocardium.

UNLABELLED

Although there are several 99mTc perfusion tracers introduced for clinical use, there are no data available directly comparing these tracers with microsphere-determined flow. The aim of this study was to compare the myocardial retention of sestamibi, tetrofosmin, and Q12 in a porcine model.

METHODS

We used a pig model with (n = 6) or without (n = 3) coronary occlusion. Each pig received a simultaneous injection of sestamibi and either tetrofosmin (group 1, n = 5) or Q12 (group 2, n = 4) labeled with either 99mTc or 95mTc (physical half-life, 61 d; photon energy, 204 keV) during pharmacologic vasodilation. Absolute myocardial retention of each tracer was calculated from the myocardial tracer activity and arterial input function.

RESULTS

The plot of all three tracers versus flow achieved a plateau at a higher flow range. However, sestamibi showed a higher mean retention than either tetrofosmin (group 1, 0.27 +/- 0.11 vs. 0.16 +/- 0.06 mL/g/min, respectively; P < 0.01) or Q12 (group 2, 0.32 +/- 0.13 vs. 0.09 +/- 0.03 mL/g/min, respectively; P < 0.01). Furthermore, when a linear regression analysis was performed to assess the relationship between retention and microsphere-determined flow, sestamibi showed a greater increment in retention than did tetrofosmin or Q12.

CONCLUSION

Although all of the tracers showed a nonlinear increase in retention as flow increased, sestamibi may display more favorable characteristics as a flow tracer in the porcine heart.