Previous studies demonstrate perfusion defect reversibility in 201Tl reinjection imaging performed after the administration of nitrates. This study tests whether the acute sublingual administration of isosorbide dinitrate (ISDN) could improve the capability of 99mTc-teboroxime to detect reversibility in exercise-induced perfusion defects.
Methods: Ten patients with previous myocardial infarction underwent exercise, redistribution and reinjection 201Tl imaging, 99mTc-teboroxime exercise and rest scans. Following the latter, 5 mg sublingual ISDN were given, 99mTc-teboroxime was reinjected and images collected.
Results: The total defect score/patient in the 201Tl images was 10.5 +/- 3.1 (mean +/- s.d.), decreasing to 7.4 +/- 2.7 after redistribution (p < 0.02) and to 4.8 +/- 2.1 after reinjection (p < 0.01 versus redistribution). The total defect score in 99mTc-teboroxime exercise images was 12.7 +/- 3.1 (p < 0.05 versus 201Tl exercise), decreasing to 7.3 +/- 3.3 at rest (p < 0.01 versus exercise, NS versus 201Tl redistribution) and to 5.6 +/- 2.6 in ISDN images (p < 0.02 versus rest, p < 0.05 versus 201Tl redistribution, NS versus reinjection). Of the 44 abnormal segments in 201Tl exercise images, the redistribution scan identified 26 defects as reversible and 18 as fixed. After reinjection, 37 defects appeared reversible and only seven fixed (p < 0.005 versus redistribution). Stress-rest 99mTc-teboroxime classified 33 segments as reversible and 11 as fixed (NS versus both 201Tl protocols). After ISDN, the uptake score increased in 19 segments. Therefore, 37 were classified as reversible and seven as fixed defects (p < 0.01 versus 201Tl redistribution, NS versus 201Tl reinjection).
Conclusions: Sublingual ISDN before 99mTc-teboroxime rest injection seemed to improve the tracer capability of detecting reversibility in exercise-induced perfusion defects.