MYOCARDIAL KINETICS OF TCN-NOET - A NEUTRAL LIPOPHILIC COMPLEX TRACEROF REGIONAL MYOCARDIAL BLOOD-FLOW

[Bis (N-etoxy, N ethyl dithiocarbamato) nitrido] Tc-99m (V) (TcN- NOET ) is a new neutral lipophilic myocardial imaging agent proposed for cl inical use for detecting coronary artery disease. We studied the relat ion between myocardial retention of TcN-NOET and myocardial blood flow (MBF) in a canine model. Methods: A wide range of MBF was induced by partial regional coronary occlusion and dipyridamole infusion (protoco ls 1, 2 and 3). Myocardial activity of TcN-NOET was determined by in v itro tissue counting at 15 or 90 min postinjection. Tracer activity wa s correlated with radiolabeled microspheres using linear regression an alysis. Results: There was a linear correlation between myocardial TcN -NOET activity and microspheres in protocol 1 (r = 094, 15 min postinj ection, protocol 2 (r = 0.94, 15 min postinjection after dipyridamole) and protocol 3 (r = 0.91, 90 min postinjection after dipyridamole). W hen arterial occlusion was discontinued (protocol 4), there was no lon ger a close linear correlation (r = 0.26). The first-pass myocardial e xtraction action of TcN-NOET was 75.5% +/- 4% under basal conditions a nd 85% +/- 2% under hyperemic conditions (p < 0.01). Conclusion: Up to 90 min after injection, the relationship between TcN-NOET myocardial retention and blood flow is excellent over a wide range of flows. Afte r reflow, TcN-NOET redistributes almost completely within 90 min.