ABSTRACT
The aims of this study were to determine the prognostic value and the accuracy of nitrate-augmented Tc-99m myocardial SPECT for myocardial viability detection. Patients with angiographic CAD and LV wall motion abnormality by MUGA were included in the study. Rest Tc-99m sestamibi SPECT MPS was performed on two consecutive days, once with 0.6 mg sublingual nitroglycerin and once without. Perfusion was graded semi-quantitatively. Reversibility score was calculated as the difference between nitrate-augmented and rest imaging perfusion scores. Repeat rest SPECT MPS was performed after at least 6 months and all patients were followed up for at least 12 months to determine the occurrence of cardiac events. Thirty-five patients were included in the study. Five patients died from myocardial infarction during the follow-up period. Eleven patients had follow-up SPECT, with five of them done after revascularization. Defect score improved significantly after revascularization compared without revascularization (7.4 versus 0.3, p=0.02). Reversibility scores correlated poorly with the subsequent occurrence of cardiac events in patients treated medically. There was no significant increase in LVEF detected after revascularization even if the patients had a positive reversibility score. By this parameter, nitrate-augmented MPS could not accurately assess myocardial viability. However, with nitrate-augmentation, defect scores significantly improved and were more predictive of post-revascularization scores compared to the rest scores. These suggest the possibility for enhanced detection of potentially viable myocardium with nitrate MPS. And due to its simplicity and safety, the routine use of nitrate-augmentation in clinical practice may be recommended.