NITRATE-AUGMENTED MYOCARDIAL IMAGING FOR ASSESSMENT OF MYOCARDIAL VIABILITY

Tl-201 myocardial perfusion imaging is presently done by several possible strategies, Stress/delayed redistribution, stress/redistribution/reinjection, and rest/redistribution imaging can be useful in the clinical assessment of myocardial viability. Unfortunately the extent of myocardial viability may still be underestimated even by Tl-201 reinjection imaging, compared with F-18-fluorodeoxyglucose positron emission tomography, Tc-99m-labeled sestamibi imaging provides results similar to those of Tl-201 imaging in the detection of coronary artery disease, but several previous studies suggest that stress/rest Tc-99m-labeled sestamibi imaging significantly underestimates myocardial viability. Recently it has been reported that the administration of nitrates, before Tl-201 reinjection, improves detection of defect reversibility. Several studies also suggested that administration of nitrates before the injection of Tc-99m-labeled sestamibi significantly improved detection of reversibility with this agent, whereas additional studies showed further that this combination improves the predictive accuracy for recovery of left ventricular function and perfusion after coronary revascularization, compared with a standard rest Tc-99m-labeled sestamibi study. Nitrate administration before the injection of Tl-201 and Tc-99m-labeled sestamibi may thus be a potentially attractive alternative for the evaluation of myocardial viability. Although the available results are encouraging, further studies are needed to evaluate the clinical value of Tl-201 and Tc-99m-labeled sestamibi imaging, in combination with nitrates, for predicting recovery of left ventricular dysfunction.