Myocardial kinetics of TcN-NOET: a neutral lipophilic complex tracer of regional myocardial blood flow.

Unlabelled: [Bis (N-etoxy, N ethyl dithiocarbamato) nitrido] 99mTc (V) (TcN-NOET) is a new neutral lipophilic myocardial imaging agent proposed for clinical use for detecting coronary artery disease. We studied the relation 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 (protocols 1,2 and 3). Myocardial activity of TcN-NOET was determined by in vitro tissue counting at 15 or 90 min postinjection. Tracer activity was correlated with radiolabeled microspheres using linear regression analysis.

Results: There was a linear correlation between myocardial TcN-NOET activity and microspheres in protocol 1 (r = 094, 15 min postinjection, protocol 2 (r = 0.94, 15 min postinjection after dipyridamole) and protocol 3 (r = 0.91, 90 min postinjection after dipyridamole). When arterial occlusion was discontinued (protocol 4), there was no longer a close linear correlation (r = 0.26). The first-pass myocardial extraction action of TcN-NOET was 75.5% +/- 4% under basal conditions and 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. After reflow, TcN-NOET redistributes almost completely within 90 min.