Comparative myocardial extraction of two technetium-labeled BATO derivatives (SQ30217, SQ32014) and thallium

The transcapillary exchange of a new class of 99mTc-labeled compounds (BATO) were compared to 201Tl in isolated, blood perfused rabbit hearts. During variable blood flow (0.15-2.44 ml/min/g), peak and net extraction (Emax and Enet, respectively), and capillary permeability-surface area product (PScap) were determined with paired indicator-dilution techniques. Serial bolus injections of 201Tl, [111In]albumin, and [99mTc]BATO; chloro[tris(cyclohexanedionedioxime)methyl boronic acid]Tc (SQ30217, n = 8) and a hydroxy-substituted derivative (SQ32014, n = 5) were given to a total of 13 hearts. Mean (+/- s.d.) SQ30217 Emax and Enet were 0.72 +/- 0.09 and 0.55 +/- 0.18, respectively, which were higher than thallium values of 0.57 +/- 0.10 and 0.46 +/- 0.17 (p less than 0.03). Mean SQ30217 PScap was 1.1 +/- 0.4 ml/min/g and was also higher than corresponding thallium determinations (0.7 +/- 0.3; p less than 0.001). SQ32014 Emax, Enet, and PScap were all significantly less than thallium values (p less than 0.001). Thallium and SQ30217 values for Emax and PScap were closely correlated with blood flow (r greater than or equal to 0.73), whereas those for SQ32014 were weakly correlated (r = 0.09). A small clinical pilot study (n = 3) was performed, which showed that SQ32014 was a poor myocardial perfusion agent in man. In summary, transcapillary exchange of SQ30217 is greater than thallium, which in turn, is greater than SQ32014. Therefore, SQ30217 appears to have good clinical potential, but SQ32014 does not.