The effect of ischemic injury on the cardiac transport of Tc-99m N-NOET inthe isolated rabbit heart

Background, Bis (N-ethoxy, N-ethyl dithiocarbamato) nitrido technetium-99m (V) (TcN-NOET) is a neutral lipophilic myocardial perfusion agent. The effe ct of ischemic injury on the cardiac transport of TcN-NOET and thallium-201 was determined in isolated rabbit hearts. Methods and Results. The multiple indicator dilution method was used to det ermine the maximum (E-max) and net extraction (E-net, at 5 minutes) of TcN- NOET and Tl-201 at control and after 10 minutes (n = 4) or 45 minutes (n = 4) of no-flow ischemia, After 10 minutes of ischemia the mean E-max for Tl- 201 was unchanged, 0.86 +/- 0.03 vs 0.85 +/- 0.02, whereas Tl-01 E-net show ed a small decrease from 0.46 +/- 0.03 to 0.40 +/- 0.03, P < .001. Forty-fi ve minutes of ischemia mildly reduced E-max for Tl-201 (0.87 +/- 0.04 to 0. 74 +/- 0.04, P < .001) and severely reduced E-net (0.46 +/- 0.03 vs 0.16 +/ - 0.01, P < .001). Neither E-max nor E-net for TcN-NOET was significantly a ffected by 10 minutes of ischemia (0.54 +/- 0.04 vs 0.58 +/- 0.03 and 0.24 +/- 0.04 vs 0.26 +/- 0.04, respectively). However, severe ischemic injury c aused significant reductions versus control in both E-max (0.59 +/- 0.06 vs 0.42 +/- 0.05, P < .001) and E-net (0.27 +/- 0.03 vs 0.18 +/- 0.05, P < .0 1). Conclusions. TcN-NOET is a new myocardial perfusion agent with moderate myo cardial extraction, Although less sensitive than Tl-201 to mild ischemic in jury, TcN-NOET extraction and retention are decreased by severe ischemic in jury, making uptake of TcN-NOET a possible marker of myocardial viability.