Nitrates improve detection of ischemic but viable myocardium by thallium-201 reinjection SPECT

Thallium-201 reinjection imaging improves myocardial viability detection when compared to standard 3-4-hr redistribution imaging, however, the extent of ischemic but viable myocardium is still underestimated. We tested whether the sensitivity of reinjection imaging could be increased by giving nitrates postexercise to improve blood flow during the redistribution period. Twenty patients with coronary artery disease were included, 11 of them with a recent myocardial infarction. All patients underwent two exercise/4-hr redistribution 201Tl SPECT protocols: one with reinjection alone and the other with nitrates and reinjection. In the latter case, 20 mg of Isosorbide Dinitrate were given to patients immediately after postexercise imaging. Fifteen patients had reversible defects with reinjection alone, three additional patients were defined as ischemic with nitrates/reinjection protocol. Reinjection alone identified 41 reversible segmental defects, all except one were also 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 redistribution extent (segments/patient) was 2.05 +/- 0.41 segments with reinjection alone and 2.75 +/- 0.38 (p < 0.01) with nitrates/reinjection. In 15 patients showing reversible defects with both protocols, the redistribution extent was 2.73 +/- 0.41 segments with reinjection alone and 3.20 +/- 0.40 (p < 0.05) with nitrates/reinjection. Thallium-201 SPECT with nitrates and reinjection improves the detection of ischemic but viable myocardium in comparison to SPECT with reinjection alone.