NITRATES IMPROVE DETECTION OF ISCHEMIC BUT VIABLE MYOCARDIUM BY TL-201 REINJECTION SPECT

Thallium-201 reinjection imaging improves myocardial viability detecti on when compared to standard 3-4-hr redistribution imaging, however, t he extent of ischemic but viable myocardium is still underestimated. W e tested whether the sensitivity of reinjection imaging could be incre ased by giving nitrates postexercise to improve blood flow during the redistribution period. Twenty patients with coronary artery disease we re included, 11 of them with a recent myocardial infarction. All patie nts underwent two exercise/4-hr redistribution Tl-201 SPECT protocols: one with reinjection alone and the other with nitrates and reinjectio n. In the latter case, 20 mg of Isosorbide Dinitrate were given to pat ients immediately after postexercise imaging. Fifteen patients had rev ersible defects with reinjection alone, three additional patients were defined as ischemic with nitrates/reinjection protocol. Reinjection a lone identified 41 reversible segmental defects, all except one were a lso evaluated as reversible with nitrates/reinjection. However, among the 54 segments showing fixed defects after reinjection only, 14 (26%) presented as reversible with the nitrates/reinjection protocol. The r edistribution extent (segments/patient) was 2.05 +/- 0.41 segments wit h reinjection alone and 2.75 +/- 0.38 (p < 0.01) with nitrates/reinjec tion. In 15 patients showing reversible defects with both protocols, t he redistribution extent was 2.73 +/- 0.41 segments with reinjection a lone and 3.20 +/- 0.40 (p < 0.05) with nitrates/reinjection. Thallium- 201 SPECT with nitrates and reinjection improves the detection of isch emic but viable myocardium in comparison to SPECT with reinjection alo ne.