ASSESSMENT OF MYOCARDIAL VIABILITY IN CHRONIC CORONARY-ARTERY DISEASEUSING TC-99M SESTAMIBI SPECT - CORRELATION WITH HISTOLOGIC AND POSITRON EMISSION TOMOGRAPHIC STUDIES AND FUNCTIONAL FOLLOW-UP

Objectives. The value of Tc-99m-sestamibi (2-methoxy-isobutyl isonitri le [MIBI]) as a viability tracer was investigated in patients undergoi ng coronary artery bypass graft surgery. Background. Initial studies c laim that rest MIBI single-photon emission computed tomographic (SPECT ) studies can be used to assess myocardial viability. Methods. Thirty patients with a severely stenosed left anterior descending coronary ar tery and wall motion abnormalities were prospectively included. The pa tients underwent a MIBI rest study, a positron emission tomographic (P ET) flow ((NH3)-N-13) and metabolism (F-18-deoxyglucose) study and nuc lear angiography before undergoing bypass surgery. A preoperative tran smural biopsy specimen was taken from the left ventricular anterior wa ll. Morphometry was performed to assess percent fibrosis. After 3 mont hs, radionuclide angiography was repeated. Results. Statistically sign ificant higher MIBI values were found in the group with myocardial via bility as assessed by PET than in the group with PET-assessed nonviabi lity (p < 0.01). Significantly higher MIBI values were found in the gr oup with enhanced contractility at 3 months (76 +/- 13% vs. 53 +/- 22% , p < 0.01). A linear relation was found between MIBI uptake and perce nt fibrosis in the biopsy specimen (r = 0.78, p < 0.00001). When maxim izing the threshold for assessment of viability with MIBI by using fun ctional improvement as the reference standard, a cutoff value of 50% w as found, with positive and negative predictive values of 82% and 78%, respectively. Conclusions. (TC)-T-99m MIBI uptake was significantly h igher in PET-assessed viable areas and in regions with enhanced contra ctility at 3 months. A linear relation was found between percent fibro sis and MIBI uptake. An optimal threshold of 50% was found for predict ion of functional recovery.