Assessment of Myocardial Viability With 99m Tc-Sestamibi Tomography Before Coronary Bypass Graft Surgery

Abstract

Background Assessment of myocardial viability by 99m Tc-sestamibi remains controversial. Accordingly, we investigated the use of sestamibi as a marker of myocardial viability, defined by histopathology, and for predicting improvement of myocardial function after coronary artery bypass graft surgery (CABG). Methods and Results 99m Tc-sestamibi perfusion tomography and radionuclide angiography were performed within 2 days before CABG in 21 patients with ≥75% stenosis of the left anterior descending coronary artery and resting anterior wall dyssynergy. During CABG, transmural myocardial biopsies were obtained from the dyssynergic anterior wall and from normal myocardial segments to determine the extent of viable myocardium by histopathology. 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 activity and the extent of viable myocardium determined morphometrically. Among 21 biopsied dyssynergic myocardial segments, 11 improved their function after CABG and 10 failed to improve. Biopsied segments with improved 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 99m Tc-sestamibi activity had positive and negative predictive values of 79% and 100%, respectively, for recovery of function after CABG in the biopsied segments. Conclusions Myocardial 99m Tc-sestamibi activity correlates well with the extent of viable myocardium and predicts improvement in regional function after CABG. This lends support to the use of sestamibi as a myocardial viability agent.