PET myocardial viability imaging is the"gold standard"for the non-invasive assessment of myocardial viability.The research aims to find out the best methods of imaging interpretation in predicting the postoperative functional recovery.Twenty-one CAD patients with multi-vessel involvement Were recruited.All pailents underwent gated myocardial perfusion imaging(G-MPI) and FDG PET myocardial imaging within 2 weeks before coronary artery bypass grafting.The postoperative G-MPI was performed in all patients 3 months after the surgery.Out of the total 420 segments,164 segments of ischemic myocardium were detected by preoperative G-MPI.Among them,93ischemic segments were identified as non-viable(difference score≥0)and the rest 71 segments Were identified as viable(difference score＜0).The proportion of viable segments(the ratio of viabl esegments versus iscbemic segments)and summed difference score of metabolism to perfusion were calculated.The patients were further divided into 2 groups according to the proportion of viable myocardium:group Ⅰ(the proportion≥50%,12 cases)and group Ⅱ(the proportion＜50%,9 cases)while another division was made according to SDS:group A(SDSE≥0),group B(-5≤SDS＜0)and group C(SDS＜-5).The diagnostic accuracy of proportion of viable segments and SDS in predicting the post-revascularization improvement in the left ventricular ejection fraction by at least 5 or more ejection fraction units was 88.89%(8/9)and 55.56%(5/9)respectively.It is concluded that both approaches allow accurate evaluation of myocardial viability.Furthermore,the proportion of viable myocardium is more reliable in predicting the postoperative functional recovery.