ASSESSMENT OF MYOCARDIAL VIABILITY WITH TC-99M-SESTAMIBI TOMOGRAPHY BEFORE CORONARY-BYPASS GRAFT-SURGERY - CORRELATION WITH HISTOPATHOLOGY AND POSTOPERATIVE IMPROVEMENT IN CARDIAC-FUNCTION

Background Assessment of myocardial viability by Tc-99m-sestamibi rema ins controversial. Accordingly, we investigated the use of sestamibi a s a marker of myocardial viability, defined by histopathology, and for predicting improvement of myocardial function after coronary artery b ypass graft surgery (CABG). Methods and Results Tc-99m-sestamibi perfu sion tomography and radionuclide angiography were performed within 2 d ays before CABG in 21 patients with greater than or equal to 75% steno sis of the left anterior descending coronary artery and resting anteri or wall dyssynergy. During CABG, transmural myocardial biopsies were o btained from the dyssynergic anterior wall and from normal myocardial segments to determine the extent of viable myocardium by histopatholog y. Improvement of regional left ventricular function was evaluated by radionuclide angiography at 6 to 8 weeks after CABG. There was a good correlation (r = .85, P<.001) between the quantified sestamibi activit y and the extent of viable myocardium determined morphometrically. Amo ng 21 biopsied dyssynergic myocardial segments, 11 improved their func tion after CABG and 10 failed to improve. Biopsied segments with impro ved postoperative function had significantly higher sestamibi activity (81+/-5% versus 49+/-16%; P<.0001) and significantly lower extent of interstitial fibrosis (7+/-4% versus 31+/-21%, P=.0002) than segments that failed to improve. A 55% threshold of Tc-99m-sestamibi activity h ad positive and negative predictive values of 79% and 100%, respective ly, for recovery of function after CABG in the biopsied segments. Conc lusions Myocardial Tc-99m-sestamibi activity correlates well with the extent of viable myocardium and predicts improvement in regional funct ion after CABG. This lends support to the use of sestamibi as a myocar dial viability agent.