TI-201 myocardial perfusion SPECT - Role of nitrate-augmented redistribution

Purpose: Tl-201 myocardial perfusion SPECT is commonly used to assess myoca rdial perfusion and viability. Nitrate-augmented redistribution with repeat ed injection facilitates the detection of reversible segments compared with standard redistribution. In this study, we investigated the potential of n itrate augmentation to improve myocardial perfusion and viability assessmen t without repeated injection and we also compared nitrate-augmented redistr ibution with delayed redistribution. Methods: Eighteen patients underwent a stress-redistribution Tl-201 SPECT s tudy. Immediately after redistribution SPECT, each patient was administered 0.6 mg glyceryl trinitrate and nitrate-augmented redistribution SPECT acqu ired 30 minutes later. Each patient then returned the next day and was inje cted with a booster dose of Tl-201 30 minutes before the delayed redistribu tion SPECT acquisition. For each SPECT study, the myocardium was divided in to 11 segments, and perfusion to each segment was scored on a four-point sc ale by consensus. An overall cardiac perfusion score was derived by summing the perfusion score for each segment. Results: Reduced stress perfusion was identified in 150 segments: 23 (15.3% ) had improved perfusion after redistribution; 60 (40%) segments had improv ed perfusion after nitrate-augmented redistribution; 52 (34.7%) segments wi th reduced stress perfusion had improved perfusion after delayed redistribu tion. The cardiac perfusion score after stress was 15.9 +/- 5.5 (means +/- SD). The score increased to 17.4 +/- 5.4 after redistribution. The perfusio n score improved to 19.7 +/- 5.8 (P < 0.05 versus redistribution) after nit rate augmentation. The cardiac perfusion score, 19.2 +/- 6.4, did not impro ve further after delayed redistribution. Conclusions: Tl-201 SPECT with nitrate-augmented redistribution is as good or better than delayed redistribution with repeated injection for myocardia l perfusion and viability assessment. Tl-201 SPECT with nitrate-augmented r edistribution has significant logistical and economic advantages over tradi tional delayed redistribution with Tl-201 repeated injection.